Split Hand Syndrome in Amyotrophic Lateral Sclerosis

Split Hand Syndrome in Amyotrophic Lateral Sclerosis

1. Split Hand Syndrome in Amyotrophic Lateral Sclerosis Ade Wijaya , MD - February 2021 -

2. Introduction Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder in which there is preferential loss of both the upper and lower motor neurons At clinical onset, manifestations appear rather focal, resulting in bulbar, cervical or lumbar phenotypes, then spreads contiguously from the site of origin, becoming diffuse and resulting in complex motor deficits Kiernan MC, Vucic S, Cheah BC, et al Amyotrophic lateral sclerosis. Lancet 2011;377:942–55 Ravits JM, La Spada AR . ALS motor phenotype heterogeneity, focality , and spread: deconstructing motor neuron degeneration. Neurology 2009;73:805–11.

3. Split Hand Syndrome Wilbourn , 1990 observe thenar muscles and first dorsal interossei muscle are frequently and substantially more denervated than the hypothenar muscles in ALS 1996  Split Hand Syndrome Wilbourn AJ . Electrodiagnostic evaluation of the patient with possible ALS. In: Belsh JM, Schiffman PL, eds. Amyotrophic lateral sclerosis. Armonk, NY: Futura Books, 1996:183. Wilbourn AJ . The “split hand syndrome”. Muscle Nerve 2000;23:138. Wilbourn AJ . Dissociated wasting of medial and lateral hand muscles with motor neuron disease. Can J Neurol Sci 1994;21( Suppl 2):S9.

4. Differential Diagnosis Autosomal dominant distal spinal muscular atrophy Spinocerebellar ataxia type 3 (Machado–Joseph disease) J uvenile muscular atrophy Spinal and bulbar muscular atrophy (SBMA ). Thenar wasting from a cervical rib and band S pondylotic cord compression Compression of the deep motor branch of the ulnar nerve Carpal tunnel syndrome C8 root lesion Eisen A, Kuwabara S. The split hand syndrome in amyotrophic lateral sclerosis. Journal of Neurology, Neurosurgery & Psychiatry. 2012 Apr 1;83(4):399-403.

5. Diagnostic Value Sensitivity (52%) High specificity (95 %) Kuwabara S, Sonoo M, Komori T, et al ; Tokyo Metropolitan Neuromuscular Electrodiagnosis Study Group. Dissociated small hand muscle atrophy in amyotrophic lateral sclerosis: frequency, extent, and specificity. Muscle Nerve 2008;37:426–30.

6. Physiology In humans, use of the APB muscle is greater than that of the ADM, which could render the former muscles (involved in split hand syndrome) subject to greater oxidative stress Kuwabara S, Mizobuchi K, Ogawara K, et al. Dissociated small hand muscle involvement in amyotrophic lateral sclerosis detected by motor unit number estimates. Muscle Nerve 1999;22:870–3. Voermans NC, Schelhaas HJ, Munneke M, et al . Dissociated small hand muscle atrophy in aging: the 'senile hand' is a split hand. Eur J Neurol 2006;13:1381–4.

7. Physiology It has been suggested that the split hand may be explained by differences in membrane properties among motor axons innervating the APB, FDI and ADM. These findings suggest that motor axons with physiologically greater persistent sodium currents—namely ALS-like—may be more vulnerable and more readily die in ALS, and this may contribute to the development of split hand Bae JS, Sawai S, Misawa S, et al . Differences in excitability properties of FDI and ADM motor axons. Muscle Nerve 2009;39:350–4.

8. Physiology The thenar complex together with the FDI is responsible for precision or ‘pincer grip’, which is the main clinical deficit of the split hand syndrome This would support the concept that the split hand deficit, and maybe ALS, are primarily cortical in origin Vucic S, Kiernan MC . Novel threshold tracking techniques suggest that cortical hyperexcitability is an early feature of motor neuron disease. Brain 2006;129:2436–46 Eisen A, Kim S, Pant B . Amyotrophic lateral sclerosis (ALS): a phylogenetic disease of the corticomotoneuron ? Muscle Nerve 1992;15:219–24 .

9. Eisen A, Kuwabara S. The split hand syndrome in amyotrophic lateral sclerosis. Journal of Neurology, Neurosurgery & Psychiatry. 2012 Apr 1;83(4):399-403.

10. Summary The split hand is a useful clinical clue to the early diagnosis of ALS The split hand of ALS is predominantly due to a corticomotneuronal lesion. Nevertheless, lower motor neuronal (anterior horn cell) and motor axonal components are likely to also contribute Measures of pincer grip integrity, yet to be developed for ALS, may prove to be the earliest and most robust documentation of the deficit.

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