Abnormal cortical brain integration of somatosensory afferents in ALS

Publication date: Available online 24 December 2017
Source:Clinical Neurophysiology
Author(s): Sina Sangari, Alain Giron, Guillaume Marrelec, Pierre-François Pradat, Véronique Marchand-Pauvert
ObjectivesInfraclinical sensory alterations have been reported at early stages of amyotrophic lateral sclerosis (ALS). While previous studies mainly focused on early somatosensory evoked potentials (SEPs), late SEPs, which reflect on cortical pathways involved in cognitive-motor functions, are relatively underinvestigated. Early and late SEPs were compared to assess their alterations in ALS.MethodsMedian and ulnar nerves were electrically stimulated at the wrist, at 9 times the perceptual threshold, in 21 ALS patients without clinical evidence of sensory deficits, and 21 age- and gender-matched controls. SEPs were recorded at the Erb point using surface electrodes and using a needle inserted in the scalp, in front of the primary somatosensory area (with reference electrode on the ear lobe).ResultsCompared to controls, ALS patients showed comparable peripheral (N9) and early cortical component (N20, P25, N30) reductions, while the late cortical components (N60, P100) were more depressed than the early ones.ConclusionsThe peripheral sensory alteration likely contributed to late SEP depression to a lesser extent than that of early SEPs.SignificanceLate SEPs may provide new insights on abnormal cortical excitability affecting brain areas involved in cognitive-motor functions.



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