Drug resistant seizures at the age of 3 months – mild form of a non-ketotic hyperglycinemia (NKH)

Introduction: Non-ketotic hyperglycinemia is a rare metabolic disorder. Postnatal patients show symptoms of respiratory failure, hypotonia, weakness of drinking and seizures. The further course is characterized by stato- and psychomotoric retardation, spasticity, blindness and epilepsy. The EEG shows a burst-suppression pattern to hypsarrhythmia. In the MRI of the brain abnormalities of the corpus callosum could be found.

Prognosis is poor. Drug and diet therapies are purely a matter of experience with no effect on the retardation.

Case report: First child of unrelated parents. Inconspicuous pregnancy, birth at 34 weeks of gestation. Postnatal respiratory problems, hypotonia and aversion to drink, which all declined. The further course was inconspicuous except for statomotoric delay. Seizures occurred at the age of 3 months. The EEG showed diffuse sharp waves and sharp slow waves in terms of hypsarrhythmia. Multiple trials of anticonvulsive drugs did not control the seizures. A marked raise of glycine in cerebrospinal fluid and in plasma was seen with an elevated liquor/plasma ratio. A NKH was diagnosed with a lack of ketosis. The cerebral MRI showed hypoplasia of the corpus callosum in combination with prenatal known hydrocephalus internus.

Discussion: Our patient suffers from a mild form of a NKH. Retrospectively the postnatal symptoms have to be interpreted in tems of the underlying disease. In addition our patient offers hydrocephalus internus beside the typical pathologies of the corpus callosum. A marked statomotor und mental retardation still exists under therapy with dextromethorphan, benzoate, folic acid and protein reduced diet with addition of glycin-free aminoacid supplements. Though, an improvement of hypotonia, absence of seizures by a moderate slowing of the EEG without signs of epilepsy could be achieved.