ABSTRACT
INJURIES MAY BE PREGANGLIONIC OR POSTGANGLIONIC (Fig. 79-2) n Root avulsions (preganglionic or supraganglionic)
• Occur proximal to intraforaminal dorsal root ganglion (DRG) • No Wallerian degeneration of sensory nerves, because cell bodies still in continuity with
axons; thus: • Sensory Nerve Action Potentials (SNAPs) are
present (pathognomonic). • It cannot be repaired with primary repair or
nerve grafting (often requires neurotization [nerve transfer]). Largely for technical reasons (It is not possible
to suture nerves back to the spinal cord itself.) • Physical examination findings Denervation of paracervical muscles Severe pain (deafferentation) in nerve
distribution Horner’s syndrome: Evidence of C8 or T1
level injury that is also highly associated with preganglionic injury Ptosis (drooping of upper eyelid) Miosis (pupillary constriction) Enophthalmos (posterior recession of the eye) Anhidrosis (lack of sweat)
n Postganglionic or infraganglionic • Injury distal to DRG • Paracervical muscles intact • Rami communicans to sympathetic ganglion intact (no Horner’s syndrome) • Wallerian degeneration in peripheral nerve fibers (absence of SNAPs) • No action potentials recordable • Surgical repair with nerve grafts or primary repair possible because a proximal portion is
intact and present
Fig. 79-2 Preganglionic versus postganglionic injury. The lower image demonstrates root avulsion.
