Bilateral Thalamic Blood Flow Activation Predicts Long-Term Efficacy of Vagus Nerve Stimulation
Abstract number :
L.07
Submission category :
Year :
2001
Submission ID :
2025
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
T.R. Henry, MD, Neurology, Emory University, Atlanta, GA; J.R. Votaw, PhD, Radiology, Emory University, Atlanta, GA; R.A. Bakay, MD, Neurosurgery, Emory University, Atlanta, GA; P.B. Pennell, MD, Neurology, Emory University, Atlanta, GA; C.M. Epstein, MD,
RATIONALE: Vagus nerve stimulation (VNS) causes activation and de-activation of synaptic activities at multiple sites in the brainstem and both cerebral hemispheres. We previously reported that acute activation of thalamic blood flow is most strongly associated with improved seizure control during chronic VNS. We now compare sites of VNS-induced blood flow alteration, after chronic VNS, with anti-seizure efficacy.
METHODS: Positron emission tomography (PET), with intravenous [oxygen-15]water, measured brain blood flow in 11 consenting partial epilepsy patients. Each had 3 control scans without VNS and 3 scans during 30 seconds of VNS, within 20 hours after VNS began (acute study), and repeated after 3 months of VNS (chronic study). After intrasubject subtraction of control from stimulation scans, images were anatomically transformed for intrasubject averaging, and superimposed on MRI for anatomical localization. T-statistical mapping established relative blood flow increases and decreases for each patient. Percent changes in frequency of complex partial seizures (with or without secondary generalization) during 12 months of VNS compared with pre-VNS baseline, and T-thresholded blood flow changes, were rank ordered across patients. Spearman rank correlation coefficients assessed associations of seizure-frequency change and T-thresholded blood flow change.
RESULTS: Acute and chronic PET studies usually showed similar VNS-induced blood flow increases over the right postcentral gyrus, and bilateral thalami, hypothalami, inferior cerebellar hemispheres, and inferior parietal lobules. Acute PET studies usually showed VNS-induced decreases in bilateral hippocampal, amygdalar and cingulate blood flow, and increased bilateral insular blood flow; these regions rarely had significant VNS-induced blood flow changes during chronic studies. Individual seizure frequency changes ranged from 12% increase to 91% decrease over one year. On chronic VNS PET studies, only the right and left thalami showed significant associations of blood flow change with seizure-frequency change. Decreased seizures correlated with increased right and left thalamic blood flow (p [lt] 0.001).
CONCLUSIONS: Over one year of VNS, seizure control improved most in patients who had bilateral thalamic activation induced by VNS on chronic PET studies. These results support earlier evidence, on acute VNS-activation PET studies, that altered thalamic processing contributes to anti-seizure effects of VNS.
Support: Cyberonics, Inc.
Disclosure: Grant - Cyberonics, Inc.; Consulting - Cyberonics, Inc.; Honoraria - Cyberonics, Inc.