Surgical technique for the insertion of grids and strips for invasive monitoring in children with intractable epilepsy.

Despite improved imaging, and electrical and magnetic external mapping, there are a large number of children with intractable epilepsy in whom a focus cannot be defined by non-invasive techniques. Invasive monitoring with depth electrodes, electrode grids and/or strips is required in up to 50% of children with a suspected focal seizure disorder. In children with suspected temporal lobe epilepsy the invasive techniques are required to identify which temporal lobe is the primary focus, to separate temporal from frontal foci, and to define the extent of involvement of the lateral temporal cortex. In children and infants with non-temporal epilepsy, invasive monitoring is required to define the epileptogenic zone and to map areas of cortical specialization. The current techniques used for surgical implantation are described here. In a correctly selected population invasive monitoring will define the epileptogenic focus or foci in 90% of children; 80% will have surgically treatable epilepsy. Infection rates are less than 1% for subdural strips and 6% for grids. In 88 cases no incidence of meningitis occurred.

Surgical treatment of focal epilepsy in children: results in 37 patients.

This report concerns 37 children and teenagers operated upon for intractable seizures between 1990 and 1994. Follow-up is at least 3 years. Fourteen children underwent pure temporal lobe resections; 71% are seizure free, and 93% have a better than 90% decrease in seizure frequency. The presence of a lesion on magnetic resonance imaging, the side of the lesion, or the presence of abnormal pathology had no influence on the result of resection. 28% of the children who had extratemporal resections are seizure free, and 83% have a greater than 90% decrease in seizure frequency. There was a trend to better results in those with a lesion on magnetic resonance imaging. In the small group with temporal plus extratemporal foci, the results were poor with only 60% showing a greater than 90% reduction in seizure frequency.

Significance of mesial temporal atrophy in relation to intracranial ictal and interictal stereo EEG abnormalities.

We studied 31 consecutive patients with temporal and extratemporal epilepsy who underwent presurgical evaluation with stereotaxic depth EEG (SEEG) to assess the relationships between amygdalo-hippocampal (AM-HF) atrophy and the location of SEEG seizure onset and SEEG interictal abnormalities. Scalp EEG recordings with sphenoidal electrodes had shown bitemporal ictal or interictal epileptic abnormalities in all. Patients underwent high quality MRI scans, including MRI volumetric measurements of mesial temporal structures. None had foreign tissue lesions. The final conclusions of the SEEG investigation coincided with the lateralization obtained by MRI volumetric measurements in the eight patients who had significant unilateral atrophy of the amygdala, hippocampus or both (> 2 SD below the mean of controls). In these patients with unilateral atrophy, all or > 75% of clinical seizures originated from the atrophic side. The seven patients with bilateral, but significantly asymmetrical, mesial atrophy had bilateral seizure onsets with > 70% originating from the more atrophic side in four, from the less atrophic side in two, and without predominance in one. The one patient with severe bilateral symmetrical atrophy had seizures originating equally from both sides. Five patients had no atrophy on MRI, but depth electrodes revealed predominant unilateral ictal temporal onsets in four of them. There was no significant correlation between the frequency of SEEG interictal spikes and the amount of AM-HF atrophy. However, we found a significant correlation between the severity of SEEG background disturbance in AM and HF and the degree of atrophy of these structures. Patients with unilateral atrophy were more frequently free of seizures after surgery than those with bilateral or no atrophy (P < 0.05). We conclude that unilateral mesial atrophy predicts ipsilateral mesial SEEG seizure onset despite bitemporal extracranial EEG foci. However, in patients with significant bilateral mesial atrophy, SEEG seizures may originate from either side, even in the presence of significant asymmetry. Finally, the identification of unilateral mesial atrophy has prognostic importance.

Naltrexone blocks the enhancing effect of novel experiences on performance in memory tests in humans.

Two experiments were carried out in healthy human volunteers in order to investigate the effect of novel experiences on retrieval, and the influence of naltrexone thereupon. Naltrexone (50 mg) and placebo (50 mg of starch) were given orally using a double blind design. In Experiment 1, the subjects were asked, on two consecutive days, to recall well-known facts or events, and to recall the year in which major events took place. On Day 2, some subjects were, and others were not, exposed to a nonsense text prior to testing, which was viewed as a novel experience by the subjects. Exposure to the text was followed by enhanced scores in both memory tests. The effect was blocked by naltrexone, but not by the placebo, given 1 hr prior to the novel experience; the treatments had no effect of their own in subjects unexposed to the nonsense text. In Experiment 2, the memory tests were the recognition of famous faces, and the dates test (see above); and the novel experience was being taken for 5 min to a room where they had never been before. Again, the novel experience was followed by increased scores in both memory tests in the untreated and placebo groups, but not in the naltrexone treated subjects. These results confirm previous findings on memory enhancement by pre-test exposure to novel experiences, and suggest that endogenous opioid, or at least naltrexone-sensitive, mechanisms are involved in the effect.