eNeuro

The connection between neuropathy and IGM

Joshua Johnson, M.D.

General neurologist, peripheral nerve disorders
Providence Portland Medical Center
The Oregon Clinic

At least 20 million Americans have a neuropathy, and nearly 10 percent of Medicare patients have neuropathy as their primary or secondary diagnosis.

However, the laboratory workup of neuropathy can be unrevealing, with a diagnostic yield of 9 to 58 percent. The recent neuropathy literature suggests a connection between neuropathy and impaired glucose metabolism (IGM), a diagnosis based on an abnormal fasting glucose level, a two-hour glucose tolerance test or hemoglobin A1C.

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Dr. Johnson discusses neuropathy in Providence medical grand rounds.

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Many patients with otherwise idiopathic neuropathy have IGM, with the frequency in the literature ranging from 48 to 62 percent.^1-2 Most of these patients do not qualify as diabetic, and their abnormal glucose levels often remain untreated.

IGM seems to cause neuropathy by the same mechanisms as diabetes,^3-7 and there is accumulating evidence that IGM should be treated aggressively in patients with neuropathy. The incidence of diabetes in patients with IGM is reduced by 58 percent with lifestyle intervention alone and by 31 percent with metformin.⁸

Similarly, patients with IGM and neuropathy decrease their neuropathic pain and objectively improve neuropathy when treated with lifestyle interventions or “intensive” glucose control.^9-10 This literature should encourage aggressive glucose control in patients with impaired glucose metabolism of any severity.

References

1. Singleton, J.R.; Smith, A.G.; Bromberg, M.B. “Painful sensory neuropathy associated with impaired glucose tolerance.” Muscle Nerve, 2001; 24:1225-1228.
2. Sumner, C.J.; Sheth, S.; Griffin, J.W.; Cornblath, D.R.; Polykefkis, M. “The spectrum of neuropathy in diabetes and impaired glucose tolerance.” Neurology, 2003; 60:108-111.
3. Hoffman-Snyder, C.; Smith, B.E.; Ross, M.A.; Hernandez, J.; Bosch, E.P. “Value of the oral glucose tolerance test in the evaluation of chronic idiopathic axonal polyneuropathy.” Archives of Neurology, 2006; 63:1075-1079.
4. Singleton, J.R.; Smith, A.G.; Russell, J.W.; Feldman, E.L. “Microvascular complications of impaired glucose tolerance.” Diabetes, 2003; 52:2867-2873.
5. Dyck, P.J.; Dyck, J.B.; Klein, C.J.; Weigand, S.D. “Does impaired glucose metabolism cause polyneuropathy? Review of previous studies and design of a prospective controlled population-based study.” Muscle Nerve, 2007; 36:536-541.
6. Smith, A.G.; Singleton, J.R. “Impaired glucose tolerance and neuropathy.” The Neurologist, 2008; 14:23-29.
7. Kissel, J. “Peripheral neuropathy with impaired glucose tolerance.” Archives of Neurology, 2006; 63.
8. Diabetes prevention program research group. “Reduction in the incidence of Type 2 diabetes with lifestyle intervention or metformin.” New England Journal of Medicine, 2002; 346:393-403.
9. Smith, A.G., et al. “Lifestyle intervention for pre-diabetic neuropathy.” Diabetes Care, 2006; 29:1294-1299.
10. Diabetes control and complications trial research group. “Effect of intensive diabetes treatment on nerve conduction in the diabetes control and complications trial.” Annals of Neurology, 1995; 38:869-880.