Abstract
Introduction
Electrodiagnostic evaluation is crucial in establishing the diagnosis of motor neuron disease (MND) and excluding other pathologies. It is recommended that sensory nerve conduction studies (NCS) include the ulnar and sural nerves, and generally accepted that sensory nerves are normal in MND. There are however previous reports in the literature documenting variable sensory abnormalities in patients with MND. We sought to determine the frequency of unexplained sensory abnormalities seen on NCS in patients with MND.
Methods
Medical records of patients attending our tertiary MND clinic over a 2 year period were reviewed. We identified 92 patients with a clinical diagnosis of MND for whom electrodiagnostic studies were available to review. Sensory abnormalities in patients without a clear underlying aetiology (eg. compressive neuropathies, diabetes) were considered unexplained.
Results
Unexplained sensory abnormalities were detected in at least one nerve in 18/92 (20%) patients. In 17 of those 18 patients, the ulnar sensory response was abnormal. 12 of 18 patients demonstrated abnormalities in 2 or more sensory nerves. Sensory abnormalities were present in 4 of 37 (10.8%) patients with bulbar onset MND and 14 of 55 (25.4%) patients with limb onset MND. Sensory symptoms were infrequently reported and did not correlate with abnormalities found on NCS.
Conclusions
Unexplained sensory nerve action potential abnormalities are not uncommon in MND, with ulnar sensory responses the most frequently affected. These findings raise the possibility of sensory nerve pathology in patients with MND and suggest that the presence of unexplained sensory abnormalities should not exclude a diagnosis of MND.