A 28-year-old motorcyclist sustains a complete avulsion injury of C8 and T1 nerve roots. In addition to claw hand deformity, which other specific finding would indicate preganglionic (root avulsion) injury rather than postganglionic traction injury?

• A Paralysis of intrinsic hand muscles and sensory loss on the medial forearm
• B Loss of triceps reflex and wrist drop
• C Paralysis of flexor digitorum profundus to the ring and little fingers
• D Ipsilateral Horner's syndrome and paralysis of serratus anterior ✓

Explanation

Preganglionic nerve root avulsion at C8-T1 level damages the T1 sympathetic outflow to the superior cervical ganglion before it joins the ventral ramus, causing ipsilateral Horner's syndrome (ptosis, miosis, anhidrosis). Additionally, C5-C7 root avulsions cause paralysis of serratus anterior (long thoracic nerve from C5-C7) and rhomboids (dorsal scapular nerve C4-C5). These muscles are innervated proximal to the brachial plexus formation, making their involvement a sign of root-level (preganglionic) injury. Postganglionic lesions affect only distal structures and spare Horner's syndrome.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.