Hemicrania continua: symptoms, diagnosis and indometacin treatment

Hemicrania literally means half of the head. In hemicrania continua the pain stays on the same side, day after day, never fully going away. NHS Scotland's Right Decisions guidance places it with paroxysmal hemicrania among the trigeminal autonomic cephalalgias (TACs), a group of headache disorders that also includes cluster headache, and groups it with other indometacin-sensitive headaches.

The Migraine Trust says the pain is usually mild to moderate. For many people there are periods of severe pain on top of the background pain.

The Migraine Trust describes the pain as present on one side of the head, with exacerbations during which other symptoms appear. NHS Scotland guidance says that a person should have at least one cranial autonomic symptom, and that restlessness or agitation is commonly present during the flares, which helps to separate it from migraine.

• Continuous pain on one side of the head that never switches sides.

• Flares of moderate to severe pain on top of the background pain.

• Watering or redness of the eye on the same side as the pain.

• A blocked or runny nostril on the same side.

• Eyelid drooping on the same side.

• Sensitivity to light, sound or smell, with nausea or vomiting during flares, as in migraine.

Because these conditions overlap, the NHS Scotland pathway sets out differences. Migraine attacks last 4 to 72 hours, cluster headache attacks 15 minutes to 3 hours, and paroxysmal hemicrania attacks 5 to 30 minutes, whereas hemicrania continua is constant. The preventive treatment differs too, with indometacin for hemicrania continua and paroxysmal hemicrania and verapamil for cluster headache.

The guidance lists no acute attack treatment for hemicrania continua and says it is prone to worsen with medication overuse. This is a reason to speak to your GP about headaches that come with frequent painkiller use, rather than treating them indefinitely yourself.

The NHS says to see a GP if headaches are not getting better or are getting worse, or if you get them regularly. Keeping a headache diary helps. The Migraine Trust says a diary is crucial for diagnosis and monitoring, and suggests recording the location of the pain, when worsening began, how often and how long flares last and other symptoms such as eye watering or nasal blockage.

Some headaches need urgent attention. The NHS says to call 999 or go to A&E if a headache comes with a seizure, numbness or weakness in the body or face, a sudden onset and extreme pain, a head injury in the last 3 months, difficulty speaking, balancing or walking, drowsiness or confusion, loss of vision, a rash that does not fade, or a very high temperature with a stiff neck. It also says to get urgent advice from NHS 111 or an urgent GP appointment for headache with vision or eye problems, or a headache triggered by coughing, sneezing, bending or exercise.

NHS Scotland guidance explains that a trial of indometacin is usually enough to confirm or exclude an indometacin-sensitive headache. In hemicrania continua indometacin should completely stop the headaches; if there is not an absolute response the diagnosis should be reconsidered. A partial response may be only a general pain-relieving effect, and these patients are at risk of medication overuse headache.

The Migraine Trust says the trial is done with a strict headache diary, with an increasing dose of indometacin over days to weeks and the pattern compared with before. In uncertain cases the Scottish guidance describes an "Indo test" in which an injected dose is compared with saline on different days as an outpatient.

The guidance recommends considering an MRI scan in anyone with a new-onset TAC or chronic symptoms.

Indometacin is the treatment of choice. It is a potent anti-inflammatory painkiller (NSAID), and the guidance says its effect appears specific, with other NSAIDs not effective. It also says 30 to 60% of patients on usual therapeutic doses have adverse effects and 10 to 20% stop it, mostly dose related. Because stomach side effects are common, protection of the stomach, usually with a proton pump inhibitor, should be considered.

Where it works and is continued, the Scottish pathway says to use the minimum effective dose, monitor regularly for side effects, regularly withhold treatment every 3 to 6 months to check that it is still needed, and look for alternative preventive treatment. The Migraine Trust says not everyone can tolerate indometacin daily and that other treatments can be useful.

Do not start, stop or adjust indometacin without medical advice. Because of the side effects described above, it needs to be prescribed and monitored by a doctor.

On the NHS, a GP may refer you to a neurologist or headache specialist, who will arrange an indometacin trial and imaging if appropriate. Because hemicrania continua is rare, it can take time to be recognised, and a headache diary is one of the most useful things to bring.

Private neurology appointments are an option for those wanting a quicker review or second opinion. The trial of indometacin and the scans are the same either way, so the differences are mostly waiting times and choice of clinician.