The Epworth Sleepiness Scale is an interesting eight item scale that measures a propensity for an individual to dose or fall asleep in these eight different situations. The lowest score you can get is zero. The highest score is 24 and you can score from zero to three on any of these items. So you can see some of these items here you may have a greater propensity to fall asleep during that than others, lying down to rest in the afternoon, hopefully more so than in a car while stopped in traffic. But you’d be surprised, this is the scary part of sleep apnea and in fact people with sleep apnea are at much higher risk for motor vehicle accidents than those that don’t have it. An abnormal score is greater than or equal to eleven on this sleepiness scale.
The two groups were in their mid to late 30s. [see Figure 12] You can see that the healthy control group was slightly more educated. Most of our subjects were Caucasian which is reflective of our population of inference. You can see that the control group was more likely to be employed and the Chiari group was more likely to be married, or living with someone. The Berlin Questionnaire, we had a higher risk of snoring in almost half of the Chiari group compared to 6% of the controls and this was significantly different. Sleepiness, almost three quarters compared to about half of the controls. Then obesity or hypertension was twice as common in the Chiari group compared to the controls. Overall when we looked at sleep disordered breathing risk we found that 69% of the Chiari I group were at high risk for sleep disordered breathing compared to 20% of the controls. And so our numbers are pretty close to the three quarters that we were quoting earlier in the other stories that have been done.
We also looked at the Epworth Sleepiness Scale [see Figure 13] and our summary scores were almost twice as high in the Chiari group, so we did find a pretty big difference in the level of sleepiness between these two groups. And this is on average almost abnormal. When you look at the percentage of people that had a score greater than or equal to eleven, almost half the Chiari group had an abnormal range Epworth Sleepiness Scale score, compared to about 9% of the controls. This is interesting and hadn’t been reported before but the self reported sleep duration is a little more than an hour less in the Chiari group than it is in the healthy controls; and it also takes the Chiari group about three times longer to fall asleep, about an hour on average to fall asleep compared to the healthy controls. Real big effects on what would be thought of as sleep quality in these individuals.
There has been one study that has looked at the effect of surgical decompression on Chiari Malformations and the effect that has on sleep apnea. [see Figure 14] That’s a study that I’m showing you here. Again, in this group of Chiari subjects, sixteen patients, three quarters had sleep disordered breathing. So we’ve seen multiple studies now showing that about three quarters of people will have significant sleep disordered breathing; again a lot more central sleep apnea than what we would expect. Sleepiness is defined a little more liberally than we do, but nonetheless, again, in about 50% of people. Eight of the twelve that had sleep disordered breathing underwent surgical decompression and they got a post-op sleep study on six of them. What they found was the biggest impact the surgery had was by reducing the central sleep apnea index. Those are the apnea that happen when a patient doesn’t breathe, their brain doesn’t tell them to breathe. The obstructive apnea index from blockage was also reduced but not significantly in this study. The arousal index was reduced, so you would imagine if you’re reducing the apneas, you’re reducing the arousals that would happen at the end of it and that is what was seen. Overall the apnea hypopnea index was reduced, not to normal, but significantly reduced. But not quite significantly. You might imagine if there were more patients in this study that you would find a significant difference here. And then again they found no change in the Epworth following surgery. So this deserves more investigation. You would expect that if you’re resolving the apnea the sleepiness would get better. But you know perhaps, a lot of times people can confuse sleepiness and fatigue. It’s really hard to know. Sleepiness is obviously being a propensity to fall asleep, fatigue maybe being more of a muscular or brain kind of fatigue and so there might be some issues with that.
In conclusion, from our work [see Figure 15] and the other work that I’ve presented here, Chiari I subjects are at much higher risk for sleep disordered breathing than controls of similar sex and age. I think we need to move this farther up the symptom scale that we get concerned about, in people that have Chiari Malformation, particularly considering that sleep disordered breathing could make the Chiari Malformations worse over time. In addition, sleep apnea is associated with cardiovascular diseases and hypertension and those are really important reasons to get it identified and taken care of. Chiari patients are sleepier than controls even though the surgery didn’t seem to necessarily improve that, but they are sleepier. The Chiari subjects sleep less and take longer to fall asleep so there is some insomnia issues going on here and there really aren’t any studies that have looked specifically at insomnia in this disorder.
I think that we need to do a lot more research in this area. We need to focus on these objective measures of these various symptoms. For instance, sleepiness can be measured subjectively with a questionnaire but a better way would be to do what’s called a multiple sleep latency test where we let an individual have between four and five opportunities to nap during the day and we measure how quickly they fall asleep. I think that we should do that test before and after decompression and get a better idea of whether or not we’re improving sleepiness in these folks. The one study that was done did show that surgical decompression can improve sleep disordered breathing and so I think that we need to think about this as part of the symptom complex that might drive the physician towards whether or not they want to proceed with surgery for this disorder.