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We performed a retrospective, multicenter, open-label study to evaluate the efficacy of vagus nerve stimulation (VNS) in all patients in the Czech Republic who have received this treatment for at least 5 years (n=90). The mean last follow-up was 6.6+/-1.1 years (79+/-13 months). The median number of seizures among all patients decreased from 41.2 seizures/month in the prestimulation period to 14.9 seizures/month at 5 years follow-up visit. The mean percentage of seizure reduction was 55.9%. The responder rate in these patients is in concordance with the decrease of overall seizure frequency. At 1 year after beginning the stimulation, 44.4% of patients were responders; this percentage increased to 58.7% after 2 years. At the 5 years last follow-up 64.4% of patients were responders, 15.5% experienced > or = 90% seizure reduction, and 5.5% were seizure-free. A separate analysis of patients younger than 16 years of age showed lower efficacy rates of VNS in comparison to the whole group. Complications and chronic adverse effects occurred in 13.3% of patients. VNS is an effective and safe method to refractory epilepsy in common clinical practice.

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SUMMARYPurpose: To determine the efficacy of gamma knife radiosurgery in the treatment of mesial temporal lobe epilepsy due to mesial temporal sclerosis. Methods: Between November 1995 and May 1999, 14 patients underwent radiosurgical entorhinoamygdalohippocampectomy with a marginal dose of 18, 20, or 25 Gy to the 50% isodose following a standard preoperative epilepsy evaluation. Results: One patient was classified as Engel Class Ib, three were Engel Class IIc, one was Engel Class IIIa, and two were Engel Class IVb in a subgroup of seven patients who were unoperated 2 years prior to the last visit and at least 8 years after irradiation (average 116 months). The insufficient effect of irradiation led us to perform epilepsy surgery on another seven patients an average of 63.5 months after radiosurgery. The average follow-up period was 43.5 months after the operation. Four patients are seizure-free; one is Engel Class IIb and one is Engel Class IId. One patient cannot be classified due to the short period of follow-up. The frequency of seizures tended to rise after irradiation in some patients. Collateral edema was observed in nine patients, which started earlier and was more frequent in those irradiated with higher doses. It had a marked expansive character in three cases and clinical signs of intracranial hypertension were present in three cases. We found partial upper lateral quadrant anopia as a permanent side effect in two patients. Repeated psychotic episodes (two patients) and status epilepticus (two patients) were also seen after treatment. No significant memory changes occurred in the group as a whole. Discussion: Radiosurgery with 25, 20, or 18-Gy marginal dose levels did not lead to seizure control in our patient series, although subsequent epilepsy surgery could stop seizures. Higher doses were associated with the risk of brain edema, intracranial hypertension, and a temporary increase in seizure frequency.

The parahippocampal cortex and hippocampus are brain structures known to be involved in memory. However, the unique contribution of the parahippocampal cortex remains unclear. The current study investigates memory for object identity and memory of the configuration of objects in patients with small thermo-coagulation lesions to the hippocampus or the parahippocampal cortex. Results showed that in contrast to control participants and patients with damage to the hippocampus leaving the parahippocampal cortex intact, patients with lesions that included the right parahippocampal cortex (RPH) were severely impaired on a task that required learning the spatial configuration of objects on a computer screen; these patients, however, were not impaired at learning the identity of objects. Conversely, we found that patients with lesions to the right hippocampus (RH) or left hippocampus (LH), sparing the parahippocampal cortex, performed just as well as the control participants. Furthermore, they were not impaired on the object identity task. In the functional Magnetic Resonance Imaging (fMRI) experiment, healthy young adults performed the same tasks. Consistent with the findings of the lesion study, the fMRI results showed significant activity in the RPH in the memory for the spatial configuration condition, but not memory for object identity. Furthermore, the pattern of fMRI activity measured in the baseline control conditions decreased specifically in the parahippocampal cortex as a result of the experimental task, providing evidence for task specific repetition suppression. In summary, while our previous studies demonstrated that the hippocampus is critical to the construction of a cognitive map, both the lesion and fMRI studies have shown an involvement of the RPH for learning spatial configurations of objects but not object identity, and that this takes place independent of the hippocampus.

Stereotactic amygdalohippocampectomy is a minimally invasive procedure with low morbidity and good results that can be the method of choice in selected patients with MTLE.

The ability to maintain central-gaze fixation was studied in 35 patients with unilateral frontal lobe lesions. The stability of central-gaze fixation was tested in 2 oculomotor tasks requiring the suppression of reflexive saccades triggered by the sudden appearance of novel, peripheral visual stimuli. In the first task ('Instructed'), maintenance of gaze fixation was based on verbal instruction, whereas, in the second task ('Non-instructed'), it was based upon a foveating mechanism maintained by sensory stimulation during the performance of a categorization task. Patients with frontal lobe lesions were classified into 3 groups: a ventrolateral (n = 18), a dorsolateral (n = 10) and a medial (n = 7) group. The control group consisted of 20 healthy subjects. In the Non-instructed task, no group differences were found in the rate of reflexive saccades. Thus, lesions of the frontal lobe did not affect reactivity to extraneous stimuli per se. The only exception to this rule was the group of patients with ventrolateral lesions in the left frontal lobe, in which a higher number of reflexive saccades directed to the contralateral hemifield was observed. In the Instructed task, 2 different patterns of deficit in suppression of reflexive saccades were found. First, a bidirectional deficit was noted in the ventrolateral group, which might be attributed to an impairment in either maintaining a selected program of behaviour 'on-line' or suppressing inappropriate alternatives interfering with that program. Second, a unidirectional deficit in voluntary suppression of reflexive saccades triggered from within the contralateral hemifield was observed in the medial group. It is suggested that this type of deficit may reflect malfunctioning of the supplementary motor area--anterior cingulate system involved in the suppression of externally triggered interfering programs. Finally, no significant impairment was found in the dorsolateral group.

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