Prospective long-term study of vagus nerve stimulation for the treatment of refractory seizures

PURPOSE

To determine the long-term efficacy of vagus nerve stimulation (VNS) for refractory seizures. VNS is a new treatment for refractory epilepsy. Two short-term double-blind trials have demonstrated its safety and efficacy, and one long-term study in 114 patients has demonstrated a cumulative improvement in efficacy at 1 year. We report the largest prospective long-term study of VNS to date.

METHODS

Patients with six or more complex partial or generalized tonic-clonic seizures enrolled in the pivotal EO5 study were prospectively evaluated for 12 months. The primary outcome variable was the percentage reduction in total seizure frequency at 3 and 12 months after completion of the acute EO5 trial, compared with the preimplantation baseline. Subjects originally randomized to low stimulation (active-control group) were crossed over to therapeutic stimulation settings for the first time. Subjects initially randomized to high settings were maintained on high settings throughout the 12-month study.

RESULTS

The median reduction at 12 months after completion of the initial double-blind study was 45%. At 12 months, 35% of 195 subjects had a >50% reduction in seizures, and 20% of 195 had a >75% reduction in seizures.

CONCLUSIONS

The efficacy of VNS improves during 12 months, and many subjects sustain >75% reductions in seizures.

Vagus nerve stimulation for medication-resistant generalized epilepsy. E04 VNS Study Group

We treated 24 generalized epilepsy patients with vagus nerve stimulation (VNS), comparing seizure rates during a 1-month baseline with 3 months of VNS. Median seizure rate reduction was -46%. Sixteen of the 24 patients had better than a -30% reduction and 11 of the 24 patients had better than a -50% reduction in seizure rate. A mild cough during stimulation occurred in six patients. Patients with higher baseline seizure rates and later ages at epilepsy onset had the best responses to VNS. Our findings suggest VNS is an effective treatment for medication-resistant generalized epilepsy even in patients as young as 4 years.

Magnetic source imaging of abnormal low-frequency magnetic activity in presurgical evaluations of epilepsy

PURPOSE

Regional cortical dysfunction associated with epileptogenic activity was predicted from interictal localized abnormal low frequency neuromagnetic activity (ALFMA) using Magnetic Source Imaging (MSI). ALFMA can be detected in patients who show no interictal spikes.

METHODS

A large array biomagnetometer was used in a blinded, rapid screening protocol. The MSI procedure required no alteration in epileptic medications. MSI results were compared with the presumed epileptogenic region as determined by a consensus of standard techniques, which included MR and electroclinical monitoring.

RESULTS

One or more sites of localized abnormality were detected by MSI ALFMA in 29 of the 33 epileptic patients. ALFMA mapped with MSI showed a 48.5% specificity with respect to the presumed epileptogenic region. MSI ALFMA was in agreement with the final consensus as often as was ictal noninvasive video EEG monitoring, and was exceeded in specificity overall only by invasive ictal video EEG monitoring, which was required for conventional localization in 21 of the 33 patients tested with MSI.

CONCLUSIONS

ALFMA measurements with MSI may augment the array of noninvasive methods used for reaching a consensus for epilepsy surgery.