1983 Volume 15 Issue 6 Pages 497-502
Serial EEG examinations of a schoolboy with phenylketonuria (PKU) were studied. The patient had been treated with a low phenylalanine (phe) diet since 3 months of age. The serum level of phe had been kept between 10 and 20 mg/dl. All his EEGs were normal before school age. After the age of 7, his serum phe level increased to over 20 mg/dl due to his eating a school lunch. Three months after he started having school lunches, his EEG showed localized spikes in the left mid-temporal and central regions, but the waking background consisted of symmetrical, regular and reactive 10.3 Hz alpha activity. After his phe intake was once more restricted, the phe serum level dropped to below 20 mg/dl. Three months after the restricted diet was reinstituted, the EEG showed no epileptiform activities and 10.3 Hz alpha activity in the waking background remained. The patient has never had convulsive attacks, even while the EEG was abnormal. But he was restless and unable to concentrate when the phe level was high.
In this patient, the EEG did not show background abnormality, but was epileptogenic. Epileptogenic change in EEG may relate to high level of serum phe, because it disappeared after reinstitution of the dietary treatment. A level of 20 mg/d/ of serum phe seems to be critical in this case in terms of EEG abnormality.
The age of termination of dietary treatment of PKU is generally suggested to be about 4 to 6 years, but even after 6 years of age it should be carefully considered whether dietary treatment should be discontinued or not. The serial EEG observations seem to be helpful in deciding on discontinuation of the treatment.
