Neurogenic
Brachial plexus compression
By far the most common form. Pain, paraesthesia and weakness in the arm and hand, typically worse with overhead or sustained activity. Diagnosis rests on history, examination and the exclusion of other causes rather than on a single test.
Venous
Subclavian vein compression
Presents with arm swelling, heaviness and bluish discolouration, often after repetitive effort. May develop into effort thrombosis (Paget–Schroetter syndrome), where the timing of thrombolysis and decompression is decisive.
Arterial
Subclavian artery compression
The least common and the most urgent. Usually associated with a bony anomaly such as a cervical rib, and may present with ischaemia, coldness, claudication of the arm or distal embolisation.