PEDIATRICS Vol. 108 No. 1 July 2001, pp. 221

Vagal Nerve Stimulation in the Epileptic Encephalopathies: 3-Year Follow-Up

To the Editor.

We have reported the effect of vagal nerve stimulation (VNS) in children with cryptogenic epileptic encephalopathies (EE) over the first 2 years of therapy. Although results were poor in the first year, there were significant improvements in the second.¹ We now report the effect of VNS on seizure severity, frequency, and quality of life (QOL) in the same group of children during their third year of treatment.¹

Inclusion/exclusion criteria, implant technique, and use of the Welcome QOL assessment (including seizure severity) were as previously described.¹ Seizure frequency was recorded for at least an 8-week baseline period before and for 1 year after implant. Recording was continued throughout the first year and then resumed for at least an 8-week period at the end of the second and third years. Stimulation commenced at 0.25 ma for 30 out of every 360 seconds. Output was increased to a maximum of 2.0 ma at the end of the first year. At that point 6 children were put on to more rapid cycling due to inefficacy. Only 1 child continued on this in the third year. The remaining children continued on the conventional settings at 1.25-2.75 ma into the third year. In addition, we review antiepileptic drug (AED) usage.

Sixteen children were studied. One device was removed immediately after implant. Of the remaining 15 children, 2 have had their devices inactivated due to inefficacy, 1 has not completed the assessment, and in 1 seizure recording has become unreliable. In the remaining 11 children, seizure frequency was unchanged compared to baseline (P = .593) as was seizure severity (P = .654). QOL was not improved in any domain (P values between .118 and .678). AED dosage had either been increased or a new drug introduced in 7 children, decreased in 2, and there was no change in 2.

Reduction in seizure frequency was not significant during the first year of treatment, but it was by the end of the second year. The third-year results were poorerno improvement in seizure frequency, severity, or QOL. The number of AEDs had only been decreased in 2 of the children remaining on VNSan aim stated by the majority of parents prior to treatment.

The deterioration may have been a consequence of the natural history of the epilepsies, changes in impedance at the electrodes, habituation to either VNS, or AEDs. The majority of the children in our study were treated once the EE had been established for many years. These children are at the severest end of the spectrum of both epilepsies and EE. There is a need for additional studies of VNS versus the newer AEDs in both EE and partial seizures.

Alasdair P.J. Parker, MD^*
Charles E. Polkey, MD
Richard O. Robinson, FRCPCH^*
* Newcomen Centre
Guy's Hospital
London, SEI 9RT, United Kingdom
 King's College Hospital
Denmark Hill
London, SE5 9RS, United Kingdom

REFERENCE

1. Parker APJ, Polkey CE, Binnie CD, Madigan C, Ferrie CD, Robinson RO Vagal nerve stimulation in epileptic encephalopathies. Pediatrics. 1999; 103:778-782 [Abstract/Free Full Text]