A 37-year-old woman, gravida 3 para 2, at 32 weeks gestation comes to the office for evaluation of leg pain and numbness. For the past few weeks, she has noticed numbness and a "pins and needles" sensation over the lateral aspect of the left thigh that has progressively worsened. The patient is a kindergarten teacher and now has difficulty standing for prolonged periods of time. She has no chronic medical conditions and her only medication is a daily prenatal vitamin. Vital signs are normal, and BMI is 37 kg/m². On examination, the patient walks with a widened gait and has an exaggerated lordosis of the lower back. The left leg has a large area of numbness over the upper lateral thigh. Straight leg raise test is negative, but the patient has pain with hip extension. There is no tenderness to palpation over the left hip or buttock. Reflexes are intact and strength is 5/5 bilaterally. Which of the following is the most likely cause of this patient's pain?

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11ec25c8_da4a_1dcb_bc81_5314deaa6f21_MD0003_00 This patient has localized pain and paresthesia in the lateral thigh consistent with meralgia paresthetica. Meralgia paresthetica 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. Extension of the hip when standing or during examination often worsens the symptoms (possibly by putting pressure on the nerve). lateral femoral cutaneous nerve (LFCN) distribution of the nerve Meralgia paresthetica is often caused by external compression by tight clothing or belts. The risk is elevated in patients who are pregnant, especially in the third trimester due to the gravid abdomen and exaggerated lumbar lordosis. The diagnosis of meralgia paresthetica is usually made clinically; no imaging is needed. Because meralgia paresthetica is a benign and self-limited condition, conservative treatment (eg, avoiding tight garments, weight loss) is usually adequate. Meralgia paresthetica associated with pregnancy typically resolves postpartum. (Choice B) Greater trochanteric pain syndrome (ie, trochanteric bursitis) can cause lateral thigh pain, but the pain is typically sharp and confined to the trochanteric region. It is worse with ambulation or lying on the affected side; sensation is not affected. (Choice C) Compression of the sciatic nerve or contributing nerve roots (eg, by a herniated disc) causes sciatica, characterized by back and buttock pain that radiates down the posterior thigh to the foot. Associated features include lower extremity weakness and a positive straight leg raise test. straight leg raise test (Choice D) Nerve root compression by a narrowed spinal canal (ie, spinal stenosis) is usually seen in patients age >60 due to degenerative arthritis. The pain is felt in the posterior thigh(s) and often radiates to the distal lower extremity; it is typically worse when ambulating with the spine extended and relieved with spine flexion. (Choice E) Shingles is caused by reactivation of latent varicella-zoster infection in sensory nerve cells. It causes pain and paresthesia in a dermatomal distribution. Shingles is uncommon in pregnancy and is usually associated with a vesicular rash. (Choice F) Stretching of the round ligament caused by the enlarging gravid uterus can cause pain due to irritation of local nerve fibers. However, the pain is typically located in the lower abdomen and ipsilateral labia and is not associated with sensory changes. round ligament Educational objective: Meralgia paresthetica is caused by compression of the lateral femoral cutaneous nerve and presents with pain and paresthesia over the upper outer thigh. Meralgia paresthetica associated with pregnancy is typically self-limiting and resolves postpartum.

A 37-Year-Old Woman, Gravida 3 Para 2, at 32 Weeks