Can we avoid AVED?

Ataxias of childhood

BACKGROUND

This review examines the causes of ataxias in children. It is a relatively common manifestation of neurological diseases in children. The etiology of ataxia covers a broad range, from infections to rare hereditary metabolic diseases. A systematic approach is required to make the correct diagnosis.

REVIEW SUMMARY

The more common causes of ataxias in children are discussed in detail. The importance of recognizing potentially reversible conditions such as vitamin E deficiency and Refsum's disease is stressed. Recent advances in molecular genetics of some of the chronic ataxias are discussed. The importance of categorizing diseases based on the duration of symptoms and associated signs is discussed. Treatment options are mentioned.

CONCLUSION

Ataxia is a common mode of presentation of cerebellar, posterior column, and vestibular disease in children. Awareness of the spectrum of disease entities that cause ataxia in childhood may lead to better diagnosis.

Vitamin E updated

An improved understanding of its physiology has led to better therapeutic use of vitamin E in recent years. It is a physiological membrane bound antioxidant, protecting cell membrane lipids from oxidant damage by free redicals. Cholestatic liver disease, abetalipoproteinemia and ataxia with vitamin E deficiency are the common deficiency states where vitamin E is of definite therapeutic value, while reports of unproven benefits abound in literature. Vitamin E status of the body can be assessed by serum levels and various functional studies. The new water soluble form, tocopherol polyethylene glycol succinate (TPGS), is therapeutically superior to the standard oral forms available. Details of physiology and therapeutic application of the vitamin are discussed.

Diagnosis of inherited metabolic disorders affecting the nervous system

Knowledge of the molecular causes for genetic diseases that affect the nervous system is rapidly expanding. Especially striking has been the finding in several autosomal dominant neurodegenerative disorders that unstable expansions of trinucleotide repeats are responsible for the genetic disorder and that the length of the repeat can be correlated with the age of onset and the severity of symptoms. Phenotypic heterogeneity in many disorders associated with enzyme deficiencies can often be linked to the amount of residual enzyme activity occurring with different gene mutations. Making a specific diagnosis of a neurological disorder associated with genetically determined metabolic defects requires access to a laboratory that can assist in arranging for appropriate testing to be carried out. In some disorders such as the aminoacidurias diagnostic metabolic studies can be performed in hospital clinical chemistry laboratories. In others, such as the lysosomal storage diseases, a laboratory that carries out special lipid analyses and white blood cell enzyme assays will be necessary. DNA mutational analyses are becoming commercially available for diagnosing many disorders such as mitochondrial diseases and those conditions associated with expanded trinucleotide repeats. It may be necessary to contact individual research laboratories when confronted with a disorder that has been newly discovered or that is very rare. A computerised directory of specialised laboratories that perform disease specific testing for genetic disorders should be useful in choosing the appropriate diagnostic or research laboratory.