This is a type of cervical rib syndrome. There is a related vascular thoracic outlet syndrome.
Diagnosis:
The diagnosis is made by clinical and electrophysiological (NCS/EMG) and then imaging to identify the underlying case.
Clinical features:
- Pain: C8 andT1
- Sensory loss C8 and T1
- Weakness: abductor pollicis brevis
- Puling on the arm (down) reproduces sensory symptoms
- Normal reflexes
Findings on investigations:
NCS:
- Medial antebrachial cutaneous nerve: SNAP reduced or absent
- Ulnar: SNAP reduced amplitude
- Median nerve: SNAPs Spared
EMG:
- More abnormalities on MEDIAN innervated muscles than ulnar innervated muscles: denervation (fibrillation potentials) reduced MUAP recruitment
X-ray: false negatives if due to cervical band
CT thorax: shows abnormal additional rib
MRI brachial plexus: assess for other lesions
Investigations to consider:
NCS/EMG
MRI brachial plexus
CT thorax
Treatment:
Surgery: excision of rib or band
Relate condition:
Vascular thoracic outlet syndrome:
Clinical features:
- Raynauds phenomenon, ulcers and gangrene of digits, thrombosis of subclavian vein after exercise, edema and discolouration of hand
- Adson’s test: decrease in pulse amplitude +symptoms on turning the head to the affected side with neck hyperextension and deep inhalation
Findings on investigations:
- X-ray: false negatives if due to cervical band
- CT: shows rib
- MRI brachial plexus: assess for other lesions
- CTA: aneurysm in rare cases