Bitemporal intractable epilepsy: could it be surgically treatable?.

BACKGROUND: The goal of this study is to retrieve the attention to the treatment opportunities for this cohort of intractable bitemporal epilepsy patients who in most cases are not considered optimal candidates for surgery. OBJECTIVES: The purpose of this study is to demonstrate that electrophysiologically guided precise surgeries on both temporal lobes can have a beneficial effect on seizures without additional cognitive decline. METHODS: Twenty-one intractable bitemporal epilepsy patients [13 men, 8 women, mean age 21 years (range 6-43), mean duration of illness 17 years (range 3-31), frequency of seizures 6-55 per month] underwent stereotactic cryosurgery on both temporal lobes guided by chronic and intraoperative depth electrode studies. RESULTS: Class I ('free of disabling seizures') outcome was achieved for 11/21 (52%), class II ('rare seizures') for 6/21 (29%), and class IV ('no worthwhile improvement') for 4/21 (19%) patients. No worsening of seizure or clinically significant cognitive or memory impairments were observed in this cohort of patients (follow-up 5-10 years). CONCLUSIONS: The minimally invasive precise surgeries on both temporal lobes confined to the removal/lesion of just the brain tissue that exhibited epileptic activity can have a beneficial effect on seizure frequency and severity without additional devastating declines in intelligence, learning and memory.

Mutually suppressive interrelations of symmetric epileptic foci in bitemporal epilepsy and their inhibitory stimulation.

OBJECTIVES: The goal of this study is to analyze the suppressive interaction of symmetric temporal lobe epileptic foci, assess some failures of epilepsy surgery, and evaluate the possibility of terminating focal seizures with stimulation of symmetric epileptic foci. MATERIALS AND METHODS: One hundred and twenty-nine intractable epilepsy patients (age range 6-53 years) with bitemporal epileptiform abnormalities in multiple scalp EEGs were evaluated with chronically implanted depth and subdural electrodes. Interelectrode coherence and power spectra were studied using internally developed software. RESULTS: Bitemporal epileptic foci were found in 85/129 (66%) patients with reciprocal relations between these foci in 57/85 (67%) patients. Temporal lobectomy was performed for 67/85 patients. 12/67 patients became free of seizures (Engel's Class I), 32/67 improved (Classes II and III), and 23/67 did not improve. 14/23 patients demonstrated post-surgical activation of the contralateral temporal lobe epileptic focus. For 8/14 of these patients, the stereotactic cryoamygdalatomy was performed in the temporal lobe contralateral to the first surgery. 5/8 patients became free of seizures. It was found that stimulation of temporal lobe deep epileptic focus may terminate focal seizures in the contralateral symmetric structures. CONCLUSION: A mutually suppressive relationship is one of variants of the interaction of symmetric epileptic foci. Some epilepsy surgery failures may be a result of post-surgical activation of the intact focus. The increase of coherence between both temporal lobes before the seizure onset of the seizure suggests the establishment of functional interrelations between two epileptic foci at an early, "hidden" phase of seizures, and may predict the direction of seizure spread. Mutually suppressive interrelations of symmetric epileptic foci might be employed for chronic therapeutic stimulation.

Electrophysiological effects and clinical results of direct brain stimulation for intractable epilepsy.

OBJECTIVE: Epilepsy can be considered as a result of the imbalance of the excitatory and inhibitory processes. Therefore, the artificial enhancement of the activity of brain inhibitory mechanisms might lead to a beneficial therapeutic effect for intractable epilepsy patients. MATERIAL AND METHODS: Studies of the inhibitory effects of electrical stimulation of the head of the caudate nucleus (HCN), cerebellar dentate nucleus (CDN), thalamic centromedian nucleus (CM), and neocortical and temporal lobe mesiobasal epileptic foci were performed on 150 patients with implanted intracerebral electrodes. Chronic brain stimulation with implanted neurostimulators was performed on 54 patients. Sixteen were followed up to 1.5 years (mean 1.2 years). RESULTS: The study demonstrated that 4-8 Hz HCN and 50-100 Hz CDN stimulation suppressed the subclinical epileptic discharges and reduced the frequency of generalized, complex partial, and secondary generalized seizures. CM stimulation (20-130 Hz) desynchronized the EEG and suppressed partial motor seizures. Direct subthreshold 1-3 Hz stimulation of the epileptic focus may suppress rhythmic afterdischarges (ADs). Seizures were eliminated for 26 of 54 patients (48%), worthwhile improvement was achieved for 23 of 54 patients (43%), and no improvement was observed in 5 of 54 patients (9%). CONCLUSION: The artificial increase of the activity of brain inhibitory system may suppress the activity of epileptic foci, and, in long run, stabilize this epileptic foci activity at a lower, perhaps normal, level. Therapeutic direct brain stimulation, therefore, might serve as a useful tool in the treatment of intractable and multifocal epilepsy, and might be combined with ablative surgical methods.