PREVALENCE AND TYPES OF DIABETIC PERIPHERAL NEUROPATHY
According to the CDC, 25.8 million children and adults in the United States (8.3% of the population) have diabetes. Approximately 60% to 70% of them have mild to severe neuropathy.1
Distal symmetric neuropathy is the most common form of diabetic peripheral neuropathy, accounting for more than 50% of cases. It is characterized by distal onset, predominately sensory polyneuropathy, and slow proximal progression.2
In contrast, diabetic amyotrophy is very rare, accounting for only 1% of all cases of neuropathy in diabetes. Prevalence is higher in those with type 2 versus type 1 diabetes (1.1% and 0.3%, respectively).3,4 The most commonly misdiagnosed of the asymmetric diabetic neuropathies, diabetic amyotrophy is characterized by acute, progressive, asymmetrical weakness and pain in the muscles of the proximal lower extremities.5 It is also been referred to as proximal diabetic neuropathy, ischemic mononeuropathy multiplex, diabetic femoral neuropathy, Bruns-Garland syndrome, and diabetic lumbosacral polyradiculopathy.5
LOCALIZATION AND PATHOGENESIS
The site of the lesion in diabetic amyotrophy remains controversial; it is theorized that diabetic amyotrophy may result from involvement of multiple sites, such as lumbosacral anterior horn cells, motor roots, plexus, or motor axons to the muscles of the proximal lower limbs.4
The pathogenesis remains unknown. One theory is that hyperglycemia may cause metabolic derangements in nerve conduction. Another is that there is ischemic damage followed by axonal degeneration. Immune-mediated inflammatory processes, such as microvasculitis, have also been proposed as causes.4,6
CLINICAL FEATURES
Diabetic amyotrophy is characterized by relatively rapid, progressive asymmetrical weakness and pain in the muscles in the proximal lower extremities; it develops over weeks to months and may continue for more than one year.2,6 It typically begins unilaterally and can progress bilaterally—normally without impairment in sensation. Patients commonly experience pain in the hip, buttock, or thigh, as well as difficulty walking, standing, or climbing stairs. Occasionally, the condition is painless and can be associated with weight loss. It causes significant acute disability, with the degree of recovery variable.2,4
Diabetic amyotrophy often presents either at diagnosis of diabetes or shortly thereafter. It most commonly affects men ages 40 to 50 and older, with higher incidence in type 2 diabetes.2,5
Physical exam findings include proximal muscle weakness and atrophy in the quadriceps, hamstring, gluteal, hip adductors/abductors, and iliopsoas muscles.4,5 Typically, there is no sensory impairment; however, mild sensory loss may be observed in patients with coexisting chronic distal sensorimotor polyneuropathy.2,4 The patellar tendon reflexes are typically diminished or absent, and the ankle reflexes may be normal or diminished.4
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