Management
The first aims of management should be to identify and treat the cause of the condition, where this is possible, and to relieve the patients symptoms, where present. In children, who rarely appreciate diplopia, the aim will be to maintain binocular vision and, thus, promote proper visual development.Thereafter, a period of observation of around 6 months is appropriate before any further intervention, as some palsies will recover without the need for surgery. Symptom relief and/or binocular vision maintenance
This is most commonly achieved through the use of fresnel prisms. These slim flexible plastic prisms can be attached to the patients glasses, or to plano glasses if the patient has no refractive error, and serve to compensate for the inward misalignment of the affected eye. Unfortunately, the prism only correct for a fixed degree of misalignment and, because the affected individuals degree of misalignment will vary depending upon their direction of gaze, they may still experience diplopia when looking to the affected side. The prisms are available in different strengths and the most appropriate one can be selected for each patient. However, in patients with large deviations, the thickness of the prism required may reduce vision so much that binocularity is not achievable. In such cases it may be more appropriate simply to occlude one eye temporarily.
However, levels of glycine in plasma and cerebrospinal fluid typically normalize within eight weeks, and in five of six cases there were no neurological issues detected at follow-up times up to thirteen years. A single patient was severely retarded at nine months. The suspected cause of transient neonatal hyperglicinemia is attributed to low activity of the glycine cleavage system in the immature brain and liver of the neonate. Treatment
A treatment of sodium benzoate, which binds to glycine and forms hippurate, and dextromethorphan, which weakly inhibits the N-methyl-D-aspartate receptors that glycine acts on has been shown to improve outcomes in select cases where the disorder is present in attenuated form. Prognosis
The prognosis is very poor. Two studies reported typical age of deaths in infancy or early childhood, with the first reporting a median age of death of 2.6 for boys and less than 1 month for girls. Research
Response to treatment is variable and the long-term and functional outcome is unknown. To provide a basis for improving the understanding of the epidemiology, genotype/phenotype correlation and outcome of these diseases their impact on the quality of life of patients, and for evaluating diagnostic and therapeutic strategies a patient registry was established by the noncommercial International Working Group on Neurotransmitter Related Disorders (iNTD). See also
List of amino acid metabolism disorders
inborn errors of metabolism

References


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