Porencephaly: Computed tomography (CT) scan findings

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  • Compulerized Rodiol. Vol. 1 I, No. I, pp. 53-58, 1987 0730-4862/X7 $3.00 t 0.00 Printed in the U.S.A. All rights reserved Copyright c 1987 Pergamon Journals Ltd


    T. M. KOLAWOLE, P. J. PATEL and A. H. MAHDI Departments of Radiology and Paediatrics, College of Medicine, King Saud University,

    Riyadh 11461, Saudi Arabia

    (Received 5 June 1986; received for publication 30 October 1986)

    Abstract-Twenty-six cases of porencephalic cysts were analyzed. The cysts were multiple in 26.9% and were associated with subarachnoid cysts in 11.5%. The main presentations were seizures, cerebra1 palsy and mental retardation. The unifocal cysts were mainly in the frontoparietal region, suggesting a congenital aetiology. Multiple cysts were noted in the basal ganglia region. A case of multiloculated cysts. of unknown aetiology, is noted. The aetiology of multifocal porencephaly and a diagnostic method of differentiating congenital from acquired porencephaly are discussed.

    Porencephaly cysts Intracerebral Computerized tomography


    Porencephaly in childhood is not an unusual appearance on CT scans. A retrospective study was, therefore, done to determine the radiological appearances of porencephalic cysts with special reference to their patterns and the progressive increase in the sizes of some of these cysts. An attempt was made to deduce the etiological basis from the radiological features. A method for differentiating congenital porencephalic cysts from acquired once and from glial tissue is suggested.


    The summary of the clinical findings in the 26 cases of the patients with porencephalic cysts with reference to the age distribution, sex ratio, symptom complexes and causation are given in Table 1.

    Table 2 shows the distribution lesions within the brain with respect to sites. The lesions were mainly focal (79.2%) and in two cases, single located within the caudate nucleus region. The lesions were

    Table I. Summary of clinical findings in 26 patients

    (a) As O-IO years I I-20 years 2 l-30 years Above 31 years


    (b) Sex Male Female


    (c) Svmptoms Seizures Cerebral palsy

    (Hemiparesis) Mental retardation Neonatal and birth trauma Prematurity Enlarging head size Infection

    I8 6 I I


    I5 II



    G) 3 2 I I I


  • 54 T. M. KOLAWOLE et al.

    Table 3. Radiological features

    Types of porencephaly Number of patients

    Table 2. Sites of lesions

    Frontal lobe 8 Parietal lobe 8 Occipital lobe 4 Cerebellar lobe 2 Temporal lobe 5 Pulvinar region 4 Multicvstic (multifocal) 2

    Focal Multifocal

    Frontal and temporal lobes Multicystic Pulvinar (bilateral) Occipital (bilateral)

    Associated with subarachnoid cyst Hydrocephalus Mass Effect Cerebral atrophy

    (Herniatrophy) (Generalized)

    Skull changes: asymmetry Communication with lateral ventricle

    I9 (73%) 7 (26.9%) I 2 2 I 5 9 3

    :;: (5)

    3 6

    mainly in the cerebral cortex, especially the frontoparietal region (Fig. 1). The cerebellum was involved only once.

    The radiological features are shown in Table 3. Multiple lesions were seen in seven cases. Bilateral lesions were present in the occipital lobes and the putamina in two cases each. Multicystic lesions were seen in two cases.


    Aetiology There is no consensus of the precise definition of porencephaly since it was described in 1859 [l].

    Porencephalic cysts could be congenital or developmental, the so-called agenetic porencephaly [2]. Familial cases of congenital hydraencephaly/porencephaly has been reported, even in monozygotic twins [3,4]. No familial cases were seen in our series. Porencephaly may also be acquired; i.e. encephaloclastic resulting from a variety of diseases which lead to destructive tissue breakdown, such as cerebral ischemia [5], infection and hematoma [6,7].

    In our series, one case of prematurity with intraventricular hemorrhage was encountered, previously demonstrated by ultrasound. The subsequent porencephalic cyst in this patient is attributable to this [Fig. 2(A)(B)].

    Clinical features The age distribution and presenting symptoms of our cases are seen in other series with

    predominance in the very young, with cerebral palsy and seizures being the most common presenting

    Fig. 1. Cavitation in the anterolateral aspect of the right anterior horn, co-existing with a quadrilateral arachnoid cyst in the right sylvian cistern.

  • Porencephaly: CT scan findings 55

    09 Fig. 2. (A) Ultrasound scan of the skull at 1 month, showing bi-ventricular echoic areas within the lateral ventricles due to intraventricular haemorrhage. (B) Four months later, a porencephalic cyst is seen in the left

    occipital lobe. The cyst communicates with the left cerebella-pontine cistern.

    symptoms [3]. Cases may present with progressive signs of raised intracranial pressure due to enlarging cysts [8]. Only one of our cases presented this way.

    Radiographic jkatures The cysts are all non-enhancing, discreet, and low attenuation areas within the brain. Fifty percent

    of the cysts are associated with cerebral atrophy, hemiatrophic or generalized types. The hemiatrophy was in the cortex within which porencephaly occurred. Hydrocephalus was a feature in nine cases (34.6%), all in the multifocal types, and in three cases of the cases in which the porencephalic cysts were associated with subarachnoid cysts. This is probably an evidence of the severity of the causative destructive intracerebral process [2].

    In only six cases, porencephalic cysts were seen communicating with the lateral ventricle (Fig. 3); and in only one case with the subarachnoid space [Fig. 2(B)].

    Mass effect was seen only in three cases, two of which were associated with subarachnoid cysts. The skull changes were expected, being asymmetrical in the three cases with severe hemiatrophic

    changes [Fig. 2(B)].

    Multiple lesions In two cases each, bilateral porencephalic changes were seen in the occipital lobes and the putamina

    (Fig. 4).

  • 56 T. M. KOLAWOLE et al.

    Fig. 3. 1 4h horn I. n tote

    luge porencephalic cyst in the right frontoparietal region communicating with the right the rim of cerebral cortex on the anteromedial aspect of the cyst and the increase in

    subarachnoid space.

    ante rior the left


    Fig 4. (A sma lller on

    ) Bilateral hydrocephalus with very low attenuation areas in the regions of the putan [es within the cortex bilaterally. (B) Multiloculated cystic spaces within the cerebral COI

    ventricular system is indistinguishable from the cysts.

    nina and rtex. The

  • Porencephaly: CT scan findings 57

    Such changes in the putamina of children and adults with previous history of cerebral hypoxia were recently reported, and it was suggested that the changes were a consequence of watershed infarcts; the putamina being a region of junctional zone between the superficial and deep branches of the middle cerebral artery [5]. Our cases suggest neonatal asphyxia/birth trauma since they dated from birth. There were also two cases of multicystic encephalomacia of unknown aetiology [Fig. 4(b)]. We believe these are similar lesions to those of the putamina, but more severe and extensive, spreading into the basal ganglia and cortical tissues. It has been asserted that due to the relative developmental immaturity of the cerebrovascular architecture in the periventricular regions of the frontoparietal cortex is more vulnerable to damage than the white matter around the posterior horns in posterior parietal and occipital cortex [9]. The fact that more lesions are seen in the anterior half of the cortex lends credence to this.

    D@erence between congenital and acquired porencephaly Congenital porencephaly usually communicates with the lateral ventricles [2, 7, 81. Nothing in the

    history of those six cases, communications of cysts with the ventricles, indicated acquired etiology, such as trauma or infection; thus, making us suspect they are probably congenital in origin. But Braun, quoting others, has suggested that partial atrophy of the brain, especially hemiatropy, is presumably due to acquired porencephaly, such as hemorrhage or encephalitis [3]. However, the co-existence of porencephalic cysts, communicating with the lateral ventricles and cerebral atrophy ipsilateral to the porencephalic cysts in three cases, contradicts the above view point. We believe that porencephalic cysts can communicate with the ventricles or cisterns, depending on the sizes and proximity of the porencephalic cyst to the ventricle or cistern. It has been suggested that angiography and histology could differentiate between congenital and acquired porencephaly [3].

    On angiography, the congenital porencephaly is characterized by continuity between the network of cortical vessels and subspendymal veins, resulting in a specific image of operculation; whereas in acquired porencephaly, the cavity is sometimes crossed by pre-existing vessels. On histological examination, the acquired cavity is circumscribed by a cicatrial glial membrane; whereas the cavity of the embryonic porencephaly is lined by ependymal tissue. Dynamic CT scanning of these lesions may, therefore, offer a means of differentiation with the congenital porencephaly showing sharper and greater enhancement than the acquired porencephaly.


    Twenty-six cases of porencephalic cysts diagnosed by computerized tomographic (CT) scan were reviewed with special reference to their features and their correlations with the etiological basis.

    The results show that the