Hypoxic-ischemic encephalopathy (HIE) is caused by lack of oxygen and blood flow to the brain in infants. Seizures are a common symptom of HIE, and those patients that survive past infancy often develop life-long problems such as mental disability, cerebral palsy, and epilepsy.

Early diagnosis and careful monitoring during treatment is critical for these patients. One of the best ways to do this is by using a combination of standard electroencephalography (EEG) and amplitude integrated EEG (aEEG).

That’s according to the authors of a new review published in the journal Neurological Frontiers.

The strength of EEG/aEEG is “its high overall availability during the early postnatal period,” according to the review. This combination is highly sensitive to electrographic seizures and can monitor therapeutic management.

Monitoring Therapeutic Hypothermia

Treatment for HIE includes the use of antiepileptic drugs along with therapeutic hypothermia, or whole-body cooling.

Therapeutic hypothermia is a prolonged process, but research shows nearly 80 percent of infants treated this way had a good outcome at 12 months. The whole body is cooled down to an esophageal temperature of 33 to 34 degrees Celsius for 72 hours. This is followed by a rewarming period.

In patients with HIE, seizures and episodes of status epilepticus can continue throughout the period of cooling and rewarming, requiring prolonged and careful EEG monitoring.

Experts consider video-EEG — a modified 10-20 system — to be the gold standard in diagnosing neonatal seizures. But, increasingly, neonatologists are also using aEEG.

Benefits of aEEG

The authors note aEEG uses fewer channels to capture raw signals and amplify, filter and compress them over time. aEEG also records electrographic-only and prolonged seizures as well as status epilepticus. In neonates with HIE, 50 percent to 80 percent of seizures can be electrographic-only.

Seizures with a minimum voltage of 2μV, or that last at least 10 seconds, are common in both preterm and term infants with HIE. And aEEG captures these seizures well.

However, when seizures are of lower amplitude or shorter duration, aEEG’s use is limited. That is why the authors recommend a combination approach.