A case of true neurogenic thoracic outlet syndrome diagnosed by dynamic evaluation in symptom-induced limb position using nerve ultrasound

Abstract

We describe nerve ultrasound in the symptom-induced limb position for a patient with true neurogenic thoracic outlet syndrome (TNTOS). A 14-year-old girl presented atrophy of the right thenar eminence and increased numbness of the right forearm by the right upper arm elevation. She was diagnosed with TNTOS based on the abnormal results of a nerve conduction study. Nerve ultrasound of brachial plexus in the intercostal space revealed the fibrous band (FB) extending from the elongated transverse process of the right C7 vertebra. Additional observation while elevating the right upper limb to exacerbate symptoms revealed that the lower trunk was gradually pushed up by the medial edge of the middle scalene muscle and squeezed in contact with the FB. After surgical removal of the FB with the tip of the elongated transverse process of the right C7 vertebra, good functional recovery was obtained. We considered that nerve ultrasound in the symptom-induced limb position would be useful for detailed identification of the site and anatomical cause of nerve disturbance in TNTOS cases.