Posterior cortical epilepsies

POSTERIOR CORTICAL EPILEPSIES

SEMINAR

The ILAE Commission (1989) classifies focal epilepsies according to their topographical/anatomical origin as:Temporal lobe epilepsiesFrontal lobe epilepsiesParietal lobe epilepsiesOccipital lobe epilepsies

These epilepsies may be idiopathic, cryptogenic or symptomatic

frontal lobe seizures prominent motor activity at

onset posturing, focal tonic activity,

and elaborate Gestures Unilateral or bilateral tonic limb

posturing, and bicycling movements

Atonic seizures (the supplementary negative motor area)

Speech arrest is often profound when it occurs

vocalizations, barking and nonverbal vocalizations

often brief, lasting under 1 minute, and typically less than 30 seconds, with little to no postictal phase

higher frequency, often have a nocturnal

Predilection more apt to secondarily

Generalize psychic symptoms- mood and

affect changes Olfactory hallucinations

temporal lobe sezures•amnesia of the event,•reactive automatisms,•duration of the seizure for longer than one minute,•prolonged postictal confusion

experiential phenomena that suggest temporal onsetIn mesial temporal onset•Autonomic- nausea and a rising epigastric sensation•psychic phenomena- panic and fear

lateral temporal lobe onset•more pronounced psychic phenomena- the sense of being in a dreamy state•Visual perceptual changes -Visual illusions ,multimodal hallucinations•Vertigo •early clonic movements

Posterior cortex epilepsies (PCEs) encompass a group of epilepsies originating from the occipital, parietal, or occipital border of the temporal lobe, or from any combination of these regions

characteristic feature of posterior neocortical seizures is the tendency to have multiple spread patterns (Salanova et al 1992, Fogarasi et al 2003).

This can occur among different patients or among different seizures in the same patient

can present with stereotyped but very different-appearing clinical seizures depending on direction of seizure spread

individual patients can have seizures that are not stereotyped from one to another, strongly suggesting multifocality

seizure propagation pathways

Seizure spread from posterior cortex

occipital focus to the ipsilateral temporal lobe through the inferior longitudinal fasciculus

Similar pathways between the occipital lobes and the

supplementary motor area and the thalamus

Between the parietal sensory cortex and the frontal motor and supplementary motor areas

Many of the disabling clinical manifestations resulted from ictal spread to adjacent cortical structures

29–88% of patients exhibited automatisms typical of temporal lobe epilepsy

38–47% had focal motor activity

seizure spread has been suggested to influence the outcome of treatment

favorable outcome when spread is to suprasylvian regions

less favorable outcome when spread is to limbic structures

Parietal lobe epilepsies

primary epileptic focus anywhere within the parietal lobe

The 1989 ILAE Commission classifies parietal lobe epilepsies among the localisation-related epilepsies

Parietal lobe epilepsies have not yet been detailed in the new ILAE diagnostic scheme

Demographic Datastart at any age Both sexes are equally affected Age at onset is much later in patients with

tumours6% of all focal epilepsies in neurosurgical

seriestwice as common as occipital lobe seizures

Clinical Manifestationsmainly simple focal without impairment of

consciousnessin order of prevalence:

somatosensorysomatic illusions (subjective disturbances of

body image)vertiginousvisual illusions or complex formed visual

hallucinationsreceptive or conductive linguistic

disturbances

Somatosensory Seizuresthe most common type (around two-thirds of

cases)Positive phenomena

tingling and a feeling of electricity, which may be confined or may spread in a Jacksonian manner

desire to move a body part or a sensation as if a part were being moved

Muscle tone may be lost

The parts most frequently involved those with the largest cortical representation

(e.g., the hand, arm, and face)

facial sensory phenomena may occur bilaterally

intraabdominal sensation of sinking, or nauseainferior and lateral parietal lobe

Negative phenomena (Non dominant parietal) numbness, a feeling that a body part is absent a loss of awareness of a part or a half of the body

(somatoagnosia)Parietal lobe visual phenomena Metamorphopsia with distortions, shortenings,

and elongations

Rarely, there may be pain superficial burning dysaesthesia, or a vague, very

severe pain

receptive or conductive language disturbancesDominant paretal

Lateralised genital sensatonsParacentral lobule

QualityTingling may be the most characteristic

symptom (76% in one study)

Pain, sometimes excruciating, is experienced by 25% of patients

Static or Jacksonian march

bilateral spread is rare

Unilateral somatosensory seizures are usually contralateral to the epileptogenic zone

Seizures ipsilateral to the side of seizure origin are exceptional

Ictal sensations in the genital areas and the rectum, and orgasmic seizures are infrequent

sexual automatisms (i.e. fondling the genitals) occur only in the postictal phase

Objective Ictal Somatosensory Deficitstwo-point discrimination was impaired in the

contralateral hand

Disturbances of Body Image and Somatic Illusions (posterior parietal lobe)

second most common ictal symptom

Ictal limb agnosia ,phantom limb sensations

Neglect is more commonly associated with the right rather than the left inferior parietal lobe

Illusions of movement

Vertigo (temporo-parietal border)about 10% as ictal manifestations

Visual illusions and complex formed visual hallucinations (non-dominant parietal regions)about 12% of patients

Linguistic Disturbances (dominant temporal-parietal lobe)alexia with agraphia and significant

calculation defects

Inhibitory motor seizures, ictal hemiplegia or negative motor manifestations,drop attacksexceptional

Seizure spreadPosterior propagation - elementary visual

hallucinations or ictal amaurosis (Williamson 1987).

Anterior spread can produce focal clonic motor activity.

spread to the supplementary motor area- asymmetrical tonic motor activity (Siegel et al 1999).

Inhibitory or hemiplegic seizures may occur, but it is not known whether this represents spread beyond the parietal lobe

posterior parietal lobe seizure spread to the temporal lobes, produce "psychoparetic" seizures (Ho et al 1994).

Parietal lobe seizures resembling panic

attacks -reflect temporal lobe seizure spread ( Sazgar et al 2003).

When seizures arise in “silent” areas of the parietal lobe and propagate anteriorly, they can be confused with frontal lobe seizures.

Frequency of seizure Spreading to Extraparietal Regions

unilateral focal clonic convulsions (57% of patients),

head and eye deviation (41% of patients),

tonic posturing of usually one extremity (28% of patients)

automatisms (21% of patients)

Secondary GTCS are usually infrequent

Duration of Seizuresfew seconds to 1–2 minProlonged isolated sensory auras

Postictal Manifestationsusually shortTodd’s paralysis (22%) dysphasia (7%)

Epileptogenic Localisationprimary sensory cortex

contralateral positive or negative symptomsalso occur with seizures emanating from

posterior parietal regionssecondary sensory area

Bilateral sensory symptoms parietal paracentral lobule

Ictal sensations in the genital areas area 5a

Ictal pain

Precipitating Factorsmovements of the affected part of the

body, tapping or other somatosensory stimuli

Sensorimotor seizures may also be triggered by music or toothbrushing

Aetiology

Non tumoural patients with parietal lobe epilepsyOut of 82 patients Salanova V reported

43% had a history of head trauma 16% a history of birth trauma the cause was unknown in 20%

• The remaining 21% – history of encephalitis– febrile convulsions– gunshot wounds to the head– forme fruste of tuberous sclerosis– hamartoma– vascular malformations– tuberculoma– arachnoid or porencephalic cysts– microgyria – post-traumatic thrombosis of the middle

cerebral artery

tumours

astrocytomas (62%)meningiomas (14%) hemangiomas (9%) oligodendrogliomas (9%)ependymoblastomas (3%).

•In reports with MRI, malformations of cortical development - the most common cause

Diagnostic Procedures

Neurological examination usually normal impaired two-point discrimination or

stereoagnosia mild limb atrophyinferior quadrantic visual field defects disturbances of written language, aphasia,

spatial orientation and right-left disorientationtumoural parietal lobe epilepsy

mild contralateral weakness is common (38%)unilateral limb atrophy is exceptional

Brain imagingHigh resolution MRI

abnormal in 60% FDG-PET and ictal SPECT

are useful in presurgical evaluations

Electroencephalography

Interictal EEGmay be normal, non-specific, or even misleadingIn symptomatic patients- localised slow waves

False localising to frontal, temporal or occipital electrodes

16% do not have epileptiform dischargessecondary bilateral synchrony is common

(32%)

• Ictal EEG• The ictal EEG may be normal in 80% of

simple focal sensory seizures• The prevalence of scalp EEG changes

– sensory seizures- 15%– as opposed to 33% when motor symptoms are

present

• Postictal EEG– focal slow wave, attenuation of background

activity or spikes

Differential DiagnosisSomatosensory seizures are misdiagnosed

as non-epileptic psychogenic fits > transient

ischaemic attacks > migraine with aura

Management

Drug treatment is similar to focal seizures and is usually effective

In intractable cases, neurosurgery achieves seizure-free state or remarkable improvement (> 65%)

Better prognostic factorsMRI abnormality concordance of different diagnostic

modalitiescompleteness of resection of the

epileptogenic zone Resection may be problematic

deficits in vision ,language, praxis, attention and higher cortical function

Occipital Lobe Epilepsies

Occipital seizures originate from an epileptic occipital focus

triggered spontaneously or by external visual stimuli

idiopathic, symptomatic or probably symptomatic

Demographic Data

Occurs at any age 5–10% of all epilepsies5% in neurosurgical series6% seen in demographic studies

Clinical Manifestations

The cardinal symptoms are mainly visual and oculomotor

Visual subjective symptoms elementary and less often complex visual

hallucinationsblindnessvisual illusionspallinopsiasensory hallucinations of ocular movementsocular pain.

Ictal objective oculomotor symptoms tonic deviation of the eyes (pursuit-like

rather than oculotonic)oculoclonic movements or nystagmusrepetitive eyelid closures or eyelid fluttering

elementary visual hallucinationsthe primary visual cortex

visual illusionsthe occipital-parietal and occipito-temporal

junctionsSeizures may spread from the occipital to

anterior regionsgenerate symptoms from the temporal, parietal

and frontal lobes secondarily hemi- or generalised convulsions

Ictal or postictal headache is frequent

Elementary Visual Hallucinations

the most common, characteristic and well-defined ictal symptoms

Often the first symptommay progress to other occipital and extra-

occipital manifestations and convulsions

mainly coloured and circulardevelop rapidly within seconds and are brief

in duration often appear in the periphery of a temporal

visual hemifield become larger and multiply in the course of

the seizure, frequently move horizontally towards the

other side

Colour, Shape and Sizeusually multicolouredShapes are mainly circular, spots, circles and

ballssquare, triangular and rectangular - less

frequentincrease in number, size or both with

progression of the seizure

Locationusually unilateraltemporal visual hemifield may appear in a normal, blind or damaged

hemifieldCentral or undefined localisation occurs in

10–30% of patients

Lateralisationcontralateral to the epileptogenic focus Conversely, this is ipsilateral to the

epileptogenic focus for unilateral visual hallucinations moving horizontally towards the other side

Visionobscured only in the area occupied by the

visual hallucinationssome patients able to read through themBlurring of vision at onset may be a form of

visual seizure

Durationdevelop rapidly within seconds usually brief, lasting from a few seconds to

1–3 minExceptionally, they last for 20–150 minutes-

focal visual status epilepticusAs a rule, last longer prior to secondarily

generalisation

Frequency and Circadian Distributionoften in multiple clusters, daily or weeklyusually diurnalRarely on awakening

Stereotypic Appearancestereotyped, particularly at onset, in all

aspects other than duration same patient experiencing different types of

seizures is exceptional

• Progression to Other Occipital or Non-Occipital Seizure Manifestations

• often progress to other ictal symptoms– complex visual hallucinations– oculoclonic seizures– tonic deviation of the eyes– eyelid fluttering or repetitive eye closures– impairment of consciousness– experiential phenomena– hemi-anaesthesia– unilateral or generalised convulsions

• extra-occipital seizure manifestations by spread to the temporal, frontal or parietal regions.

Complex Visual Hallucinations, Visual Illusions and Other Symptoms from More Anterior Ictal Spreading

Complex visual hallucinations 

persons, animals, objects, figures or scenesfamiliar or unfamiliar, friendly or frighteningsmall or large area of a hemifield, or in the centre and the

whole of the visual fieldstatic, move horizontally, expand or shrink, approach or move

awaydo not have the emotional character of temporal lobe seizurescomplex visual hallucinations may appear in the defective

visual field

Ictal autoscopiaoriginate from occipito-parietal and occipito-

temporal junction areasVisual illusions 

Metamorphopsia,micropsia or macropsia,achromatopsia,monochromopsia

Palinopsiapersistence or recurrence of visual images with right posterior parieto-temporal lesions.

Sensory Hallucinations of Ocular Movementssensation of ocular movement in the absence of

detectable motion - rare

Ictal Blindness often occurs as a starting or the only ictal

seizure manifestation with abrupt onsetmay follow the visual hallucinationsmay last for hours or days (status epilepticus

amauroticus).one-third of patients with symptomatic and two-

thirds of patients with idiopathic occipital epilepsy

Tonic Deviation of the Eyes, Oculoclonic Seizures and Epileptic NystagmusTonic deviation of the eyes often, followed by

ipsilateral turning of the head (40–50% of cases) – The most common non visual symptom

Consciousness is often impaired when eye deviation occurs

The epileptogenic focus is contralateral if consciousness is not impaired

Ictal nystagmus quick phase of the nystagmus is opposite to the

epileptic focusin the same direction of eye and head deviation

Repetitive eyelid closures, eyelid fluttering and eyelid blinking heralds the impending secondary GTCS

Eyelid opening, or ‘eyes widely opened’well-described symptom in occipital epilepsytypical symptom of mesial temporal lobe

seizures

ConsciousnessNot impaired during hallucinationsmay be disturbed or lost at the time of eye

deviation or eye closure

Ictal or Postictal Headachefrequently associated - 50% of casesmainly orbitaloften indistinguishable from migrainepostictal headache often occurs 3–15 min

from the end of the visual seizure, ( ‘asymptomatic interval’)

Seizure Spread

Infra-calcarine occipital foci will propagate to the temporal lobe causing

complex focal seizuressupra-calcarine foci

tend to propagate to the parietal and frontal areas giving rise to predominantly motor seizures.

Aetiology

Idiopathic, structural or metabolicMalformations of cortical development are a

common causeMetabolic or other derangements, such as

eclampsia, may have a particular predilection for the occipital lobes

Occipital seizures may be the first manifestation of celiac disease,Lafora disease or mitochondrial disorders

PathophysiologyElementary visual hallucinations

primary visual cortex complex visual hallucinations

occipito-parietal-temporal junction areasvisual illusions

non-dominant parietal regionsIctal blindness

contralateral seizure spread to involve both occipital lobes or to inhibition of the visual cortex by the seizure discharge

postictal headacheoccipital lobes are preferentially associated

with the trigeminovascular or brainstem mechanisms responsible for headache

related to serotonergic mechanisms and respond to oral sumatriptan

Another similarity with migraine - asymptomatic interval’ 

Diagnostic Proceduressymptomatic occipital epilepsies

haematology and biochemistry screening for metabolic disorders, molecular DNA analysis, or even skin or other tissue biopsy

 High resolution MRIcalcifications of CD – CT scanf-MRI- practical value in neurosurgical cases.

Electroencephalography

• Interictal EEG• In symptomatic cases

– Background EEG is usually abnormal with posterior lateralised slow waves

– Unilateral occipital spikes or fast multiple spikes and, occasionally, occipital paroxysms occur

– There may be occipital photosensitivity

In idiopathic casesthe background interictal EEG is normal

Eg:Gastaut-type idiopathic childhood occipital epilepsy and photosensitive occipital epilepsy

Occipital spikes and occipital paroxysms, spontaneous, evoked or both, are often abundant

disappear with age

Ictal EEGparoxysmal fast activity, fast spiking or both,

localised in the occipital regions

occasional gradual anterior spreading and generalisation with irregular spike wave discharges or monomorphic spike and wave activity

Brief occipital flattening may be seen before the fast rhythmic pattern.

symptomatic occipital lobe epilepsy the ictal discharge is more widespreadpostictal localised slowing when the seizure

is prolonged or progresses to secondarily GTCS

30% of the ictal surface EEG -  normal in occipital seizures

Differential Diagnosisshould be first differentiated from

migraine normal phenomenaPsychogenic

Occipital epilepsy Migraine with aura Basilar migraineVisual hallucinations

Duration for seconds to a minute Exclusive None None

Duration for 1–3 minutes Frequent Rare Rare

Duration for 4–30 minutes Rare As a rule As a rule

Daily in frequency As a rule Rare None

Mainly coloured circular patterns As a rule Rare Exceptional

Mainly achromatic or black and white linear patterns

Exceptional As a rule Rare

Moving to the opposite side of the visual field

Exclusive None None

Expanding from the centre to the periphery of a visual hemifield

Rare As a rule Frequent

Evolving to blindness Rare Rare As a rule

Evolving to tonic deviation of eyes Exclusive None None

Evolving to impairment of consciousness without convulsions

Frequent Rare Frequent

Evolving to impairment of consciousness with convulsions

Frequent Exceptional Rare

Associated with post-ictal/post-critical headache

Frequent As a rule Frequent

Blindness and hemianopia

Without other preceding or following symptoms

Frequent None Frequent

Other neurological symptoms

Brain stem symptoms None None Exclusive

Post-ictal/post-critical vomiting Rare Frequent Frequent

Post-ictal/post-critical headache

Post-ictal or post-critical severe headache Frequent As a rule Frequent

Occipital seizure Migrane with aura Basilar migrane

Differentiating Idiopathic from Symptomatic Occipital Epilepsy

symptomatic visual seizures progress to other extra-occipital seizure

manifestations and mainly temporal lobe seizures

temporal lobe symptoms are nearly exclusiveHigh resolution MRI

Prognosis

good to intractable or progressivedepends on the underlying cause and

extent of the lesions

Management

AED treatment is similar to that for any other type for focal seizures

usually effective Should be initiated as soon as possibleCarbamazepine is the drug of choicepostictal headache - oral sumatriptanNeurosurgery is effective in around 70% of

patients with 30% becoming seizure free

The Drug Treatment of Focal Epilepsies

In head-to-head comparisons among old AEDs overall treatment success was highest with

carbamazepine or phenytoin intermediate with phenobarbitone lowest with primidone

carbamazepine vs valproatecarbamazepine provided better control of

complex focal seizures CBZ had fewer long-term adverse effects

than valproateBoth drugs were comparably effective for the

control of secondarily GTCS

The new AEDsgabapentin, lamotrigine, levetiracetam,

oxcarbazepine, tiagabine, topiramate, vigabatrin and zonisamide

nearly equal efficacy to carbamazepine, phenytoin and valproate

Efficacy

Tolerability

Serious adverse events

Drug–drug interaction

Pharmacokinetics

Titration

Need for laboratory testing

Mechanism of action

Levetiracetam

High Excellent no no Ideal Fast minimal

Novel SV2A- ligand

Lamotrigine

Low Excellent

yes yes Poor Very slow

maximal

Na+

Topiramate

High Poor yes yes Satisfactory

Very slow

Maximal

multiple

Oxcarbazepine

Medium

poor yes yes Poor Slow Maximal

Na+

Zonisamide

Medium

good yes no satisfactory

slow maximal

multiple

Surgical treatment

Rasmussen (1975),first reported good outcome after removal of nontumoral epileptogenic lesions in 86 parietal cases and 25 occipital cases

Removal of a temporal lobe has also been reported to provide favorable results in some patients in whom the dominant seizure symptomatology was a result of spread of seizure discharge to that temporal lobe

Occipital epilepsy is often associated with a large epileptogenic zone

complete resections difficult

more extensive resections are a key to improved seizure control

In functionally critical areas such as the primary sensory cortex, multiple subpial transsections of the epileptogenic areas have been reported to be successful

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Clinical Features of Patients with Posterior Cortex Epilepsies and Predictors of Surgical Outcome

Charles L. Dalmagro et al

epilepsia, , 2005 Department of Neurology, Federal University of

Santa Catarina, Brazil

Surgical treatment was highly effective (p < 0.001) when compared with previous pharmacologic treatment alone.

28/44 (65.11%) patients became seizure free

Posterior cortex epilepsy: Diagnostic considerations and surgical outcome

Tao Yu et al

Seizure (2009), Beijing Institute of Functional Neurosurgery, China

Thirty-one (72.1%) had favorable surgical outcome (Engel class I and II)

26 (60.5%) seizure free patients

Cognitive changes after epilepsy surgery in the posterior cortex (R Luerding)J Neurol Neurosurg Psychiatry 2004Epilepsy surgery in the posterior cortex bears

no risk for substantial decline in general cognition

some discrete impairment in performance intelligence may occur

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