02.01 - Contemporary Management of Malformations of Cortical Development.pdf

HEMISPHERECTOMY TECHNIQUES 129

in an abstract in 199213 and recently described in more detail.& It includes the following features:

1. Small parasagittal craniotomy 2. Complete callosotomy and opening of

roof of lateral ventricle (see Fig. 6E) 3. Anterior disconnection of the hemisphere

through frontobasal white matter 4. Disconnection of the insular cortex and

hemispheric white matter by dissection from the lateral ventricle through the lateral parts of the basal ganglia block to the mesial aspect of the temporal lobe

5. Dorsomesial disconnection connecting

5. Temporomesial disconnection by resection of the hippocampal head and amyg- dalum and cutting the tail of the hip- pocampus dorsally

Shin-&u and Maehara38 reported on a large series, including many cases with CD. The series included 14 CD cases and 12 HME cases. Intraoperative blood transfusion was performed in 79% of these cases, with a mean volume of 225 mL. There were three incomplete disconnections requiring reoperation. Five shunts were inserted, and all were needed in pediatric patients with HME.

the callosotomy with the subinsular temporomesial disconnection line SPECIAL ASPECTS OF THE

PEDIATRIC POPULATION

The results in 53 cases, including 20 CD or HME cases and six SWD cases, were recently reported. There was one death in the series. Ten patients (all HME cases) needed a shunt. In general, results were excellent, with 80% of patients seizure-free, but half of the 10 patients who were not seizure-free had HME, pointing out the significance of cause.

JAPANESE MODIFIED PERI-INSULAR HEMISPHERECTOMY

This technique38 is the fourth modification and is thought of as a replacement for Rasmussens technique (see Fig. 6D). It com- bines elements of the peri-insular window technique (see Fig. 6C) with subcortical access to the mesial temporal lobe as described by Delalande et al (see Fig. 6E).13 The following main steps are included:

1. Medium-sized craniotomy over the whole length of the lateral ventricle, including the trigone

2. Resection of the frontal operculum and upper half of the insular cortex

3. Transection of subinsular white matter to the lateral ventricle and transventricular callosotomy

4. Subcortical disconnection of the insula with access to the mesial temporal lobe

The physiologic and pathophysiologic profiles in children are well known to be quite different; as a result, pediatric hemispherectomy requires special precautions because of the differences in body fat, body surface-to-body volume ratio, metabolism, and, most importantly, blood volume. Special care needs to be taken to prevent hypothermia, to start blood replacement early, and to cor- rect disturbed serum parameters quickly.8, l5 Because hemispherectomies may be necessary even in small babies, the utmost care and precision are necessary to manage loss of blood components to avoid coagulation disorders or hypotensive periods. It should not be forgotten that in the few reports on neu- roanesthesia for HME and pediatric epilepsy surgery, the particularly dangerous aspects of hemispherectomies have been mentioned, including episodes of severe hypotension, hemodynamic instability, metabolic acidosis, hypothermia, and even episodes of cardiac ar-est 8,9.15.22.30

The modem warming methods (e.g., Bair Hugger [Augustine Medical, Eden Prairie, MN]), frequent analysis of serum parameters, surgical technique that avoids blood loss and long duration of surgery, and metic- ulous replacement of blood components and coagulation factors help to avoid most of these problems. It is obvious that a surgical technique that helps to avoid significant

130 scHRAh4M

disturbances of homeostasis is better than even the most refined and up-to-date anes- thesiologic management of them. If seizure outcome is equivalent, a surgical technique that minimizes severe negative effects on homeostasis seems preferable.

SPECIFli= CONSIDERATIONS IN HEMIMEGALENCEPHALY

Hemimegalencephaly poses specific chal- lenges for, the surgeon. The increase in brain volume increases the amount of work, the depth of the field, and the expected blood loss. The voluminous and partly hamartoma- tous structures around the ventricle make ori- entation more difficult, particularly because a clear-cut border between superficial gray substance or the deeper indentations of the cortical gray substance and the white matter is frequently obscured by ectopic gray matter (see Fig. 2). Some authors also report higher blood loss from increased vascularization and a greater tendency to bleed in surgery for ljME.3t4.14

Voluminous and dysplastic gyri of the dis- eased hemisphere may bulge beyond the midline in an irregular fashion and make orienta- tion about the midline difficult (see Fig. 2). The sagittal sinus may be displaced to the good side, rendering the midline craniotomy for a hemidecortication or anatomic removal more dangerous. Despite the increase in volume, the ventricle is frequently enlarged but may be malformed (see Fig. 2). The handling of the vessels depends on the type of surgery in- tended. In anatomic resections, it would be useful to clip the middle cerebral artery and anterior cerebral artery early during the procedure, leaving some veins open. In the smaller disconnection procedures combined with a smaller degree of resection,37,B,Q it would be unwise to clip middle cerebral artery branches or veins as described, because postoperative swelling in an HME patient can lead to a dangerous situation. The large brain volume, the tendency to an already displaced midline, and the smaller resections used in the disconnection procedures should enhance the awareness of some degree of postoperative swelling in

the face of less rese,rve space and should lead to a well-planned degree of volume resection, leaving enough space for some postoperative swelling.

The recommended procedure in HME should include adequate exposure of brain landmarks (limen insulae, frontal opercuhun, anterior tip of the frontal horn, trigone, and anterior tip of the temporal horn), an adequate degree of tissue resection, and well-visualized total disconnection of the remaining hemisphere. A minimalistic procedure such as the trans-sylvian, transventricular, functional hemispherectomy with only amygdalohippocampectomy is not ideal for HME cases, although the authors have performed this procedure. 37 They would recommend cre- ating some room either by performing a standard anterior temporal lobectomy or by resecting the frontal operculum, which makes the approach to the lateral ventricle easier. This corresponds to modification 2 from their first hemispherectomy procedure36 and is similar to the two other techniques that involve frontal opercular resection3 or resection of frontal and temporal operculum plus white matter down to the ventricle.42 If the opercular resection is chosen, the temporal resection can be restricted to the mesial part of the temporal lobe just like in selec- tive amygdalohippocampectomy (see Fig. 6B). Alternatively, mesiotemporal disconnection is performed with minimal resection (see Fig. 6C).

Hemispherectomy for HME can be achieved by several functional hemispherectomy techniques. It is not of importance which of the functional hemispherectomy techniques is used: Rasmussens, trans-sylvian with modification,37 perisylvian window technique, or the variation of Shin&u and Maehara38 or Delalande et a1.13 The authors believe that the anatomic resections (including Adams modification) and the hemidecortication procedures may be chosen but are certainly associated with much longer operation times, extensive exposures, higher infection rates, more blood loss, less security concerning completeness, and, according to Holthausen et als review, less success. The Rasmussen type of

HEMISPHERECTOMY TEC?lNIQUES 131

functional hemispherectomy is, of course, a good alternative, although it involves much more work, a larger exposure, and a longer operating time.

POSTOPERATIVE MANAGEMENT

Patients should be brought to the intensive care unit (KU) and extubated when fully awake and at a normal temperature, which usually takes place between 2 and 8 hours after surgery. The classic parameters are monitored, including state of wakefulness, motor reaction, pupillary reaction, and verbal response as well as pulse frequency, temperature, and blood pressure. Some blood replacement is sometimes necessary in the early postoperative period. Except for HME cases, the ICU stay can be restricted to the next morning after surgery. In small infants less than 6 months of age, the ICU stay may be prolonged. The preoperative medication is continued in the authors service without interruption (usually for at least 2 years). If adjustment in the postoperative anticonvulsant regimen is necessary, the pretreating epileptologist would be the ideal partner. Classically, hemispherectomy patients run a mild to moderate temperature for 7 to 12 days, usually without positive CSF culture, which all authors ascribe to contamination of the CSF by detritus and blood. If postoperative early seizures occur, their semiologic characteris- tics should be carefully noted to be able to discriminate between the older well-known seizures and possibly a new type coming from the good hemisphere. The significance of early postoperative seizures in other types of epilepsy surgery is considered to be low; in hemispherectomy, it seems unclear.

REOPERATIONS AND POSTOPERATIVE SEIZURES

Reoperations have been described for most functional resection types. Reoperation is meant to complete an incomplete disconnection in the Rasmussen type procedure,

to remove residual cortex in the decortica- tion procedures, to complete a disconnection in the hemispherotomy procedures, or to place a disconnection line more ideally and thus disconnect some residual cortex. The need to consider reoperation after a functional hemispherectomy arises after it has been determined whether persistent seizures come from the operated or good hemisphere. Reoperations in this context are not meant to be those for the various complications that may occur with any type of cerebral surgery such as subdural effusions, infections, membrane resections, or shunt insertions. Reoperations for complications are of interest, however, if one wants to have a general assess- ment of a specific type of surgery. A good way to keep the number of reoperation cases with persisting seizures low is to avoid stretches of disconnected cortex. One way to do this seems to be always to opt for removal of insular cortex during the first surgery. The value of this maneuver remained unproved in the review by Holthausen et aP9 as well as for some other authors,*47 but in persisting seizures, it eliminates the need for a second operation just to make sure and to exclude this possible cause. In trans-sylvian-transventricular and perisylvian disconnection procedures,36*37 the authors have occasionally noted some spared cortex lying frontobasally posteriorly (see Fig. 9). This can be avoided if the frontobasal disconnection is done right in front of the anterior cerebral artery. Another way to achieve sec&e knowledge about the degree of deafferentation is to do early postoperative MR imaging (within 72 hours), in which the blood-tinged Surgicel perfectly outlines the disconnections right down to the arach- noid on the basal and mesial hemispheric surface (see Figs. 6 and 8).

Persisting seizures are not infrequent in CD (see seizure-free rates in section on previous experience with hemispherectomy in CD). In- complete disconnection has been mentioned by many authors as the reason.*4,9*30*38*41 Re- operation to complete disconnection has been done in these cases. Another reason may be the radiologic presence of dysplastic features in the good hemisphereN,3 or contralate&

132 SCHRAMM

electroencephalographic abnormalities. In an analysis of six publications with postmortem findings in 10 children with unilateral mega- lencephaly, only 3 cases had contralateral abnormal findings. The significance of contralateral spikes over the good hemisphere is discussed, but even in a large review of over 300 cases, this question could obviously not be settled. In a series of 38 cases from Oxford, England, five of six patients with active bilaterally independent spiking de- veloped recurrent seizures within 6 months of surgery?

Persisting seizures seem to be more dependent on cause than on surgical technique. In one report, it was stressed that the development of disconnection techniques (for all causes) has not led to poorer seizure outcome figures in general. In particular, it was noted that patients with dysplasias did less well compared with patients with other causes with all surgical techniques. In cases with dysplasia, the functional hemispherectomy techniques even had a lower success rate than the hemispherotomy techniques. Still, at the present time, the question as to whether cause or surgical technique is more important for outcome in CD has not been settled definitely.

SUMMARY

Hemispherectomy techniques are reviewed with reference to various forms of CD. The history of the development of these techniques and previous experiences with hemispherectomies in CD are summarized. The authors own CD cases are briefly described. The anatomic hemispherectomy techniques and the reasons for their less frequent use are described. Several functional hemispherectomy techniques are reviewed, including their advantages and disadvantages. Three special aspects are covered: special pediatric considerations, specific aspects of HME, and reoperation in postoperative seizures. It can be summarized that CD poses a particular chal- lenge for the surgeon. A thorough knowledge

of the available techniques is of particular interest for any neurosurgeon who wants to take up this type of surgery. Evidence is increasing that the outcome for CD is worse than for other causes treated by hemispherectomy. HME has the worst prognosis of all subgroups and a higher shunt rate. Several hemispherectomy techniques involving less and less resection of the brain and a greater degree of disconnection are available. Because the more recent hemispherotomy techniques seem to have fewer intraoperative and postoperative problems but comparable results, this trend to modern hemispherotomy techniques seems justified.

AC!KNOWLEDGMENTS

Erika Heunemann and GerIinde Walther helped with manuscript preparation; Thomas Kral, MD, helped with patient data; Gerard Rao, MD, helped with referencing; and Jens Krahe helped with figure preparation.

References

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HEMISPHERECTOMY TECHNIQUES 133

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15. Eldredge EA, Soriano SG, Rockoff MAz Neu- roanesthesia. Neurosurg Clin North Am 6505-520, 1995

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18. Griffith HB: Cerebral hemispherectomy for infantile hemiplegia in the light of the late results. Ann R Coil Surg Engl41:183-201,1967

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21. Kanev PM, Foley CM, Miles D: Ultrasound-tailored functional hemispherectomy for surgical control of seizures in children. J Neurosurg 86:762-767, 1997

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25. Maehara T, Shimizu H, Shigetomo R, et al: Functional hemispherectomy for children aged 2 years or less for the treatment of intractable epilepsy caused by cortical dysgenesis (in Japanese). No To Hattatsu 32: 395-400,2000

26. McKenzie KG: The present status of a patient who had the right cerebral hemisphere removed. JAMA 111:168-183,1938

27. Meagher-VilIemure K: Neuropathological findings in paediatric functional hemispherectomies. In Tuxhom I, Holthausen H, Boenigk H feds): Paediatric Epilepsy Syndromes and Their Sur- gical Management. London, John Libbey, 1997, pp 713-721

28. Moyes PD, Jenkins LC, Doll WA: Hemispherectomies with particular reference to the anaesthetic management. British College of Medicine Journal 13241-243, 1971

29. Oppenheimer DR, Griffith HB Persistent intracra- nial bleeding as a complication of hemispherectomy. J Neurol Neurosurg Psychiatry 29229-240, 1966

30. Peacock WJ: Hemispherectomy for the treatment of intractable seizures in childhood. Neurosurg CIin North Am 6:549-563,199s

31. Peacock WJ, Wehby-Grant MC, Shields WD, et al: Hemispherectomy for intractable seizures in children: A report of 58 cases. ChiIds Nerv Syst 12376-384, 1996

32. Prayson RA, Bingaman W, Frater JL, et al: Histo- pathologic findings in 37 cases of functional hemispherectomy. Annals of Diagnostic Pathology 3:205- 212,1999

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34. Rasmussen T Postoperative superficial hemosiderosis of the brain, its diagnosis, treatment and prevention. Transactions of the American Neuro- logic Association 9813~137,1973

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37. Schramm J, Kral T, Clusmann H: Transsylvian key- hole functional hemispherectomy. Neurosurgery 49: 891-901,200l

38. Shirnizu H, Maehara T Modification of peri-insular hemispherotomy and surgical results. Neurosurgery 47:367-3722000

39. Verity CM, Strauss EH, Moyes ID, et al: Long-term follow-up after cerebral hemispherectomy: Neuro- physiologic, radiologic, and psychological findings. Neurology 32:629-639,1982

40. Villemure JG: Hemispherectomy: Techniques and complications. In Wyllie E fed): The Treatment of Epilepsy: Principles and Practice. Philadelphia, Lea & Febiger, 1993, pp 1116-1119

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46. Wilson PJ: More second thoughts on hemispherectomy in infantile hemiplegia. Dev Med Child Neurol 12:799-800,1970

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Germany

e-mail: johannes.schrammQukb.uni-bonnde

CONTEMPORARY MANAGEMENT OF MALFUNCTIONS OF CORTICAL DYSPLASIA!3 1042-3680/02 $15.00 + .OO

OUTCOME AFTER SURGICAL TREATMENT

Katherine D. Holland, MD, PhD, and Elaine Wyllie, MD

Although hippocampal sclerosis is the most common cause of surgically treated epilepsy in adults, malformation(s) of cortical development (MCD) are increasingly recognized as an important cause of medically intractable epilepsy MCD is the cause in up to one quarter of adults and at least 50% of infants and childreng*23.34 referred for surgery to treat intractable epilepsy. Additionally, microscopic evidence of MCD can be seen as a dual pathologic finding with hippocampal sclerosis or developmental low-grade tumors.

MCD comprises a range of developmental abnormalities, including focal microscopic cortical dysplasia, abnormalities of gyration (macrogyria, microgyria, and agyria), schizencephaly, hemimegalencephaly, subependymal heterotopia, and subcortical laminar heterotopia. These malformations may be seen with either generalized or focal epilepsy Patients are usually considered candidates for epilepsy surgery if there is evidence of a localized or regional epileptic process. The determination that a patient is a candidate for surgery is based on evidence from interictal and ictal electroencephalography (EEG), seizure semi- ology, magnetic resonance (MR) imaging of the brain, and positron emission tomography (PET). Additional information from ictal

single-photon emission tomography and MR spectroscopy can be helpful in some cases.

Surgical approaches for MCD include focal resection, multilobar resection, and anatomic or functional hemispherectomy. Patient age and the extent of resection are not independent. For example, most hemispherectomies and multilobar resections are performed in infants and young children. Also, the goals of epilepsy surgery in infants and young children are often different from those in adolescents and adults. In infants with multiple daily seizures, the goals for surgery are reduction in seizure burden and improvement in behav- ior and development. In contrast, the goals for surgery in adolescents and adults usually include independence, ability to drive, and improved employment, which require seizure freedom. .

Before the 199Os, limitations of the available imaging modalities meant that MCD was often not identified before surgery. The abnormality was identified by histopathologic examination after epilepsy surgery. As a result, the extent of the malformation may not have been appreciated at the time of surgery. Early outcome series do not reflect current experience. This discussion is restricted to experience that includes the use of modem era

From the Section of Pediatric Epilepsy, Department of Neurology, The Cleveland Clinic Foundation, Cleveland, Ohio

NEUROSURGERY CLINICS OF NORTH AMERICA

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136 HOLLAND & WYLLIE

MI? imaging techniques. Probably as a result of improvements in neuroimaging in recent years, the surgical outcome for MCD has improved. Overall, seizure-free outcome after surgery for focal epilepsy caused by MCD is approximately 50% in most series (Table 1). Although this frequency of postoperative freedom from seizures is lower than that seen in hippocampal sclerosis or tumor,*1,35 a substan- tial number of people with intractable focal epilepsy from MCD are effectively treated with surgery

The results from surgical treatment far surpass those achieved during controlled trials of new antiepileptic drugs for patients with intractable focal epilepsy.7*8- Patients who do not become seizure-free during treatment with their initial antiepileptic drug because of lack of efficacy have less than a 15% chance of becoming seizure-free with a second or third drug. I7 Drug combinations are also rarely effective in refractory patients. When the initial treatment fails because of intolerable side effects or idiosyncratic reactions, the response to a subsequent medication is better. Response to the third medication is again poor, however. When patients with focal MCD fail to respond to medical therapy after several medication trials, the potential for surgical treatment should be evaluated, because surgical management affords a better chance of seizure control.

The greater effectiveness of surgery compared with medical management in patients with refractory temporal lobe epilepsy has been demonstrated in a controlled study.32 Candidates for resective surgery were randomized to immediate surgery or to contin-

uation of medical therapy After 1 year, 58% of the surgically treated patients were seizure- free compared with 8% of the medically man- aged patients (P < 0.001). Although the study included adults and most patients (70%) had mesial temporal sclerosis, results may be rel- evant to patients with different causes, including MCD.

In appropriate cases, surgery also seems to offer more advantages than vagus nerve stimulation (VNS) and the ketogenic diet. Free- dom from seizures is obtained for less than 5% of patients treated with VNS and for 3% of patients treated with the ketogenic diet.12 Di- rect comparisons between VNS, the ketogenic diet, and surgery are not available, however. Moreover, VNS and the ketogenic diet are typically not used in patients who are good candidates for focal resection.

SURGICAL OUTCOME

Factors Affecting Postsurgical Outcome for Focal or Lobar Malformation(s) of Cortical Development

Results from surgical series of patients with MCD have been variable, with 11% to 70% of patients becoming seizure-free.6* g, lo* 21* ~3, 35 The reason for this variability is unclear; however, the results of studies based on patients selected for surgery after 1990 are more uniform. Variability may be influenced by patient selection factors such as imaging, by surgical differences such as the extent or location of resection, or by differences in the histopathologic profile of the MCD.

Table l.A COMPARISON OF SURGICAL OUTCOMES FOR MALFORMATIONS OF CORTICAL DEVELOPMENT (EXCLUDING OUTCOME FOLLOWING HEMISPHERECTOMY)

Article Age Range Mean Follow-Up (years) Seizure-Free (%)

Edwards et aP 3 months-47 years 3.4 Paolicchi et al=+

17135 (49%j 6 months-12 years 5.0

Sugimoto et aP 22/42 (52%)

3-34 months 2.8 Duchowny et alg+

2/B (25%) 6-32 months z-1.0

Wyllie et al% 4/10 (40%)

Chugani et al6 3 months-12 years 3.7 16/31 (52%) 5 months-4 years 2.5 7/10 (70%)

; Series from same center (Cleveland Clinic) may include some overlapping patients. Series from same center (Miami Childrens Hospital) may include some overlapping patients.

Rare Seizures (%)

8/35 (23%) 11/42 (26%)

2/B (25%) 2/10 (20%) 6/31 (19%) 2/10 (20%)

OUTCOME AFTER SURGICAL TREATMENT 137

Seizure Outcome and the Role of Seven infants (70%) became seizure-free, and Magnetic Resonance Imaging another two had a significant reduction in

MR imaging plays an important role in the presurgical evaluation of patients with MCD and intractable epilepsy. In a study of infants with intractable seizures, the presence of a discrete lesion on preoperative neuroimaging correlated with favorable outcome. Fifteen (83%) of 18 infants with discrete lesions became seizure-free compared with 4 (36%) of 11 infants with normal or nonspecific abnormalities on MR imaging (16 patients) or CT (two patients) (P < 0.01). Although this study included infants with pathologic findings other than MCD, over two thirds of the infants had cortical dysplasia.

The extent of the MR-imaged abnormality

seizures after lobar or multilobar resection. In the hemispherectomy group, two of five patients became free of seizures, and another patient had only occasional seizures.

The use of PET was also suggested by the Cleveland Clinic report on surgical outcome for MCD.O Nine (75%) of 12 patients who had interictal PET hypometabolism in the region or lobe that was resected became seizure-free. In contrast, of the 10 patients whose PET findings did not correspond to the region resected, only three (30%) became seizure-free. The numbers were small, however, and this difference did not reach statistical significance.

also seemed to have prognostic importance in another study in adults and children. Of

Seizure Outcome by Completeness

21 patients with MCD localized by means of of Resection

MR imaging to one lobe or region, 10 (48%) were free of seizures after surgery and seven (33%) had rare seizures. In contrast, of four patients with hemispheric or multilobar MCD, only one (25%) was free of seizures after surgery and 1(25%) had rare seizures.

Seizure Outcome and the Role of Positron Emission Tomography Scans

Chugani and colleague& demonstrated that infants with catastrophic epilepsy as a result of MCD with focal dysfunction of glucose use as determined by fluorodeoxyglucose PET scanning could be successfully treated surgically even in the absence of MR-imaged abnormalities. In a series of 23 infants who underwent focal cortical resection or hemispherectomy for infantile spasms or seizures with a prior history of infantile spasms, MCD was identified as the cause of spasms in 15 patients. Of this group, only seven had their MCD identified preoperatively on MR imaging or CT scanning, although all 15 patients had localized abnormalities on PET scans. Ten of these patients had lobar or multilobar resections of the PET-defined abnormal region, and five had hemispherectomies. Electrocorticography (ECoG) was used to aid in determining the extent of resection in the focal resection group.

Complete resection of the MR imaging- defined region with MCD may correlate with favorable surgical outcome.0,23 In one series based on pre- and postoperative MR imaging findings, 58% of the adolescents and adults with complete resection of malformations were seizure-free and 33% had rare seizures compared with 27% of patients who were seizure-free and 36% with rare seizures in the group with incomplete resections; this difference was not statistically significant, however.O Although outcome was improved when the MCD was co-mpletely resected, 3 of 11 patients had a favorable outcome even with partial resection. All three of the patients with bilateral MCD continued to have persistent seizures.

Other measures quantifying the extent of resection have, also been shown to predict surgical outcome. Palmini and, colleagues** evaluated the electrographic patterns seen in intractable epilepsy associated with cortical dysplasia. Patients with ictal or continuous epileptogenic discharges during intraoperative ECoG had a more favorable outcome if this activity could be completely excised. Nine of the 12 patients with complete resection of cortical regions exhibiting this pattern became seizure-free or had only infrequent seizures compared with none of the

138 HOLLAND & WYLLE

6 patients with incomplete resection of this pattern (P < 0.01). Cortical regions with ictal or continuous epileptogenic discharges often colocalized to imaging evident? of the cortical dysplasia. Not all the patients in this study had MR unaging scans, and the MR imaging scanners used at the time of the study were less powerful than those currently available. As a result, the relative importance of MR imaging and ECoG cannot be determined from this study

Another study looking at the predictors of outcome for epilepsy surgery in infants and children also identified complete resection of the MR-imaged extent .of the lesion and an electrographically abnormal region as the most significant predictors of surgical outcome.23 For the purp oses of the study, complete resections were defined as those with total removal of any MR-imaged lesion and of the region with a significant ictal or interictal abnormality on extra- or intraoperative ECoG. Freedom from seizures was seen in 76% of 49 children who had a complete resection and in 27% of 26 children who had an incomplete resection. For statistical analysis, the authors defined good outcome as rare or no seizures. This was seen in 92% of children who had a complete resection and in 50% of children with an incomplete resection (P < 0.001). Forty-two of the 75 patients (56%) in this series had MCD.

Another study compared the surgical outcome of patients with malformations (n = 20) in the temporal lobe with that of patients with isolated mesial temporal sclerosis (n = 36).16 Interestingly, dual pathologic findings were often present, with unilateral or bilateral hippocampal atrophy seen in 16 (80%) of the 20 patients with temporal lobe MCD. In this study, the surgical outcome was not significantly different between the patients who had a temporal lobectomy for MCD or hippocampal sclerosis, with a greater than 90% reduction in seizure frequency noted for 71% of patients with MCD and 91% of patients with hippocampal sclerosis. Complete resection of potentially epileptogenic brain regions affected outcome, however. Patients with bilateral hippocampal atrophy were more likely to have an unfavorable outcome than

those with unilateral atrophy irrespective of the presence or absence of coexistent MCD.

Seizure Outcome and Type of Resection

Studies in infants, children, and adults with MCD do not show a significant difference in surgical outcome of temporal and extratemporal resections.g*0,23,35 For example, in one series of patients with MCD,O 53% of patients became seizure-free and 18% had only rare seizures after extratemporal resection compared with 33% seizure-free patients and 50% with rare seizures after temporal resection. Al- though the numbers were small, outcome after multilobar resections was generally not different than when resections were confined to one lobe. In another pediatric series, children with multilobar resections had a lower frequency of a seizure-free outcome (22%) than did those with focal resections (59%) (P = 0.05). The overall numbers were small, however, and for this part of the analysis, the authors did not provide separate results for patients with cortical dysplasia and those with other pathologic findings.

Seizure Outcome and Age at Surgery

The percentage of patients who are seizure- free after surgery does not seem to be dependent on age. Throughout all age ranges, approximately 50% of patients who have surgically treatable MCD become seizure-free and another 25% have only rare seizures (Table 1). In one study, however, there was a tendency toward seizure freedom with younger age at surgery. Surgical outcome is also not dependent on preoperative seizure frequency.

Seizure Outcome and Invasive Electroencephalographic Monitoring

The effect of the use of subdural grids on seizure outcome is controversial. Although Palmini and colleagues showed that ECoG may be important to surgical planning, other studieslo have not demonstrated that the use of subdural grids improves seizure outcome.

In an MR imaging-based series, seizure outcome was not different between patients who underwent subdural grid evaluation and those who did not. The cases selected for study with subdural electrodes were usually more complicated than those that progressed to surgery based on noninvasive tests; thus, a selection bias was operant. Invasive monitoring with subdural electrodes may be especially helpful to define seizure onset in relation to functional areas of cortex.

Seizure Outcome and Pathologic Findings of Lesions

In adult series, differences have been noted based on cause with hippocampal sclerosis portending a better prognosis than MCD for postoperative freedom from seizures. Some adult surgical outcome series35 have also shown that seizure-free outcome is less frequent for patients with MCD than for patients with tumors or vascular lesions. In one pediatric surgical outcome study,35 seizure- free outcome was less frequent in patients with cortical dysplasia (52%) than in patients with tumors (82%). In contrast, in another pediatric study,23 pathologic diagnosis did not correlate with outcome. In both pediatric studies,23*35 the number of children with hippocampal sclerosis was too small to permit this comparison.

Within MCD, there may be certain histopathologic features that are associated with a poor outcome. MCD with only dyslamination of cellular elements and that with a mild degree of dysplastic neurons may have a better surgical outcome than MCD

OUTCOME AFTER SURGICAL TREATMXNT 139

with abnormal cellular elements that contain neuronal and glial properties. Nevertheless, detailed reports of studies on outcome for MCD based on histopathologic findings of surgical specimens have not been published since the current neuroimaging technology has become widely available.

Factors Affecting Outcome for Hemispheric Malformations of Cortical Development

The surgical procedure of choice in cases with extensive hemispheric malformation and preexisting hemiparesis is usually anatomic or functional hemispherectomy. These procedures remove or disconnect all potentially epileptogenic tissue in the affected hemisphere. Although the available literature is limited, it seems that the surgical outcome of hemispherectomy for MCD is similar to that for lobar and multilobar resections for more limited MCD. The results of several recent studies are summarized in Table 2. Seizures are completely controlled in one half of the patients and are significantly reduced in another one quarter. The factors that influence the outcome are discussed next.

Surgical Outcome and Magnetic Resonance Imaging Extent of the Pa thoiogic Findings

The surgical outcome after functional hemispherectomy for MCD may be dependent on the extent of the cortical malformation. A recent study of seizure outcome after functional

Table 2. A COMPARISON OF SURGICAL OUTCOMES OF HEMISPHERECTOMY FOR MALFORMATlONS OF CORTICAL DEVELOPMENT

Hemispherectomy Rare Article Age Range We

Perioperative Seizure-Free (%) Seizures (%) Mortality*

Carreiio et al4 2 months-12 years Functional 6/12 (50%) 0 Sugimoto et aP+

4/12 (33%) 4-54 months Anatomic 314 (75%) o/4 (0%) 0

Duchowny et al9 1-36 months Functional 6/9 (67%) l/9 (11%) 2 Viig et aP 3 months-18 years Anatomic B/21 (38%) Chugani et al6

6/21(21%) 5-10 months Not stated 2/5 (40%) l/5 (20%)

l Patients who died from complications of surgery were not included in seizure outcome data. Three of the patients in this series had hemispherectomies after more limited pro~&~s failed,

,140 HOLLAND & WYLLE

hemispherectomy for hemispheric MCD in 12 -patients (infants and children) exam- ined surgical outcome based on Ml&imaged features.4 Three MR imaging patterns were identified. Six patients had hemimegalencephaly defined as a diffuse hemispheric malformation of cortical development with increased hemispheric size; four l-tad extensive hemispheric MCD with relative preservation of cortical architecture in part of one lobe; and three had hemispheric MCD with atrophy. The patients who had hemimegalencephaly usually had abnormalities in the white matter in the affected hemisphere, a dysplastic appear- ance of basal ganglia, and a small contralateral hemisphere. These abnormalities were absent or less pronounced in patients with hemispheric MCD with partial preservation of one lobe or hemispheric MCD M;ith hemispheric atrophy. After functional hemispherectomy, five of the six patients with hemimegalencephaly (83%) continued to have seizures. In contrast, five of the six patients with partial preservation of one lobe or atrophy were seizure-free after surgery

Even patients with persistent seizures ben- efited from surgery. 4 Preoperatively, these patients all had severe epilepsy and developmental delay, with many seizures every day After functional hemispherectomy, five of seven patients with persistent seizures had marked improvement in the seizure frequency and severity The caregivers also reported increased alertness and social interaction even in patients who were not completely seizure-free.

Surgical Outcome and lnterictal and lctal Electroencephalography

Compared with neuroimaging, EEG features may be a weaker predictor of seizure- free outcome in patients with hemispheric MCD. In the aforementioned series,4 bilateral independent epileptiform discharges and generalized ictal EEG patterns were seen in some patients who became free of seizures after functional hemispherectomy. All the patients had focal seizures arising from the malformed hemisphere, with or without addi-

tional generalized electrodecrements during infantile spasms, however, and none of the patients had focal EEG seizures arising inde- pendently from the contralateral hemisphere. Doring and colleagues8 noted that bilateral EEG abnormalities were common in children with extensive unilateral MCD. In a follow-up study, 47% of these children became seizure- free after hemispherectomy.

Functidnal Versus Anatomic Hemispherectomy

It is unclear whether functional or anatomic hemispherectomy is the more effective procedure. There are no studies that directly compare these two procedures. In the largest series of patients treated with anatomic hemispherectomy for MCD, the surgical outcome is similar to that for functional hemispherectomy (Table 2). The group at John Hopkins3 reviewed their experience with anatomic hemispherectomy in infants and children. Of 21 patients with cortical dysplasia, eight (38%) were seizure-free and an additional six (29%) had mild seizures after surgery In contrast, surgical series after functional hemispherectomy for MCD report 50% to 67% of patients seizure-free with an additional 11% to 33% having only rare seizures (Table 2). Although numbers are small in all these studies and the radiologic involvement of MCD is not well outlined in some of these reports, these results suggest that functional hemispherectomy is at least as effective as anatomic hemispherectomy. The frequency of complications may also be lower after functional hemispherectomyF9 Nevertheless, of five patients with hemimegalencephaly who continued to have seizures after functional hemispherectomy, three had seizures that arose from the operated hemisphere and two had seizures arising from the contralat- era1 hemisphere .4 These results suggest that anatomic hemispherectomy may be more effective in patients with hemimegalencephaly and that functional hemispherectomy may be appropriate for patients with more restricted hemispheric MCD. This is an area that requires more study

OUTCOME AFTERSURGICALTREATh4ENT 141

NEUROLOGIC OUTCOME

Complications and Postoperative Neurologic Deficits

After Focal Resection

The most frequent complication of temporal lobe resection is an asymptomatic homonymous superior quadrantanopia.5 This occurs in up to approximately 50% of patients.32 Memory and language problems have been reported after temporal lobe resection in adults, with risk factors that include higher preoperative functioning or left resection.5 Few systematic data are available from pread- olescent children because of the difficulties in performing neuropsychologic tests in this age group, the lag in development of appropriate testing instruments for use at young ages, and the low numbers of children who have undergone the operation. Preliminary results suggest that the neurocognitive risks of temporal lobe resection may be similar in children and adults, with IQ remaining stable and a possible decrease in memory function., I30 2s

For extratemporal resections, chronically implanted subdural electrodes can be used to define the epileptogenic region and to permit functional mapping of language, motor, and sensory cortex. This information is used to limit complications of extratemporal resection in the frontal lobe, central region, and posterior portion of the temporal lobe. Visual field deficits are associated with posterior parietal and occipital resections.

After Hemispherectomy

In the Johns Hopkins series?r 2 of 24 children who had an anatomic hemispherectomy for cortical dysplasia died within several hours of completing the procedure. Ventricu- loperitoneal shunting was required almost in half of the patients in one series after anatomic hemispherectomy.31 Late postoperative complications of hemispherectomy include hemorrhage into the hemispherectomy cavity, which is predominantly seen after anatomic hemispherectomy.2s Super- ficial cerebral hemosiderosis is a long-term

complication of anatomic hemispherectomy that can occur years after the surgery and is associated with neurologic deterioration and death.29 The mortality and long-term complications associated with anatomic hemispherectomy have led to the development of the functional hemispherectomy procedure. In a series of 12 patients who had a functional hemispherectomy, surgical complications included a bone flap infection in one patient and obstructive hydrocephalus in three patients. No deaths were reported in this small series,* although operative mortality has been reported after functional hemispherectomy in other surgical series.6*9,23 Mortality may be higher in infants because of their smaller blood volumes and greater problems with perioperative bleeding and fluid management.

Patients who are candidates for hemispherectomy typically have a preoperative hemiparesis. Motor impairment is unchanged or improved after hemispherectomy in most of these patients. 29 If the preoperative hemiparesis is mild, the deficit may be more pronounced after hemispherectomy. After hemispherectomy in the setting of congenital hemispheric MCD, patients develop language commensurate with their global cognitive leve1.6

Hemispherectomy candidates may have a preexisting homonymous hemianopia. In patients without this deficit, however, the hemianopia that follows functional hemispherectomy typically does not result in functional deterioration or affect activities of daily living, except for driving.29 In the presence of some other preexisting visual abnormality (e.g., am- blyopia or retinopathy of prematurity), the effect of a postoperative homonymous hemianopia may be more serious.

SPECIAL ISSUES IN INFANCY

Catastrophic Epilepsy

Epilepsy in infancy can be associated with severe and frequent seizures. The high seizure burden can significantly affect the quality of life of the infant and family and may also

142 HOLLAND & WYLLIE

adversely affect the infants development. As a result, even if the infant does not become seizure-free after surgery, a reduction in seizure frequency can have a significant positive impact.

Effect of Surgery on Development

There is limited information available re- garding the postoperative developmental outcome in infants undergoing surgery for extensive MCD. Preliminary observations suggest that early relief from catastrophic infantile epilepsy may allow resumption of developmental progression during critical stages of brain maturation. One study exam- ined developmental outcome in 24 children with infantile spasms who had resective surgery at a mean age of 21 months; 17 of these children had MCD. The authors found a significant increase in developmental assess- ment scores at 2 years after surgery compared with preoperative levels, although only 4 of the 24 children had a normal rate of development. Another report noted favorable intellectual development and improvement in developmental delay in 12 of 21 patients who had an anatomic hemispherectomy for MCD, with six patients having normal in- telligence or only mild retardation.31 Others have also noted improved and catch-up development in infants after surgery for MCD, although many of the children continue to exhibit some degree of delay.6 The team at the University of California at Los Angeles reported a cautionary case.26 A 25-month-old patient with several seizures per week caused by mild right hemimegalencephaly had nearly complete remission of seizures and good developmental progression after craniotomy and ECoG without cortical resection. The authors pointed out that a localized developmental brain abnormality in a child with intractable seizures should not necessarily lead to cortical resection, especially if the child is meeting developmental milestones.

There is more information available about the effects of epilepsy surgery on development than is available for the effects of the newer antiepileptic drugs on infant development.

Because most antiepileptic medications are associated with cognitive side effects in adults,is it is possible that these medications could have adverse effects on intellectual development, especially because the cognitive effects of medication may be more insidious in a nonverbal patient (e.g., an infant). Prospective studies to further clarify the developmental effects of epilepsy surgery and anticonvulsant medications in infancy are needed before the relative risks and benefits of surgical or medical management can be fully assessed.

Plasticity

Surgery in infancy may lead to less severe neurologic deficits than occurs with surgery later in life. If left hemisphere damage and hemiparesis occur during the first 4 or 5 years of life (before language development), functional hemispherectomy produces little or no change in language function.3* 13, i9* 33 Never- theless, the language that is transferred to the nondominant hemisphere is typically not completely normal even if language shifted at an early age.7, 2s

Infantile Spasms and Hypsarrhythmia

In most cases, this seizure type and its diffuse EEG pattern are associated with diffuse brain abnormalities. In some cases, however, they can be the result of a focal process. Chugani and colleague9 were the first to report successful surgical treatment of patients with infantile spasms and hypsarrhythmia caused by focal MCD. PET and MR imaging were used to identify the malformation and location of cortical dysfunction. Other clues to a localized process included a history of partial seizures before the onset of spasms, focal abnormalities on neurologic examination, and some focal EEG feature in addition to diffuse hypsarrhythmia. In a series of 15 infants and children who originally presented with infantile spasms caused by MCD, nine became seizure-free after focal resection or hemispherectomy.6

OUTCOME AFTER SURGICAL TREATMENT 143

Complications References

Infants with catastrophic focal epilepsy caused by MCD often require extensive multilobar resection or hemispherectomy, and in these patients, anesthesia management is complicated by small blood volume. Periop- erative mortality may be higher in infancy than later in life. One or two deaths have been reported in most series of epilepsy surgery in infants.6*9,23,31*41 Perioperative mortality may be reduced by a team of pediatric sur- geons, anesthesiologists, and intensivists with experience in epilepsy surgery in infants. In contrast to perioperative mortality, the risk for postoperative neurologic deficits after surgery in infancy may be reduced as a result of developmental plasticity and greater potential for neurologic recovery

SUMMARY

Outcomes from surgery for epilepsy caused by MCD in pediatric and adult series are similar. Overall, approximately 50% of patients with cortical dysplasia become seizure-free after resection and another 20% have significant improvement in seizure frequency The outcome seems to be improved when the cortical dysplasia is completely resected. Some patients have significant improvement in seizure frequency even with partial resection of the dysplasia, however. MR imaging, EEG, and PET scans are useful in determining the extent of the dysplasia. Invasive monitoring with subdural electrodes can help to determine the extent of resection, especially by defining seizure onset in relation to functional areas of cortex. The results of surgical treatment in this group of medically refractory epilepsy patients far surpass those achieved during controlled trials of new antiepileptic drugs for patients with intractable focal epilepsy. Surgery for catastrophic epilepsy caused by MCD in infancy may afford the potential for greater neurologic recovery because of developmental plasticity, but it also entails a higher risk of mortality than does surgery later in childhood.

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2. Asamow RF, LoPresti C, Gutherie D, et al: De- velopmental outcomes in children receiving resection surgery for medically intractable infantile spasms. Dev Med Child Neurol39:430440,1997

3. Basser LS: Hemiplegia of early onset and the faculty of speech with special reference to the effects of hemispherectomy. Brain 85:427-460,1962

4. Carreiio M, Wyllie E, Bingaman W, et al: Seizure outcome after functional hemispherectomy for malformations of cortical development. Neurology 57: 331-333,200l

5. Chelune GJ, Naugle RI, Liiders HO, et al: Predi- cation of cognitive function as preoperative ability status among temporal lobe epilepsy patients seen at 6-month follow-ma. Neurolow 41:399404.1991

6. Chugani HT, Siewmon l%, Shields WD, et al: Surgery for intractable infantile spasms: Neuroimag- ing perspectives. Epilepsia 34:764-771,1993

7. Dennis M: Capacity and strategy for syntactic com- prehension after right or left hemidecortication. Brain Lang l&287-317,198O

8. Doring S, Cross H, Boyd S, et al: The significance of bilateral EEG abnormalities before and after hemispherectomy in children with unilateral hemispheric lesions. Euileusv Res 3465-73.1999

9. Duchowny M, jayakar P, Resnick T, et al: Epilepsy surgery in the first three years of life. Epilepsia 39:737-743,1998

10. Edwards JC, Wyllie E, Rugger PM: Seizures outcome after surgery for epilepsy due to malformation of cortical development. Neurology 55:1110-1114,200O

11. Engel J Jr: Surgery for seizures. N Engl J Med 334: 647-652,1996

12. Freeman JM, Vining El, Pillas DJ, et al: The efficacy of the ketogenic diet: A prospective evaluation of the intervention in 150 children. Pediatrics 1021358 1363,1998

13. Harbord MG, Manson JI: Temporal lobe epilepsy in childhood: Reaouraisal of etiolow and outcome. Pe- diatr Neurol3:%..268,1987 ,

14. Hirabayashi S, Binnie CO, Janot I, et al: Surgical treatment of epilepsy due to cortical dysplasia: Clinical and EEG findings. J Neurol Neurosurg Psychiatry 56:765770,1993

15. Katz A, Awad IA, Kong AK, et al: Extent of resection in temporal lobectomy for epilepsy. II. Memory changes and neurologic - comphca&ons. Epilepsia 30:76X71,1989

16. Kuzniecky R, Ho SS, Martin R, et al: Temporal lobe developmental malformations and hippocampal sclerosis. Neurology 52:479-484,1999

17. Kwan P, Brod& MJ: Early identification of refractory euileosv. N Enal I Med 3423314319.2000

18. Mars& AG, I?ahir ZA, Chadwick DW: New antiepileptic drugs: A systematic review of their efficacy and tolerability. BMJ 313:1169-1174,1996

19. McFie J: The effects of hemispherectomy on intellectual functioning in cases of infantile hemiplegia. J Neurol Neurosurg Psychiatry 24240-249, 1961

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20. Morris GL, Mueller WM: Long-term treatment with vagus nerve stimulation in patients with refractory epilepsy. The Vagus Nerve Stimulation Study Group EOl-E05. Neurology 53:1731-1735,1999

21. Palmini A, Gambardella A, Andermann F, et al: In- trinsic epileptogenicity of human dysplastic cortex as suggested by corticography and surgical results. Ann Neurol37:476-487,1995

22. Palmini A, Gambardella A, Andermann F, et al: Op- erative strategies of patients with cortical dysplastic lesions and intractable epilepsy. Epilepsia 35fsuppl 6):S57S71,1994

23. Paolicchi JM, Jayakar I, Dean P, et al: Predictors of outcome in pediatric epilepsy surgery. Neurology 54:642-647,2000

24. Peacock WJ, Comair Y, Chugani HT, et al: Epilepsy surgery in childhood. In Liiders HO fed): Epilepsy Surgery. Philadelphia, Lippincott-Raven, 1991, pp 589-598

25. Rankin JM, Aram DM, Horwitz SJ: Language ability in right and left hemiplegic children. Brain Lang 14:292-306,198l

26. Shields DW, Shewmon AD, Peacock WJ, et al: Surgery for the treatment of medically intractable infantile spasms: A cautionary case. Epilepsia 40: 1305-1308,1999

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28. Szabb CA, Wyllie E, Stanford LD, et al: Neu- ropsychological outcome of temporal lobe resection in children with epilepsy Epilepsia 39:814-819, 1998

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Address reprint requests to

Katherine D. Holland, MD, PhD The Cleveland Clinic Foundation, Desk S51

9500 Euclid Avenue Cleveland, OH 44195

e-mail: [email protected]

CONTEMPORARY MANAGEMENT OF MALFUNCTIONS OF CORTICAL DYSPLASIA5

INDEX

Note: Page numbers of article titles are in bold face type.

Adams hemispherectomy modification, 121 Agyria, pathology of, 17-18 Amino-3-hydroxy-S-methyl-4-isoxazol acid (AMPA)

receptors, epilepsy and, 29

Balloon cells, in cortical dysplasia, 3,5-7,22,43,72 Band heterotopia, radiologic-pathologic correlations in,

51-52 Behavioral disorders, in cortical dysplasias, 36 Blood oxygen level-dependent (BOLD) functional

magnetic resonance imaging. See Magnetic resonance imaging, functional.

CaBosotomy, in cortical dysplasia, 108 Central vertical hemispherectomy, 128-129 Cobblestone lissencephaly, radiologic-pathologic

correlations in, 51,53 Cognitive function, in cortical dysplasias, hemispheric,

106 Cortical dysplasias

abnormal cell proliferation in, 41-50 agyria, pathology of, 17-18 balloon cells in, 3,5-7,22,43,72 bilateral opercular, 57-58 cellular migration disorders, 51-56 classification of, 1-16 clinical features of, 35-36 coactivation in, functional magnetic resonance imaging

of, 65 conditions associated with, 22-23,72-73 cortical disorganization, 56-61 deep infolding in, 54,56 dysmorphic neurons in, 3-46-8 electroencephalography in, 36-39,87-88,105,

138-140 embryology of, 41,51,56 epileptogenicity of, 27-33,73-74 familial diffuse, electroencephalography in, 38 focal, P-10,87-92

clinical relevance of, V-10 diagnosis of, 88 epileptogenicity of, 27-33,73-74 imaging of, 9,88-89 pathology of, 71-72 radiologic-pathologic correlations in, 43,45-46

subdural electrode studies of, 89-91 surgical treatment of, 93-102

age considerations in, 138 case study of, 97-98 functional mapping before, 94-95 invasive monitoring before, 94-95 outcome of, 136-139,141 postoperative concerns in, 95 preoperative evaluation for, 9%94 techniques for, 95 Yale University experience in, 95-98

Taylor type, 6,35 types of, 9

four-layered, 51 functional magnetic resonance imaging in, 6369,137,

139-140 functionality of, 74 giant neurons in, 5-6 hemimegalencephaly. See Hemimegalencephaly hemispheric malformations in, 103-111

clinical features of, 104-105 surgical treatment of

evaluation before, 105-106 outcome of, 139-141 techniques for, 106-108 timing of, 108-110

heterotopias. See Heterotopias. histopathology of, 6-8 imaging in, 36. See also specific techniques. immature neurons in, 5-6 lissencephaly, 17-18,37-38,5I, 53 magnetic resonance imaging in. See Magnetic

resonance imaging. microcephaly, 42 microdysgenesis, 3,61 microscopic patterns of, 20-22 mild, 8-P neuropsychology of, 36 pachygyria, 17-18 1 pathogenesis of, 1 pathology of, 17-25,71-73

agyria, 17-18 focal, 71-72 heterotopias, 18-20 lissencephaly, 17-18 pachygyria, 17-18 surgical outcome and, 139 versus surgical outcome, 139-140

polymicrogyria, 11-12

145

146 INDEX

Cortical dysplasias (Continued) positron emission tomography in, 77-82

in infantile spasms, 79-82 in localization-related epilepsies, 77-79 methodology of, 77 surgical outcome and, 137

preoperative evaluation of, 35-39 radiologic-pathologic correlations in, 41-62

focal, 43,45-46 in abnormal cell proliferation, 41-50 1 in cellular migration disorders, 51-56 in cortical disorganization, 56-61

schizencephaly, 12,57-60 single photon emission computed tomography in,

74-77 clinical applications of, 75-77 methodology of, 74-75

surgical treatment of, 93-102 hemispherectomy in, 113-134 in hemisphefic malformations, 103-111 outcome of, 13.5-144

in focal malformations, 136-139,141 in hemispheric malformations, 139-141 in infantile spasms, 142 in infants, 141-143 in lobar malformations, 136-139 neurologic, 141 versus medical treatment, 136

terminology of, 2-6 treatment of, subdural grids in, 87-92 tumors in, N-11,22-23,43,48-50 without balloon cells, 58,61

Developmental delay cortical dysplasia surgery effects on, 142 in cortical dysplasias, 35

Double cortex syndrome, electroencephalography in, 38 Dysembryoplastic neuroepithelial tumors, lO-11,23,43,

48-49 Dyslamination, in cortical dysplasias, 6 Dysmorphic neurons, 3-4,6-8 Dysplasias, cortical. See Cortical dysplasias. Dysplastic tumors, U&11,22-23

radiologic-pathologic correlations in, 43,48-50

Electrodes, subdural, in focal cortical dysplasia, 89-91 Electroencephalography, in cortical dysplasias, 36-39

focal, 87-88 hemispheric, 105 surgical outcome and, 139-140 versus functional magnetic resonance imaging, 66

Eloquent cortical regions, localization of functional magnetic resonance imaging in, 65-66 subdural electrodes in, 90

Epilepsia partialis continua, electroencephalography in, 38

Epilepsy, in cortical dysplasias. See Cortical dysplasias. Epileptogenic zone concept, in cortical dysplasia, 64-65

Familial diffuse cortical dysplasia, electroencephalography in, 38

Functional mapping, for cortical dysplasia surgery, 94-95

Gamma-aminobutyric acid receptors and circuits, epilepsy and, 29-30

Gangliogliomas, N-11,48,50 Giant neurons, in cortical dysplasia, 5-6 Glutamate receptors, ionotropic, epilepsy and, 28-29 Grids, subdural electrodes in, in focal cortical dysplasia,

89-91

Hemianopia, homonymous, after hemispherectomy, 141 Hemidecortication, in cortical dysplasia, 114,121-122 Hemimegalencephaly, 11

electroencephalography in, 38 hemispherectomy in, 116-118,130-131

Hemiparesis, after hemispherectomy, 141 Hemispherectomy, 107,113-134

definition of, 113 outcome of, 139-141 persistent seizures after, 131-132 postoperative management in, 131 repeated, 131-132 techniques for

Adams modification of, 121 anatomic, 119-121,140 central vertical, 128-129 development of, 114-115 functional, 140 hemidecortication in, 114,121-W in hemimegalencephaly, 116-118,130-131 in pediatric patients, 129-130 Japanese per&insular, 129 peri-insular, 127-129 previous experience with, 115-118 Rasmussens functional, 122 transsylvian, transventricular functional, 122-127 types of, 118-119

terminology of, 113 Hemispheric malformations, of cortical development,

103-m clinical features of, 104-105 surgical treatment of, 108-110

evaluation before, 105-106 outcome of, 139-141 techniques for, 106-108. See R/SO Hemispherectomy. timing of, 108-110

Hemispherotomy, in cortical dysplasia, 113 Hemosiderosis, after hemispherectomy, 141 Heterotopias, 5-6,12-13

band, 51-52 laminar, 19 marginal, 21 pathology of, 18-20 periventricular nodular, 51,54 radiologic-pathologic correlations in, 51-56 subcortical gray matter, 54-55 subependymal, 54,56

Holoprosencephaly, electroencephalography in, 37 Homonymous hemianopia, after hemispherectomy, 141 Homonymous quadrantanopia, after focal cortical

dysplasia resection, 141 Hypomelanosis of Ito, electroencephalography in, 38 Hypsarrhythmia, surgical treatment of, 142

Imaging. See also specific modalities. Immature neurons, in cortical dysplasia, 5-6

INDEX 147

Infantile spasms, surgical treatment of, 142 Intellectual impairment, in cortical dysplasias, 36 Ionotropic glutamate receptors, epilepsy and, 28-29

Japanese per&insular hemispherectomy, 129

Language, cortical regions for functional magnetic resonance imaging of,

65-66 subdural electrode localization of, 90

Lissencephaly cobblestone, radiologic-pathologic correlations in,

51,53 electroencephalography in, 37-38 pathology of, 17-18

Magnetic resonance imaging, in cortical dysplasias, 36,137

functional, 63-69 advantages of, 64 electroencephalographic-correlated, 66 epileptic zone concept in, 64-65 language sites in, 65-66 principles of, 63-64 task-related, 65-66

hemispheric, 105-106,139-140 Malformations, of cortical development. See Cortical

dysplasias. N-Methyl-D-aspartate receptors, epilepsy and,

28-29 Microdysgenesis

definition of, 3 radiologic-pathologic correlations in, 61

Micropolygyria, pathology of, 18 Migration, neuronal, disordered, to cortex,

- radiologic-pathologic correlations in, 51-56 Miller-Dieker syndrome, lissencephaly in, 53 Multilobar resection, in cortical dysplasia, 107

Neuroepithelial tumors, dysembryoplastic, W-11,23,43, 48-49

Neuron(s) disordered migration of, to cortex,

radiologic-pathologic correlations in, 51-56 dysmorphic, 3-4,6-B giant, in cortical dysplasia, 5-6 immature, in cortical dysplasia, 5-6

Neuronal heterotopias, 5-6,12-13 Neuropsychologic testing, in cortical dysplasias,

hemispheric, 106 NMDA (N-methyl-D-aspartate) receptors, epilepsy and,

28-29 Noonan syndrome, electroencephalography in, 38

Pachygyria, pathology of, 17-18 Pediatric patients

cortical dysplasias in, surgical treatment of, outcome of, 141-143

hemispherectomy in, 129-130 Per&insular hemispherectomy, 127-129 Perisylvian syndrome, 57-58 PET. See Positron emission tomography. Polymicrogyria, 11-12

radiologic-pathologic correlations in, 57-58 Positron emission tomography, in cortical dysplasias,

77-82 hemispheric, 106 in infantile spasms, 79-82 in localization-related epilepsies, 77-79 methodology of, 77 surgical outcome and, 137

Psychiatric disorders, in cortical dysplasias, 36

Quadrantanopia, homonymous, after focal cortical dysplasia resection, 141

Rasmussens functional hemispherectomy, 122

Schizencephaly, 12,57-60 Seizures, in cortical dysplasias. See Cortical dysplasias. Single photon emission computed tomography, in

cortical dysplasias, 74-77 clinical applications of, 75-77 hemispheric, 106 methodology of, 74-75

Spasms, infantile - in cortical dysplasias, positron emission tomography

in. 79-82 surgical treatment of, 142

SPECT (single photon emission computed tomography), in cortical dysplasias, 74-77,106

Stereoencephalography, in focal cortical dysplasia, 87-88 Strips, subdural electrodes in, in focal cortical dysplasia,

89-91 Subcortical gray matter heterotopias, 54-55 Subdural electrodes, in focal cortical dysplasia, 89-91 Subependymal heterotopias, radiologic-pathologic

correlations in, 54,56 Sylvian fissures, primitive, 57-58

Taylor type focal cortical dysplasia, 6,35 Transsylvian, transventricular functional

hemispherectomy, 122-127 Tumor(s)

dysembryoplastic neuroepithelial, lO-11,23,43,48-49 dysplastic, U&11,22-23,43,48-50 gangliogliomas, lO-11,48,50

Documents

02.01 - Contemporary Management of Malformations of Cortical Development.pdf