Patients diagnosed with the neurodegenerative disorder amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig disease) frequently develop dissociated atrophy of the lateral intrinsic hand muscles (figure, A).1 Preferential wasting of abductor pollicis brevis and first dorsal interosseous muscles, with relative preservation of the lateral abductor digit minimi, is termed the ALS split hand.2 Differential cortical representation of these muscles, linked to the evolution of an opposable thumb, is one postulated explanation.2
Figure. Dissociated atrophy of intrinsic hand muscles: The ALS split hand.
Lou Gehrig (1903–1941), the New York Yankees baseball player nicknamed “the Iron Horse,” began a streak of 2,130 consecutive games in June 1925 that ended when he developed left leg weakness 14 years later. The ALS split hand refers to preferential wasting of abductor pollicis brevis and first dorsal interosseous muscles, with relative preservation of the lateral abductor digit minimi (A). A photograph of Gehrig (B, right) with teammate “Babe” Ruth (B, left) on display at Yankee Stadium, confirms wasting of his left first dorsal interosseous (C). It developed after initial ipsilateral leg weakness, and this pattern of spread of symptoms to contiguous body regions is typical in ALS. ALS = amyotrophic lateral sclerosis.
Footnotes
Author contributions: Prof. Turner contributed to concept, design, and revision of the manuscript. Prof. Kiernan contributed to concept, design, and revision of the manuscript.
Study funding: No targeted funding reported.
Disclosure: Martin R. Turner receives funding support from the Medical Research Council & Motor Neurone Disease Association Lady Edith Wolfson Senior Clinical Fellowship. Matthew C. Kiernan receives funding support from National Health and Medical Research Council of Australia (Forefront Program Grant). He serves as Editor-in-Chief of the Journal of Neurology, Neurosurgery & Psychiatry (BMJ Publishers). Go to Neurology.org for full disclosures.
References
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