engleski

A neuropathological basis for pain in diabetic amyotrophy

Pain is a major feature of diabetic amyotrophy. We have studied 10 Type II diabetic patients (Age-65.4 ą 7.2 yr., duration of diabetes- 10.2 ą7.6 yr., duration of amyotrophy- 4.2 ą 1.8 months, HbA1c- 7.7 ą 1.3 %) with amyotrophy (DA), 14 diabetic patients (DN) with an equivalent degree of neuropathy without amyotrophy, and 14 control subjects (C). Diabetic patients with amyotrophy had marked pelvifemoral weakness (MRC- 15.9 ą 3.5/30) and pain (Visual Analogue Score of 7.8 ą 1.6/10). The intermediate cutaneous nerve of the tigh (ICNT) and sural nerve were biopsied in DA and the sural nerve alone in DN and C. Myelinated fibre density (no.mm-2) was significantly reduced in the ICNT (3104 ą 181, P<0.0004) and sural nerve (2756 ą 454, P<0.0009) of DA v DN (4042 ą 539) and C (6049 ą 342). Myelinated fibre area (&#956; m2) did not differ significantly between ICNT (27.7 ą 2.4) and sural (28.9 ą 2.2) of DA v DN (31.8 ą 1.9) or C (29.1 ą1.6). However, myelinated fibre axonal area (&#956; m2) was significantly reduced in the ICNT (5.9 ą 0.4, P<0.0001) and sural (7.1 ą 0.3, P<0.0008) of DA v DN (10.8 ą 0.8) and C (10.5 ą0.8). Unmyelinated fibre degeneration (% unassociated Schwann cell profiles) was increased in ICTN of DA (47.8 ą5.6) (p<0.002) v the sural of C (20.6 ą 1.9) but was not different from the sural of DN (57.9 ą 4.5). Unmyelinated axon density was significantly increased in the ICNT of DA (101020 ą 9513) v C (64116 ą 4889) (p<0.0005). Diabetic amyotrophy is characterised by a distal loss of myelinated fibres with axonal atrophy and unmyelinated fibre regeneration. These significant structural as opposed to functional changes may account for the severe and protrached pain in this condition.

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