Abstracts

Vagus Nerve Stimulation (VNS) was approved by the FDA in 1997 as adjunctive therapy in refractory epilepsy patients with partial-onset seizures older than 12 years. Only limited published data regarding its use in younger children and other epilepsy syndromes is available.
We have reviewed our experience with VNS therapy in pre-adolescent children with medically intractable epilepsy. We identified 22 patients under 12 years of age among the 181 consecutive patients with intractable epilepsy, who underwent VNS implantation at our institution during 1997-2003. These patients did not qualify for resective epilepsy surgery (2 had failed previous surgery).
Charts were reviewed for pre- and postoperative seizure types and frequency, epilepsy diagnosis, MRI, EEG and seizure semiology, antiepileptic drugs, magnet settings, and side effects. All patients had at least one baseline assessment within 4 to 8 weeks before surgery. Minimal follow-up was 6 months post-implantation. Nonparametric statistical analysis using the Wilcoxon signed ranks test was performed. Complete pre- and post-VNS data were available for 21/22 pre-adolescent patients. Median age at implantation was 8 years (range from 2.3 to 11 years) and median duration of epilepsy 6.1 years (1.9 to 10.6 years). Median age at onset of epilepsy was 9 months (range from birth to 8.7 years). Follow-up intervals extended to 12 months in 17/21, 24 months in 11/21, 36 months in 8/21 and 48 months in 6/21 patients.
Six children had focal epilepsy and 15 had a generalized epilepsy syndrome. Eight children had a normal brain MRI. One had hypothalamic hamartoma and 4 patients had cortical malformation (2 had tuberous sclerosis and 1 lissencephaly). MRI showed generalized volume loss in 5 and nonspecific abnormalities in three. Mild to severe developmental delay was present in all but 1 patient.
Compared to baseline, median seizure frequency reduction at 3 and 6 months was 60% and 71% respectively (n=20, p[lt]0.01). In the setting of declining numbers of patients followed longer, [gt]75% seizure reduction was maintained at 12 (n=17, p[lt]0.01), 24 (n=11, p[lt]0.01), 36 (n=8, p[lt]0.05) and 48 months (n=6, p[lt]0.05). Two patients became seizure-free 6-12 months after implantation. There was no difference in the number of AEDs used before and after VNS. VNS-related side effects were mild and transient. However, three patients developed postoperative wound infection, necessitating explantation of the device in two. VNS therapy is well-tolerated and effective in pre-adolescent children [lt] 12 years with generalized or focal pharmacoresistant epilepsy. Comparing to published series of VNS in adolescents and adults, younger children appear to respond more favorably irrespective of the epilepsy syndrome.