title: Central modulation in cluster headache patients treated with occipital nerve stimulation: an FDG-PET study.
abstract: BACKGROUND
  Occipital nerve stimulation (ONS) has raised new hope for drug-resistant chronic cluster headache (drCCH), a devastating condition. However its mode of action remains elusive. Since the long delay to meaningful effect suggests that ONS induces slow neuromodulation, we have searched for changes in central pain-control areas using metabolic neuroimaging.
  
  
  METHODS
  Ten drCCH patients underwent an 18FDG-PET scan after ONS, at delays varying between 0 and 30 months. All were scanned with ongoing ONS (ON) and with the stimulator switched OFF.
  
  
  RESULTS
  After 6-30 months of ONS, 3 patients were pain free and 4 had a ≥ 90% reduction of attack frequency (responders). In all patients compared to controls, several areas of the pain matrix showed hypermetabolism: ipsilateral hypothalamus, midbrain and ipsilateral lower pons. All normalized after ONS, except for the hypothalamus. Switching the stimulator ON or OFF had little influence on brain glucose metabolism. The perigenual anterior cingulate cortex (PACC) was hyperactive in ONS responders compared to non-responders.
  
  
  CONCLUSIONS
  Metabolic normalization in the pain neuromatrix and lack of short-term changes induced by the stimulation might support the hypothesis that ONS acts in drCCH through slow neuromodulatory processes. Selective activation in responders of PACC, a pivotal structure in the endogenous opioid system, suggests that ONS could restore balance within dysfunctioning pain control centres. That ONS is nothing but a symptomatic treatment might be illustrated by the persistent hypothalamic hypermetabolism, which could explain why autonomic attacks may persist despite pain relief and why cluster attacks recur shortly after stimulator arrest. PET studies on larger samples are warranted to confirm these first results.
authors.affiliation: University Neurology Department, Liège, Belgium.
authors.forename: Delphine
authors.initials: D
authors.lastname: Magis
authors.forename: Marie-Aurélie
authors.initials: MA
authors.lastname: Bruno
authors.forename: Arnaud
authors.initials: A
authors.lastname: Fumal
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Gérardy
authors.forename: Roland
authors.initials: R
authors.lastname: Hustinx
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
authors.forename: Jean
authors.initials: J
authors.lastname: Schoenen
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D003027:Cluster Headache / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism / Q000628:therapy*; D004599:Electric Stimulation Therapy / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000150:complications / Q000000981:diagnostic imaging; D059408:Pain Management; D049268:Positron-Emission Tomography / Q000379:methods*; D013127:Spinal Nerves / Q000502:physiology*
chemical_list: D019788:Fluorodeoxyglucose F18; D005947:Glucose