Does impaired glucose metabolism cause polyneuropathy? Review of previous studies and design of a prospective controlled population-based study

Neuropathy associated with prediabetes: what is new in 2007?

Length-dependent polyneuropathy has long been recognized as a frequent complication of diabetes. A decade of observational and epidemiologic studies support the concept that intermittent hyperglycemia or insulin resistance associated with prediabetes may be sufficient to damage distal nerves. Features of the metabolic syndrome have been implicated as independent neuropathy risk factors in large population-based studies of diabetic patients. Preferential injury to small unmyelinated nerves is suggested by prominent neuropathic pain, predominant sensory injury, and early autonomic dysfunction. Small uncontrolled trials suggest that diet and exercise may transiently improve distal nerve function and neuropathy symptoms in these patients. Patients with prediabetes neuropathy may permit greater insight into the balance between distal axonal injury and nerve regenerative capacity that determines neuropathy progression, and will be good candidates for evaluation of rational therapy based on known pathophysiology of hyperglycemic neuropathy.

Drug therapy for chronic idiopathic axonal polyneuropathy

BACKGROUND

Chronic idiopathic axonal polyneuropathy is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, it reduces quality of life.

OBJECTIVES

To assess whether drug therapy for chronic idiopathic axonal polyneuropathy reduces disability, ameliorates neurological symptoms and associated impairments, and whether treatment is safe.

SEARCH STRATEGY

We searched Cochrane Library (Cochrane Neuromuscular Disease Review Group Register, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effectiveness, and the Cochrane Central Register of Controlled Trials), MEDLINE, EMBASE, ISI, and ACP Journal Club's Best Evidence, from 1981 until December 2002. We also hand searched the reference lists of relevant articles, reviews and textbooks identified electronically, and contacted authors and other experts in the field to identify additional studies.

SELECTION CRITERIA

We sought all randomised or quasi-randomised (alternate or other systematic treatment allocation), unconfounded trials that examined the effects of any drug therapy in patients with chronic idiopathic axonal polyneuropathy at least one year after the onset of treatment. Patients with chronic idiopathic axonal polyneuropathy had to fulfil the following criteria: age 40 years or older, distal sensory or sensorimotor polyneuropathy, absence of systemic or other neurological disease, chronic clinical course not reaching a nadir in less than two months, exclusion of any recognised cause of the polyneuropathy by medical history taking, clinical or laboratory investigations, electrophysiological studies in agreement with axonal polyneuropathy without evidence of demyelinating features. The primary outcome was the proportion of patients with a significant improvement in disability. Secondary outcomes were change in the mean disability score, change in the proportion of patients who make use of walking aids, change in the mean Medical Research Council sum score, degree of pain relief and/or reduction of other positive sensory symptoms, change in the proportion of patients with pain or other positive sensory symptoms, and frequency of adverse effects.

DATA COLLECTION AND ANALYSIS

Two reviewers independently reviewed and extracted details of trial methodology and outcome data of all potentially relevant trials.

MAIN RESULTS

Eighteen studies were identified and assessed for possible inclusion in the review, but all were excluded because of insufficient quality or lack of relevance.

REVIEWERS' CONCLUSIONS

Even though chronic idiopathic axonal polyneuropathy has been clearly described and delineated, no adequate randomised or quasi-randomised controlled clinical treatment trials have been performed. In their absence there is no proven efficacious drug therapy.