What Causes an Alarm Clock Headache?

A Closer Look at the Origin of Cluster Headaches

What Causes a Cluster Headache — Also Known as an Alarm Clock Headache
Getty Images/Martin Barraud

Why are cluster headaches called alarm clock headaches? Why do these headaches commonly occur at night? One theory is that cluster headaches originate from the hypothalamus – the regulator of a person's sleep and circadian rhythm. Let's explore this theory a little deeper.

Why are Cluster Headaches Called Alarm Clock Headaches?

Cluster attacks tend to start at night – about one to two hours after a person has fallen asleep.

  They also typically occur at the same time everyday or every night, and they usually recur at the same time of year – known as seasonal variation. This is why cluster headaches are sometimes referred to as alarm clock headache — they tend to occurr at specific intervals of time, like clockwork.

The fact that many cluster attacks begin at night has led scientists to believe that somehow our hypothalamus — our biological clock — is involved in its origin.

What is the Hypothalamus?

The hypothalamus is a structure located in at the base of the brain. It serves many roles including:

A “cluster” of nerve cells in the hypothalamus – known as the suprachiasmatic nucleus (SCN) – serves as the master circadian clock – interpreting the length of day and night based on information from our eyes. The SCN then sends messages to another part of the brain, called the pineal gland – a small gland in the brain that secretes a hormone called melatonin.

The secretion of melatonin is maximum during the night when it is dark and low during the daytime when it is light out. Melatonin is involved in a complicated feedback loop back to the hypothalamus.

The hypothalamus is also involved in sending nerve signals to the side of your face in which you experience pain.

This nerve activation is called the trigeminal-autonomic reflex — a fancy scientific term for an intricate nerve loop in the face that relays pain messages to the brain.

Is This Theory Supported By Science?

There are studies that support the theory that the hypothalamus – especially the suprachiasmatic nucleus (SCN) – is involved in the formation of cluster headaches. One study in the Journal of Neurology, Neurosurgery & Psychiatry found that nighttime melatonin secretion was abnormally low during a cluster attack.

Treatment Evidence that Also Points Toward the Hypothalamus

In terms of therapy, there is evidence that targeting the hypothalamus can help alleviate cluster headaches. A study in Cephalalgia randomized twenty patients with cluster headaches to receive either 10mg of melatonin or placebo – a sugar pill – for two weeks during a cluster attack. Results of this small study revealed that the patients taking the melatonin had a reduction in the number of their daily cluster attacks.

Five of the patients stopped having cluster headaches after five days of treatment.

Hypothalamic brain stimulation is another form of treatment for cluster headaches that is reserved for those who have not responded to medications. This procedure is done by a neurosurgeon and involves placing an electrode in the hypothalamus. While this technique is an emerging therapy, it does carry the risk of intracerebral hemorrhage, or bleeding into the brain.

Take Home Points

  • Cluster headaches are also known as "alarm clock" headaches due to their tendency to recur at the same time of day and year.
  • The origin of cluster headaches, while largely unknown, likely involves the hypothalamus.
  • Understanding the cause of cluster headaches is important for the development of therapies, like melatonin and hypothalamic brain stimulation.
  • If you suffer from cluster headaches, you may consider discussing your sleep patterns with your neurologist or headache specialist for further insight into how your circadian rhythm and head pain are linked.


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