Wartenberg's sign

Wartenberg's sign is a neurological sign consisting of involuntary abduction of the fifth (little) finger, caused by unopposed action of the extensor digiti minimi.

This commonly results from weakness of some of the ulnar nerve innervated intrinsic hand muscles -in particular the palmar interosseous muscle to the little finger- caused by damage to their nerve supply (denervation). There may be different causes for this denervation and muscle imbalance including:

Differentiation of the cause of Wartenberg's sign is based on associated clinical findings in the history and examination and sometimes involves investigations including radiographs and/or MRI of the cervical spine, elbow/wrist/hand and/or nerve conduction studies and EMG.

Wartenberg's sign is not a feature of, and should not be confused with, Wartenberg's syndrome. The later involves compression at the wrist of the superficial sensory branch of the radial nerve which does not innervate hand muscles.

Robert Wartenberg (1887-1956) was a neurologist born in Belarus who worked in Germany until 1935 when he emigrated to the United States, he was widely published and described a number of neurological signs and clinical tests.

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