Bob Hamilton: A 42-Year-Old Male With Numbness in the Lateral Thigh

Learning Objectives

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Learn the common causes of lower extremity numbness.
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Develop an understanding of the unique relationship of the lateral femoral cutaneous nerve to the inguinal ligaments.
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Develop an understanding of the anatomy of the lateral femoral cutaneous nerve.
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Develop an understanding of the causes of meralgia paresthetica.
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Develop an understanding of the differential diagnosis of meralgia paresthetica.
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Learn the clinical presentation of meralgia paresthetica.
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Learn the dermatomes of the lower extremity.
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Learn how to use physical examination to identify meralgia paresthetica.
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Develop an understanding of the treatment options for meralgia paresthetica.

Bob Hamilton

Bob Hamilton is a 42-year-old construction worker with the chief complaint of, “I have burning pain and numbness in the side of my left thigh.” Bob stated that over the past several months, he began noticing that he started getting a pins-and-needles sensation in his left thigh after he had been sitting in his recliner watching Netflix. He noted that if he didn’t get up and move around that the sensation would get worse until he just had to get up to “shake it off.” I asked Bob if he had experienced any numbness or weakness in his legs and he replied, “Doc, it’s funny that you asked, because over the last couple of weeks, if I am squatting down at work for any length of time, my left leg gets continually more numb.” “Both legs?” I asked, and he said no, only the left leg. “Bob, does this pins-and-needles sensation and numbness go below the knee?” He shook his head and said, “Never.” ( Fig. 4.1 ) I asked Bob what he thought was causing his symptoms and after a moment he replied, “Doc, this may be crazy, but I am beginning to wonder if it is my tool belt.” I asked Bob what he had tried to make it better and he said that he had tried shifting his tool belt to the right side, but it made it harder to get his tools out, and taking Motrin just upset his stomach. He said that he also tried not putting the leg rest all the way up on his recliner to take pressure off his bum leg. He also volunteered that he had quit sleeping with his pajama bottoms because the skin over the numb area was so sensitive. “It’s kinda like a burn. Also, Tylenol PM seems to help some—at least with sleep.” “Interesting,” I said. “Any intentional weight loss or weight gain?” Bob gave me a sheepish grin and said, “I know, Doc, I need to cut back on the beer and Doritos. I have really packed it on since my leg started bothering me.”

I asked Bob to show me where the pins-and-needles sensation and numbness were and he pointed to his left lateral thigh. “Right here, Doc, and it’s really driving me crazy.” I asked Bob about any fever, chills, or other constitutional symptoms such as weight loss, night sweats, etc., and he just shook his head no. He denied any antecedent lower extremity trauma, but noted that sometimes the pins-and-needles pain woke him up at night.

He went on to say that he could live with the numbness, but the pins-and-needles pain and the sensitive skin were really bothering him. He then asked, “Doc, do you think this could be cancer? You know, my dad died of colon cancer last year, and this really has me freaked out.” I clapped Bob on the shoulder and said that I was pretty sure what was causing his symptoms, and I seriously doubted it was cancer.

On physical examination, Bob was afebrile. His respirations were 18, his pulse was 74 and regular, and his blood pressure (BP) was 132/78. His body mass index (BMI) was 35.2. His 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 left lower extremity was unremarkable. There was no rubor or color, but there was allodynia in the distribution of the lateral femoral cutaneous nerve on the left. There was no obvious infection. I asked Bob to squat; after about 30 seconds he had to stand up because the pins-and-needles sensation was too much for him to tolerate.

A careful neurologic examination of both lower extremities revealed decreased sensation in the distribution of the left lateral femoral cutaneous nerve, but no sensory abnormalities below the knee were identified ( Fig. 4.2 ). His left motor exam was within normal limits. His right lower extremity neurologic examination was completely normal. Deep tendon reflexes were normal bilaterally. There was a positive Tinel sign over the left lateral femoral cutaneous nerve ( Fig. 4.3 ).

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

The History

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A history of onset of a pins-and-needles sensation of the left lateral thigh that does not radiate below the knee
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Numbness of the left lateral thigh that does not radiate below the knee
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Pins-and-needles sensation and numbness exacerbated by sitting or squatting for long periods of time
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No symptoms in the right lower extremity
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History of recent weight gain
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History of wearing a heavy tool belt
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No fever or chills

The Physical Examination

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The patient is afebrile
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High BMI
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Positive Tinel sign over the lateral femoral cutaneous nerve on the left (see Fig. 4.3 )
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Decreased sensation in the distribution of the left lateral femoral cutaneous nerve
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Allodynia in the distribution of the left lateral femoral cutaneous nerve
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No motor deficit in the right lower extremity
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Deep tendon reflexes within normal limits bilaterally

Other Findings of Note

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Normal HEENT examination
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Normal cardiovascular examination
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Normal pulmonary examination
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Normal abdominal examination
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No peripheral edema

What Tests Would You Like to Order?

The following tests were ordered:

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Ultrasound of the left lateral femoral cutaneous nerve at the level of the inguinal ligament
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Electromyography (EMG) and nerve conduction velocity testing of the left lateral femoral cutaneous nerve

Test Results

Ultrasound examination of the lateral femoral cutaneous nerve at the level of the femoral triangle reveals no obvious tumor or mass compressing the lateral femoral cutaneous nerve ( Fig. 4.4 ). EMG and nerve conduction velocity testing revealed slowing of lateral femoral cutaneous nerve conduction across the femoral triangle.