Unusual neurologic manifestation of compressive radiculopathy of the first thoracic root (T1)

Introduction:

First thoracic (T1) root lesions are uncommon and not easily defined. Only few case reports of such patients are available. We report one further patient with isolated T1 root lesion with a quite unusual presentation, which has not been described so far. Case report:

A 70-year-old man presented with a 4-week history of left sided neck and shoulder pain irradiating in the left ulnar side of the forearm and digits 4 and 5. He described a reduced handgrip. His examination showed hypesthesia to pin testing in dermatome C8, but not in T1. Motor testing showed a moderate weakness of the APB and the intrinsic hand muscles. Additionally, a left sided Horner's syndrome, as confirmed by cocaine testing was present. Needle electromyography demonstrated fibrillation potentials in the APB. In the APB, IODI, ADM, and paravertebral muscles at T1 neurogenic motor unit potential changes and a reduced recruitment pattern of MUP was observed. Sensory and motor electroneurography of the ulnar and median nerve were normal except a reduced CMAP amplitude of the median nerve. The sympathic skin responses of both hands were normal. Spinal MRI disclosed a lateral T1/2 disc prolapse which was confirmed intraoperatively, demonstrating a compression of the T1 root. The C8 root was definitely not involved. Postoperatively, the patient experienced an immediate resolution of pain.

Discussion:

T1 radiculopathy is an uncommon finding. Our patient showed denervation of the APB confirming that this muscle is mainly innervated by the T1 root. Additionally, the sympathetic fibres from the ganglion spinale were affected which also travel within the T1 root. The unusual finding in our patient was that the sensory fibres innervating the C8 dermatome exceptionally also travelled along the T1 root, which has not been reported so far.