Brain stimulation in the treatment of epilepsy

Evolution in practice: how has British neurosurgery changed in the last 10 years?

INTRODUCTION

Neurosurgery is a fast-evolving surgical subspecialty driven by technological advances, socio-economic factors and patient expectations. In this study, we have compared the work-load volume in a single institution in the years of 1994 and 2004 and commented on the possible reasons for the changes and the impacts they may have for the future.

PATIENTS AND METHODS

A retrospective, log-book review of all operations performed in the years 1994 and 2004 in a single, tertiary, neurosurgical centre was performed.

RESULTS

Neurosurgical practice has evolved over this period. Current practice has moved away from clipping of aneurysms and towards coil embolisation performed by interventional radiologists. Electrode stimulation of deep brain regions for movement disorders is the current practice, whereas 10 years ago the same disorders were dealt with by lesioning of the relevant regions. In spinal neurosurgery, instrumentation is increasingly favoured currently. In the field of neuro-oncology, current practice favours minimal access to the target area by the use of stereotactic localisation.

CONCLUSIONS

Changes were most pronounced in the subspecialties of vascular, functional and spinal neurosurgery within this 10-year period. Knowledge of such dynamics is valuable in health resource management as well as planning for neurosurgical training programmes.

Effects of high-frequency stimulation on epileptiform activity in vitro: ON/OFF control paradigm

PURPOSE

To determine the effects of high-frequency electrical stimulation on electrographic seizure activity during and after stimulation (ON-effect and OFF-effect).

METHODS

The modulation and suppression of epileptiform activity during (ON-effect) and after (OFF-effect) high-frequency electrical stimulation was investigated using the high-K(+) and picrotoxin hippocampal slice epilepsy models. Uniform sinusoidal fields (50 Hz) were applied with various intensity levels for 1 min across brain slices. Extracellular and intracellular activity were monitored during and after stimulation.

RESULTS

The ON-effects of high-frequency stimulation were highly variable across individual slices and models; ON-effects included modulation of activity, pacing, partial suppression, or activity resembling spreading-depression. On average, epileptic activity, measured as power in the extracellular fields, increased significantly during stimulation. Following the termination of electrical stimulation, a robust poststimulation suppression period was observed. This OFF suppression was observed even at relatively moderate stimulation intensities. The duration of OFF suppression increased with stimulation intensity, independent of ON-effects. Antagonism of GABA(A)function did not directly effect OFF suppression duration.

CONCLUSIONS

The present results suggest that "rational" seizure control protocols using intermittent high-frequency electrical stimulation should control for both ON and OFF effects.