Occipital sawtooth: a physiological EEG pattern in very premature infants

Objective: To evaluate EEG maturational features in preterm infants below 27 weeks postmenstrual age. Methods: EEGs recorded from 5 preterm infants (postmenstrual age 24–26 weeks) were examined and selected maturational features were scored and quantified. The five infants also had serial cranial ultrasound scans (US) and magnetic resonance images of the brain within the first weeks after birth. Results: Background activity was markedly discontinuous in all patients and very variable. Temporal sawtooths occurred but less frequently than in older preterm infants. All 5 infants also showed a particular novel feature, characterized by rhythmic, regularly shaped, medium-high amplitude 4–7 Hz activities, lasting 0.5–3 s and located in the occipital regions. This pattern was symmetrical but sometimes asynchronous. Conclusions: Occipital sawtooth, so called because it shares shape and frequency with temporal sawtooth but has an occipital localisation, constitutes a physiological EEG pattern characteristic of premature infants between 24 and 26 weeks of postmenstrual age.