NERVE BIOPSY FINDINGS IN DIFFERENT PATTERNS OF PROXIMAL DIABETIC NEUROPATHY

Besides distal symmetrical sensory polyneuropathy (DSSP), middle-aged diabetic patients may present with focal or multifocal neuropathies, i ncluding proximal neuropathy of the lower limbs, the pathophysiologica l features of which are uncertain. We studied 10 non-insulin-dependent diabetic patients, 45 to 72 years of age, who developed a painful pro ximal neuropathy of the lower limbs for which other causes of neuropat hy were carefully excluded. The proximal neuropathy was asymmetrical i n all patients, sensory in 4, motor and sensory in the others. Signs o f DSSP were present in all. A sample of the intermediate cutaneous ner ve of the thigh, a sensory branch of the femoral nerve, was taken by b iopsy and examined by light and electron microscopy. Examination of th e nerve specimens revealed ischemic nerve lesions in 3 patients. Nerve ischemia was associated with vasculitis and inflammatory infiltration in 2 of them. In the other patients the lesions of the cutaneous nerv e of the thigh included a varying incidence of axonal and demyelinativ e lesions similar to those observed in DSSP, with mild inflammatory in filtration in 4 of them. The density of myelinated and of unmyelinated was variably decreased. This study shows that axonal and demyelinativ e lesions similar to those found in diabetic DSSP are present in proxi mal nerves in mild forms of proximal diabetic neuropathyl while nerve ischemia, inflammatory infiltration, and vasculitis are encountered in the most severe forms of proximal diabetic neuropathy.