Review Question - QID 217736

This patient who presents with shooting and burning pain on the plantar surface of her foot and a positive Tinel sign (shooting pain elicited by tapping on the tarsal tunnel) likely has tarsal tunnel syndrome. Tarsal tunnel syndrome is caused by an entrapped or damaged distal tibial nerve.

The tibial nerve is a branch of the sciatic nerve and is derived from the L4-S3 nerve roots. The tibial nerve provides motor innervation to the posterior compartment of the leg, including the biceps femoris, triceps surae, plantaris, popliteus, and flexor muscles of the foot. The nerve also provides sensation to the plantar surface of the foot. Deficits of tibial nerve function can therefore cause anesthesia of the plantar surface of the foot and an inability to invert or plantarflex the foot. The tibial nerve may be damaged by knee trauma, Baker cysts, and tarsal tunnel syndrome. Tarsal tunnel syndrome may present in patients with flat feet, patients with ankle sprains or fractures, or after a period of overuse of the foot and ankle. Distally, the tibial nerve has also been referred to as the posterior tibial nerve and functions as a sensory nerve, leading to primarily sensory symptoms in tarsal tunnel syndrome. Tarsal tunnel syndrome affects the distal tibial nerve and presents with neuropathic pain of the plantar surface of the foot and weakness of the intrinsic foot muscles. Elicitation of pain with tapping over the tarsal tunnel (Tinel sign), electromyogram (EMG), and magnetic resonance imaging (MRI) may be used to diagnose tarsal tunnel syndrome. Management of tarsal tunnel syndrome is typically conservative (e.g., rest and non-steroidal anti-inflammatory drugs, proper fitting shoes, physical therapy); however, surgery may be indicated in severe cases.

McSweeney and Cichero review tarsal tunnel syndrome and the treatments. They recommend surgery for tarsal tunnel syndrome when a space-occupying lesion (e.g., lipoma, sarcoma) is the cause.

Incorrect Answers:
Answer 1: The deep peroneal nerve is a branch of the common (fibular) peroneal nerve (L4-S2). It supplies sensation to the webspace between the first 2 digits of the foot and motor innervation of the tibialis anterior. Damage to the deep peroneal nerve would cause anesthesia between the first 2 toes and an inability to dorsiflex the foot.

Answer 2: The saphenous nerve is a branch of the femoral nerve (L2-L4) and the longest nerve in the body. It provides sensation to the medial and anterior surface of the leg. The nerve may be affected by entrapment after prolonged walking or prolonged quadriceps use, causing knee pain and loss of sensation of the medial leg.

Answer 3: The superficial peroneal nerve is a branch of the common (fibular) peroneal nerve (L4-S2). It supplies sensation to the dorsum of the foot and motor innervation of the peroneus longus and brevis. Damage to the superficial peroneal nerve would present with sensory deficits of the dorsal surface of the foot.

Answer 4: The sural nerve is a purely sensory nerve that provides sensation to the posterolateral calf and distal leg. The sural nerve may be damaged during orthopedic surgery procedures and trauma.

Bullet Summary:
The tibial nerve is derived from the L4-S3 nerve roots and is implicated in tarsal tunnel syndrome, which presents with shooting and burning pain on the plantar surface of her foot.