Motor Cortex Excitability in Epilepsy Patients Treated with Vagus Nerve Stimulation
Abstract number :
1.129
Submission category :
Year :
2001
Submission ID :
3037
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
A.C. Dean, MD, PhD, Neurology, New York Weill Cornell Medical Center, New York, NY; A.T. Wu, MD, Neurology, New York Weill Cornell Medical Center, New York, NY; F.T. Burgut, MD, Neurology, New York Weill Cornell Medical Center, New York, NY; D.R. Labar, M
RATIONALE: Vagus nerve stimulation (VNS) has demonstrated efficacy in the treatment of epilepsy. To investigate the neurophysiologic mechanism of action of VNS in human subjects, we studied the effect of VNS on motor cortex excitability.
METHODS: Motor cortex excitability was assessed by measuring resting motor threshold (RMT) and the cortical silent period (C-SP) in response to transcranial magnetic stimulation (TMS). The duration of the C-SP produced by a single magnetic pulse at 120% of RMT was measured in the maximally contracted abductor pollicis brevis. Subjects were epilepsy patients exposed to VNS for 6 to 12 months. Each subject was tested during active VNS (ON) and one hour after VNS was turned off (OFF). We compared RMT and C-SP for each subject in the ON versus OFF conditions.
RESULTS: There was a trend towards increasing RMT in patients in the ON vs. OFF conditions. C-SP duration was significantly prolonged in patients with VNS ON. In one subject the C-SP duration in the ON condition was 67% longer than that seen with VNS OFF. The magnitude of these C-SP differences may be directly correlated with clinical response to VNS.
CONCLUSIONS: Motor cortex excitability is altered in response to VNS. This was reflected in increased RMT and C-SP duration during active VNS. This finding suggests potential mechanisms by which VNS may suppress epileptic seizures.
Support: Cyberonics, Inc.
Disclosure: Grant - Cyberonics, Inc. Honoraria - Cyberonics, Inc.