Neurologic causes to consider
Spinal stenosis is caused by central canal narrowing secondary to congenital abnormalities, trauma, or, most commonly, degenerative changes in the lumbar spine. Spinal stenosis is generally seen in men or women ages 50 to 70 years.38 Patients experience unilateral or bilateral claudication that improves with sitting or flexion of the spine5 and may develop bilateral lower extremity numbness and tingling from the buttocks that radiates down the legs. Diagnosis is typically made with a combination of a lumbar x-ray and an MRI, which will show nerve compression and bony overgrowth.38 CT myelogram, another imaging option, isless sensitive in the acute phase, but can be used to monitor the disease course.
Initial treatment includes physical therapy and NSAIDs.5 If conservative therapy fails, epidural or nerve root corticosteroid injections and surgical decompression or laminectomy are options.38
Nerve entrapment is a less common source of lower extremity pain in which the superficial peroneal nerve is most often affected.4,12,17,39 Trauma is the usual cause of nerve entrapment, but it may also be associated with overuse, most notably related to dance, soccer, or tennis.2,14,40,41 The most likely anatomic site is where the nerve exits the deep fascia within the lateral compartment in the lower third of the leg.39,40 Less frequently, the common peroneal nerve at the fibular neck, the saphenous nerve as it passes through Hunter’s canal, the posterior tibial nerve at the tarsal tunnel, and the sural nerve in the posterior calf may be affected.3,4,12,17,20,40,41 Entrapment of the peroneal nerve may be associated with activities involving repetitive inversion and eversion, such as running and cycling. Injury of the saphenous nerve is seen in sports involving repetitive knee flexion like rowing and cycling. Sural nerve entrapment is a result of crural fascia compression of the nerve during activities like running and track.3,14,40,42,43
Patients typically experience burning, tingling, and radiation of pain with activity. Symptoms worsen with continued exercise. The physical exam is often normal, especially early in the disease process, but may reveal sensory loss, motor weakness, and a loss of reflexes.2,40 Patients with superficial peroneal nerve involvement may have distal lateral leg pain that radiates into the dorsum of the foot, often exacerbated by lower leg percussion and resulting in diminished sensation.1 Common peroneal nerve involvement may alter sensation of the lateral leg, as well, but may also cause foot drop.2 The saphenous nerve can cause medial knee or leg symptoms, while the sural nerve can yield pain in the lateral ankle and foot.2
To diagnose nerve entrapment, electromyography and nerve conduction velocities at the level of the lesion may yield positive results 3 to 4 weeks after symptom onset.2,13,40 There are wide ranges of sensitivity and specificity for these studies, but they are nonetheless considered the tests of choice for nerve entrapment.1,44 Conservative treatment with activity modification, physical therapy, massage, and NSAIDs is often sufficient,2 with surgical management warranted only for refractory cases.2,14,40,41
CORRESPONDENCE
Jonathan A. Becker, MD, CAQSM, University of Louisville Department of Family and Geriatric Medicine, 201 Abraham Flexner Way, Suite 690, Louisville, KY 40202; jon.becker@louisville@edu.