How do you tell which came first, the RERA or the leg movement? There are quite a few patients that it appears to be both a RERA and leg movement when watching the video. How should this be scored?
The most useful starting point for this discussion centers on the conventional wisdom that most leg jerks are parsimoniously explained as arousals at the end of sleep breathing events. This approach to patient care is reliable in that the majority of patients who present with leg jerks on their diagnostic studies will demonstrate a clear decrease in limb movements during PAP therapy. Of course, there are also reverse order cases in which no leg jerks appeared on the diagnostic study yet mysteriously appeared during the titration. Then again, it would not be so mysterious if the patient reported RLS or PLMD symptoms at intake, because night-to-night variability might explain their appearance on the PAP titration instead of the diagnostic study. Other theories abound on these relationships.
So, the clarifying news is that aggressive treatment of sleep breathing events, including RERAs, should lead to less limb movements in a substantial proportion of patients, and for these patients no further treatment is required unless the patient suffers RLS without PLMD, which certainly could mandate therapy. However, in our clinical experience, a notable minority of patients report resolution of RLS with PAP therapy.
Now, we must tackle the greater complexity of those patients who appear to have RERAs and leg jerks and where the etiology is in question: are both conditions in play, did the RERA cause the leg jerk, and, strangely, could a leg jerk cause a RERA?
Are both conditions in play is actually an odd question in so far as we would first want to know what attempt was made to eradicate the RERAs by fully normalizing the airflow curve. While this point is controversial among sleep professionals, it cannot go without saying that the paradoxical AASM guidelines clearly state scoring RERAs is optional on diagnostic studies, but targeting and treating RERAs on a titration is mandatory. What then is the best treatment: PAP, dental devices, surgery, hypoglossal nerve stimulator, body position, hypnotics? There are many practicing sleep specialists who might report their own successful clinical experiences when using any of these treatments for RERAs.
Yet, what exactly defines successful treatment of a RERA? Moreover, with the new hypopnea scoring rule, what constitutes the best definition of a RERA? If hypopneas can now include a 30% reduction in the airflow, is a RERA 29% or less? And, how do we quantify the lessor variant? Is a 20% reduction still a RERA? What about 10%? For that matter, what constitutes a normalized airflow curve? As discussed in many earlier posts, we use the model of “rounding the airflow signal on inspiration and expiration.” We first were exposed to this idea in reading Condos et al (1994) regarding a rounded signal in which “normal” breathing was associated with a reduction in daytime sleepiness.
From our vantage point at the time, we were equally interested in the impact of rounding the curve (on inspiration and expiration) among insomnia patients with sleep apnea (so-called “complex insomnia”). Among these patients, we also noticed not only the improvement in daytime sleepiness but also in night time insomnia.
Thus, it needs to be stated here that we approach any degree of abnormality of the airflow curve as abnormal. If there is just a tad of notching of the airflow signal that some might measure as a 5% to 10% reduction on inspiration, we presume it is abnormal and must be treated. Moreover, if a signal appeared almost normal but was not entirely rounded (let’s call it <5% reduction), we would still aggressively attempt to round the signal, because in our clinical experience we have pursued this strategy with patients reporting sleepiness or insomnia or both, and in a substantial proportion of patients we are continually surprised by their report of improvements in both symptoms. We were surprised, because when we looked at this shape on the airflow signal coupled with the relative paucity of sleep fragmentation signs, we always informed such patients of the lower probability of PAP helping their symptoms. And yet, lo and behold, in the majority of such patients, PAP decreased sleepiness or insomnia or both, such that some of these patients simply bought their PAP devices regardless of their DME coverage from a particular insurance carrier.
As you can see, so far, the idea of RERA and leg jerk on the tracing mandates a strong PAP therapy effort as the first line of attack. We reported on this phenomenon in our paper on ASV treatment of complex insomnia. But, let me be equally clear that we also reported how difficult in may be to treat RERAS in any OSA or UARS patients, and especially so among insomniacs.
What if you attempted the RERA treatment to the best of your capabilities, but the leg jerks remain? Clearly, the next step would be to discern patient outcomes. After all, not all leg jerks create the same effects, although that remains controversial as well. Leg jerks that clearly show evidence of arousals in this situation would warrant treatment in a patient still complaining about sleep quality or continuity. Indeed, this scenario would be the single most common setting among PAP users who were compliant yet reported sub-optimal responses. The sleep fragmenting effects of the limb movements apparently have sufficient impact to prevent the PAP user from gaining optimal benefit. In these patients, adequate treatment of leg jerks almost invariably enhances the response to a near optimal or even optimal one. If the leg jerks do not show obvious signs of sleep fragmentation, they can still be treated aggressively, based on studies showing leg jerk activity inducing autonomic arousals not visible on the EEG.[5,6] Here, too, we do see improved outcomes, albeit inconsistently, when treating the leg jerks in some of these patients who are otherwise struggling to gain benefits with PAP therapy.
From the above discussion, the scoring aspects must perforce follow the reasoning that breathing events must be treated first, therefore the leg jerks observed with a RERA must still be caused by the RERA (or presumably so), which means the RERA scoring takes precedence over the limb movement. That is, the limb movement would need to be scored as respiratory-related and not independent. Even if you are seeing the limb movement on video, it’s coupling to the breathing event dictates treatment of that breathing event to determine whether the PLM disappears. Once the breathing event is treated and the leg jerks persist, you score the limb movement as independent. At that point, we also make the determination of whether or not leg jerks are associated with arousal activity in order to guide our clinical decision-making.
A couple papers written about 15 years ago on this topic still shine considerable light on this problem. I encourage reading these works for more insights.[7,8]
1. Hornyak, M., Feige, B., Riemann, D., and Voderholzer, U. Periodic leg movements in sleep and periodic limb movement disorder: prevalence, clinical significance and treatment. Sleep Med. Rev. 2006;10:169-177.
2. Kushida, C. A., Chediak, A., Berry, R. B., Brown, L. K., Gozal, D., Iber, C., Parthasarathy, S., Quan, S. F., and Rowley, J. A. Clinical guidelines for the manual titration of positive airway pressure in patients with obstructive sleep apnea. J Clin Sleep Med 4-15-2008;4:157-171.
3. Condos, R., Norman, R. G., Krishnasamy, I., Peduzzi, N., Goldring, R. M., and Rapoport, D. M. Flow limitation as a noninvasive assessment of residual upper-airway resistance during continuous positive airway pressure therapy of obstructive sleep apnea. Am.J Respir.Crit Care Med 1994;150:475-480.
4. Krakow, B., Ulibarri, V. A., Romero, E. A., Thomas, R. J., and McIver, N. D. Adaptive servo-ventilation therapy in a case series of patients with co-morbid insomnia and sleep apnea. Journal of Sleep Disorders: Treatment and Care 2013;2:1-10.
5. Winkelman, J. W. The evoked heart rate response to periodic leg movements of sleep. Sleep 8-1-1999;22:575-580.
6. Yang, C. K., Jordan, A. S., White, D. P., and Winkelman, J. W. Heart rate response to respiratory events with or without leg movements. Sleep 2006;29:553-556.
7. Exar, E. N. and Collop, N. A. The association of upper airway resistance with periodic limb movements. Sleep 3-15-2001;24:188-192.
8. Stoohs, R. A., Blum, H. C., Suh, B. Y., and Guilleminault, C. Misinterpretation of sleep-breathing disorder by periodic limb movement disorder. Sleep Breath. 2001;5:131-137.