Diabetic Amyotrophy

Last month’s Video Case Challenge (available on PracticalNeurology.com) presented a 55-year-old woman with subacute severe right pelvis and anterior thigh pain that was followed by weakness of bilaterial quadriceps.

THe MOST LIKELY DIAGNOSIS IS:

1. LS polyradiculopathy

2. Vasculitis

3. Atypical polymyositis

4. Diabetic amyotrophy

5 .Arachnoiditis

The Correct answer is 4 (Diabetic Amyotrophy)

• Diabetic amyotrophy (diabetic lumbosacral radiculoplexus neuropathy) is a characteristic syndrome that mostly affects diabetic patients and constitutes about one percent of diabetic neuropathies.

• Diabetic neuropathies are grouped into two main categories according to their pathology:

• Metabolic/ischemic mechanisms explain the most common distal sensory diabetic neuropathy.

• Microvasculitis explains diabetic amyotrophy and diabetic third cranial nerve palsy.

• The second category is pathologically characterized by microvasculitis and unlike the former one it usually occurs in well controlled diabetes mellitus with minimal end organ damage (retinopathy, nephropathy)

• Other causes of thigh pain in diabetic patients should be considered, including:

• L3 radiculopathy: L3 nerve root is not a common target for degenerative spine disease but it can lead to severe
anterior thigh pain.

• Diabetic muscle infarction: This usually affects the quadriceps muscles and presents with pain and indurated swelling in the anterior thigh. An MRI of the area shows infarction of the muscle.

• Meralgia paresthetica: Severe lateral thigh pain due to entrapment of the lateral femoral cutaneous nerve is
common in diabetic patients. Knee jerk and quadriceps strength are preserved.

• Diabetic amyotrophy may be as benign as a transient thigh pain that does not even reach the attention
of the physician.

• However, more than a third of cases are bilateral and 15 percent of cases lead to bilateral foot drop, while 12 percent of cases spread to the arms (diabetic thoracoabdominal radiculopathy).

• The progression of pain and weakness despite good diabetes control causes significant frustration.

• Lumbar surgery is frequently performed due to the presence of incidental LS degenerative spine disease.

• Most cases regain significant strength, but it may take a year for recovery to start and two years to be maximum. n

Aziz Shaibani, MD, FACP, FAAN, FANA is Director of the Nerve & Muscle Center of Texas. He is also Clinical Professor of Medicine at Baylor College of Medicine in Houston, and an Adjunct Professor of Neurology at Kansas University Medical Center in Kansas City.