Correlation of Cerebral Blood Flow Changes Induced by Acute and Chronic Vagus Nerve Stimulation and Therapeutic Outcome, a SPECT Activation Study.
Abstract number :
1.226
Submission category :
Year :
2001
Submission ID :
2854
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
K. Vonck, MD, Neurology, Ghent University Hospital, Gent, Belgium; K. Van Laere, MD, PhD, Nuclear Medicine, Ghent University Hospital, Gent, Belgium; J. De Reuck, MD, PhD, Neurology, Ghent University Hospital, Gent, Belgium; R. Dierckx, MD, PhD, Nuclear M
RATIONALE: The mechanism of anti-seizure activity of vagus nerve stimulation (VNS) remains to be clarified. In this study SPECT was used to evaluate VNS-induced acute and chronic cerebral blood flow (CBF) changes.The results were correlated with clinical outcome during long-term follow-up.
METHODS: 23 patients (12F,11M) with mean age of 32 years (range: 9-47 years) and mean duration of complex partial seizures of 21 years (range: 3-44 years) were treated with VNS. Seizure frequency was assessed every three months. Average follow-up was 19 months (range: 6-48 months). All patients underwent a split-dose 99m-Tc-ECD activation study before (baseline condition) and immediately after (acute activation condition) the initial stimulation train (0.5 mA, 30sec) on a high resolution triple head gamma camera. Ten patients also underwent an activation study, 6 months after implantation, with an additional stimulation train (0.25 mA, 30 sec) (chronic activation condition). Data were analyzed using an automated semiquantitative volume-of-interest analysis after stereotactic anatomical Talaraich standardization.
RESULTS: VNS in the acute activation condition induces left-sided thalamic (p=0.007) and right-sided amydalar, parahippocampal, hippocampal and occipital hypoperfusion (p[lt]0.011). In a subgroup of patients, the degree of right amygdalar hypoperfusion was correlated with good outcome at maximal follow-up. Both thalami, medial temporal lobe structures and the left caudate were hypoperfused in patients after 6 months of VNS when compared to baseline condition (-3.8 to -5.4 %). Right hippocampal and amydalar hypoperfusion was significantly correlated with favourable clinical outcome. (p=0.018). In the chronic activation condition a significant left-sided thalamic hyperperfusion was found (p[lt]0.001).
CONCLUSIONS: VNS produces different cerebral flow changes in both acute and chronic activation conditions.The mechanism of long-term efficacy may be based mainly on medial temporal and thalamic inhibition. Medial temporal hypoperfusion may be predictive of favorable long-term outcome.
Support: Funded by a grant from the F.W.O.-Flanders and the Ghent University Hospital Clinical Epilepsy Grant 1999-2001.