Proximal diabetic neuropathy

Proximal diabetic neuropathy, more commonly known as diabetic amyotrophy, is a nerve disorder that results as a complication of diabetes mellitus. It can affect the thighs, hips, buttocks or lower legs. Proximal diabetic neuropathy is a peripheral nerve disease (diabetic neuropathy) characterized by muscle wasting or weakness, pain, or changes in sensation/numbness of the leg.^[1] Diabetic neuropathy is an uncommon complication of diabetes. It is a type of lumbosacral plexopathy, or adverse condition affecting the lumbosacral plexus.

There are a number of ways that diabetes damages the nerves, all of which seem to be related to increased blood sugar levels over a long period of time. Proximal diabetic neuropathy is one of four types of diabetic neuropathy.^[2]

Proximal diabetic neuropathy can occur in type 2 and type 1 diabetes mellitus patients however, it is most commonly found in type 2 diabetics.^[3] Proximal neuropathy is the second most common type of diabetic neuropathy and can be resolved with time and treatment.^[4]

Signs & symptoms

Signs and symptoms of proximal diabetic neuropathy depend on the region of the plexus which is affected. The first symptom is usually pain in the buttocks, hips, thighs or legs. This pain most commonly affects one side of the body and can either start gradually or come on suddenly. This is often followed by variable weakness in the proximal muscles of the lower limbs. These symptoms, although often beginning on one side, can also spread to both sides.^[1] Weakness in proximal diabetic neuropathy is caused by denervation of the specific muscles innervated by regions of the plexus affected and can thus these muscles may start exhibiting fasciculations.

Note that diabetic amyotrophy is a condition caused by diabetes mellitus, but separate from the more common condition of polyneuropathy.

Causes

The nerve damage associated with the disease was first thought to be caused by metabolic changes such as endoneurial microvessel disease, which is the degeneration of pericytes due to hyperglycemia, and the reproduction of basement membranes when the pericytes are no longer regulating their cell cycle. The decreased size of the lumen plus the absence of the pericyte, which regulate capillary blood flow and phagocytosis of cellular debris, leads to ischemia. Nerve biopsies have shifted the view toward an immune mechanism that causes Micro Vasculitis, which could eventually lead to ischemia.^[5] Experimental treatments using immunosuppressive proteins have provided further corroborative evidence to the immune mechanism theory.^[6] Although this disease does occur in patients without diabetes the prevalence is much greater in the diabetic indicating that although hyperglycemia does not directly cause the nerve damage it may play a role.^[5]

Diagnosis

Patients with diabetes and proximal (hip, thigh) pain and weakness are often suspected of having diabetic amyotrophy. More definitive diagnosis is commonly made with electrodiagnostic studies including nerve conduction studies (NCS) and electromyogram (EMG).^[7] Diabetic amyotrophy is often a diagnosis of exclusion in diabetic patients with a lumbosacral plexopathy for whom no other cause of lumbosacral plexopathy can be determined.

Treatment

Proper management of diabetes mellitus can prevent proximal diabetic neuropathy from ever occurring.

The incidence of proximal diabetic neuropathy incidence is thought to be correlated to blood glucose control in diabetics, and is likely reversible with better control.

Medication helps reduce the pain involved in proximal diabetic neuropathy. Most patients take oral medication that is prescribed by a doctor. Common types of medication used to treat diabetic amyotrophy include anticonvulsives (e.g. gabapentin, pregabalin) as well as opioid medications, although the latter category is not optimally indicated for neuropathic pain.

References