Electroencephalography and clinical neurophysiology
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Electroencephalogr Clin Neurophysiol · Jul 1991
Comparative StudyLaser-evoked brain potentials in patients with dissociated loss of pain and temperature sensibility.
Brief heat stimuli, elicited by a CO2 laser (10.6 microns wave length), activate the most superficial cutaneous nerve terminals of the thin myelinated A delta and unmyelinated C fibres which mediate heat and pain sensations. This paper investigates late cerebral potentials (SEPs) in response to laser pulses in comparison with those to conventional electrical stimulation in 18 patients with a dissociated sensory deficit (intact mechano-sensibility and disturbed temperature and pain sensation). Patients were stimulated in the most disturbed limb (affected area) and in a corresponding control area. ⋯ Highest correlations between sensory deficits and abnormal SEPs were found in all those patients in whom computer tomography or MR imaging documented a localized destructive process in the CNS. All patients with the smallest SEP modulations despite a considerable sensory deficit had an inflammatory aetiology. Preliminary criteria to define a laser-evoked SEP as pathological are discussed.