Hypnic headache syndrome, also known as hypnic headache or "alarm clock headache," is a rare primary headache disorder that primarily affects older adults. It is characterized by recurrent headaches that occur exclusively during sleep, leading to awakening from sleep due to the pain. These headaches typically start after the age of 50, although they can also affect younger individuals.
The primary distinguishing feature of hypnic headache syndrome is the regularity of the attacks, which tend to occur at the same time every night. The pain is typically described as throbbing or pulsating, affecting one side of the head, although it can also be bilateral. The intensity of the headache can vary, ranging from mild to severe, and it usually lasts for around 15-180 minutes. In some cases, the headache can be accompanied by autonomic symptoms, such as tearing, eyelid drooping, or nasal congestion.
The exact cause of hypnic headache syndrome is unknown, but there are theories that suggest it may be related to the trigeminal-autonomic reflex system, which regulates pain and autonomic functions. The diagnosis of hypnic headache syndrome is based on the observation of characteristic features, the exclusion of other potential causes, and the response to treatment with a rapid-acting headache medication, such as caffeine or indomethacin.
Although hypnic headache syndrome is typically a benign condition, it can significantly disrupt sleep patterns and lead to chronic sleep deprivation. Treatment options include preventive measures, such as daily caffeine intake or the use of indomethacin, a nonsteroidal anti-inflammatory drug. However, the effectiveness of these treatments varies among individuals, and some may require additional medications to manage the pain.
