What is foot drop?

It is a term to describe a type of foot weakness when the foot becomes flaccid. When the patient lifts the foot up from the ground; it does not come up and seems to fall.

What exactly is the reason for the foot drop?

It is caused by the weakness of muscles in front of the leg and top of the foot. The defect leading to muscle weakness can be in multiple places all along its circuitry, from muscles to the brain. It can be understood as follows:

1. Muscles: Muscular dystrophy, myopathy.
2. Neuromuscular junction: Rare, like in myasthenia gravis.
3. Peroneal nerve: Probably the most common cause of foot drop. Peroneal nerve is vulnerable at knee level as it loops around a bone. Excessive or heavy physical activity involving knees may cause the nerve injury. Peroneal nerve injury could be localized with rest of the nerves relatively intact, or it could be a part of generalized peripheral neuropathy.
4. Sciatic nerve: Rarely injured, usually from mechanical trauma like gunshot.
5. Plexus: Lumbosacral plexus can be injured within the pelvis. Usual causes are metabolic (uncontrolled diabetes), hematoma (a complication of blood thinners), infectious (usually viral), or a tumor.  
6. Roots: Lumbosacral radiculopathy, in the lower back, typically caused by a disc herniation, or spinal stenosis.
7. Nerve cell body: As in motor neuron disease, or ALS.
8. Cauda equina: Rare. Causes include disc herniation, malignancy, infection, or cancer.
9. Spinal cord: Causes include inflammation like in MS, infection, stroke, or tumor.
10. Brain: Common causes are stroke, tumor, or any other structural lesion.

How is foot drop diagnosed?

It is diagnosed by physical examination.

How is the cause of foot drop determined?

Thorough history and physical exam are usually effective.  A neurologist first tries to determine if the cause is central (in the spinal cord or the brain), or peripheral, which is all causes outside of the brain and the spinal cord. Each level described above presents with its unique findings on the physical examination. Once the location of the problem is determined, appropriate test is performed, if needed.  

 

What diagnostic tests are used to diagnose the cause of foot drop?

1. Nerve conduction studies and electromyogram to diagnose the location of problem with nerves and muscles.
2. MRI spine or brain, if the examination suggests a diagnosis in these places.

How is foot drop treated?

The weakness is treated with physical and occupational therapy procedures, especially in mild to moderate cases. A brace, usually called an AFO (ankle-foot orthosis), helps to improve walking and avoid falling. Most patients are treated with a prefabricated plastic brace. There are variety of other options, some quite expensive. This can be discussed further with a physical or an occupational therapist. More specific treatment for the cause of foot drop is variable. Some conditions are treatable while others may not be.  

What should I do if I have foot drop?

If possible, consult a neurologist for proper diagnosis. Otherwise, see a general medical doctor.

Where may I find more information about foot drop?

American Academy of Neurology

American Academy of Physical Medicine & Rehabilitation