Commentary–Ten years of chronic cluster – attacks still cluster
Tim Jürgens is a post-doc working for Arne May at the Department of Systems Neuroscience, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany—and by “post-doc”, I am using academic slang to mean someone who is in the first few years after receiving their MD, but before their first official faculty position. Despite his junior status, Dr. Jürgens has been remarkably prolific in the field of cluster headache research these past few years. Last week we looked at what he had to say about impairment in cluster headache; this week we will examine another paper he wrote recently about periodicity in chronic cluster headache. It’s Jürgens-Fest 2010, woo-hoo!
We all know that cluster headache is a circadian-linked disorder, with attacks occurring at much the same time every day and—even more interestingly—much the same time every year. Some people find that their cluster periods occur twice a year, in spring and autumn, for example; I have one patient whose cluster periods occur for one month every seven months, precessing around the calendar and occurring at a different but predictable time each year.
What about chronic cluster headache, however? One tenth to one fifth of cluster headache patients don’t have episodic attacks with clear cluster periods; they have attacks year-round. Do these vary rhythmically as well? I think—yes. For one thing, I observe it in my own chronic cluster headache patients. For another, I think that the distinction between chronic and episodic cluster headache is artificial. I believe that cluster headache is like epilepsy—just as anyone can be provoked into having a seizure under the right set of circumstances, so anyone can be provoked into having a cluster attack. Just as there is a “seizure threshold”, that can be raised or lowered with the appropriate environment, biochemistry, and drugs, so there is a “cluster attack threshold” that rises and falls, sometimes to the point where attacks will occur spontaneously. Some patients can tell when they are in a cluster period because of some indefinable subjective change, some “penumbra”, even if their prophylactic meds are working and they are not even experiencing any attacks! According to my view, chronic cluster headache patients are merely those unfortunate few whose cluster attack threshold never rises to the oint that they cease to have spontaneous attacks. Others (Sjaastad) have argued that this may be true for secondary chronic cluster headache (the form where episodic has evolved over time into the chronic form), it’s not true for primary chronic (which started that way to begin with), which doesn’t show a circadian link. What’s lacking is hard data either way!
So what should fall into Dr. Jürgens’ lap but a patient with cluster headache—starting at age 51, diagnosed at age 54, and converting to chronic at age 55—who had meticulously recorded every single cluster attack that he had for the next ten years in electronic form; 5447 in all. Only in Germany! I dream of having a patient like that. I always hand out headache diaries, but I can count on one hand the number of times I’ve ever received one back filled in. Dr. Jürgens then conducted a “spectral analysis”, which is a advanced mathematical technique for analyzing phenomena that occur in cycles by looking at them in terms of superimposed frequencies.
What he found was the following: His patient had an average of 45 attacks a month, lasting an average of 23 minutes each (treated). The frequency of attacks DID vary cyclically, with one peak occurring every 13 to 15 months, and smaller cycles occurring every 2, 4, 6, 7, and 9 months. There was also a daily cycle, which (oddly) corresponded better with 24.5 hours than 24. Attacks were slowly diminishing as the years went by.
Why is this important? As Dr. Jürgens point out, this one case confirms scientifically what has long been suspected—that chronic cluster headache patients cycle also (although it does not address Sjaastad’s theory that primary chronic patients do not). Practically speaking, this means that if a prophylactic medication stops working with a chronic cluster headache patient, it’s a mistake to conclude that it’s stopped working and switch to something else. It may just be that the disease is in an upswing and will get better in a few weeks, in which case it is better to stay on the medication and wait it out.