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Ovid: Fifty Neurologic Cases from Mayo Clinic

Editors: Noseworthy, John H. Title: Fifty Neurologic Cases from Mayo Clinic, 1st Edition Copyright ©2004 Oxford Unversity Press (Copyright 2004 by Mayo Foundation for Medical Education and Research) > Table of Contents > Case 4: Twenty years of daily seizures Case 4: Twenty years of daily seizures CASE 4 History A 21-year-old man presented for evaluation and treatment of an intractable seizure disorder. He was 15 months old at seizure onset. Initially, he experienced up to 50 1-minute episodes daily of behavioral arrest and staring. At age 11 years, he developed a different type of clinical event associated with pupillary dilatation and jerking of the right arm or leg, followed by generalized stiffening, pelvic flexion and rocking, and repetitive bilateral leg movements. He often fell during these seizures. At the time of the evaluation, the majority of the six to eight daily seizures occurred during sleep and each was approximately 30 to 45 seconds long. The patient would awaken and, without warning or aura, experience a “convulsion” that often resulted in physical trauma. The parents would be awakened by his seizure activity. The longest seizure-free interval in the past several years was 72 hours. Multiple combinations of antiepileptic medications had failed to decrease the frequency or tendency of the seizure activity. He lived with his parents, was unemployed, and required supervision with bathing. He was the product of a normal pregnancy, but labor was prolonged. At age 2, he had a near-drowning experience that required resuscitation. Paternal cousins had seizure disorders. Examination The patient had a mild chronic global static encephalopathy. He appeared sedated because of the antiepileptic drug therapy. Investigations A wake and sleep electroencephalogram (EEG) demonstrated mild diffuse slowing without epileptiform discharges. A magnetic resonance imaging (MRI) head seizure protocol was normal. Scalp-recorded ictal EEG monitoring did not show a lateralized or localized seizure pattern. A subtracted peri-ictal single-photon emission computed tomography (SPECT) study coregistered to MRI of the patient’s head (subtraction of interictal from ictal SPECT coregistered to three-dimensional MRI [SISCOM]) demonstrated a prominent localized region of cerebral hyperperfusion in the inferior and lateral aspect of the left anterior frontal lobe (Figure). He was considered a candidate for intracranial EEG monitoring and possible focal cortical resection. A subdural grid P.14
was placed stereotactically over the dorsal convexity of the left anterior frontal lobe. The patient’s characteristic seizure activity was associated with an ictal EEG pattern that was intimately related to the localized SISCOM alteration. The ictal onset zone, as determined with intracranial EEG monitoring, was resected.

FIGURE. SISCOM study in the, A, coronal and, B, sagittal (right) planes shows a localized region of cerebral hyperperfusion in the left frontal lobe (see color insert).

DIAGNOSIS CASE 4 Intractable partial epilepsy of left frontal lobe origin related to focal cortical dysplasia
Commentary by Dr. Gregory D. Cascino Pathologic examination of the epileptic brain tissue showed focal cortical dysplasia. The patient has been seizure-free and asymptomatic for more than 5 years after resection. There were no operative complications. The patient’s behavior and neurocognitive performance have improved markedly, and he is now employed and does not require supervision. Also, there has been a pronounced reduction in the adverse effects of antiepileptic drug medication. Partial or localization-related epilepsy is the most common seizure disorder. Approximately 90% of the adult incident cases of epilepsy have recurrent and unprovoked partial seizures. An estimated 20% of patients with epilepsy have an intractable seizure disorder, that is, pharmacoresistant seizures that are physically and socially disabling. Coexisting comorbid conditions associated with an intractable seizure disorder often include cognitive impairment, behavioral problems, psychosocial isolation, and the inability to operate a motor vehicle or to be gainfully employed. Patients with medically refractory seizures may also require a supervised living situation or caregiver. A prognostic indicator for an unfavorable response to antiepileptic drug therapy is the identification of a structural lesion as the cause of the seizure disorder. Potential alternative forms of therapy for patients with intractable epilepsy include the use of newer antiepileptic drug medications, surgical treatment, and vagus nerve stimulation. Epilepsy surgery is safe and effective for selected patients with medically refractory partial epilepsy. For patients with medically refractory seizures, focal resection of the epileptogenic cortex compares favorably with antiepileptic drug treatment and vagus nerve stimulation. Fewer than 10% of patients with intractable seizure disorders are rendered seizure-free with “newer” antiepileptic drug therapy or electronic stimulation. The surgically remediable epileptic syndromes include medial temporal lobe epilepsy and localization-related epilepsy associated with foreign-tissue lesions. Approximately 60% to 80% of favorable surgical candidates are rendered seizure-free after epilepsy surgery. The surgical pathologic lesion most commonly associated with medial temporal lobe epilepsy is mesial temporal sclerosis. Lesional pathology includes tumors, vascular anomalies, and malformations of cortical development. The rationale for operative intervention is to substantially reduce seizure P.16
tendency and to allow the person to become a participating and productive member of society. Focal cortical dysplasia is a malformation of cortical development that may be associated with an early age at seizure onset, cognitive deficits, and medically refractory seizures. MRI, with various degrees of specificity and sensitivity, may demonstrate a localized alteration in patients with a malformation of cortical development, depending on the specific histopathologic features of the lesion. Unremarkable MRI findings, however, do not exclude the presence of focal cortical dysplasia as the cause of a partial seizure disorder. SISCOM is a recent innovation that may assist in localizing epileptogenic cortex. Functional neuroimaging is particularly important in patients with nonlesional extratemporal seizures. Overall, the outcome of epilepsy surgery for extratemporal seizures is less favorable than for medial temporal lobe epilepsy. Peri-ictal imaging may provide a “target” indicating the likely site of seizure onset and may alter the operative strategy. The use of intracranial EEG monitoring is necessary to map the ictal onset zone and to determine the boundaries of the resection. SISCOM is a reliable indicator of epileptic brain tissue in patients being considered for surgical treatment. The presence of a SISCOM-identified localized region of cerebral hyperperfusion is a predictor of a favorable operative outcome. REFERENCE O’Brien TJ, So EL, Mullan BP, et al. Subtraction peri-ictal SPECT is predictive of extratemporal epilepsy surgery outcome. Neurology 2000;55:1668-77.

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