title: Abnormalities of axonal excitability are not generalized in early multifocal motor neuropathy.
abstract: The clinical and neurophysiological features of multifocal motor neuropathy (MMN) indicate selective involvement of motor axons, but pathological abnormalities in sensory axons suggest a more widespread disease process. The present study was undertaken to determine whether the focal abnormalities are associated with widespread subclinical abnormalities in motor axons. Threshold tracking was used to measure excitability properties (stimulus-response curves, strength-duration properties, recovery cycle, and threshold electrotonus) of the median nerve in five patients with MMN with lesions proximal to the site of testing. Patients were compared with 25 healthy controls. The changes in excitability indices were similar to those in controls, and in one patient there was no alteration after treatment with intravenous gammaglobulin. In this patient, indices of axonal excitability were also measured before, during, and after ischemia of the arm for 10 min. Again no differences were detected. This study provides no evidence for a generalized subclinical abnormality in MMN, at least when disease duration is less than 6 years.
authors.affiliation: Department of Clinical Neurophysiology, Prince of Wales Hospital and Prince of Wales Medical Research Institute, University of New South Wales, Barker Street, Randwick, Sydney, New South Wales 2031, Australia.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Cappelen-Smith
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kuwabara
authors.forename: Cindy S-Y
authors.initials: CS
authors.lastname: Lin
authors.forename: David
authors.initials: D
authors.lastname: Burke
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D001369:Axons / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007511:Ischemia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D011115:Polyneuropathies / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology