Scalenus Syndrome: A Literature Review

Abstract

Scalenus syndrome is often diagnosed as thoracic outlet syndrome (TOS). We performed literature searching reporting scalenus syndrome and we narratively describe the finding in this review. Scalenus syndrome is a unique clinical entity and commonly occurred. This syndrome can be classified into neurogenic TOS (nTOS) on the interscalene triangle, which also related to myofascial pain syndrome. There are three factors that contribute to scalenus syndrome, which are congenital anomaly, trauma, traumatic myositis, and hypertrophy of scalenus anterior muscle. The symptoms of scalenus syndrome can be divided into two types, which are neurologic and vascular symptoms. The neurologic manifestation can originate from the somatic and sympathetic nervous system. There is microscopic evidence of inflammation, hypertrophy, degeneration, and fibrosis of scalenus anterior muscle in scalenus syndrome cases. Scalenus syndrome can be treated surgically or conservatively. Non-surgical or conservative treatment can be applied to mild scalenus syndrome, especially nTOS, in the initial phase. Surgical management should be performed in persistent symptoms of nTOS or involving subclavian artery manifesting as arterial TOS (aTOS). Scalenus syndrome has quite similar clinical manifestation as nTOS and aTOS. However, this clinical syndrome should be considered as different entity because of different pathophysiology compared to TOS. Scalenus syndrome is caused by dynamic pathology of anterior scalenus muscle.