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
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