What Are Hypnic Headaches?
Headaches have been among the leading causes of morbidity for years. Hypnic headaches are also known as clockwise headaches or alarm clock headaches. The hypnic headache usually occurs during sleep at night. This type of headache is characterized by attacks of dull headaches that occur after the age of 50 years. It is said to occur 15 times every month, at night, with no associated symptoms. The attacks usually last for about 15 minutes after waking. This type of headache can last for years. It is most commonly seen in patients with a history of hypertension and migraine compared to others.
What Are the Causes of Hypnic Headaches?
The exact cause of hypnic headaches is not known yet. However, it could be associated with the brain's parts involved in melatonin production, pain management, or REM sleep.
What Are the Symptoms of Hypnic Headaches?
Hypnic headache is usually described as a frequent recurrent headache that occurs only during sleep. This headache causes them to wake up, lasting up to four hours. There are no characteristic symptoms of these types of headaches. But according to ICHD-3 criteria, they are:
-
These headaches occur only during sleep.
-
It lasts up to 15 minutes or more or 4 hours after waking.
-
Do not have associated cranial autonomic symptoms or restlessness.
-
Occur ten times or more than ten in a month.
-
Nausea and sensitivity to light.
Other characteristic features include:
-
Age - It has been reported to occur in people aged 50 and above.
-
Gender - This condition affects both genders equally.
-
Time - These headaches usually occur during sleep at night.
-
Duration - These headaches are typically short-lasting. They can last up to three hours.
-
Character - These headaches are typically dull but can be throbbing or pulsating.
-
Location - They are bilateral and diffuse.
-
Associated Features - They are rarely associated with migraines, nausea, vomiting, photophobia, phonophobia, conjunctival injection, and lacrimation.
What Is the Pathophysiology for Hypnic Headaches?
Some studies have reported a relation in the timing of hypnic headache and diabetes insipidus with the feeling of thirst and the involvement of hypothalamic structures. Sleep-disordered breathing is not of high prevalence in patients diagnosed with hypnic headaches. Providing nocturnal oxygen supply and positive airway pressure did not improve the symptoms in patients with hypnic headaches. The occurrence of hypnic headaches is related to rapid eye movement sleep. This association could connect to the low oxygenation and arterial hypertension that occurs during REM sleep—the suprachiasmatic nucleus (SCN) is a region at the origin of hypnic headaches. There is a decrease in melatonin as the body ages, and the cell numbers present in the SCN also decrease. Hence the release of melatonin will be affected by the reduced SCN cells.
What Is the Diagnosis of Hypnic Headaches?
The diagnosis of patients with nocturnal headaches includes ruling out conditions like giant cell arteritis, cerebral tumors, obstructive sleep apnea, and other sleeping disorders. Specific tests like an MRI (magnetic resonance imaging) brain with and without the contrast are needed to rule out any abnormalities like tumors, and it may also show gray matter reduction in the hypothalamus. An overnight polysomnography study is necessary to rule out obstructive sleep apnea and other sleeping disorders. It is essential to rule out other reasons for headaches. This diagnosis is based on ICHD-3 diagnostic criteria. Depending upon the history and symptoms, the doctor may perform specific tests such as:
-
Blood Tests - To check the signs of infections, clotting problems, electrolyte imbalances, sugar levels, etc.
-
Blood Pressure Tests - To rule out high blood pressure.
-
Head CT (Computed Tomography) Scan - To better view the head's blood vessels, bones, and soft tissues.
-
Home Sleep Test - To detect sleep apnea.
-
Brain MRI - To create an image of the brain.
-
Carotid Ultrasound - To create images of the inside of the carotid arteries.
-
Nocturnal Polysomnography - This test helps to monitor breathing patterns: blood oxygen levels, movements, and brain activity.
What Is the Treatment for Hypnic Headaches?
The treatment of hypnic headaches requires a lot of evaluation. However, certain medications have helped in managing hypnic headaches. They are:
-
Lithium - Some studies have proved that lithium is effective in treating hypnic headaches. The dose ranges from 150 - 600 mg per day. To be taken in divided or single doses to a serum level of 0.5 to 1.0 mmol/L.
-
Caffeine - Caffeine is also beneficial in treating hypnic headaches and is used as a first-line drug in the treatment of these headaches. There are promising results seen with 40 mg to 60 mg of caffeine. It does not interfere with sleep and is well tolerated in older adults.
-
Indomethacin - Indomethacin has shown positive results in the management of hypnic headaches. It is beneficial in patients with hemicranial hypnic headaches. The dose for Indomethacin is 25 to 150 mg at bedtime. The physician should be aware of the side effects before prescribing this drug.
What Is the Prognosis of Hypnic Headaches?
It has been reported that 17 % of patients have recovered over time, but some have continued to suffer. However, other studies have reported that 40 % of people have benefited from this treatment. The prognosis of hypnic headaches varies depending on the individual. In most cases, the headaches are not serious and do not cause any long-term damage. However, they can be quite disruptive to sleep and can lead to daytime fatigue and difficulty concentrating.
What Is the Differential Diagnosis for Hypnic Headaches?
The differential diagnosis of hypnic headache includes other sleeping disorders. They are:
-
Migraine.
-
Cervicogenic headache.
-
Short-lasting, unilateral, neuralgiform headache (SUNCT).
Conclusion
Hypnic headaches are uncommon primary headaches that occur exclusively during sleep in people over the age of 50 and are characterized by dull or throbbing pain that lasts up to four hours. The precise cause is unknown, but it may be linked to melatonin production, pain management, or REM sleep. All healthcare members should be familiar with such a condition as it is not very common, but they must be well managed as it occurs in the real world.
