Impaired short- and long-latency afferent inhibition in amyotrophic lateral sclerosis.

INTRODUCTION: To test the hypothesis of impaired cholinergic activity in amyotrophic lateral sclerosis (ALS), we studied short- and long-latency afferent inhibition (SAI and LAI).

METHODS: The ulnar nerve was stimulated at the wrist preceding transcranial magnetic stimulation (TMS), 21 ms for SAI and 200 ms for LAI, in 21 patients and 17 control subjects. Short-interval intracortical inhibition (SICI) and cognitive function was assessed in ALS patients using automatic threshold tracking and the Montreal Cognitive Assessment (MoCA).

RESULTS: The SAI paradigm resulted in inhibition in all control subjects, whereas inhibition was observed in 13 of 21 (62%) patients. Mean SAI and LAI values were significantly reduced in ALS. No significant correlation existed between afferent inhibition and other neurophysiological data. The MoCA was normal in all but 1 patient.

DISCUSSION: LAI and SAI are both impaired in ALS, probably unrelated to increased cortical excitability or cognitive dysfunction. Muscle Nerve 59:699-704, 2019.