C5-8 brachial plexus root injury: the "T-1 hand".

Object: Classically, C5-7 root injuries of the brachial plexus have been associated with palsies of shoulder abduction/external rotation, elbow flexion/extension, and wrist, thumb, and finger extension. However, current myotome maps generally indicate that C-8 participates in the innervation of thumb and finger extensors. Therefore, the authors have hypothesized that, for palsies of the thumb and finger extensors, the injury should affect the C-5 through C-8 roots.

Methods: The authors tested their hypothesis in 30 patients with upper-type palsies of the brachial plexus. They traced a correlation between clinical findings and root injury, as documented by CT myelography, direct visualization during surgery, and electrophysiological studies.

Results: In C5-8 root injuries, shoulder abduction and external rotation were paralyzed, and in all patients, wrist extensors were paralyzed. However, in 22 of the 30 patients, wrist extension was possible, because of contraction of the extensor digitorum communis and extensor pollicis longus. Wrist flexion and pronation also were preserved. The T-1 root contributed significantly to innervation of the thumb and finger flexors, ensuring 34% grasping and 40% pinch strength relative to the normal side. Hand sensation was largely preserved.

Conclusions: Based on the authors' observations, they suspect that the clinical scenario previously attributed to a C5-7 root injury is, in fact, a C5-8 root injury. The authors propose referring to this partial palsy of the brachial plexus as a "T-1 hand."