P. G. Newrick

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 (SD 10.2) mm Hg. In all but one patient compared with none of four non-neuropathic subjects the mean nerve oxygen tensions were below dorsal foot vein values. This unphysiological state may have a role in the aetiology of diabetic neuropathy.

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.