Frontal Lobe Epilepsy:Clinical Features and Surgical Treatment

PGR 2008.9.2

Pediatric Neurology

Seoul National University Children’s Hospital

Seoul, Korea

Frontal lobe epilepsy

• Frontal lobe epilepsies (FLE) manifest with seizures originating from a primary epileptic focus anywhere within the frontal lobe

 • Demographic data

Start at any age and both sexes equally affected 1-2% of all epilepsies Second (20-30%) after TLE in neurosurgical series

Frontal lobe seizure types

Supplementary motor area (SMA) seizures Cingulate seizures Anterior frontopolar seizures Orbitofrontal seizures Dorsolateral seizures Opercular seizures Motor cortex seizures

• Prominence of motor manifestations-automatisms as well as tonic-clonic activity

• Rapid secondary generalization-little or no evidence of focal onset

• Focal clonic motor activity with or without march• Prominent asymmetric tonic posturing• Complex, bizarre motor automatisms• Explosive onset and sudden ending with minimal postictal

confusion• Frequent, brief seizures often in clusters

General characteristics of FLE

• Mainly simple motor seizures• Simple focal motor clonic or tonic-clonic seizures with or without

jacksonian march Localized, rhythmic or arrhythmic, clonic movements

contralateral to the focus Distal > proximal Hand (thumb) and face (lips) preferentially affected

(homunculus of Penfield) Remain highly localized or march to neighboring motor

regions (jacksonian march)• Myoclonic seizures: predominantly facial or distal in the limbs• Tonic postural motor seizures

Seizures from motor cortex

• Frequent, brief episodes occurring in clusters• Explosive onset and offset with no postictal confusion• Nocturnal preponderance• Prominent tonic posturing, usually of the contralateral

upper extremity• Contraversive head and eye deviation• Fencing or M2e posture• Preservation of consciousness in some• Postictal Todd’s paresis (mild)

SMA seizures

• Frequent, brief seizures occurring in clusters• Sudden onset and offset with little or no postictal confusion:

consciousness partially retained but commonly amnesic for episodes

• Nocturnal preponderance• Complex motor automatisms-semipurposeful motor activity often

in combination with tonic-clonic motor manifestations• Vocalization from simple humming to shouted expletives• Prominent mood changes• Sexual automatisms• Overall bizarre hysterical appearance “pseudovoluntary nature”• Commonly misdiagnosed as psychogenic attacks

Frontal lobe CPS

FLE and TLE

Frontal lobe seizures: generally thought to be brief, motor phenomena, cluster in sleep

But, variable among the cases Distinguishing features of temporal lobe seizures

Presence of epigastric auras and hand automatism

rarely seen in FLE Longer post-ictal periods of drowsiness or confusion

Comparison with TLE

Have failed to attain adequate seizure control with adequate trials of anticonvulsant drugs (drug-resistant epilepsy)

Suffer from surgically remediable syndromes Have a reasonable chance of benefiting from

surgery

Candidate for epilepsy surgery

Absolute contraindication Underlying degenerative or metabolic disorders Supervening medical illness Benign epilepsy syndromes: benign rolandic epilepsy,

benign focal epilepsy of childhood with occipital spikes

Relative contraindication Medication noncompliance Interictal psychosis Severely dysfunctional family dynamic

Contraindications to surgery

Correct seizure type and epilepsy syndrome diagnosed

Optimal use of at least two AEDs appropriate for seizure type

Good compliance with the medications

Absence of major medical or psychosocial disturbance that interferes with seizure control

Seizure control or improvement is likely to reverse disability or improve quality of life

Consideration for surgery

Concept introduced to promote early surgical intervention for certain forms of epilepsy with well-defined pathophysiological substrates that are known to have a poor prognosis after failure of a few AEDs and an excellent surgical prognosis

Mesial temporal lobe epilepsy with hippocampal sclerosis (hippocampal epilepsy)

Certain temporal or extratemporal neocortical symptomatic focal syndromes with discrete easily resectable structural lesions

Epilepsies of infants and small children that can be treated with hemispherectomy

Lesional vs. Non-lesional

Surgically remediable epileptic syndromes

Hippocampal sclerosis Neoplastic lesions

Neuronal and glial neoplasm: Ganglioglioma, DNET Glial neoplasm: Pilocytic astrocytoma, Low-grade astrocytomas, Pleomorphic xanthoas-

trocytoma, Oligodendroglioma, Oligoastrocytoma Developmental lesions

Malformations of cortical development Focal malformations of cortical development Periventricular heterotopia Polymicrogyria and schizencephaly

Tuberous sclerosis complex Hypothalamic hamartoma

Vascular lesions: Arteriovenous malformations, Cavernous angioma Chronic inflammatory focal lesions: Tuberculoma, Cysticercosis Focal encephalomalacias Large hemispheric lesions

Rasmussen encephalitis Hemimegalencephaly/hemi-hemimegalencephaly Hemiconvulsion-hemiplegia-epilepsy syndrome Sturge-Weber syndrome

Surgically remediable “lesional” syndromes

Nonlesional epilepsy syndromes: recurrent seizure disorder not due to a structural tissue lesion that replaces the volume of the normal brain anatomy

Lesion: structural alterations that can be visually identified by imaging studies before the surgery

Does not preclude that the tissue may possess microscopic or histologic abnormalities

Presurgical evaluation: more complex, due to the lack of any anatomical evidence for the origin of the seizures

Operative outcome less favorable than those with MRI-identified epileptogenic lesions

Surgically remediable “nonlesional” syndromes

Well-circumscribed structural lesion on MRI

Well-localized interictal epileptiform discharges on EEG

Clinical features of habitual seizures indicating frontal onset

Absence of discordance between the above features

The focus suggested by above features is surgically acces-sible and involves little or no eloquent cortex

Absence of other potentially epileptogenic abnormalities

Better surgical outcomes

Defining epileptogenesisArea Definition Mode of definition

Epileptogenic lesion Structural brain abnormality that is the di-rect cause of seizures

Structural imaging, tissue pathology

Irritative (spiking) zone Area that generates interictal spikes EEG and MEG

Ictal onset zone Area of cortex that generates seizures EEG and MEG

Symptomatogenic zone Area that produces the initial clinical symptomatology

History, observation during video-EEG monitoring

Functional deficit zone Cortical area with functional abnormalitiesNeurologic examination, neu-ropsychological testing, EEG, MEG, PET, SPECT

Epileptogenic zoneArea of brain that is necessary for generating seizures and whose removal or disconnection abolishes seizures

Theoretical concept

Zone of surgical resection

• Zone resected at surgery, ideally it should be identical to epileptogenic zone but is often larger due to uncertainty in completely localizing the epileptogenic zone and at times may exclude some areas of the epileptogenic zone to avoid resec-tion of eloquent areas

Epilepsy surgery in FLE

Surgical outcome in FLE

Prognostic factor to show good surgical outcome Potentially epileptogenic lesion in neuroimaging Absence of febrile seizures, generalized or bilateral

epileptiform activity on surface EEG widespread epileptiform activity in ECoG

Neoplasm as etiology Strong predictor for poor outcome

Residual epileptogenic tissue as assessed by seizures/frequent spikes ECoG or MRI

Prognostic factor

Immediate complication: Intracranial or scalp/skull infections, hemorrhage, edema, neurological deficits and seizures in up to 20-25% ~ 40-50%

Permanent neurological deficits in 2-3% of the patients

 

Postoperative complication