MKSAP quiz: Leg pain and numbness
This month's quiz asks readers to evaluate a patient with diabetes, back and thigh pain, and difficulty walking.
A 63-year-old man is evaluated for a 2-week history of low back pain, occasional numbness and intense pain of the left anterior thigh, buckling of the left knee, chronic paresthesias of the feet, and difficulty walking. The thigh pain keeps him up at night. His gait has worsened over the past 2 days because of intermittent pain in the right leg. Six weeks ago, he developed a severe flulike illness with symptoms of nausea, vomiting, diarrhea, and a 6.8-kg (15.0-lb) weight loss. He has a 2-year history of diet-controlled type 2 diabetes mellitus. His only medication is codeine.
On physical examination, vital signs are normal; BMI is 31. The patient uses a cane when walking and has an antalgic gait. Atrophy of the left anterior thigh muscles is noted. Muscle strength testing reveals marked weakness of hip flexors (3/5 on the left and 4/5 on the right) and of knee extensors (3/5 on the left and 4/5 on the right). Muscle strength in the ankle dorsiflexors is 5/5, bilaterally. The patellar stretch reflex is absent on the left and normal on the right. Achilles reflexes are diminished bilaterally. Sensory examination reveals decreased sensation to light touch and pinprick over the left anteromedial thigh but normal findings in the bilateral legs and feet.
Results of laboratory studies show an HbA1c value of 7.5%.
Which of the following is the most likely diagnosis?
A. Diabetic amyotrophy
B. Diabetic polyneuropathy
C. Guillain-Barré syndrome
D. Meralgia paresthetica
MKSAP Answer and Critique
The correct answer is A. Diabetic amyotrophy. This item is available to MKSAP 16 subscribers as item 87 in the Neurology section. Information about MKSAP 16 is available online.
This patient's symptoms and clinical findings are typical of diabetic amyotrophy, a lumbar polyradiculopathy affecting primarily muscles of the thigh (L2 through L4 spinal levels). Diabetic amyotrophy, which can follow a period of significant weight loss in persons with diabetes mellitus, classically presents with severe pain at onset followed by development of weakness and numbness. Progression occurs over weeks to months, sometimes with spread to the contralateral lower extremity or upper extremities. The disorder can occur in severe, mild, and even undiagnosed diabetes.
Diabetic polyneuropathy is a length-dependent dying-back axonopathy presenting with distal to proximal sensory loss, paresthesias, pain, and distal lower extremity weakness. Clinical examination typically reveals absent or significantly decreased Achilles reflexes, a gradient stocking distribution of sensory loss, and weakness of the distal lower extremity muscles. This patient's anterior thigh pain and normal distal extremity sensation argue against this diagnosis.
Although Guillain-Barré syndrome (GBS) can present with significant low back pain, this patient's severe thigh pain would be very unusual in GBS. Numbness and, frequently, weakness in GBS are typically symmetric and radiate distally to proximally. Tendon reflexes would be diffusely hypoactive or absent in both legs.
Meralgia paresthetica causes only sensory loss with mild to moderate dysesthesia over the lateral thigh without any associated lower extremity weakness.
Electromyography after at least 3 weeks of symptoms is useful in differentiating among these 4 conditions.
Key Point
- Diabetic amyotrophy is a lumbar polyradiculopathy affecting primarily muscles of the thigh (L2 through L4 spinal levels) that classically presents with severe pain at onset followed by development of weakness and numbness over weeks to months.