The split hand in ALS has a cortical basis.

Full Abstract

Loss of highly fractionated movement involving the thumb and index finger is an early characteristic of hand dysfunction in many ALS patients. These movements are largely subserved by the 'thenar complex' including the first dorsal interosseus muscle (FDI), whereas the 'hypothenar complex', innervated by the same myotome, has less ability to fractionate and is relatively spared. This suggests that in ALS, hand dysfunction and wasting is related to corticomotoneuronal representation and input. To determine whether corticomotoneuronal input to the thenar spinal pool is preferentially impaired compared to the hypothenar spinal pool in ALS, we studied 18 ALS patients and 11 normal subjects. Compound muscle action potentials (CMAPs) and motor evoked potentials (MEPs) of the thenar and hypothenar complexes were evoked by peripheral nerve stimulation and transcranial magnetic stimulation. In healthy control subjects the cortical/peripheral (MEP/CMAP) ratios were significantly larger for the thenar complex suggesting a stronger corticomotoneuronal input to this muscle complex (P<0.005). This was not the case in ALS patients. Comparing the ratios between control subjects and patients revealed a significant reduction for the thenar complex (P<0.02) in ALS patients but not for the hypothenar complex. We conclude that corticomotoneuronal input to the thenar complex is preferentially affected in ALS and that corticomotoneuronal disease may be the prime determinant of hand dysfunction and wasting.

Author information

Author/s: Weber, M (M); Eisen, A (A); Stewart, H (H); Hirota, N (N);

Affiliation: The Neuromuscular Diseases Unit, Vancouver Hospital and the University of British Columbia, 855 West 12th Avenue, Vancouver, Canada V5Z 1M9. maus(-atsign-)interchange.ubc.ca

Journal and publication information

Publication Type: Journal Article

Journal: Journal of the neurological sciences (J Neurol Sci), published in NETHERLANDS. (Language: eng)

Reference: 2000-Nov; vol 180 (issue 1-2) : pp 66-70

Dates: Created 2000/12/28; Completed 2001/01/25; Revised 2004/11/17;

PMID: 11090867, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

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