Impaired blood flow and arterio-venous shunting in human diabetic neuropathy: a novel technique of nerve photography and fluorescein angiography

Abstract

Summary. New techniques of sural nerve photography and fluorescein angiography which are able to provide an index of nerve blood flow have been developed. Under local anaesthetic, 3 cm of sural nerve was exposed at the ankle using an operating microscope. Without disturbing the epineurium, vessels were identified and photographed at a standard magnification ( x 30). These were independently graded by an ophthalmologist not otherwise involved with the study. Fluorescein angiography was then carried out on the exposed nerve. The fluorescein appearance time and intensity of fluorescence were quantified, using computer analysis of digitised images. Thirteen subjects with chronic sensory motor neuropathy, five non-neuropathic diabetic and nine normal control subjects were studied. The mean epineurial vessel pathology score of the neuropathic group was significantly higher than the combined normal control and non-neuropathic diabetic groups (p < 0.01). Direct epineurial arteriovenous shunting was observed in six neuropathic and one non-neuropathic diabetic patients and not in any of the normal control subjects. The nerve fluorescein appearance time was significantly delayed in subjects with chronic sensory motor neuropathy (51.5 + 12 s) compared to both normal (34.7 _+ 9 s, p < 0.01) and non-neuropathic diabetic subjects (33.4 + 11 s,p < 0.025). The mean intensity of fluorescence at 96, 252 and 576 s, was significantly lower in subjects with chronic sensory motor neuropathy compared with both of the other groups (p < 0.05). The epineurial vessel pathology score was significantly related to reduced sural (p < 0.01) and peroneal (p < 0.001) nerve conduction velocities, elevated vibration (p < 0.01) and thermal (p < 0.001) perception and the severity of retinopathy (p < 0.002). The fluorescein appearance time was significantly related to reduced sural sensory (p <0.02) conduction velocity, elevated vibration (p < 0.01) perception and epineurial vessel (p < 0.002) pathology score, but it failed to relate to peroneal motor (p = 0.06) conduction velocity, thermal (p = 0.1) perception and the severity ofretinopathy (p = 0.3). Intensity of fluorescence was significantly related to fluorescein appearance time (at 96 s,p < 0.001; at 576 s,p < 0.05) but did not relate to measures of neuropathic severity. These techniques have enabled us to observe that epineurial vessel anatomy is abnormal and that nerve blood flow is impaired in subjects with chronic sensory motor neuropathy. In addition epineurial arterio-venous shunting may be a feature of diabetic neuropathy. These techniques may further be applied to study nerve blood flow in early diabetic neuropathy.

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The calcium hypothesis of brain aging and neurodegenerative disorders: Significance in diabetic neuropathy

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