Abstracts

RATIONALE: At the end of this activity the participants will be able to discuss the neurophysiological data as an additional tool to clinical work up and neuroimaging studies in patients with hereditary metabolic disorders (HMD). EEG is of limited help in specific diagnosis of patients with HMD. However it can provide complementary functional information in the clinical work up of patients with HMD.
METHODS: We present 83 patients with 18 different types of clearly documented metabolic disorders. Female/male ratio was 37/46. Age at the time of evaluation ranged between 1 month and 17 years (mean: 4 years 9 months), age at the time of diagnosis ranged between 1 month and 16 years (mean: 1.5 years). Parents were relatives in 62 patients. Routine EEG was obtained in all patients . VEP was done in 65 patients and BAEP in 66. Forty-six patients underwent psychometric evaluation, and 38 patients had neuroimaging studies (cranial ultrasonography, CT and/or MRI).
RESULTS: Forty-eight patients initially presented with seizures, yet at the time of evaluation 34 had associated seizure disorder. Sixty patients (72%) had an abnormal EEG. The most common abnormality was background slowing seen in 42 patients (50.4%). Epileptiform abnormality was seen in 27 patients (32.4%), asymmetry was present in 18 (21.6%). Patients with no obvious seizures had an abnormal EEG in 60%, and 14 % showed epileptiform activity. EEG abnormalities were most common in patients with dihydropteridine reductase deficiency, urea cycle disorders, maple syrup urine disease (MSUD), and glutaric aciduria. Epileptiform activity was most common in MSUD, whereas background slowing was predominant in dihydropteridine reductase deficiency, and asymmetry in urea cycle disorders. Of 65 patients who had a VEP study 50% were found abnormal, with bilateral delayed P1 latencies being the most common abnormality. BAEP was obtained in 66 patients, and 47% had abnormal results. Bilateral prolonged I-V interpeak latencies were seen in majority of cases. Psychometric evaluation was performed in 46 patients; 3 had severe mental retardation (MR), 8 had moderate MR, and 11 had mild MR. Twenty-six of 38 patients had abnormal neuroimaging findings; white matter involvement was the leading abnormal feature on MRI.
CONCLUSIONS: EEG is recommended in evaluation and follow up of patients with HMD. EEG may detect cerebral dysfunction and show epileptiform abnormality in the absence of severe cognitive deficits and seizure disorder. Background slowing on EEG and prolonged latencies in evoked potentials are supportive of white matter disease. Neurophysiological studies may help early detection or improvement in patients with HMD as an additional tool to clinical features and neuroimaging studies.