Boundary Between Chronic and Episodic Migraine Is “in Flux”

David B. Kudrow, MD

THE TREATMENT OF PATIENTS with migraine has undergone massive change since the turn of the century. And with the introduction of calcitonin gene-related peptide (CGRP)–targeted medicines in 2018, the field was transformed once again. Clinicians now have a variety of migraine-specific treatment options available after many years without such therapeutic approaches.

Even with the availability of treatment options, challenges remain. One of the major roadblocks is the limited number of headache specialists available to treat the more than 40 million individuals with the disease. The need has never been greater for a wider range of physicians to understand migraine and available therapies.

In a recent NeurologyLive® Insights™ series, DAVID B. KUDROW, MD, medical director of California Medical Clinic for Headache in Santa Monica, offered his perspective on treating patients with migraine and discussed the impact of these new medicines.

Differences Between Episodic and Chronic Migraine

Chronic migraine is defined as at least 8 migraine days per month in a total of 15 or more migraine and headache days per month. Episodic migraine, on the other hand, includes headache occurring at a frequency of up to 14 headache days per month.

Because of how the disease functions, “I find that 15-day limit between the 2 diagnostic categories to be rather arbitrary,” Kudrow said. “Three percent of patients who have episodic migraine will become chronic over the course of 1 year, and [approximately] 25% of patients who have chronic migraine may revert to episodic migraine over the course of a year.”

Kudrow pointed out the American Headache Society’s Harold G. Wolff Lecture Award given in 2021 to Ryotaro Ishii, MD, PhD, for his examination of a large database of patients with migraine. Study results showed that with respect to the degree of disability that patients experience, those with 8 to 14 migraine days per month were not significantly different from patients with 15 to 23 migraine days per month. Those who had 24 or more headache days per month had the greatest degree of disability.

“That traditional arbitrary boundary between chronic and episodic is in flux at this point,” Kudrow said. “Why is that important? Because there are some medications that we use for patients who have chronic migraine that may be beneficial for patients who have less than chronic migraine. It’s important to understand and recognize that those diagnostic categories are relatively fluid.”

Kudrow explained that the difference in the acute migraine attacks themselves is essentially null for these patients, whether they have episodic or chronic disease. As for symptoms, they have similar characteristics with only the frequency differing. Kudrow explained that migraine attack is defined as moderate to severe headache that tends to be unilateral and can be associated with nausea, light sensitivity, and sound sensitivity. Patients don’t want to move, the headache worsens with exertion, and the headache can occur with a visual aura.

Great scientific thinkers have introduced these therapies that are... migraine-specific, effective, and better tolerated. Why would we need to jump through hoops and try things that are less effective...?”

—DAVID B. KUDROW, MD

“Migraine is a long-lasting phenomenon. We recognize the acute attack as the most obvious clinical observation in a patient who has migraine, but there’s a prodrome to the attack that can be several hours to days in duration,” Kudrow said. “There’s also a postdrome to the attack that can be several hours to days in duration, which prolongs the time of the acute migraine attack. The more frequent migraine becomes, the fewer headache-free days a patient has. That’s important to point out in recognizing how increasing frequency of migraine contributes to disability of the patient’s experience and the need for effective acute and preventive therapeutics.”

Deciding on Treatment Options

Kudrow explained that the process of treatment, whether prescribing an acute pharmacotherapy or a preventive therapy for migraine, always begins with a discussion with the patient. An informed patient is more likely to be adherent to the medication regimen that’s prescribed, and more information and dialogue improve the process for all involved.

But the variability in how each patient’s disease responds to treatment options complicates the process. “With respect to acute treatment for migraine, there are patients who have varying intensities or severities of migraine. Some patients can get away with using an OTC medication for some of their migraines, or the same patient may have more severe migraines that require a more migraine-specific abortive agent. Everybody who has migraine should be armed with an acute migraine medication,” Kudrow said.

When it comes to preventive treatment, Kudrow said that the bar for success is changing because of the recent introduction of migraine-specific, mechanism-specific medications that have better adverse effect profiles and better efficacy compared with older options. The American Headache Society recommends that patients with as few as 2 migraine days per month be considered for preventive treatment if those migraine days are accompanied by significant disability and that any patient with at least 4 migraine days per month should be considered for migraine preventive therapy, irrespective of the degree of disability.

“In my own practice, it’s a sliding scale,” Kudrow said. “I have patients who may have 4 to 6 migraine days per month, and they’ve been using a triptan that works very effectively for them without much in the way of adverse events. They don’t want to take preventive medication and want to just keep using their acute medication. That’s a reasonable choice.

“On the other hand, there are patients who have 1 or 2 severe migraine days per month and are debilitated by them. Even if they use their acute medication, that medication may help the headache but then has adverse effects that incapacitate the patient or prevent them from working. Not many patients can tolerate losing 1 or 2 days of work per month without getting fired. If we can’t get those headaches under control with a good acute treatment, then even those patients should be considered for preventive therapy,” he said.

Ultimately, it begins with a physician-patient discussion. Ensuring that patients are educated about adverse effects and are part of the treatment decision process is important. Kudrow said that the discussion of when and whether to start a preventive treatment and which treatment to select is critical for the therapeutic regimen’s success.

Advice for Neurologists

“It has become easier to treat patients who have migraine. We have a new class of medications that has a very favorable safety profile, a favorable tolerability profile, and a favorable efficacy profile,” Kudrow said, adding that he would advise not fearing the use of the CGRP class of medications, either monoclonal antibodies or small molecule antagonists, because of the adverse effect profile and tolerability profiles.

Kudrow noted that expense was the greatest barrier to new therapeutics coverage. For those without insurance, the new medications can be “phenomenally expensive,” he said. For those with insurance, many of the pharmaceutical manufacturers are offering the medicines at discounts for at least 1 year, though not all patients are eligible for those discounts. But even for those with insurance, many payers are inquiring with physicians about attempting traditional oral preventive medications prior to using the new anti-CGRP monoclonal antibodies or small molecule antagonists. “In many cases, physicians are going to have to step through those options before being able to use these medications,” Kudrow said.

“My attitude is a little different,” he said. “We’ve come a long way. Great scientific thinkers have introduced these therapies that are disease-specific, migraine-specific, effective, and better tolerated. Why would we need to jump through hoops and try things that are less effective, during which time patients continue to [experience] migraine attacks, disability, and affected quality of life?”