Studies on Sural Nerve Biopsies in Endemic Skeletal Fluorosis

Sural nerve biopsies from 13 patients with radiologically confirmed skeletal fluorosis were studied for myelinated fibre densities, frequency distribution of their diameters, and single teased nerve fibre preparations. It was observed that most of the biopsies showed a marked reduction in myelinated fibre densities with more than half of them involving the smaller fibres of less than 7 gm diameter. Teased fibre measurements of internodal lengths and internodal diameters point to myelinated fibre dropout being due to axonal degeneration with secondary demyelination. The selective loss of small fibres is unlikely to be due to an entrapment neuropathy alone, and possibility of primary toxic injury needs to be considered.