On the face of it, the symptoms, as described, make it sound like it's relatively easy to diagnose CH as a syndrome. However, this is often very difficult because other types of headache can mimic the symptoms and features of CH. Apart from the other TACs as mentioned, the main alternative options that are considered include 'secondary' causes of CH, migraine and hypnic headache.
1. Secondary causes of CH
Before CH is definitively diagnosed, it is usual to attempt to exclude any possible secondary or external causes. Symptoms of CH can also be caused through abnormalities caused by disease or injury. Any such circumstances reported by the sufferer, with the exception of sinking in of the eyeball, drooping of the eyelid or pupil constriction (known as partial Horner's Syndrome) warrants further investigation by the neurologist to search for potential organic causes.
One-sided headaches, migraine symptoms and autonomic features can occur in both migraine and CH, and therefore, differentiating between the two can be difficult in some cases. The most useful features for differentiating CH from migraine include: -
- Short-lasting headaches
- Abrupt start and finish
- Occurring at regular times during the day
- Triggered within an hour of drinking alcohol
- Restlessness during an attack
- Clustering of attacks broken by periods of pain-free remission (in ECH)
3. Hypnic Headache
Hypnic headache differs in that it is more likely to occur amongst much older people and females. Sufferers of hypnic headache are often awakened from sleep by headaches that frequently occur on both sides of the head but may also be one sided. These are also not usually associated with autonomic features. The headaches are brief - lasting between 5 minutes and 3 hours - and can occur up to three times per night. These can be effectively treated by bedtime dosages of lithium, indomethacin or caffeine.
The diagnosis of CH is based purely on assessing the history of the sufferer and a detailed neurological examination. Because of the difficulty in differentiating other types of headache, a magnetic resonance image (MRI) scan of the brain is a very good screening investigation.