title: On the relation between sensory deafferentation, pain and thalamic activity in Wallenberg's syndrome: a PET-scan study before and after motor cortex stimulation.
abstract: Decrease of thalamic blood flow contralateral to neuropathic pain has been described by several groups, but its relation with sensory deafferentation remains unclear. Here we report one instance where the thalamic effects of sensory deafferentation could be dissociated from those of neuropathic pain. A 50-year-old patient underwent a left medullary infarct leading to right-sided thermal and pain hypaesthesia up to the third right trigeminal division, as well as in the left face. During the following months the patient developed neuropathic pain limited to the left side of the face. Although the territory with sensory loss was much wider in the right (non painful) than in the left (painful) side of the body, PET-scan demonstrated significant reduction of blood flow in the right thalamus (contralateral to the small painful area) relative to its homologous region. After 3 months of right motor cortex stimulation the patient reported 60% relief of his left facial pain, and a new PET-scan showed correction of the thalamic asymmetry. We conclude that thalamic PET-scan hypoactivity contralateral to neuropathic pain does not merely reflect deafferentation, but appears related to the pain pathophysiology, and may be normalized in parallel with pain relief. The possible mechanisms linking thalamic hypoactivity and pain are discussed in relation with findings in epileptic patients, possible compensation phenomena and bursting thalamic discharges described in animals and humans. Restoration of thalamic activity in neuropathic pain might represent one important condition to obtain successful relief by analgesic procedures, including cortical neurostimulation.
authors.affiliation: INSERM E342, Central Integration of Human Pain, Hopital Neurologique, 59 Bd Pinel, 69003 Lyon, France; Université Claude Bernard Lyon1, France. larrea@univ-lyon1.fr
authors.forename: Luis
authors.initials: L
authors.lastname: Garcia-Larrea
authors.forename: Joseph
authors.initials: J
authors.lastname: Maarrawi
authors.forename: Roland
authors.initials: R
authors.lastname: Peyron
authors.forename: Nicolas
authors.initials: N
authors.lastname: Costes
authors.forename: Patrick
authors.initials: P
authors.lastname: Mertens
authors.forename: Michel
authors.initials: M
authors.lastname: Magnin
authors.forename: Bernard
authors.initials: B
authors.lastname: Laurent
mesh_terms: D002422:Causalgia / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D046690:Deep Brain Stimulation; D006801:Humans; D014854:Lateral Medullary Syndrome / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex; D049268:Positron-Emission Tomography; D013788:Thalamus / Q000000981:diagnostic imaging / Q000503:physiopathology*