DISCUSSION:
Chiari Type 1 malformation is known to be associated with obstructive sleep apnea and or central sleep apnea (CSA) with or without hypoventilation. This association has been documented in numerous studies with multiple hypotheses as to why it occurs however periodic breathing has not been an area of focus. Periodic breathing is described as a recurrent central apnea events with intermittent respiratory effort1 and it is indicative of instability of respiratory control. Periodic breathing is well described in all premature infants less than 1 kg birth weight and some normal full-term infants and it gradually fades during the first year of life2. The periodic breathing pattern is due to increased gain of feedback from chemoreceptors along with longer latency in feedback causing fluctuation in minute ventilation.3 More simply: during the central sleep apnea phase of the periodic breathing the CO2 tension will increase and the oxygen tension will decrease leading to the hyperventilation phase.2,4 During the hyperventilation phase the CO2 tension will fall below the apnea threshold and causing respiratory pause to start and so on. The American Academy of sleep medicine recommends scoring respiratory event as periodic breathing if there are> 3 episodes of central pauses in respiration (absent airflow and inspiratory effort) lasting > 3 seconds and separated by <20 seconds of normal breathing.3 Central sleep apnea that occurs within the run of periodic breathing should be scored as individual apnea as well. Oxygen has a role in regulation of breathing with improvement in central apnea and periodic breathing in children placed on supplemental oxygen during sleep.5 Our Patient had an extensive pattern of periodic breathing during her initial sleep study which is unusual at age 3 years. Central sleep apnea/ periodic breathing in early infancy is normal finding however beyond infancy these findings would be abnormal, and a thorough work up would be indicated. Although neurological disorders, more specifically Chari Malformations, a known cause of CSA in a non-preterm pediatric patient, other etiologies including genetic, endocrine, gastro reflex disease, epilepsy and anatomical malformations must also be considered.