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Quiz: How Much Do You Know About Foot Drop?

Craig C. Young, MD; James W. Pritchett, MD

July 07, 2015

Foot drop is a simple name for a potentially complex problem. It can be defined as a significant weakness of ankle and toe dorsiflexion. This weakness results in the foot and toes pointing down and walking with an altered gait, which is sometimes referred to as "steppage gait" because individuals tend to walk with an exaggerated flexion of the hip and knee to prevent the toes from catching on the ground. Do you know the best practices surrounding this condition? Test yourself with this quick quiz.

Which of the following is recognized as a common behavioral cause of foot drop?

Prolonged standing

Use of improper footwear

Dehydration

Habitual crossing of the legs

A common behavioral cause of foot drop is habitual crossing of the legs. These cases typically resolve with discontinuance of the habit.

Neurologic causes of foot drop include mononeuropathies of the deep peroneal, common peroneal, or sciatic nerve. Lumbosacral plexopathy, lumbar radiculopathy, motor neuron disease, or parasagittal cortical or subcortical cerebral lesions also can manifest as foot drop. These lesions can be differentiated by means of clinical and electrodiagnostic examinations.

Foot drop also may be seen as a combination of neurologic, muscular, and anatomic dysfunction. Charcot foot is one example.

For more on the etiology of foot drop, read here.

Which of the following causes of foot drop is associated with the best prognosis?

Partial peroneal nerve palsy

Blunt trauma to the peroneal nerve

Penetrating trauma to the peroneal nerve

Nerve root compressive neuropathy

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.

Which of the following compartments is most commonly involved in chronic compartment syndrome associated with foot drop?

Lateral

Anterior

Superficial posterior

Deep posterior

Increased pain with passive stretch of the involved muscles is a consistent diagnostic indicator of a compartment syndrome. The usual initial presenting symptom is pain that is out of proportion to the injury. Paresthesias follow, but at this point, irreversible myoneural injury is likely to have occurred. Foot drop may also be noted; the time of presentation varies with the compartment involved. A form of chronic compartment syndrome, exertional compartment syndrome may occur in athletes who have exercise-induced pain in the lower leg or foot within 20-30 minutes of beginning to exercise. Often, this occurs after a recent increase in intensity or duration of training, or after a change in the training routine. The symptoms resolve after 15-30 minutes of rest; however, as the syndrome progresses, pain occurs earlier and takes longer to resolve. The anterior compartment is the one that is most commonly involved.

For more on compartment syndrome and foot drop, read here.

Which of the following is indicated if a tumor or compressive mass lesion to the peroneal nerve is suspected as the cause of foot drop?

Radiography

Ultrasonography

Magnetic resonance neurography

Electromyography

If a tumor or a compressive mass lesion to the peroneal nerve is being investigated, magnetic resonance neurography (MRN) may be considered. MRN provides high-resolution images of peripheral nerves, as well as associated intraneural and extraneural lesions.

MRN can be performed by using a standard 1.5 Tesla MRI system and special phased-array imaging surface coils. These coils acquire image data simultaneously from multiple receive-only surface coils. Image data from each coil in the array are combined to form a composite image with an improved signal-to-noise ratio.

Compared with standard MRI, MRN allows faster acquisition of anatomically detailed images, a smaller field of view, higher resolution, and thinner sections. These features provide images capable of showing the fascicular organization of normal peripheral nerves, thereby rendering the nerves more clearly distinguishable from other tissue (eg, tumor or blood vessels)

For more on the workup of foot drop, read here.

Which of the following foot drop causes warrants early surgical repair?

Blunt laceration

Lesions in continuity

Peroneal nerve palsy due to knee arthroplasty

Sharp laceration with suspected nerve transection

For sharp laceration with suspected nerve transection, early repair is warranted. Blunt lacerations are repaired 2-4 weeks after injury. Lesions in continuity usually are monitored for several months by clinical examination and electromyography for signs of early regeneration. If spontaneous regeneration does not occur, surgical exploration and intraoperative nerve action potential recordings are used to determine the need for repair, either with end-to-end sutures or with nerve grafts.

Patients with peroneal nerve palsy after knee arthroplasty or tibial osteotomy should initially be treated by removing all constrictive dressings and repositioning the knee to 20°-30° of flexion. If an expanding hematoma is noted, urgent exploration is warranted. If functional recovery does not occur within 2 months, nerve exploration or release is advocated. The time interval between symptom onset and decompression appears to affect the final functional outcome. However, the severity of the preoperative palsy does not seem to affect recovery.

For more on the treatment of foot drop, read here.

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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.

Cite this article: Craig C. Young, James W. Pritchett. Quiz: How Much Do You Know About Foot Drop? Medscape. Jul 07, 2015.