| Summary: | Purpose: An epidemic of subacute optic neuropathy with sensori-neural hearing loss and peripheral neuropathy has affected Tanzania. The primary objective of this thesis was:- To describe the clinical features of the disease. To describe the magnitude of the epidemic To investigate the aetiology of the disease To determine if daily oral B-complex supplements improved prognosis. Methods: 225 acute cases in Dar es Salaam, Tanzania and 105 acute cases in Mogadishu, Somalia were assessed for signs and symptoms of optic neuropathy, peripheral neuropathy, and hearing loss. Blood and urine samples were collected from very acute cases (< 2 weeks of disease onset) in Tanzania and matched controls for aetiological studies. The same Tanzanian cases were recruited to the treatment study, of which 209 cases came back for 1 month re-assessment and a further 173 patients completed the three month treatment and returned for re-assessment. Ophthalmic, neurological and audiometric examinations were undertaken at baseline and follow-up. Population-based surveys were conducted in Dar es Salaam, Tanzania and Gambia to determine the magnitude of the epidemic. Results: The optic neuropathy is characterised by bilateral and symmetrical loss of visual acuity and colour vision, and central or caeco-central scotomas. On fundoscopy hyperaemia and swelling of the optic discs were observed at the early stages, as all cases progressed to temporal optic atrophy and nerve fibre layer loss in the papillomacular bundle. 35% of the Tanzanian cases and 59% of the Somalian cases had an accompanying peripheral neuropathy, 65% of the Tanzanian cases and 28% of the Somalian cases had sensori-neural hearing loss.
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