Sleep Study Part II: The Curve Ball

I keep trying to collect my thoughts on this, but I don't think that is going to happen any time soon. Please bear with any rambling, as it is the result of a very concerned and exhausted mother.

Nolan's sleep study found something else, in addition to the obstructive sleep apnea. Actually, this other finding was far more prominent and significant than the other finding.

Nolan has severe central sleep apnea. This is much more serious than obstructive sleep apnea, because it means there is a problem with Nolan's brain. When he goes to sleep, his brain forgets to tell his body to breathe. This happened sixty times during Nolan's sleep study, for a duration of more than ten seconds, and with oxygen desaturations.

For the more technically inclined, here is a list of statistics:

Lowest oxygen level during the sleep study: 79%
Number of obstructive sleep apnea events: 3
Number of central sleep apnea events: 60
Number of hypopneas: 41
Total number of respiratory events (apnea and hypopnea): 104
Sleep efficiency: 69% (poor)
Number of desaturations 3% or greater: 161
Number of desaturations/hour (non-REM sleep): 30.6/hour
Number of desaturations/hour (REM sleep): 41.6/hour

When Nolan's brain fails to tell his body to breathe, his oxygen levels drop and he wakes up, which causes him to start breathing again. Thank heaven the arousal function in his brain is not broken, because the autonomic control for breathing is broken. The official report states:

"The overall respiratory disturbance index was 19.9 (central index: 11.4, obstructive index: 8.5) with a minimum oxyhemoglobin saturation of 79% following a central apnea. Desaturations to 87%-89% were also seen several times following central apneas. Most central apneas were 10 seconds in length. Also, frequent central apneas were seen without arousals and desaturations (that were not scored) were seen. Repetitive central apneas were noted, however not with a periodic pattern. Obstructive apneas/hypopneas were also seen frequently. Mean oxyhemoglobin saturation was 96%. There was no particular worsening during supine or REM sleep. Paradoxical breathing was not noted. Carbon dioxide level was not elevated during the study. Total time of study with oxygen less than 90% was 5 minutes.

These findings indicate the presence of severe central and obstructive sleep apnea (for the pediatric age range normal RDI <1.5). Considering the prominence of central events, a neurogenic cause (i.e. Arnold-Chiari) may be considered. Also, developmental immaturity of the respiratory system may be at play, although he is clearly out of the normal age group range for this finding. If clinically indicated, evaluation by ENT for possible tonsillectomy and adenoidectomy could be considered for the obstructive portion. Clinical correlation is suggested."

Our pediatrician nixed the idea of developmental immaturity as the cause (this is primarily seen in premature babies, and sometimes in full-term infants, but not in 30 month olds). Arnold-Chiari is also very unlikely, because Nolan had a CT scan of his head as an infant and it was normal.

This is an issue on top of the staring spells we have been seeing. The sleep study EEG only uses four electrodes, and is only used to monitor REM vs. non-REM sleep. Because of this, the EEG isn't even mentioned in the report, other than to state the stage of sleep Nolan was in when respiratory events happened.

There are several issues now pointing to a neurological issue, so it is good we have a neurology appointment set up. We see our ENT on Monday to discuss the next step with this particular issue. There isn't much they can do to treat the central portion of his apnea, though supplemental oxygen at night, a biPAP machine, or medication are sometimes used. We will know more after we discuss this with his ENT.

His EEG is scheduled for tomorrow morning, so we will be keeping him up very late and waking him up very early (putting him to bed after midnight and waking him by 5:00am) in the hopes of stacking the deck for observing possible seizure activity.

At least we are getting more pieces to the puzzle, and we know why he doesn't sleep. His erratic behavior after waking from his naps and bedtime is also easier to understand- he wakes up sleep and oxygen deprived. I pray that we can find the cause of his breathing issues, and find a way to manage or solve them.