An electroencephalogram, commonly known as an EEG, is a diagnostic test for assessing brain waves that doctors may use in treating patients with phenylketonuria (PKU).
The technique primarily is used to diagnose seizures, which may occur in up to 50% of PKU patients. However, an EEG also may provide information about developmental delays and behavioral disorders.
The following is more information about EEGs and how they work.
What is an EEG and what does it measure?
An EEG monitors the electrical activity of the brain. During an EEG, clinicians place electrodes at multiple locations on your head. These electrodes measure the activity of nerve cells, which gives doctors an idea of how they are behaving in several parts of the brain.
Each individual nerve cell causes its own electrical activity when it sends messages to other nerve cells. The combination of the electrical activity of many nerve cells becomes large enough that the electrodes can measure them once they pass through the skull and skin of the head.
Doctors can diagnose a number of different conditions by looking at an unusual activity pattern in the brain. For example, EEGs may help diagnose such brain disorders as epilepsy, tumors, stroke, Alzheimer’s disease, and narcolepsy, a sleep-related disease. Such scans can even tell if the patient is intoxicated.
Why would doctors use EEG in PKU?
Around 50% of PKU patients experience seizures, with up to 25% possibly having generalized seizures that affect the whole brain at once. Neurologists can use the EEG recordings to determine where in the brain seizures might be starting and to develop a treatment plan.
Research also has shown that there may be a relationship between unusual EEG activity and behavioral disorders such as attention deficit hyperactivity disorder, known as ADHD, oppositional defiant disorder, and generalized anxiety. Such testing also may show autistic behavior in PKU patients.
Unusual EEGs also may be a sign of developmental delays in children with PKU.
Treatment efforts to correct the differences seen in the EEG may be a way to improve development and correct behavioral disorders in people with PKU.
How could PKU cause an unusual EEG?
The exact relationship between PKU and unusual EEG activity is not clear. One idea is that high phenylalanine levels are toxic to nerve cells and lead to damage in the brain. This, in turn, may cause irregular activity that might lead to unusual EEG signals.
Are there any risks?
There are no real risks of undergoing an EEG besides being tired and having possible skin irritation from the electrodes.
In some cases, doctors may try to induce a seizure during an EEG to check for abnormal brain activity. They could do this by asking the patient to change their breathing (hyperventilate) or look at flashing lights.
Last updated: Jan. 28, 2021
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