The anterior scalene is the key muscle in thoracic outlet syndrome — the subclavian artery and brachial plexus pass between the anterior and middle scalenes (interscalene triangle). The subclavian vein passes anterior to the anterior scalene.
| Origin | Anterior tubercles of the transverse processes of C3-C6 |
|---|---|
| Insertion | First rib — scalene tubercle (Lisfranc's tubercle) |
| Nerve Supply | Ventral rami of C4-C6 |
| Blood Supply | Ascending cervical artery |
| Actions | Elevates the first rib during deep inspiration; Ipsilateral lateral flexion of the neck; Contralateral rotation when acting bilaterally to flex the neck |
|---|
Anterior scalene resection (scalenectomy) is the surgical treatment for neurogenic thoracic outlet syndrome. The phrenic nerve (C3, C4, C5) lies on the anterior surface of the anterior scalene — it must be identified and preserved during scalenectomy. Anterior scalene botulinum injection is used as a diagnostic test for TOS.
Palpated posterior to the SCM at the lateral neck during deep inspiration.
Interscalene triangle compression of the brachial plexus between the anterior and middle scalenes producing neurogenic TOS, managed by scalenectomy with phrenic nerve preservation.
