Electrographic monitoring for seizure detection in the neonatal unit: current status and future direction

Abstract

Neonatal neurocritical intensive care is dedicated to safeguarding the newborn brain by prioritising clinical practices that promote early identification, diagnosis and treatment of brain injuries. The most common newborn neurological emergency is neonatal seizures, which may also be the initial clinical indication of neurological disease. A high seizure burden in the newborn period independently contributes to increased mortality and morbidity. The majority of seizures in newborns are subclinical (without clinical presentation), and hence identification may be difficult. Neuromonitoring techniques most frequently used to monitor brain wave activity include conventional electroencephalography (cEEG) or amplitude-integrated EEG (aEEG). cEEG with video is the gold standard for diagnosing and treating seizures. Many neonatal units do not have access to cEEG, and frequently those that do, have little access to real-time interpretation of monitoring. IMPACT: EEG monitoring is of no benefit to an infant without expert interpretation. Whilst EEG is a reliable cot-side tool and of diagnostic and prognostic use, both conventional EEG and amplitude-integrated EEG have strengths and limitations, including sensitivity to seizure activity and ease of interpretation. Automated seizure detection requires a sensitive and specific algorithm that can interpret EEG in real-time and identify seizures, including their intensity and duration.

Fig. 1. Montages that may be used when recording EEG and aEEG.

a This montage may be used in neonates and young children. b A reduced neonatal montage is proportionate to term neonatal skull size. c Electrode placement for aEEG using minimal electrodes.

Fig. 2. EEG of a term-born infant undergoing therapeutic hypothermia.

Commencement of a seizure on the cEEG begins on the left side (red trace) with rapid frequency and low amplitude propagating to the right side (blue trace), during which amplitude increases whilst the frequency slows as the seizure progresses.

Fig. 3. EEG shows an established seizure coming to an end, evident by a decrease in amplitude, particularly on the right side, i.e., the blue trace.

The red arrow indicates the point on the aEEG when the seizure occurred, and the corresponding display of raw EEG is below.

Fig. 4. EEG of a term infant undergoing therapeutic hypothermia.

Low-amplitude seizure on cEEG seen localised to the left central-occipital area. The red arrow indicates the point on aEEG where the seizure occurred and the corresponding display of raw EEG below. The seizure was not detected on aEEG (no upward deflection). The green bar on aEEG indicates one hour of EEG recording.

Fig. 5. aEEG displaying sleep-wake cycling.

A complete sleep-wake cycle, AS and QS are highlighted in rectangular boxes. The awake state is identified by a circle. An upper amplitude of 10 µV and a lower amplitude of 5 µV are indicated by a dashed line. Black unbroken lines indicate one hour of EEG recording.

Fig. 6. The future direction of EEG interpretation.

Future interpretation of EEG will combine expert interpretation (through visual analysis and behavioural observation) with the use of artificial intelligence (AI). AI uses an objective mathematical computer-based approach to analyse EEG data thus creating intelligent machines that can interpret EEG previously dependent on human expertise alone.