Neurologic manifestations of compressive radiculopathy of the first thoracic root.

Neurologic deficits in the first thoracic (T1) root distribution are uncommon and not easily defined. Myotomal charts indicate that distal arm and hand muscles receive significant contributions from both the C8 and T1 roots. A patient with focal T1 radiculopathy is presented who demonstrated motor axon loss isolated to the abductor pollicis brevis muscle. This finding provides another source of evidence that the abductor pollicis brevis is the primary T1 motor structure in the upper extremity, improving precision in clinical and electromyographic diagnosis.