Small-fibre involvement in diabetic patients with neuropathic foot pain.
OBJECTIVE
To assess small-fibre involvement in diabetic patients with neuropathic pain.


METHODS
Peripheral nerve function was assessed in 30 patients with Type 2 diabetes mellitus (T2DM, n = 24) or impaired glucose tolerance (IGT, n = 6), and clinical symptoms of neuropathic pain in the feet, using nerve conduction studies, autonomic tests, thermal quantitative sensory testing (T-QST) and quantification of intra- and subepidermal nerve fibre densities in skin punch biopsies.


RESULTS
Clinical signs of isolated small-fibre sensory involvement were present in 13 patients [pure small-fibre neuropathy (pSFN)], seven patients had isolated positive sensory symptoms without neurological deficits (pSFN-). Ten patients had concomitant electrophysiological and/or clinical signs of large-fibre sensory involvement [mixed-fibre 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-fibre neuropathy (SFN) were met in all 20 patients without large-fibre involvement. Small-fibre involvement was also present in the 10 MFN patients. Both T-QST and skin biopsy parameters revealed significant differences between these clinical subgroups, with increased severity of small-fibre 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-fibre dysfunction and pathology irrespective of autonomic or large-fibre involvement.
Department of Neurology, Faculty Hospital and Medical Faculty of the Masaryk University, Brno, Czech Republic. evlckova@email.cz
E
E
Vlckova-Moravcova
J
J
Bednarik
J
J
Belobradkova
C
C
Sommer
D000328:Adult; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis* / Q000503:physiopathology; D017719:Diabetic Foot / Q000175:diagnosis* / Q000503:physiopathology; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D010146:Pain / Q000209:etiology* / Q000503:physiopathology; D012678:Sensation Disorders / Q000175:diagnosis / Q000503:physiopathology; D012684:Sensory Thresholds / Q000502:physiology*; D012867:Skin / Q000294:innervation*