Pitfalls in measuring cerebrospinal fluid glycine levels in infants with encephalopathy.

In encephalopathic infants, cerebrospinal fluid hyperglycinemia and elevated cerebrospinal fluid to plasma glycine ratio are considered pathognomonic of nonketotic hyperglycinemia. To evaluate the significance of cerebrospinal fluid hyperglycinemia and elevated cerebrospinal fluid to plasma glycine ratio in acutely encephalopathic infants, a retrospective chart review of all cases of isolated elevation of cerebrospinal fluid glycine levels at Arkansas Children's Hospital from January 1995 to December 2000 was performed. Twenty-two patients (14 males) were included. The most common diagnosis was hypoxic ischemic encephalopathy (n = 8). Nine patients had elevated cerebrospinal fluid to plasma glycine ratio, which was transient in 7 patients. This study shows that elevated cerebrospinal fluid to plasma glycine ratio can be encountered in a variety of clinical conditions. The significance of this observation in light of the poor prognosis of nonketotic hyperglycinemia and the possible role of glycine in the mechanism of ischemic neuronal injury is addressed.