Episodic vs chronic cluster headache

Episodic cluster headache

Episodic cluster headache is the more common form, affecting approximately 85% of people with the condition. It is characterised by active "cluster periods" separated by "remission periods" during which there are no attacks at all.

Cluster periods

A typical cluster period lasts 4–12 weeks, though anywhere from 2 weeks to 6 months is possible. During this period, attacks occur daily - most patients have 1–3 attacks per day, though up to 8 per day can occur in severe cases. The period usually begins and ends relatively abruptly.

Many patients with episodic cluster headache have periods that start at around the same time each year - often around the spring or autumn equinox - reflecting the circadian (body clock) component of the condition.

Remission periods

Between cluster periods, episodic patients typically have complete freedom from attacks. Remissions last at least three months under ICHD-3 criteria, and commonly one to several years. Some patients have only one cluster period per year; others have two or three.

During a remission, alcohol no longer triggers attacks, sleep is not disrupted by pain and patients can live entirely normally. This complete remission is one of the features that distinguishes cluster headache from chronic daily headache disorders.

Chronic cluster headache

Chronic cluster headache is defined as cluster headache where attacks continue for one year or more without remission, or with remission periods lasting less than three months. Approximately 10–15% of people with cluster headache have the chronic form.

Chronic cluster headache is significantly more disabling than episodic. There is no relief period - patients may have attacks every day for years. The impact on work, relationships and mental health is profound. Preventive treatment is critically important but also more challenging, often requiring neurologist involvement and potentially multiple preventive agents.

Transition between forms

The episodic and chronic forms are not fixed categories. Some patients with episodic cluster headache transition to chronic over time - remissions become shorter and eventually disappear. Conversely, some patients with chronic cluster headache develop spontaneous remissions, or achieve remission through treatment.

If your remission periods have been getting shorter over time or have stopped altogether, tell your neurologist or GP - this is clinically important and may indicate that your treatment plan needs to change.

Does the type affect treatment?

Acute treatments (oxygen and sumatriptan) are the same for both forms.

For preventive treatment, the approach is similar but the goals differ:

• For episodic cluster headache, the goal is to suppress attacks for the duration of the cluster period, then taper the preventive off once the period ends.
• For chronic cluster headache, preventive treatment is ongoing indefinitely. Achieving complete suppression is more difficult and specialist involvement is usually necessary. Some patients require combination preventive therapy.