Abstract
We report an infant with neonatal nonketotic hyperglycinemia (NKH), diagnosed early
and treated with dextromethorphan (DM) and sodium benzoate therapy from the 65th hour
of life. Initially the patient responded to treatment showing clinical and electroencephalographic
improvement: myoclonic jerks disappeared, muscular tone, reactivity to stimuli and
spontaneous movements increased, assisted ventilation was no longer necessary and
bottle feeding was initiated successfully; on EEG the suppression-burst pattern disappeared
and the background activity was well-organized.
At three months of age he developed flexor spasms and hypsarrhythmia. In spite of
increasing doses of DM as high as 40 mg/kg/day and persistent therapy with sodium
benzoate the child progressively deteriorated and died at the age of 5 months and
7 days.
We stress that the adverse clinical course occurred in our patient even though DM
and sodium benzoate therapy was started much earlier than in other reported cases.
It is possible that prenatal brain damage and probable genetic variants (i.e. absent
or minimal residual enzymatic activity and interindividual variations in DM metabolism)
affect the response to therapy.
Abbreviations
EEG: Electroencephalogram
MRI: Magnetic resonance imaging
VER: Visual evoked potential responses
BAER: Brainstem auditory evoked responses
CSF: Cerebrospinal fluid
Key words
Nonketotic hyperglycinemia - Dextromethorphan - N-Methyl-D-Aspartate receptor
