Infraclavicular median nerve compression caused by a lipoma.

The most common site of median nerve compression is in the carpal tunnel, the most common of all entrapment neuropathies. Less frequent entrapment neuropathies of the median nerve include the anterior interosseous and pronator syndromes in the proximal forearm. Even less commonly seen is entrapment at the infraclavicular segment of the brachial plexus. Median nerve compression at the level of the axilla has been reported as being caused by anomalous axillary arch muscles, anomalous vascular perforations of the nerve or its roots, the pectoralis minor muscle, and a thickening of the deltopectoral fascia. To the authors' knowledge, this is the first report of compression at that level by a benign tumor.