The majority of patients undergoing thoracic outlet decompression are under the age of 50 and thus the risk from serious systemic complication is extremely low. However, all surgery performed under a general anaesthesia is associated with an element of risk no matter how fit and active the individual is. The vast majority of complications following TOS surgery relate to the difficulties of operating in a confined area of the body through which a number of important vessels, nerves and lymphatics travel. Hence, the importance of choosing a surgeon with experience in operating in this region of the body. Possible complications associated with a supraclavicular approach include: •Nerve related •Nerves are very susceptible to bruising and even the minimal handling necessary to mobilise them during TOS surgery may result in them not functioning properly in the immediate post-operative period. Thankfully the majority of injuries are temporary, but some may remain beyond one year despite the nerve being intact. Specific nerves that are prone to injury include: •Phrenic Nerve oThis nerve supplies the diaphragm on the side of the operation (ipsilateral side). Injury is rare, but may occur as a result of the nerve being stretched during dissection, particularly if it is anomalous in its course through the thoracic outlet. Injury to the nerve paralyses the ipsilateral hemi-diaphragm reducing one’s exercise capacity. Injury is often temporary, but recovery may take a few weeks to several months and occasionally, longer than 1 year. •Brachial Plexus oInjury to the brachial plexus nerves is rare and for the majority of clients temporary. When it does occur it can result in numbness, pins and needles and weakness affecting the arm and hand. •Long Thoracic Nerve of Bell oThis nerve supplies the serratus anterior muscle that attaches between your shoulder blade (scapula) and rib cage and pulls the scapula onto the rib cage when swinging your arm. Injury may occur during resection of scalenus medius or a cervical rib as it is often displaced from its normal position. This may result in ‘winging’ of the scapula during aforementioned movements. •Chest Wall Sensory Nerves oThe nerves that supply sensation to parts of the upper chest wall on the side of the surgery may be damaged during surgery, deliberately sacrificed to improve access (rarely required), or incorporated into scar tissue during the healing process. This may result in patchy areas of numbness in the clavicle region, but does not cause significant morbidity. •Sympathetic Chain injury oThe sympathetic chain may very rarely be damaged during the cautery of small blood vessels at the site of rib removal from the spine. This can result in a drooping eyelid, a constricted pupil, and reduced sweating of the face on the side of the operation (Horner’s syndrome). For this reason we minimise the use of cautery (diathermy) during these types of operation and in turn have not seen a case of Horner’s syndrome caused by TOS decompression. •Other •Pneumothorax oThe lining of the lung is intimately associated with the thoracic outlet and may be breached during thoracic outlet decompression allowing air to enter into the lung cavity. This is often recognised and repaired during the primary surgery with a one-way drain left in for 48 hours to allow any residual air to escape. We advise clients not to travel by air for 2 weeks post-surgery if a pneumothorax has occurred. •Thoracic duct injury oTOS decompressive surgery on the left side is complicated by the presence of the thoracic duct and its tributaries, which drains lymph fluid from the body into the venous system. Injury to the main duct or its tributaries can result in lymph leak and post-operative fluid collection in the wound. Although the majority are successfully treated without a re-exploration of the surgical field occasionally a second operation is required to ligate the injured duct. •Injury to the Subclavian Artery and Vein oThis is a very rare complication that if occurs is repaired during the operation •Recurrence oThoracic outlet symptoms may recur when abnormal scar tissue builds up around the brachial plexus, causing adhesions between the nerves and the surrounding structures. The commencement of passive and active neck, shoulder and arm exercises as early as the day after surgery is the key to preventing recurrence.