From compression to denervation: Multimodality imaging of cervical rib-related arterial thoracic outlet syndrome.

Thoracic outlet syndrome (TOS) encompasses a spectrum of disorders caused by compression of neurovascular structures at the thoracic outlet. Arterial thoracic outlet syndrome (aTOS) is rare, accounting for less than 1% of cases, yet carries significant morbidity due to arterial injury, thrombosis, and distal embolization. We present a 34-year-old woman with progressive pain, paresthesia, and bluish discoloration of the left upper limb. Doppler ultrasound demonstrated reduced ulnar artery calibre with a tardus-parvus waveform, indicating distal arterial compromise. CT angiography revealed a fused cervical rib causing focal compression of the left subclavian artery with associated poststenotic dilatation. The patient underwent surgical decompression with cervical rib excision, thrombus evacuation, and arterial reconstruction, resulting in restoration of distal perfusion. Postoperatively, MRI of the shoulder-performed for persistent pain-demonstrated edema of the infraspinatus and teres minor muscles without fatty infiltration, suggestive of acute denervation edema. This case illustrates the full imaging continuum of aTOS, from structural vascular compression and distal ischemia to postoperative neural involvement, underscoring the critical role of multimodality imaging in both diagnosis and follow-up.