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Featured Case
Contributed by Sameer Al Mehmadi, MD
The Hospital for Sick Children, Toronto, Canada
A term newborn was born by spontaneous vaginal delivery unresponsive with no respiratory effort or heart rate. Positive pressure ventilation and chest compressions were performed for 2 minutes after which her heart rate returned, but there was no respiratory effort so she was intubated and ventilated. Initial venous blood gas demonstrated a pH of 6.8. On examination she was hypotonic with no spontaneous movements, unresponsive to stimuli and only occasionally breathed above the ventilator. Her pupils were fixed in mid-dilation and non-reactive. Corneal reflexes, the vestibulo-ocular reflex (VOR) and gag/suck reflexes were absent. She was diagnosed with severe neonatal encephalopathy and therapeutic hypothermia was commenced.
During the first day of life, she was reported to have jerking movements of the right arm suspected to represent seizures. She received 0.1 mg/kg of lorazepam followed by 30 mg/kg of phenobarbital. Bedside amplitude-integrated EEG demonstrated waveforms suspicious for seizures without any accompanying clinical signs. Continuous EEG monitoring was commenced, which demonstrated several epochs illustrated in Figures 1 and 2.
Question: What do these EEG patterns represent?
Figures 1 and 2. Continuous EEG recordings presented in an AP bipolar neonatal montage displayed at 7μV/mm, LFF= 1Hz, HFF=70 Hz, timebase = 15 mm/sec. Reference electrode was Pz’.
Figure 1:
Figure 2:
Answer & Discussion
The EEG patterns illustrated in Figures 1 and 2 represent electrographic seizures originating from the right frontal head region and spreading to the midline and left frontal head region.
According to the 2013 ACNS Neonatal EEG Terminology, electrographic neonatal seizures are a “sudden, abnormal EEG event defined by a repetitive and evolving pattern with a minimum 2 mV peak-to-peak voltage and duration of at least 10 seconds … ‘Evolving’ is defined as unequivocal evolution in frequency, voltage, morphology, or location”.(1) In contrast, Brief Rhythmic Discharges (BRDs) are patterns that resemble seizures but last less than 10 seconds. BRDs are considered of uncertain clinical significance, but they are associated with a high risk for seizures and therefore may also warrant therapy.(1)
The patterns depicted in Figures 1 and 2 fulfill the criteria for an electrographic neonatal seizure because of their clear onset and offset, and clear evolution in both amplitude and location. Review of time-locked video showed no evidence of accompanying clinical signs, eye movement or handling of the baby. In addition, the electrographic seizures did not recur following a 20mg/kg dose of phenobarbital. A rich variety of ictal morphologies has been described in neonatal seizures from simple sinusoidal to complex bizarre patterns of different frequencies. The most helpful feature that distinguishes genuine ictal patterns form artifacts is clear evolution in morphology.(2) The majority of neonatal seizures are of focal onset, and most commonly arise from the central and temporal head regions, but may also arise from occipital and frontal head regions, as demonstrated in this case.(2,3)
Further Reading: