Abstracts

RATIONALE: EEG is of limited help in the specific diagnosis of hereditary metabolic disorders (HMD). However, it can provide complementary functional information in the clinical work up of patients with HMD. We report clinical and EEG features of four patients with HMD.
METHODS: All patients presented with infantile encephalopathy, seizures, developmental delays, and/or autistic features. In addition to EEG and MRI, a thorough metabolic work up was performed in all patients. Muscle biopsy was done in one patient.
RESULTS: The first patient was a 3 year old boy with profound developmental delays, autistic features and seizures starting at 7 months of age. Physical exam was remarkable for microcephaly, growth retardation, and ichthyosis. EEG showed bilateral independent spikes in both hemispheres with left posterior region being the most active focus. Most striking finding was generalized bursts of high amplitude spikes followed by suppression periods. Examination of the CSF showed very low serine level. Skin fibroblasts were obtained for enzyme analysis, and the patient was placed on serine supplement. EEG showed improvement with decreased duration and frequency of bursts compared to pre-treatment EEG. The second patient was a 6 month old boy with seizures and developmental delays. Organic acid analysis in urine revealed increased glyceric acid excretion. Analysis of the optical form of glyceric acid by spectropolarimetry supported the diagnosis of D-glyceric aciduria. EEG showed hypsarrhythmia. MRI showed white matter lesions with cerebral atrophy particularly in the frontotemporal regions, and reversible abnormalities in the mesencephalon, thalami, and globus pallidi resolving after fructose restriction in diet, along with improvement of the EEG. The third patient was an 8 month old girl, diagnosed with Leigh Syndrome. She was placed on vitamins, coenzyme Q, and carnitine, and received anticonvulsants. EEG showed burst-suppression pattern with bursting most prominent over the posterior regions. The fourth patient was diagnosed with biotinidase deficiency at 3 months of age. EEG showed burst-suppression pattern similar to the patient with Leigh Syndrome. She was placed on biotin, and follow up EEG at 9 months showed background slowing, and burst-suppression pattern disappeared.
CONCLUSIONS: EEG may be helpful in the assessment of response to treatment in patients with HMD. Burst-suppression pattern can be seen in relatively rare and newly recognized HMD. EEG may help early detection of deterioration or improvement in patients with HMD as an additional tool to evaluation of clinical features, and neuroimaging studies.