It’s complicated but here in the red box [see Figure 9] is probably the most common reasons why people with Chiari Malformations will have this. One is this sort of won’t breathe factor, so the pressure being put on those dorsal and ventral respiratory groups in the brain stem that I showed you earlier, pressure’s being put on that and those receptors that measure CO2 and Oxygen don’t function like they should. That causes problems. Also the output to the muscles that sub-serve respiration can also be affected, more so by co-morbid Syringomyelia but also by the Chiari Malformation itself, and then of course everybody that’s asleep has a loss of the wakefulness stimulus to breathe.
Let’s talk about a couple of the studies that have been done that have looked at Chiari I Malformations and sleep disordered breathing. This one here, [see Figure 10] looked at 46 Chiari Malformation patients, 20 were children and 26 were adults. Here they did have 5 with Chiari II Malformations. What they found was a very high prevalence of sleep disordered breathing, 73% of adults had sleep disordered breathing. And that would be defined as an apnea, hypopneas, which is more than five per hour. As you can see, the majority had obstructive sleep apnea but a pretty high number also had central sleep apnea. This is much higher central sleep apnea than we would expect to see in the general population. As far as the children are concerned the numbers were still quite high. There was a little bit more central sleep apnea in this group and this was due to the Chiari II group which had more severe central sleep apnea. There’s something about the Chiari II that’s causing more problems with the respiratory control.
I’ve talked about this prevalence of 2-4% in adults. The prevalence is 1-3% in children; these numbers are much, much higher than that! so this kind of thing to me just tells me that we need to move sleep disordered breathing up the list of symptoms that people with Chiari Malformations are having because it seems to be so common.
This study [see Figure 11] looked at 13 Chiari I patients and they’d had a control group that did not have Chiari Malformations, and you can see again the apnea, hyperpnoea index was higher. On average it was 13 compared to 3 for control. So if the cut off is 5, the average in the Chiari’s is abnormal, the average in the control is normal. You can see that also when you look at just who was above 5, 59%, again a very high number had clinically significant sleep disordered breathing compared to the controls. Not only that but it also affected the level of oxygen in these individual’s blood so the lowest oxygen level went down to 80% in the Chiari group as opposed to 90% in the normal group. The Chiari group then also spent 24% of the night with an oxygen level below 90%. Generally speaking we like to keep the oxygen level in the 90s, so this is of concern to us.
They looked at Epworth Sleepiness Scale, and I’ll talk more about this in a minute but the bottom line is that there was no major difference in the amount of sleepiness that was being endorsed between the two groups. So this was kind of interesting and contrary to what we might think. Central apneas were more common in the Chiari group and then the basilar invagination that Dr. Oro was talking about in the Syringomyelia is also more commonly associated with these central apneas.
Let’s talk about the research that Dr. Ellenbogen and myself have been involved in. We recruited Chiari I patients from Rich’s specialty clinic and then we got health age matched controls from the Seattle area. All the subjects in our study were female because all of Chiari subjects happened to be female. We did MRI of the brain including this cardiac gated phase contrast CINE MRI on all subjects. Then we administered some questionnaires that were related to sleep. The Berlin Questionnaire is a validated questionnaire that measures risk of sleep apnea. The Epworth Sleepiness Scale which measures propensity to fall asleep. We looked at how long these individuals sleep and how long it takes them to fall asleep. Then we had a few other miscellaneous sleep disordered breathing questions.
The Berlin Questionnaire is a ten item questionnaire where we assess three categories; snoring, sleepiness and then whether or not obesity or hypertension is present. In order to be considered high risk for sleep apnea you have to basically be high risk in two out of these three categories. You have to have snoring or breathing pauses greater than three to four times a week; sleepiness greater than three to four times a week or drowsy driving; or a body mass index greater than 30 or a history of hypertension. So if you’re high risk, which is what this is here in two of these three, then you’re high risk for sleep disordered breathing.