In a peripheral compressive neuropathy, recovery can be expected in up to 3 months, provided that further compression is avoided. A partial peroneal nerve palsy after total knee replacement has a uniformly good prognosis. A variable amount of recovery is seen with a complete postoperative palsy. Follow-up electromyography and nerve conduction studies may be useful for assessing recovery.
A partial palsy recovers faster because of local sprouting. With complete axonal loss, reinnervation is achieved solely through proximal-to-distal axonal growth, which usually proceeds at a rate of 1 mm/day. Thus, injuries of a nerve close to its target muscle also have a more favorable outcome. In a nerve root compressive neuropathy, one study concluded that severe motor weakness lasting longer than 6 months, a negative straight leg-raising test, and old age were poor prognostic factors for recovery of dorsiflexion.
When direct injury to the peroneal nerve occurs, the outcome is more favorable for penetrating trauma than for blunt trauma; a traction or stretch injury to the nerve has an intermediate outcome. When nerve grafting is performed, functional recovery depends on the severity of injury and thus on the length of the graft used. With grafts longer than 12 cm, good functional recovery is rare.
For more on the prognosis of foot drop, read here.
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Cite this: Craig C. Young, James W. Pritchett. Fast Five Quiz: How Much Do You Know About Foot Drop? - Medscape - Jul 07, 2015.