Prompt recognition of a urea-cycle disorder and treatment with both sodium phenylacetate and sodium benzoate, in conjunction with other therapies, such as intravenous arginine hydrochloride and the provision of adequate calories to prevent catabolism, effectively lower plasma ammonium levels and result in survival in the majority of patients. Hemodialysis may also be needed to control hyperammonemia, especially in neonates and older patients who do not have a response to intravenous sodium phenylacetate and sodium benzoate.

We studied 26 children with inborn errors of urea synthesis who survived neonatal hyperammonemic coma. There was a 92 per cent one-year survival rate associated with nitrogen-restriction therapy and stimulation of alternative pathways of waste nitrogen excretion. Seventy-nine per cent of the children had one or more developmental disabilities at 12 to 74 months of age; the mean IQ was 43 +/- 6. There was a significant negative linear correlation between duration of Stage III or IV neonatal hyperammonemic coma and IQ at 12 months (r = -0.72, P less than 0.001) but not between the peak ammonium level (351 to 1800 microM) and IQ. There was also a significant correlation between CT abnormalities and duration of hyperammonemic coma (r = 0.85, P less than 0.01) and between CT abnormalities and concurrent IQ (r = -0.75, P less than 0.02). These results suggest that prolonged neonatal hyperammonemic coma is associated with brain damage and impairment of intellectual function. This outcome may be prevented by early diagnosis and therapy.

Aim-A large longitudinal interventional study of patients with a urea cycle disorder (UCD) in hyperammonaemic crisis was undertaken to amass a significant body of data on their presenting symptoms and survival. 1982 and 2003, as part of the FDA approval process, data were collected on patients receiving an intravenous combination of nitrogen scavenging drugs (Ammonul ® sodium phenylacetate and sodium benzoate, 10%, 10%) for the treatment of hyperammonaemic crises caused by urea cycle disorders. Methods-BetweenResults-A final diagnosis of a UCD was made for 260 patients, representing 975 episodes of hospitalisation. Only 34% of these patients presented within the first 30 days of life and had a mortality rate of 32%. The most common presenting symptoms were neurological (80%) or gastrointestinal (33%). This cohort is the largest collection of patients reported for these diseases and the first large cohort in the USA. Conclusion-Surprisingly, the majority (66%) of patients with heritable causes of hyperammonaemia present beyond the neonatal period (>30 days). Patients with late-onset presenting disorders exhibited prolonged survival compared to the neonatal-presenting group.

Girls with symptomatic ornithine transcarbamylase deficiency who are treated with drugs that activate new pathways of waste-nitrogen excretion have fewer hyperammonemic episodes and a reduced risk of further cognitive decline.