Small-fiber involvement in diabetic patients with neuropathic foot pain



Year of publication 2008
Type Article in Periodical
Magazine / Source Diabetic Medicine
MU Faculty or unit

Faculty of Medicine

Field Neurology, neurosurgery, neurosciences
Keywords Diabetic neuropathy; pain; small-fiber; thermal threshold; skin biopsy
Description Aims: To assess small-fiber involvement in diabetic patients with neuropathic pain. Methods: Peripheral nerve function was evaluated in a cohort of 30 patients with diabetes mellitus type 2 (DM2, 24 patients) or impaired glucose tolerance (IGT, 6 cases), and clinical symptoms of neuropathic pain in the feet, using nerve conduction studies, autonomic tests, thermal quantitative sensory testing (T-QST) and the quantification of intra- and subepidermal nerve fiber densities in skin punch biopsies. Results: Clinical signs of isolated small-fiber sensory involvement were present in 13 patients (pure small-fiber neuropathy - pSFN), 7 patients had isolated positive sensory symptoms without neurological deficits (pSFN-). Ten patients had concomitant electrophysiological and/or clinical signs of large-fiber sensory involvement (mixed-fiber neuropathy - MFN). Twenty seven patients (90%) had both reduced skin innervation and abnormalities of the T-QST parameters. Two other patients displayed either abnormal skin innervation or T-QST and only one patient had normal findings on both tests. The criteria of small-fiber neuropathy (SFN) were met in all 20 patients without large-fiber involvement. Small fiber involvement was also present in the10 MFN patients. Both T-QST and skin biopsy parameters revealed significant differences between these clinical subgroups, with increased severity of small-fiber involvement in the MFN group. Autonomic dysfunction was found in 43% of patients and did not correlate with either clinical, T-QST or skin biopsy data. Conclusions: Although the exact mechanism of neuropathic pain in diabetic patients is not known, pain is almost invariably accompanied by small-fiber dysfunction and pathology irrespective of autonomic or large-fiber involvement.
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