Thoracic outlet syndrome (TOS) is a condition where the blood vessels and nerves of the upper limb are compressed in the neck and shoulder resulting in pain, pins and needles and weakness in the arm and hand. The compression can be mainly of the nerves (neurogenic TOS) or blood vessels (Vascular TOS) or a combination.
There are many different causes of compression at the thoracic outlet. There are some anatomical variations that can predispose people to the problem like accessory ribs in the neck, fibrous bands or altered positions of the neck muscles. Injury can result in TOS and occupational causes from bad posture or overhead work are well described.
The classic combination of symptoms is pain in the neck and shoulders and pins and needles in the hands, particularly brought on by lifting the hands above the head. As the problem potentially involves all the nerves to the upper limb, the symptoms can vary widely with different combinations of pain, numbness and weakness affecting anywhere from the neck to the fingertips.
MRI scanning can help to image any anatomical features in the neck that can predispose to thoracic outlet compression. Nerve conduction and EMG testing can help with the diagnosis and also look for other peripheral nerve compression syndromes that can mimic or co-exist with TOS. Duplex ultrasound is crucial for the diagnosis of vascular TOS and can give useful information about neurogenic TOS.
Despite the many tests involved with thoracic outlet assessment, the most important part of the diagnosis is a clinical examination by a clinician experienced in dealing with the problem.