A 45-year-old man comes to the office for evaluation of pain in his right lateral thigh. The pain has been present for 2 weeks and is described as a "pins and needles" sensation; it is exacerbated when he strains for bowel movements. The patient has never had this pain before and has no associated leg weakness or back pain. Medical history is significant for recently diagnosed type 2 diabetes mellitus, for which he was prescribed metformin 3 months ago. Vital signs are normal. BMI is 37 kg/m2. Examination shows loss of light touch and pinprick sensation in an area of the upper lateral thigh. There is no tenderness to palpation of the lateral femoral epicondyle. Knee and hip examinations are normal. A straight leg raising test is negative bilaterally and strength is 5/5 in both extremities. Which of the following is the most appropriate next step in management?
Meralgia paresthetica | |
Etiology | Lateral femoral cutaneous nerve entrapment or injury due to:
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Clinical |
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Management |
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NSAIDs = nonsteroidal anti-inflammatory drugs. | |
This patient has localized pain and paresthesia in the lateral thigh consistent with meralgia paresthetica (MP). MP is caused by compression of the lateral femoral cutaneous nerve (LFCN) where it passes under the inguinal ligament into the thigh. Patients experience symptoms in the distribution of the nerve but have no weakness because the nerve contains no motor fibers.
MP is often caused by tight clothing or belts or by abdominal straining; the risk is increased in patients who are pregnant, obese, or have diabetes mellitus. The diagnosis is made clinically; no imaging is needed. Because MP is a benign and self-limited condition, conservative treatment (eg, avoiding tight garments, weight loss) is usually adequate and improves symptoms in >90% of cases. Patients with persistent symptoms may respond to anticonvulsants (eg, gabapentin) or local nerve block.
(Choice A) Long-term use of metformin has been associated with vitamin B12 deficiency and a possible increased risk of peripheral neuropathy, but this would typically affect the distal extremities and would not be seen within 3 months. However, metformin can facilitate weight loss and may therefore alleviate MP.
(Choice B) MRI of the lumbar spine is indicated for suspected spinal pathology, as in certain patients with sciatica (eg, back pain radiating to posterior leg, positive straight leg raise test) who have concerning neurologic deficits (eg, saddle anesthesia, urinary retention) or in whom malignancy (eg, weight loss) or epidural abscess (eg, fever, intravenous drug use) is suspected. MP is due to peripheral nerve compression.
(Choice C) Nerve conduction studies (NCS) can be helpful to diagnose MP in doubtful cases; however, this patient has classic symptoms, and in most patients MP is a clinical diagnosis.
(Choice D) Physical therapy is sometimes prescribed to certain patients with sciatica (eg, persistent symptoms), although the effectiveness may be variable. For MP, aerobic exercise can facilitate weight loss and reduction of symptoms, but skilled physical therapy is not needed.
(Choice E) X-ray of the hip and pelvis can identify osteoarthritis of the hip joint. Osteoarthritis and other intrinsic disorders of the hip occasionally cause upper lateral thigh pain, but deep anterior groin pain is more typical, and loss of sensation is not seen.
Educational objective:
Meralgia paresthetica is caused by compression of the lateral femoral cutaneous nerve under the inguinal ligament and presents with localized pain and paresthesia in the lateral thigh without weakness. Patients are usually treated conservatively with weight loss and avoidance of tight garments.