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AN35.1-10 | Deep structures in the neck — SDL Guide (Part 3)

Cervical Rib and Thoracic Outlet Syndrome (AN35.9)

Cervical rib:
- Anomalous rib arising from C7 vertebra (0.5–1% population; bilateral in 50%; more symptomatic in women)
- Articulates with the 1st rib anteriorly (complete) or terminates in fibrous band (incomplete)
- Compresses the lower trunk of the brachial plexus (C8, T1) and/or the subclavian artery (Part 3)

Thoracic Outlet Syndrome (TOS) — two types:

Type	Structure compressed	Presentation
Neurological (more common)	Lower trunk (C8, T1)	Wasting + weakness of medial forearm/hand muscles; Hypothenar and thenar wasting (T1 > C8); numbness on medial side of forearm/hand (C8, T1 dermatome)
Vascular	Subclavian artery/vein	Ischaemia of arm; Raynaud's in young women; subclavian artery post-stenotic dilation; venous TOS → axillary vein thrombosis (effort thrombosis)

Adson's test: extend the arm, rotate head toward the affected side, deep inspiration → obliterates radial pulse (positive in vascular TOS)

Treatment: physiotherapy first; surgical resection of cervical rib + fibrous band if refractory.

Cervical Rib and Thoracic Outlet Syndrome (AN35.9) — Cervical rib and TOS: C7 rib compressing lower trunk and subclavian artery, neurogenic vs vascular TOS clinical features, and Adson's test for diagnosis

Thoracic Outlet Syndrome (TOS) — two types: — Side-by-side neurogenic vs vascular TOS: neurogenic with lower trunk compression and hand muscle wasting, vascular with subclavian artery compression and distal embolism, both showing cervical rib relationship to scalene muscles

SELF-CHECK

A. Upper trunk of brachial plexus (C5, C6)

B. Middle trunk of brachial plexus (C7)

C. Lower trunk of brachial plexus (C8, T1)

D. Right phrenic nerve

Reveal Answer

Answer: see explanation below

The lower trunk (C8, T1) is the most commonly compressed by a cervical rib. C8, T1 supply the intrinsic hand muscles and the medial cutaneous nerve of forearm. Upper trunk compression (C5, C6) causes Erb's palsy pattern (deltoid, biceps weakness) — not seen here.

SELF-CHECK

A. Right CN III palsy from uncal herniation

B. Interruption of the right cervical sympathetic chain by the Pancoast tumour

C. Right facial nerve palsy

D. Disruption of the hypothalamic sympathetic output

Reveal Answer

Answer: see explanation below

Pancoast (superior sulcus) tumour at the lung apex compresses the cervical sympathetic chain → Horner syndrome (ptosis, miosis, anhidrosis). It also often compresses the lower trunk (C8–T1) → wasting of small hand muscles. CN III palsy causes complete ptosis + mydriasis (not miosis) — the opposite pattern.

CLINICAL PEARL

Retropharyngeal abscess — don't miss it: In Indian ENT practice, retropharyngeal abscess (often secondary to TB cervical lymphadenitis or upper respiratory infection in children) presents with fever, neck stiffness, dysphagia, and stridor. The retropharyngeal space lies between the posterior pharyngeal wall and the alar fascia. The danger: infection can spread through the 'danger space' (between alar and prevertebral fasciae) directly into the posterior mediastinum → descending necrotising mediastinitis (mortality >40% without surgery). Diagnosis: lateral soft-tissue X-ray of neck shows widening of the prevertebral soft tissue (>7 mm at C2, or >14 mm at C6 in adults). CT neck with contrast is definitive. Treatment: urgent surgical drainage + IV antibiotics + airway management.