Possible Pathophysiology of Neurologic Abnormalities Associated with Nonketotic Hyperglycinemia

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Abstract
To the Editor: Nonketotic hyperglycinemia, characterized by elevated levels of cerebrospinal-fluid glycine and neurologic abnormalities, may be due to a reduction of glycine-cleavage enzyme activity in brain.1 The pathophysiology of the neurologic disturbances induced by this metabolic defect is not understood. It is reasonable to suspect, however, that high glycine levels in cerebrospinal fluid reflect abnormally high concentrations of this amino acid (a presumed inhibitory neurotransmitter2) in the brain extracellular space, and that this condition is in some way related to impaired neural function. Electrophysiologic observations on cultured mouse spinal cord have revealed two mechanisms by which high extracellular . . .