The Diabetic Neuropathies

Practical and Rational Therapy

J. Robinson Singleton, M.D.; A. Gordon Smith, M.D.

Disclosures

Semin Neurol. 2012;32(3):196-203. 

In This Article

Focal, Acute, and Regional Forms of Diabetic Peripheral Nerve Injury

Compressive mononeuropathies, especially ulnar, median, and peroneal, are more common in diabetes. Bilateral and nondominant median mononeuropathy at the wrist are more common in diabetes,[3] although obesity, rather than diabetes, may be the primary driver of increased carpal tunnel syndrome risk.[4] Hand numbness suggests bilateral median mononeuropathies at the wrist (carpal tunnel syndrome) and/or ulnar mononeuropathy at the elbow (cubital tunnel syndrome) in preference to advanced DSP. Nerve conduction studies should be performed to confirm compressive ulnar or median mononeuropathies, and to screen for associated axonal injury. Those with pure demyelinating injury may respond to nocturnal neutral wrist splints and a regimen of studious avoidance for positional cubital tunnel compression. Patients with active denervation should be referred for carpal tunnel decompression, which is nearly as effective for diabetes patients as for normoglycemic controls, improving digital sensation in two-thirds.[5] Ulnar transposition from the cubital tunnel improves symptoms in only 50 to 60% of ulnar mononeuropathy patients.

Diabetes is associated with several acute neuropathic complications. Diabetic lumbosacral radiculoplexus neuropathy (DLRPN or "diabetic amyotrophy") typically presents with the abrupt onset of severe unilateral thigh pain. This is followed by progressive atrophy and weakness, involving proximal more than distal muscles. Patients may experience dramatic weight loss and many are rendered wheelchair dependent.[6] Distal onset and contralateral limb involvement are common, and patients with severe upper-extremity symptoms or variant DLRPN with motor predominance, absence of pain, and greater clinical symmetry have been described, further broadening the spectrum of this disorder.[7] Most patients experience progression over many months with subsequent improvement, but are left often with permanent deficits.[6]

Diabetic lumbosacral radiculoplexus neuropathy typically affects older patients with type 2 diabetes. Unlike DSP, DLRPN risk is not related to diabetic control or duration. Indeed, DLRPN patients typically have shorter diabetes duration than those with DSP. Electrodiagnostic studies demonstrate evidence of a polyradiculoneuropathy. Cerebrospinal fluid examination is characterized by elevated protein concentration without pleocytosis. Nerve biopsies demonstrate a microvasculitis.[8] These features support an autoimmune etiology. A retrospective case series reported benefit for neuropathic pain in five DLRPN patients treated with intravenous immunoglobulin (IVIg),[9] but a small randomized trial did not demonstrate significant disease modification with IV methylprednisolone. A recent Cochrane review concluded that definitive studies are lacking,[10] perhaps setting the stage for a carefully designed randomized trial of IVIg in this disorder.

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