The different syndromes caused by compression of the nerves in the brachial plexus, subclavian artery and/or vein along the costoclavicular passages have been grouped under the term of thoracic outlet syndrome (TOS) which produces weakness, muscle wasting, pain and vascular symptoms in the hand and arm.

A 19-year-old boy presented with a year history of weakness and wasting in the right hand, and complained of coldness. Physical examination revealed wasting of the intrinsic hand muscles, hypesthesia on the right fifth finger and multiple cafe-au-lait macules on the trunk and upper extremities.

The electrodiagnostic study revealed no compound muscle action potential of the median nerve, diminished amplitude of ulnar motor and sensory action potentials, and prolonged ulnar F-wave latency. Signs of chronic partial denervation were found in thenar and hypothenar muscles representing the lower trunk of the brachial plexus. These findings were suggestive of neurogenic TOS. At surgical exploration of the right brachial plexus, the compression of the lower trunk by a neurofibroma was noted originating from right first and second intercostal nerves.