title: Investigation into the mechanisms of vagus nerve stimulation for the treatment of intractable epilepsy, using 99mTc-HMPAO SPET brain images.
abstract: Vagus nerve stimulation (VNS) has gained recognition as a treatment for refractory epilepsies where surgical treatment is not possible. While it appears that this treatment is effective in some patients, the mechanism of action is not clearly understood. The purpose of this study was to clarify findings of other positron emission tomography and single-photon emission tomography (SPET) investigations by measuring the acute effect of VNS on patients who have normal cerebral anatomy on magnetic resonance imaging and who have not previously been exposed to VNS. We investigated six subjects (two males and four females, mean age 29.5 years, range 21-39 years) with intractable epilepsy. One patient had primary generalised epilepsy causing generalised tonic-clonic seizures; the remaining five patients had localisation-related epilepsy causing complex partial seizures. SPET imaging was performed using 250 MBq of (99m)Tc-HMPAO and a four-scan paradigm - two with and two without stimulation. The stimulation began at VNS current levels of 0.25 mA and was increased according to the limit of patients' tolerance, usually defined by coughing or discomfort. The stimulating waveform was of continuous square wave pulses of 500 micro s duration at 30 Hz. Image analysis was by SPM99. Reduced perfusion during stimulation was observed in the ipsilateral brain stem, cingulate, amygdala and hippocampus and contralateral thalamus and cingulate. The study provides further evidence of the involvement of the limbic system in the action of vagal nerve stimulation.
authors.affiliation: Department of Clinical Physics, Institute of Neurological Sciences, Southern General Hospital, 1345 Govan Road, Glasgow G51 4TF, UK.
authors.forename: Anna
authors.initials: A
authors.lastname: Barnes
authors.forename: Roderick
authors.initials: R
authors.lastname: Duncan
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Chisholm
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lindsay
authors.forename: James
authors.initials: J
authors.lastname: Patterson
authors.forename: David
authors.initials: D
authors.lastname: Wyper
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D002908:Chronic Disease; D004599:Electric Stimulation Therapy / Q000379:methods*; D004827:Epilepsy / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000628:therapy*; D005260:Female; D006801:Humans; D008032:Limbic System / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014630:Vagus Nerve / Q000503:physiopathology*
chemical_list: D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime