Histologic evidence of brachial plexus compression sites at the thoracic inlet and variations in formation of the lower trunk in cadavers.

We report histologic changes consistent with chronic compression of the upper and lower plexus in the thoracic inlet at hypothesized sites of brachial plexus compression that may correlate with clinical neck/shoulder (upper trunk) and "ulnar nerve-like" (C8-T1/lower trunk) symptoms. Anatomic anomalies identified should alert the surgeon to variations of lower trunk formation at compression sites.