A cellist with arm pain: thermal asymmetry in scalenus anticus syndrome. We report on a cellist with pain and coldness of the upper extremity. Abnormal thermographic studies were instrumental in uncovering intermittent compression of the subclavian artery, and this prompted us to study the effects of cello playing on skin temperature asymmetry. Temperature asymmetry was defined as the temperature difference (delta-T) from one hand to the other. In 57 controls, mean delta-T at rest was .309 +/- .254C. Exercising the upper extremities by prolonged elbow flexion or by movements mimicking cello playing in controls did not significantly affect delta-T. In our patient, delta-T was ten times control (3.6C). Angiography showed extrinsic compression of the subclavian artery occurring only after cello playing; sympathetic ganglion block relieved the pain. Our patient's abnormal skin temperature may have reflected sympathetic vasomotor hyperactivity. Intermittent neurovascular compression and sympathetic hyperactivity appear to be factors in scalenus anticus syndrome. 