Wartenberg's thumb adduction sign
In this particular case, a 35 year old woman presented with painless weakness of the right hand; EMG showed diffuse denervation in a multi-root, multi-nerve distribution raising concern about motor neuron disease. Reflexes in the right arm were equivocally increased. Wartenberg’s thumb adduction sign was strikingly positive, providing strong evidence of upper motor neuron involvement in the same extremity and making any alternative diagnosis much less likely.
There are other “Wartenberg signs.”
1. Campbell WW. DeJong's the neurologic examination, 7th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2013. 2. Campbell WW. Clinical signs in neurology : a compendium. Philadelphia: Wolters Kluwer Health, 2016. 3. Massey EW, Pleet AB, Scherokman BJ. Diagnostic Tests in Neurology: A Photographic Guide to Bedside Techniques. Chicago: Year Book Medical Publishers, Inc, 1985. 4. Wartenberg, R. The Examination of Reflexes. Chicago: Year Book Publishers, 1945.