Split hand syndrome explained

Specialty:	neurological

In medicine, split hand syndrome is a neurological syndrome in which the hand muscles on the side of the thumb (lateral, thenar eminence) appear wasted, whereas the muscles on the side of the little finger (medial, hypothenar eminence) are spared. Anatomically, the abductor pollicis brevis and first dorsal interosseous muscle are more wasted than the abductor digiti minimi.

If lesions affecting the branches of the ulnar nerve that run to the wasted muscles are excluded, the lesion is almost sure to be located in the anterior horn of the spinal cord at the C8-T1 level.^[1] It has been proposed as a relatively specific sign for amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease).^{[2] [3]} It can also occur in other disorders affecting the anterior horn, such as spinal muscular atrophy, Charcot-Marie-Tooth disease, poliomyelitis and progressive muscular atrophy.^[1] A slow onset and a lack of pain or sensorial symptoms are arguments against a lesion of the spinal root or plexus brachialis.^[4] To an extent, these features can also be seen in normal aging (although technically, the apparent muscle wasting is sarcopenia rather than atrophy).^[5]

The term split hand syndrome was first coined in 1994 by a researcher from the Cleveland Clinic called Asa J. Wilbourn.^{[6] [7]}

Notes and References

1. https://www.drugs.com/dict/split-hand-syndrome.html Split hand syndrome
2. Kuwabara S . Dissociated small hand muscle atrophy in amyotrophic lateral sclerosis: frequency, extent, and specificity . . 37 . 4 . 426–30 . April 2008 . 18236469 . 10.1002/mus.20949 . vanc. Sonoo M . Komori T . 3 . Shimizu . Toshio . Hirashima . Fumiko . Inaba . Akira . Misawa . Sonoko . Hatanaka . Yuki . Tokyo Metropolitan Neuromuscular Electrodiagnosis Study Group. 18500530 .
3. Kuwabara S, Mizobuchi K, Ogawara K, Hattori T . Dissociated small hand muscle involvement in amyotrophic lateral sclerosis detected by motor unit number estimates . . 22 . 7 . 870–3 . July 1999 . 10398204 . 10.1002/(SICI)1097-4598(199907)22:7<870::AID-MUS9>3.0.CO;2-O. https://archive.today/20130105134035/http://www3.interscience.wiley.com/journal/62003411/abstract. dead. 2013-01-05.
4. Schelhaas HJ, van de Warrenburg BP, Kremer HP, Zwarts MJ . The "split hand" phenomenon: evidence of a spinal origin . . 61 . 11 . 1619–20 . December 2003 . 14663056 . 10.1212/01.wnl.0000096009.50213.6c. 39361741 .
5. Voermans NC, Schelhaas HJ, Munneke M, Zwarts MJ . Dissociated small hand muscle atrophy in aging: the 'senile hand' is a split hand . . 13 . 12 . 1381–4 . December 2006 . 17116225 . 10.1111/j.1468-1331.2006.01477.x . 26868415 .
6. Wilbourn AJ, Sweeney PJ . Dissociated wasting of medial and lateral hand muscles with motor neuron disease . . 21 . S2 . S9 . 1994 .
7. Wilbourn AJ . The "split hand syndrome" . . 23 . 1 . 138 . January 2000 . 10590421 . 10.1002/(SICI)1097-4598(200001)23:1<138::AID-MUS22>3.0.CO;2-7 . https://archive.today/20130105181238/http://www3.interscience.wiley.com/journal/68500984/abstract. dead. 2013-01-05. free .