Harding AE at the Institute of Neurology, London, author of the Hereditary Ataxias and Related Disorders (Edinburgh, Churchill Livingstone, 1984) reviews the classification, causes, clinical characteristics and treatment of degenerative ataxias. A combination of genetic and environmental factors is the most common origin for this complex group of over 50 distinct diseases, subdivided according to clinical and genetic features. Metabolic defects such as arylsulfatase-A in metachromatic leukodystrophy are recognizable but untreatable but some deficiency diseases (e.g. Vitamin E) are amenable to treatment with supplements. The cause of Friedreich’s ataxia, an autosomal recessive disorder, is unknown and reported deficiencies of pyruvate dehydrogenase and mitochondrial malic enzymes have not been confirmed. Similarly, in olivoponto-cerebellar atrophy, a late onset ataxia, recent studies have not confirmed an earlier report of reduced leucocyte glutamate dehydrogenase activity. Most attempts at treatment of degenerative ataxias have been disappointing but promising results using thyrotropin releasing hormone have been reported from Japan. 
COMMENT. Degenerative ataxias resembling Friedreich’s ataxia that may be amenable to treatment include Vitamin E, B12, folate and biotin deficiencies and Refsum’s disease, responsive to a diet low in phytol and phytanic acid.