| Summary: | Abstract Objective Detect the occurrence and characteristics of A-waves in amyotrophic lateral sclerosis (ALS) and demyelinating neuropathies (DN). Methodology Nerve conduction studies (NCS) of 28 patients (14 patients with ALS and 14 patients with DN) were reanalyzed to look for A-waves. Results We studied 61 nerves of the ALS group and 64 nerves of DN. In the ALS group, A-waves were detected in 21 nerves out of 61 nerves (34.4%). In the DN group, A-waves were recorded from 25 nerves out of 64 nerves (39%). In the DN group, A-waves were detected more often in nerves of upper extremities than lower extremities (out of a total of 25 nerves with A-waves, 18 median and ulnar nerves showed A-waves (72%) and that was statistically significant (P = 0.0021)). Complex A-waves (CAWs) occurred exclusively in patients with DN. Conclusion Most of the A-waves in the DN group were recorded more frequently from nerves of the upper extremities than those from lower extremities. CAWs occurred only in DN. Significance CAW seems to be a useful specific electrodiagnostic tool to distinguish DN from ALS.
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