Impaired pain processing and its association with attention disturbance in patients with amyotrophic lateral sclerosis.

ABSTRACT

BACKGROUND: Cognitive dysfunction characterized by executive dysfunction and persistent attention function has been reported in patients with amyotrophic lateral sclerosis (ALS); however, it is unclear if this contributes to the pain processing deficits associated with the disease. OBJECTIVE: We clarified the relationship between pain processing and both cognitive function and sensory symptoms in patients with ALS. METHODS: We enrolled 23 patients with ALS and 14 healthy control subjects. We examined pain-related somatosensory evoked potentials (SEPs) using an intra-epidermal needle electrode. We evaluated cognitive function and the clinical characteristics of sensation and analyzed their relationships with pain-related SEPs. RESULTS: Pain-related SEP amplitudes were significantly lower, while the rate of amplitude attenuation due to habituation or change in attention was significantly greater in patients with ALS than in control subjects. There were no significant differences in pain-related SEP parameters between patients with or without sensory symptoms. Instead, pain-related SEP amplitude and its rate of attenuation were correlated with cognitive dysfunction, particularly with attention domains. CONCLUSIONS: Our results suggest that attention deficit, but not sensory nerve involvement, is a major cause of the alterations in pain-related SEP in patients with ALS.