A lower motor neuron injury at T1 affects which muscles?

A lower motor neuron injury at the T1 level primarily affects the intrinsic muscles of the hand, particularly the palmar and dorsal interossei. These muscles, which are responsible for the fine motor control of finger abduction and adduction, receive their innervation from the ulnar and median nerves.

When there is a lower motor neuron injury, such as at T1, the signals from the spinal cord to these muscles are disrupted, leading to weakness or paralysis. This results in significant challenges with hand function, as the ability to effectively manipulate or grip objects is often compromised. In contrast, the other muscle groups listed, such as the flexor digitorum muscles, deltoid and biceps, and wrist flexors, are innervated by different spinal levels or nerve roots, thus would not be directly impacted by a lower motor neuron injury specifically at T1. Therefore, understanding the innervation of hand muscles is crucial for recognizing the clinical implications of lower motor neuron injuries at this level.