ENDONEURIAL LOCALIZATION OF MICROVASCULAR DAMAGE IN HUMAN DIABETIC NEUROPATHY

Twenty diabetic patients with neuropathy underwent clinical and neurop hysiological evaluation together with a detailed morphometric assessme nt of capillary pathology in endoneurial and epineurial microvascular beds of the sural nerve. Morphological data were compared with ten non -diabetic control subjects. There were no significant differences in c ontrol subjects between basement membrane area. endothelial cell area, endothelial cell profile number or luminal area of endoneurial when c ompared with epineurial capillaries. In contrast, when compared with e pineurial capillaries, endoneurial capillaries from diabetic patients demonstrated a significant increase in basement membrane (p < 0.001) a nd endothelial cell (p < 0.001) area and a significant reduction in lu minal area (p < 0.001). There was no significant difference in endothe lial cell profile number between endoneurial and epineurial capillarie s amongst diabetic patients. Previous studies have demonstrated a good correlation between the degree of microangiopathy and measures of neu ropathic severity. In the present study increased endoneurial capillar y basement membrane area was significantly related to reduced peroneal nerve conduction velocity (p < 0.001), myelinated fibre density (p < 0.001) and elevated vibration (p < 0.05) and thermal (p < 0.001) perce ption. Increased endothelial cell area and reduced luminal size were r elated to a reduced peroneal nerve conduction (p < 0.05, p < 0.01, res pectively), reduced myelinated fibre density (p < 0.05, p < 0.01) and elevated thermal perception (p < 0.05, p < 0.001). Epineurial capillar y basement membrane, endothelial cell and luminal area failed to relat e to measures of neuropathic severity. This study has demonstrated mor e advanced microangiopathy and a more significant relationship to neur opathic severity in endoneurial compared with epineurial capillaries, thus providing further support for the role of microangiopathy in the pathogenesis of human diabetic neuropathy.