Aims/hypothesis: The early pathological features of human diabetic neuropathy are not clearly defined. Therefore we quantified nerve fibre and microvascular pathology in sural nerve biopsies from diabetic patients with minimal neuropathy. Methods: Twelve diabetic patients underwent detailed assessment of neuropathy and fascicular sural nerve biopsy at baseline, with repeat assessment of neuropathy 8.7±0.6 years later. Results: At baseline, neuropathic symptoms, neurological deficits, quantitative sensory testing, cardiac autonomic function and peripheral nerve electrophysiology showed minimal abnormality, which deteriorated at follow-up. Myelinated fibre density, fibre and axonal area, and g-ratio were normal but teased fibre studies showed paranodal abnormalities (p<0.001), segmental demyelination (p<0.01) and remyelination (p<0.01) without axonal degeneration. Unassociated Schwann cell profile density (p<0.04) and unmyelinated axon density (p<0.001) were increased and axon diameter was decreased (p<0.007). Endoneurial capillaries demonstrated basement membrane thickening (p<0.006), endothelial cell hyperplasia (p<0.004) and a reduction in luminal area (p<0.007). Conclusions/interpretation: The early pathological features of human diabetic neuropathy include an abnormality of the myelinated fibre Schwann cell and unmyelinated fibre degeneration with regeneration. These changes are accompanied by a significant endoneurial microangiopathy.

Clinical, electrophysiological and ultrastructural morphometric observations were made in 5 diabetic non-neuropathic patients, 5 diabetic patients with mild neuropathy and 11 diabetic patients with severe neuropathy. Capillary abnormalities were assessed in simultaneous nerve, muscle and skin biopsies and compared with results from 6 age-matched, non-diabetic control subjects. Nerve capillaries demonstrated markedly greater pathology than skin and muscle capillaries. Endoneurial capillary density was significantly reduced in severely neuropathic diabetic patients (p less than 0.01) when compared with control subjects. Capillary basement membrane (p less than 0.002), endothelial cell (p less than 0.003) and total diffusion barrier (endothelial cell, pericyte, basement membrane) (p less than 0.001) thickness were significantly increased, and oxygen diffusing capacity was significantly reduced (p less than 0.001) in the nerves of patients with severe diabetic neuropathy when compared to control subjects. Endothelial cell profile number and luminal perimeter were significantly increased in asymptomatic (p less than 0.01), (p less than 0.05) and severely neuropathic (p less than 0.001), (p less than 0.05) diabetic patients respectively. However, endothelial cell outer perimeter, a measure of capillary size, showed no significant increase in diabetic patients when compared with control subjects. An association was observed between neurophysiological and neuropathological measures of neuropathic severity. There was no significant correlation between the duration of diabetes and HbA1 levels with capillary pathology or with neuropathic severity. Very few abnormalities of muscle and skin correlated with neuropathic severity. However, all measures of nerve capillary pathology correlated significantly with neurophysiological and neuropathological measures of neuropathic severity.

Peripheral nerve oxygen tensions were assessed in vivo by using microelectrodes to measure endoneurial oxygen tension in exposed sural nerve. In 11 diabetic patients with chronic sensorimotor neuropathy the mean endoneurial oxygen tension was 39 7

Dynamic foot pressure has been studied in 44 diabetic subjects of mean age 52 years with no clinical evidence of neuropathy and in an age and sex matched non-diabetic control group. Vibration perception threshold (VPT), sensory (SCV), and motor conduction velocities (MCV) were also measured in the diabetic subjects. Sixteen diabetic subjects (Group A) had abnormally high pressures under the metatarsal heads (greater than 10 kg/cm2), whereas the remaining 28 diabetic subjects had normal results (Group B). The ratio of toe to metatarsal head loading (normal 0.112) was significantly reduced in Group A (0.077) compared to Group B (0.127: p less than 0.05). VPT and sural nerve SCV were also significantly abnormal in Group A subjects compared with Group B (p less than 0.005 and p less than 0.02, respectively), though there were no differences in MCV. A significant inverse correlation was obtained between toe loading and VPT. It is concluded that abnormalities of foot pressure occur in early sensory neuropathy and may precede clinical abnormalities. Assessment of the toe-loading ratio may provide a sensitive measure of motor dysfunction in early diabetic neuropathy.

Patients and methodsUsing data from our recent study of 42 motor neuron disease patients we reviewed our records of those with persistent pain of more than trivial severity. We sought details of the pain duration, timing in the course of the disease, pain quality, site and efficacy of treatment measures.

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1. Splanchnic haemodynamic changes were studied in seven healthy subjects during hypoglycaemia induced by the intravenous infusion of insulin. Superior mesenteric artery blood flow and cardiac output were examined non-invasively by a Doppler ultrasound technique. 2. Blood glucose concentration fell from 4.5 (0.14) mmol/l basally to 1.5 (0.09) mmol/l [mean (sem), P < 0.003] at the hypoglycaemic reaction (‘R’) and recovered to baseline by ‘R’ + 60 min. There was an associated rise in plasma glucagon, adrenaline and noradrenaline levels. 3. Superior mesenteric artery blood flow rose at ‘R’ from a basal value of 532 (38) ml/min to a peak of 803 (73) ml/min at ‘R’+10 min [mean (sem), P < 0.005] and remained significantly elevated until ‘R’ + 40 min. Resistance in this vessel fell by 33% at ‘R’+ 10 min (P < 0.005) and remained significantly low until ‘R’ + 40 min. 4. Cardiac output rose by 33% at ‘R’ (P < 0.004) and returned to normal by ‘R’ + 20 min. This was associated with a 24% rise in pulse rate (P 0.03), but no change in stroke volume or mean arterial pressure. Total peripheral resistance fell by 21% at ‘R’ (P 0.005) and had returned to normal by ‘R’ + 20 min. 5. The sustained rise in splanchnic blood flow during hypoglycaemic recovery may be of homoeostatic importance by providing metabolic fuel to the liver for gluconeogenesis.