Discordant occurrence of cerebral unilateral heterotopia and epilepsy in monozygotic twins

Cerebral developmental malformations are increasingly recognized as a cause of epilepsy. Magnetic resonance imaging (MRI) has advanced our understanding of these disorders and their relation to epilepsy. We report the occurrence of discordant unilateral heterotopia and epilepsy in monozygotic twins. The affected individual developed intractable focal seizures at age 16 years. Mild cognitive difficulties had been present in early life. Evaluation showed right hemisphere EEG epileptogenic abnormalities, and the MRI scan showed massive right hemisphere heterotopia. EEG and MRI examinations in the patient's twin brother were normal. These findings suggest that the development of some developmental brain malformations and epilepsy is strongly influenced by nongenetic factors such as an environmental insult.

Proton nuclear magnetic resonance spectroscopic imaging of human temporal lobe epilepsy at 4.1 T

We performed proton magnetic resonance spectroscopic imaging (MRSI) at high magnetic field (4.1 T) to study N-acetylaspartate, creatine, and choline levels in the brains of normal control subjects and patients with intractable temporal lobe epilepsy. We compared the results of MRSI to those of other presurgical techniques to determine the sensitivity of this method in the lateralization of the epileptic focus. The normal hippocampal creatine-N-acetylaspartate ratio was 0.71 +/- 0.14 with no differences between left and right. Using the mean control hippocampal creatine-N-acetylaspartate ratio plus 2 standard deviations to identify statistically significant changes, we found lateralizing metabolic abnormalities corresponding to the operated temporal lobe in all patients. Four patients (40%) had contralateral abnormalities, and 2 of them had bilateral independent seizure onset confirmed by intracranial electroencephalographic studies. Statistically significant increases in the choline-N-acetylaspartate ratio in comparison to healthy volunteers were observed in 8 of the 10 patients. With the creatine-N-acetylaspartate ratio, MRSI demonstrated a 100% sensitivity compared to magnetic resonance imaging, which identified pathology in 70% of the patients. These findings suggest that proton MRSI yields a distinctive metabolic profile in patients with temporal lobe epilepsy and is sensitive in detecting bilateral metabolic abnormalities in some patients. These preliminary findings suggest that MRSI is more sensitive than magnetic resonance imaging in the lateralization of epileptic foci in temporal lobe epilepsy.

Frontal and central lobe focal dysplasia: clinical, EEG and imaging features

The authors studied 11 patients with developmental malformations and seizures originating from the frontal and central regions. Patients with centrally located seizures had primary involvement of the face or mouth; clonic activity involving the limb was also seen. Seizures among those with frontal lesions were primarily unilateral or bilateral tonic motor. Secondary generalized tonic-clonic seizures preceded by focal manifestations occurred infrequently in those with central localization, but were not rare in the frontal group. MRI revealed abnormalities in 10 patients, nine of whom underwent surgical resection with good results. Focal cortical dysplasia may be the underlying epileptogenic abnormality in young patients with clinical features suggestive of central or frontal cortical involvement.

Physical exercise, stressful life experience, and depression in adults with epilepsy

Adults with epilepsy completed self-report measures of exercise participation, barriers to exercise, stressful life experience, depression, and general psychosocial adjustment (n = 133) as part of routine outpatient visits. Descriptive statistics showed lower levels of depression among patients who exercised regularly. Structural equation analyses confirmed the fit of a path model that included significant direct effects of exercise and stressful life experience on depression. These effects were independent of each other, and independent of the influence of other predictor variables, such as seizure frequency, age, and gender. Stressful life experience also had a direct unique effect on seizure frequency in the multivariate models. These results suggest that problems with depression, which are common in adults with epilepsy, are significantly lower among those who exercise regularly and avoid stressful life change.

Placebo-controlled study of the efficacy and safety of lamotrigine in patients with partial seizures. U.S. Lamotrigine Protocol 0.5 Clinical Trial Group

We evaluated the efficacy and safety of lamotrigine (300 and 500 mg/day) as add-on therapy in a multicenter, randomized, double-blind, parallel-group, placebo-controlled study of 216 patients with refractory partial seizures. During 6 months of treatment, median seizure frequency decreased by 8% with placebo, 20% with 300 mg lamotrigine, and 36% with 500 mg lamotrigine. Seizure frequency decreased by > or = 50% in one-third of the 500-mg group and one-fifth of the 300-mg group. Reductions in seizure frequency and seizure days were statistically significant, compared with placebo, for the 500-mg group but not the 300-mg group. Most adverse events were minor and resolved over time. Nine percent of patients on lamotrigine withdrew because of adverse experiences. Lamotrigine plasma concentrations appeared to be a linear function of dose, and the drug did not affect plasma concentrations of concomitant antiepileptic drugs. Lamotrigine was safe, effective, and well tolerated as add-on therapy for refractory partial seizures.

Current role of electroencephalography in cerebral ischemia

BACKGROUND

The electroencephalogram has been largely supplanted by neuroimaging techniques for the diagnosis and localization of ischemic stroke. However, because of its close correlation with cerebral metabolism and its ability to detect brief transient alterations in cortical function, the electroencephalogram may still be useful for certain diagnostic applications in stroke.

SUMMARY OF REVIEW

The relation of electroencephalographic phenomena to cerebral blood flow and metabolism is reviewed. Ten clinical questions that can be addressed by the electroencephalogram in patients with stroke are posed. The presence of seizures, confirmation of diagnosis, intraoperative monitoring, and level of consciousness are areas of proven usefulness. The electroencephalogram provides less worthwhile information about the time course, prognosis, and localization of strokes. Computerized techniques are of potential but unproven value.

CONCLUSIONS

The electroencephalogram retains a worthwhile place in the evaluation of patients with cerebral ischemia when it is used to answer specific questions. All patients with strokes do not need electroencephalograms, but the test can provide uniquely useful data in some.

Felbamate monotherapy for partial-onset seizures: an active-control trial

We evaluated felbamate (FBM) monotherapy in 111 patients with uncontrolled partial-onset seizures in a multicenter, double-blind, parallel-group trial. During the 56-day baseline period, patients had at least eight partial-onset seizures and received one standard antiepileptic drug (AED) at a therapeutic level; a second AED was allowed if at a subtherapeutic level. Patients received either FBM 3,600 mg/d or valproate (VPA) 15 mg/kg/d. The baseline AED at therapeutic levels was discontinued by one-third decrements on study days 1, 14, and 28 and the sub-therapeutic AED, if any, was discontinued completely on study day 1. Study endpoints were completion of 112 study days or fulfilling one or more escape criteria. Criteria for escape relative to baseline were (1) twofold increase in monthly seizure frequency, (2) twofold increase in highest 2-day seizure frequency, (3) single generalized tonic-clonic seizure (GTC) if none occurred during baseline, or (4) significant prolongation of GTCs. The primary efficacy variable was the number of patients in each treatment group who met escape criteria. Thirty-seven patients on VPA and 18 on FBM met escape criteria (p < 0.001). Even when we considered FBM dropouts to have fulfilled escape criteria and VPA dropouts to have completed the 112-day trial, the treatment difference remained statistically significant (p = 0.039) in favor of FBM. Adverse experiences with FBM were all mild or moderate in severity. The frequency of adverse experiences was much lower during monotherapy. FBM monotherapy was effective in the treatment of partial-onset seizures with or without secondarily generalized seizures and demonstrated a favorable safety profile.

Magnetic resonance imaging in childhood intractable partial epilepsies: pathologic correlations

We conducted a retrospective single-blind study assessing the value of MRI in 44 children surgically treated for partial epilepsy, and correlated the MRI findings with the pathology in all cases. MRI revealed abnormalities in concordance with the clinical and electroencephalographic data in 84% of patients. Developmental neuronal migration pathology was present in 25% of patients and was relatively more common in the sensorimotor cortex. There was hippocampal sclerosis in 50% of patients with temporal lobe resection; however, only two of the 10 children with hippocampal sclerosis were below the age of 12 years. Similarly, ganglio-glial tumors were more common than astrocytomas in children below age 12. These results indicate that MRI is sensitive in the detection of pathologic abnormalities in most pediatric candidates for epilepsy surgery, and that the distribution and type of pathology appear to be age related in this population.

Predictive value of magnetic resonance imaging in temporal lobe epilepsy surgery

The predictive value of magnetic resonance imaging (MRI) was assessed by a prospective study of 34 patients selected for surgical treatment of temporal lobe epilepsy. The MRIs were interpreted using standardized visual diagnostic criteria and the imaging findings were correlated with the surgical outcome. Lateralized MRI abnormalities were found in 25 (74%) of 34 patients. Significant associations were found between either the presence of a restricted foreign-tissue lesion or hippocampal atrophy and an excellent surgical outcome. An abnormal MRI had an 82% predictive value and a normal MRI had a 56% predictive value for surgical success. A history of febrile convulsions and the presence of hippocampal atrophy best predicted outcome (predictive value, 86%). These results suggest that specific MRI findings in candidates for temporal lobe epilepsy surgery are predictive of surgical outcome. The information provided by MRI may be of value for counseling patients prior to surgical intervention.

Ictal EEG wave forms from epidural electrodes predictive of seizure control after temporal lobectomy

Ictal wave form characteristics--frequency, spatial distribution, and duration--were analyzed for 140 complex partial seizures recorded from epidural strip electrodes implanted in 28 patients. None had abnormalities on imaging studies. All had bilateral electrode placements, unilateral seizure onsets, temporal lobectomies, and were followed for a mean of 33 months postoperatively. Sixteen patients (57%) became free of complex partial seizures: 12 had reductions in seizure frequency of at least 50% but were not seizure-free. The only predictor of the seizure-free state was the presence of low voltage fast activity (LVF), in the alpha or beta ranges, localized to one gyrus. This phenomenon occurred in 14/16 seizure-free patients, 2/12 of others (P < 0.001). As seizures progressed, LVF typically increased in amplitude, propagated, and slowed into the theta range. Wave forms were classified into 8 categories based upon their frequency and morphology. Stepwise discriminant analysis of these wave forms, with consideration of whether they were localized or regional, revealed that both frequency and localization were critical for the post-surgical prognosis. The mere presence of a localized seizure onset was unreliable unless the wave form was taken into account. Well-localized rhythmic activity over 8 Hz at seizure onset from epidural subtemporal electrodes predicts surgical success. Slower rhythms imply greater separation in space and time from seizure onset.

Antiepileptic drug treatment after temporal lobe epilepsy surgery: a randomized study comparing carbamazepine and polytherapy

Temporal lobectomy is an effective treatment in selected patients with medically intractable temporal lobe epilepsy (TLE). Postoperative antiepileptic drug (AED) treatment guidelines have not been established, and patients are often treated with polytherapy postoperatively. We prospectively randomized 40 patients undergoing temporal lobectomy to monotherapy with carbamazepine (CBZ, 20) or to continuation of their presurgical polytherapy (20) to assess the efficacy and safety of each regimen during the first year after operation. No significant differences between groups were noted with respect to seizure recurrence rate and type or time of recurrence. Patients in the polytherapy group had a 30% incidence of drug-related side effects as compared with only 10% in the CBZ group. These results suggest that after temporal lobectomy for intractable epilepsy, patients can be safely treated with CBZ monotherapy and that treatment with multiple AEDs is not necessary.

Lateralization of epileptic foci by magnetic resonance imaging in temporal lobe epilepsy

A retrospective single-blind study was carried out to assess the reliability of magnetic resonance imaging (MRI) for determining lateralization of the electrographic focus in 45 patients with intractable temporal lobe epilepsy. With strictly defined MRI diagnostic criteria, the electroencephalographic (EEG) focus was correctly lateralized in 86% of patients. Excluding patients with structural lesions, the criteria provided for correct lateralization of the epileptogenic focus in 78% and false lateralization in 5%. Hippocampal atrophy on T1-weighted images and increased signal intensity from mesial structures on T2-weighted scans were highly reliable for lateralization. Postoperative outcome did not differ between the patients with normal and those with abnormal findings on MRI, but the group sample was inadequate to assess the issue of surgical outcome. These findings suggest that with appropriate techniques and strictly defined diagnostic criteria, MRI can provide reliable seizure lateralization in patients with intractable temporal lobe epilepsy.

Electroencephalographic correlations of extracranial and epidural electrodes in temporal lobe epilepsy

Thirty patients with medically intractable complex partial seizures of temporal lobe origin, but no structural abnormalities on neuroradiologic investigations, had both extracranial (scalp) and epidural EEG recordings. Fifteen patients (50%) had localized, unilateral, ictal, scalp EEGs, but one of these had bilateral independent temporal seizure onset according to epidural recordings. Of the 15 patients in whom scalp EEGs were non-localizing, 12 had well-localized epidural ictal EEGs, and 3 had multifocal or bilateral independent temporal ictal recordings. Epidural recordings provide information for determination of site of onset of temporal lobe seizures in selected patients.

Cortical dysplasia in temporal lobe epilepsy: magnetic resonance imaging correlations

Cortical dysplasia has been documented in histological specimens surgically removed for treatment of refractory temporal lobe epilepsy. We studied 10 patients with cortical dysplasia and complex partial seizures who underwent temporal lobectomy. Magnetic resonance imaging revealed abnormalities in 5 of the patients who had microscopically detectable major abnormalities. Magnetic resonance imaging revealed an abnormal cortical-white matter architectonic pattern in 2 patients with moderate cortical dysplasia. In the remaining 3 patients, magnetic resonance imaging findings were unremarkable. These observations suggest that magnetic resonance imaging is sensitive in the detection of certain dysplastic lesions in temporal lobe epilepsy. Preoperative identification of these abnormalities by magnetic resonance imaging may permit early and optimal surgical treatment in patients with refractory epilepsy.

Surgical treatment of epilepsy: initial results based upon epidural electroencephalographic recordings

We describe our initial results in 50 consecutive patients who had investigation for possible surgical treatment of intractable focal epilepsy. Forty-three were investigated using intracranial epidural or foramen ovale electrodes. Forty-five had cortical resection (43 temporal, one frontal, and one parietal). Thirty-two patients who had resection have been followed up for 6 months to 4 years, and 29 (90%) have had good results. Our findings suggest that epidural recordings are valuable in patients with epilepsy who are being considered for surgical resection. They offer an alternative to depth intracerebral investigations in the majority of patients.

Seizures after primary intracerebral hemorrhage

We followed 123 patients with primary intracerebral hemorrhage (ICH), defined as bleeding without known precipitating cause except hypertension, for an average of 4.6 years or until death in order to determine the incidence, prevalence, and type of epileptic seizures. Twenty-five percent had seizures. In one-half of these, the seizures began within 24 hours of the hemorrhage. Survival table analysis predicted a potential cumulative seizure incidence of 50%, had all patients survived 5 years. Seizure incidence was high with bleeding into lobar cortical structures (54%), low with basal ganglionic hemorrhages (19%), and zero with thalamic hemorrhages. Within the basal ganglia, caudate involvement predicted seizures; within the cortex, temporal or parietal involvement predicted seizures. Although seizure incidence was high, prevalence of chronic epilepsy was much lower: 13% in 30-day to 2-year survivors and 6.5% in 2- to 5-year survivors. Seizure incidence is higher than previously reported after ICH because small lobar hemorrhages are the most epileptogenic and are now easily recognized with computed tomography.

Patterns of EEG frequency content during experimental transient ischaemia in subhuman primates

EEGs were recorded with depth electrodes in 8 monkeys undergoing transient middle cerebral artery ligation. Electrodes measured EEG, cerebral blood flow (CBF), and tissue oxygen simultaneously during and after occlusion. An EEG frequency analysis was performed. Electrode sites were examined microscopically, and infarction size, tissue vacuolization index, and neuronal morphology were described quantitatively. Serial neurological examinations were performed. Two patterns of EEG frequency change were delineated, dependent upon degree of ischaemia. Mild ischaemia, as indicated by less severe clinical deficits, higher CBF during occlusion, and minor pathological changes was associated with large increases in slow EEG activity and decreases in fast EEG activity during occlusion, with recovery of slow activities to baseline, but continued suppression of fast activities 24 h later. Severe ischaemia was associated with suppression of both fast and slow frequencies during occlusion, with slow activities returning to baseline and fast activities remaining suppressed 24 h later. The best quantitative EEG indicator of severity of ischaemia was suppression of slow wave activity during occlusion. The best EEG indicator that an ischaemic event had occurred 24 h previously was continued suppression of fast EEG activities. These data may be helpful in the design of EEG frequency analysis studies for monitoring the time course of human cerebral ischaemia and for retrospective diagnosis of transient ischaemic attacks (TIAs).

Methaqualone withdrawal syndrome with photoparoxysmal responses and high-amplitude visual evoked potentials

Methaqualone is a sedative hypnotic that is often abused. Tolerance and habituation may develop, and the withdrawal syndrome may include seizures. In the patient studied, methaqualone withdrawal was manifested by myoclonic and tonic-clonic seizures, an EEG photoparoxysmal response (PPR), and a high-amplitude visual evoked potential (VEP) to pattern-reversal stimuli. The EEG and VEP returned to normal after resolution of the withdrawal state. Substance withdrawal should be considered in the differential diagnosis of PPR or of an unusually high-amplitude VEP in a person with no previous history of epilepsy. Disappearance of these phenomena may be a useful indicator of the end of the withdrawal state.

Self-induced photosensitive absence seizures with ictal pleasure

A 32-year-old woman was treated for self-induced photosensitive seizures that included strong subjective feelings of pleasure and masturbatory behavior. Electroencephalograms demonstrated generalized polyphasic spike-wave discharges in response to stroboscopic stimulation. The behavioral sequences leading to seizures and the effects of treatment can be explained in terms of operant conditioning theory. Data from human and animal studies indicate a correlation between ictal pleasure or reinforcement and the subject's ability to induce seizures. Ictal pleasure is rare in spontaneous seizures that are not under the control of the patient.

Brainstem auditory evoked responses in brainstem infarction

Brainstem auditory evoked responses (BAERs) were recorded in 40 patients with clinically definite brainstem infarction, and results were compared to localizations from physical signs and CT scans. The BAER was abnormal in 92% of patients with evidence on physical examination of dysfunction of lateral structures in the pons or midbrain. Normal BAERs were seen with medially-situated or medullary lesions. When both rostrocaudal level and lateralization were considered, the BAER indicated damage in additional areas not evident on physical examination in 25% of patients. However, physical signs indicated damage in areas not reflected by the BAER in 22% of patients. Therefore, the BAER complements the localization obtained from physical findings. BAERs were abnormal in more of these patients than were CT scans, and thus are useful for confirmation of bedside impressions.