Dual Neuropathies in Tandem: Lower Trunk Plexopathy with Superimposed Carpal Tunnel Syndrome Due to an Atypical Lesion Mechanism

Case Diagnosis: Lower Trunk Plexopathy with Superimposed Carpal Tunnel Syndrome

Case Description or Program Description: A 74-year-old male patient reports right-hand numbness and tingling, associated with neck and right upper extremity pain that has been present for years and has gradually worsened. The symptoms started after trying to turn on an electric generator. Although symptoms somewhat improved with modalities and oral pain medications, they continued to linger.

Setting: Secondary Care

Assessment/Results: Physical examination revealed limited range of motion of neck in all planes specially in rotation and extension, and right-hand intrinsic muscle atrophy, mostly in ulnar distribution, along with weakness in hand grip and finger abduction. Sensory deficits extended from the right little finger to the ulnar side of the forearm, while reflexes remained intact. A cervical MRI showed multilevel degenerative changes in the spine. An electrodiagnostic study was performed to elucidate etiology of symptoms with findings of right lower trunk plexopathy with superimposed carpal tunnel syndrome, and no evidence of cervical radiculopathy.

Discussion (relevance): Lower trunk plexopathy cases are classified as traumatic, neoplastic, or iatrogenic. Most traumatic injuries occur when the head is pushed away, or the arm is pulled upward. This case describes an unusual right lower trunk plexopathy resulting from sudden arm motion while pulling the starting rope of an electric generator, without prior symptoms. Clinicians must maintain a high level of suspicion to assess unexplained symptoms not accounted for by common factors found in the literature.

Conclusions: This case illustrates that traumatic lower trunk plexopathy caused by an uncommon and previously unreported injury mechanism can be a a significant cause of pain, numbness, and weakness in a patient. Although conservative management options may be attempted, electrodiagnostic testing may guide targeted management approach in refractory cases possibly requiring other options such as targeted interventional procedures, nerve repair or grafting, to restore function and quality of life in a patient.