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.