Interactions between cortex and brainstem during REM-sleep in preterm and newborn infants with subclinical myoclonus

Objective: Subclinical myoclonus of the chin and eye muscles synchron to cortical activation can be recorded during REM-sleep in preterm and newborn infants. The question is whether the interactions between the different nerves of the brainstem and the cortex are of different significance.

Methods: In 72 preterm and newborn infants (26 to 40 weeks of gestational age) suspected to have subtle seizures, polysomnographic recordings were performed (8 channel EEG, EMG, EOG, nasal flow, thoracal and abdominal respiration, ECG, pulse and oxygen saturation). In all patients 2–3 spontaneous sleep cycles (REM-NREM-sleep) were analyzed.

Results: During REM-sleep 3 of the 72 children had subclinical myoclonus of the eyes, distinguishable from rems by clear rhythmicity and lower amplitude. 3 children had subclinical myoclonus of the chin muscles characterized by a small amplitude and a rhythmic activity of high frequency in the EMG. This was different from spindle like jittering and the slower movements of rhythmic nonnutritive sucking. In 4 children both muscle groups were involved. None of the mature infants had a myoclonus of the chin. While the myoclonus of the eyes was more often in synchrony with rhythmic discharges of theta-activity of the EEG, the myoclonus of the chin muscles were repeatedly associated with beta-rhythms. After anticonvulsant therapy in 8 of the ten children, all but one had normal development during the next 6 to 24 months.

Conclusion: Subclinical myoclonus of the eyes and chin muscles are associated with distinctive EEG pattern. Different mechanisms of interactions between the brainstem nerves and the cortex have to be supposed, possibly dependent on the maturity of the brain. Keywords: REM-sleep, neonates, subclinical myoclonus