An electroencephalogram, or EEG, is a diagnostic test that measures and records the electrical activity of the brain, often referred to as brain waves. Using small sensors placed on the head, the procedure captures the brain’s electrical signals to provide a look at its function. It is a common, non-invasive, and painless tool that provides a functional assessment of the maturing brain in infants.
Medical Reasons for an Infant EEG
A physician may recommend an EEG for an infant for several reasons related to specific symptoms. One of the most common is to investigate suspected seizures. In infants, seizures can be subtle and may not look like convulsive movements; they can appear as brief staring spells, repetitive facial movements, slight stiffening of the body, or small, jerky motions of a limb. An EEG can help confirm if these events are seizures and provide information to classify the seizure type.
Unexplained developmental delays or a loss of previously acquired skills also warrant investigation. If an infant is not meeting developmental milestones, such as rolling over, sitting up, or babbling, an EEG can be used to explore underlying neurological issues. It helps assess if the brain’s electrical patterns are appropriate for the infant’s age.
Other abnormal movements or concerning behaviors can prompt an EEG. Conditions like infantile spasms, a specific and serious type of seizure disorder in infants, can be identified with this test. Additionally, an EEG is used to assess brain function following a known or suspected brain injury. This can occur after a difficult birth, a head trauma, or a serious illness like meningitis or encephalitis, which is an infection of the brain.
The Infant EEG Procedure
Preparation for an infant EEG begins at home. Parents are instructed to wash their baby’s hair the night before the test but to avoid using any oils, lotions, or sprays. Clean hair helps ensure the electrodes can maintain good contact with the scalp. Depending on the goal of the test, the physician may recommend sleep deprivation by keeping the baby awake longer than usual to encourage sleep during the procedure.
Upon arrival, the test is conducted by a trained technologist in a quiet, often dimly lit room to create a calming environment. The technologist will measure the infant’s head and use a gentle, washable marker to indicate where the electrodes will be placed. The electrodes are then attached to the scalp using a mild, sticky paste or by fitting the infant with a soft cap with embedded electrodes. The paste is easily removed after the test.
Once the electrodes are in place, the recording begins. The goal is for the infant to remain as calm and still as possible, and ideally to fall asleep, as different brain wave patterns emerge during sleep. A routine recording lasts between 20 and 60 minutes. The technologist monitors the recording from an adjacent room and may come in to reattach any loose electrodes.
To see how the brain responds to different inputs, the technologist might introduce specific stimuli, such as showing the infant flashing lights. These activations can elicit abnormal brain activity that might not appear while the infant is at rest. While rare, these stimuli can trigger a seizure in susceptible infants, but medical staff are prepared to manage this. After the recording is complete, the technologist removes the electrodes, cleans the paste from the infant’s hair with warm water, and the family can then go home.
Types of Infant EEGs
While a routine EEG is the most common type, a physician might order a different kind to gather more specific information about an infant’s brain activity. The specific clinical question being asked will determine which test is most appropriate.
A sleep-deprived EEG follows the routine procedure but requires limiting the infant’s sleep beforehand. The purpose is to increase the likelihood that the infant will fall asleep during the test. Sleep can unmask certain abnormal electrical patterns in the brain that are not visible during wakefulness.
A video EEG is used for more comprehensive analysis, recording brain wave activity and a video of the infant at the same time. This allows doctors to precisely match the infant’s physical actions with the electrical activity occurring in the brain at that moment. This is particularly useful for clarifying whether a specific, unusual movement is a seizure. Video EEGs can last a few hours or may be part of a longer hospital stay for continuous monitoring.
An ambulatory EEG may be ordered to understand brain activity over a longer period in the child’s natural environment. For this test, the electrodes are secured to the scalp and connected to a small, portable recording device that the infant wears. The infant goes home and continues their normal routine for 24 to 72 hours. This extended recording time increases the chances of capturing an infrequent event and provides insight into brain function during typical activities.
Understanding EEG Results
After the EEG is completed, the recorded data is analyzed by a pediatric neurologist, a physician specializing in the infant’s brain and nervous system. This specialist examines the patterns, frequencies, and amplitudes of the brain waves, looking for features that are expected for an infant of that specific age. The interpretation also takes into account the infant’s state, such as whether they were awake, drowsy, or in different stages of sleep.
The neurologist’s report will classify the EEG findings as either normal or abnormal. A normal result means the brain’s electrical activity shows patterns consistent with the infant’s age and state. An abnormal result points to specific deviations from expected patterns. The report might mention “slowing,” where brain waves are less frequent than expected, or “epileptiform abnormalities” like sharp waves or spikes, which are patterns associated with a predisposition to seizures.
An EEG is just one diagnostic tool, and the results are considered with the infant’s clinical symptoms, physical examination, and other diagnostic tests. An abnormal EEG does not automatically confirm a specific diagnosis, and a normal EEG does not completely rule one out, as some abnormal brain activity only occurs sporadically. Based on this evaluation, the neurologist will discuss the findings and recommend next steps, which could include observation, medication, or other imaging studies.