Scott English: A 32-Year-Old Truck Mechanic With Pain and Electric Shocklike Sensation Radiating Into the Dorsum of the Foot

Learning Objectives

•

Learn the common causes of ankle and foot pain.
•

Learn the common causes of foot numbness.
•

Develop an understanding of the unique relationship of the deep peroneal nerve to the dorsalis pedis artery and the ligaments and bones of the ankle and foot.
•

Develop an understanding of the anatomy of the deep peroneal nerve.
•

Develop an understanding of the causes of deep peroneal nerve entrapment at the ankle.
•

Develop an understanding of the differential diagnosis of deep peroneal nerve entrapment at the ankle.
•

Learn the clinical presentation of deep peroneal nerve entrapment at the ankle.
•

Learn how to examine the ankle and foot.
•

Learn how to examine the deep peroneal nerve.
•

Learn how to use physical examination to identify deep peroneal nerve entrapment at the ankle.
•

Develop an understanding of the treatment options for deep peroneal nerve entrapment at the ankle.

Scott English

Scott English is a 32-year-old truck mechanic who has been my patient for the last several years. I last saw him for a subungual hematoma after he mashed his thumb with a hammer ( Fig. 4.1 ). His chief complaint today is, “The top of my foot is going to sleep.” Scott stated that over the past several months, in addition to the numbness, he began waking up at night with deep, aching right foot pain. “At first, I thought it was those damned steel-toed shoes that they make me wear. I think they make me wear them because if I get injured, they only have to pay worker’s comp on a couple of toes getting chopped off by the steel rather than a bunch of crushed toes! In this state, a chopped off big toe isn’t worth much. Anyway, I just got a new pair of steel-toed shoes, and at first I thought they would fit fine after I broke them in, but they are just a smidge tight across the top of my foot. I don’t tie them very tight, but they still pinch the top of my foot. I wore them, so I can’t take them back.”

I asked Scott if he had experienced any other symptoms, and he replied, “Doc, it’s funny that you asked because I noticed that when I wash between my toes, the duck web between my big toe and the next one is kind of numb. That’s really crazy, isn’t it? I am having a real hard time when I have to squat down to check a tire pressure or patch a tire. If I squat for too long, the top of my right foot gets these little electric shocks. It makes me want to scream. Not that it hurts that bad, it just really gets on your nerves, and I absolutely have to stand up. I have to be careful when the boss is around. He is always giving me the hairy eyeball.” I asked Scott what he had tried to make it better, and he said that taking his shoes off was about the only thing that helped. Scott went on to say that he tried to use a heating pad on his foot when he got home from work, and it “seemed to make the pins and needles worse. Tylenol PM seemed to help some, at least with sleep. You know, I have to be really careful what I take because I never know when that jackass I work for is going to make me pee in a cup.” I asked Scott about any fever, chills, or other constitutional symptoms such as weight loss or night sweats, and he shook his head no. He denied any antecedent foot trauma, but he again noted that most nights, the foot pain woke him.

I asked Scott to point with one finger to show me where it hurt the most. He pointed to the dorsum of the right foot. He went on to say that he could live with the numbness between the toes, “but the crazy way the top of my foot feels kind of scares me. I have to be able to squat if I want to keep my job.” He then asked, “Doc, do you think I can get the worker’s comp or go on disability?” I said that I thought that would be a heavy lift, but that I would do everything I could to get him better.

On physical examination, Scott was afebrile. His respirations were 16, his pulse was 64 and regular, and his blood pressure was 110/68. Scott’s head, eyes, ears, nose, throat (HEENT) exam was normal, as was his cardiopulmonary examination. His thyroid was normal. His abdominal examination revealed no abnormal mass or organomegaly. There was no costovertebral angle (CVA) tenderness. There was no peripheral edema. His low back examination was unremarkable. Visual inspection of the right foot was unremarkable. There was no ecchymosis, rubor, or color, and there was no obvious infection. There was a positive Tinel sign over the right deep peroneal nerve at the foot. There was weakness of the extensor digitorum brevis on the right. Examination of Scott’s toes revealed no stigmata of osteoarthritis or rheumatoid arthritis. The left foot examination was normal. A careful neurologic examination of the lower extremities revealed decreased sensation in the distribution of the distal deep peroneal nerve ( Fig. 4.2 ). Deep tendon reflexes were normal. Scott exhibited a positive Tinel sign over the deep peroneal nerve ( Fig. 4.3 ).

Key Clinical Points—What’s Important and What’s Not

The History

■

A history of the onset of right foot pain with associated paresthesias into the distribution of the deep peroneal nerve
■

Numbness of the web space between the big and second toe on the right
■

Foot weakness
■

No history of previous significant foot pain
■

No fever or chills

The Physical Examination

■

Patient is afebrile
■

Positive Tinel sign over the deep peroneal nerve at the dorsum of the right foot (see Fig. 4.3 )
■

Numbness in the distribution of the deep peroneal nerve (see Fig. 4.2 )
■

Weakness of the extensor digitorum brevis
■

No evidence of infection

Other Findings of Note

■

Normal HEENT examination
■

Normal cardiovascular examination
■

Normal pulmonary examination
■

Normal abdominal examination
■

No peripheral edema
■

Normal left upper extremity neurologic examination, motor and sensory examination

What Tests Would You Like to Order?

The following tests were ordered:

■

Electromyography (EMG) and nerve conduction velocity testing of the right upper extremity
■

Ultrasound of the right foot
■

Magnetic resonance imaging (MRI) of the right foot

Test Results

EMG and nerve conduction velocity testing revealed slowing of deep peroneal nerve conduction across the ankle.

Ultrasound examination of the right foot revealed flattening and enlargement of the deep peroneal nerve as it passed beneath the superficial fascia ( Fig. 4.4 ).