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LETTER TO THE EDITOR |
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Year : 2015 | Volume
: 8
| Issue : 5 | Page : 686-687 |
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Split hand sign
Prasanna Venkatesan Eswaradass, Balakrishnan Ramasamy, Ramadoss Kalidoss, Gnanagurusamy Gnanashanmugham
Department of Neurology, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
Date of Web Publication | 10-Sep-2015 |
Correspondence Address: Prasanna Venkatesan Eswaradass 3, Vijayarahavachari Road, Gandhi Road, Salem - 636 007 India
Source of Support: None, Conflict of Interest: None | Check |
DOI: 10.4103/0975-2870.164966
How to cite this article: Eswaradass PV, Ramasamy B, Kalidoss R, Gnanashanmugham G. Split hand sign. Med J DY Patil Univ 2015;8:686-7 |
Sir,
We report a 45-year-old man who presented to us with a history of insidious onset of gradually progressive weakness and wasted of small muscles of the hand right more than left for 2 month's duration. Evaluation and localization of small muscle wasting is a great challenge to physicians. Lower cervical cord lesion, C8T1 radiculopathy, lower trunk plexopathy, ulnar neuropathy and anterior horn cell disease can all produce small muscle wasting. It is important to clinically localize the lesion before proceeding to investigations like Magnetic resonance imaging of the spine or electrophysiological studies.
The primary importance of evaluating a patient with small muscle wasting is to rule out amyotrophic lateral sclerosis (ALS) which is progressive neurodegenerative disease affecting the motor neurons. ALS can present with asymmetrical hand wasting without upper motor neuron signs in the early phase. Dissociated atrophy of hand muscles is a characteristic feature of ALS. The split hand sign was first noted in ALS characterized by preferential wasting of thenar muscles abductor pollicis brevis and first dorsal interossei with relatively preserved hypothenar eminence.[1] It is highly specific for ALS because a lesion in ulnar nerve or lower trunk will cause predominant wasting of first dorsal interossei and hypothenar with preserved thenar as it is innervated by median nerve. Whereas a C8T1 root lesion will cause wasting of both thenar and hypothenar as both median and ulnar nerve receive C8T1 innervation. It is called split hand sign as it preferentially affects lateral hand (abductor pollicis brevis and first dorsal interossei) and sparing medial hypothenar. This pattern of dissociated wasting does not correspond to a nerve or plexus or root distribution.
Kuwabara et al., studied 77 ALS patients and compared with normal controls. Electrophysiologically decreased abductor pollicis brevis/abductor digiti minimi ratio was found in 41% of ALS patients and 5% of normal controls and hence they concluded that split hand sign is very specific for ALS.[2] The exact cause for this sign is not known. The pincer grasp is essential for humans that involves the use of abductor pollicis brevis and first dorsal interossei. Excessive use of pincers grasp probably results in increased oxidative stress to motor neurons of abductor pollicis brevis and first dorsal interossei resulting in preferential wasting of lateral hand.[3] There is also a cortical basis for split hand sign proposed by Weber et al. which suggests corticomotorneuronal input to the thenar complex is preferentially affected in ALS.[4]
Our patient was diagnosed of ALS as he had a normal MRI spine and electrophysiology showed widespread active denervation and reinnervation. [Figure 1] shows wasting of thenar muscles with preserved hypothenar muscles. [Figure 2] shows first dorsal interosseous wasting. Split hand sign is a simple bed side clinical sign which should be stressed upon the physician and hence that ALS can be differentiated from their mimics.
References | | |
1. | Wilbourn AJ. The "split hand syndrome". Muscle Nerve 2000;23:138. |
2. | Kuwabara S, Sonoo M, Komori T, Shimizu T, Hirashima F, Inaba A, et al. Dissociated small hand muscle atrophy in amyotrophic lateral sclerosis: Frequency, extent, and specificity. Muscle Nerve 2008;37:426-30. |
3. | Benny R, Shetty K. The split hand sign. Ann Indian Acad Neurol 2012;15:175-6. [ PUBMED] |
4. | Weber M, Eisen A, Stewart H, Hirota N. The split hand in ALS has a cortical basis. J Neurol Sci 2000;180:66-70. |
[Figure 1], [Figure 2]
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