Ultrasound-guided hydrodissection of the subclavius muscle region in neurogenic thoracic outlet syndrome: a case report

Background: Thoracic outlet syndrome (TOS) is frequently underdiagnosed due to nonspecific symptoms and the absence of definitive radiographic findings. Neurogenic TOS (nTOS), the most common subtype, is typically caused by compression of the brachial plexus within anatomically constrained spaces. While muscular contributors such as the scalene and pectoralis minor muscles have been widely discussed, the role of the subclavius muscle remains underrecognized. Case presentation: A 53-year-old male presented with an 18-month history of progressive right upper limb weakness and medial paresthesia refractory to prior treatments for presumed cervical spondylosis. Electrodiagnostic studies demonstrated persistent proximal motor slowing of the right ulnar nerve. Ultrasonography revealed marked atrophy of the right subclavius muscle compared with the contralateral side. Ultrasound-guided hydrodissection using 30 mL of 5% dextrose in water (D5W) was performed in the infraclavicular region with particular attention to the subclavius muscle and costoclavicular space. Immediate post-procedural assessment showed greater than 70% improvement in paresthesia, with subtle objective motor improvement on bedside examination that was not yet sufficient to change the MRC grade. Following six treatment sessions, complete resolution of symptoms and full motor strength recovery were achieved. Conclusion: In a patient with unexplained proximal neuropathy, ultrasonography identified focal subclavius muscle atrophy as a potential compressive contributor within the costoclavicular space, and ultrasound-guided hydrodissection of the infraclavicular region resulted in rapid and sustained clinical improvement. While the injectate volume (30 mL) likely affected adjacent structures such as the pectoralis minor and surrounding fascial planes, this minimally invasive approach may be a feasible option for selected patients with refractory nTOS. To our knowledge, this is the first reported case of ultrasound-guided hydrodissection of the infraclavicular region with attention to the subclavius muscle for neurogenic thoracic outlet syndrome associated with muscle atrophy. Further studies are warranted to confirm efficacy and to refine patient selection criteria.