What Are Hypnic Headaches?

Also known as 'alarm clock headaches,' hypnic headaches were first identified in 1988, and they are most prevalent in adults over fifty years old. Unlike other types of headaches, hypnic headaches occur only during the night. These headaches are relatively rare among the general population, and they are not due to underlying medical conditions. Since hypnic headaches can be diagnosed only through ruling out other illnesses, it may take years to obtain a proper diagnosis. Current research suggests women have a higher risk of experiencing hypnic headaches as compared to men. Given the rarity of this type of headache disorder, patients who suspect they have the condition should be assessed and treated by a neurologist.

Key Symptoms of Hypnic Headaches

Each patient's experience of a hypnic headache is unique. Some of the key symptoms of hypnic headaches that may occur include nausea, sensitivity to light, sensitivity to sound, and bilateral pain. Patients with these headaches will generally experience pain on both sides of the head, and it may range from mild to severe. While the pain usually occurs only at the front part of the head, some individuals might develop pain in the sides of the head, and the pain may also be present across the whole head. A throbbing sensation could develop, and the pain generally begins suddenly. The pain and other symptoms are typically severe enough to wake patients up at night. Symptoms may last for as little as fifteen minutes, but some patients could have symptoms that persist for up to four hours.

What Makes Them Different?

Hypnic headaches have several clinical features that help doctors in distinguishing them from other benign headache disorders. Primarily, what makes them different is that they occur only at night, never during the day. In fact, many patients experience repeated episodes at the same time at night, and this feature is why they are sometimes called 'alarm clock headaches.' Although they wake the patient from sleep, hypnic headaches rarely occur if the patient takes a nap during the daytime. Hypnic headaches also differ from other types in terms of their frequency. To be diagnosed with these headaches, patients must experience at least ten episodes each month. Up to fifty percent of patients with hypnic headaches will have episodes every night. The headaches interfere with sleep, and some patients are chronically unable to get sufficient rest.

Causes of Hypnic Headaches

Currently, experts continue to research possible causes of hypnic headaches. At the moment, doctors agree these headaches should be classified as a primary headache disorder, meaning they are benign and not caused by underlying medical conditions such as brain tumors. Studies suggest there may be a link between hypnic headaches and certain stages of sleep, particularly rapid eye movement (REM) sleep. Additional research suggests patients with this condition could have functional issues in the regions of the brain responsible for pain control and melatonin production. For some patients, headaches may be triggered or exacerbated by environmental factors. Insufficient or excessive sleep, exposure to bright light, and stress are recognized triggers. In addition, hormonal changes, dehydration, and the use of certain medications might cause or worsen headaches too. To help the patient determine if any triggers may be exacerbating their hypnic headaches, a neurologist will take a thorough health history, asking about sleep patterns, stress levels, diet, and medication use.

Diagnosing The Headaches

The process of diagnosing the headaches is often lengthy, and it includes a battery of tests. To help the doctor in the diagnostic process, patients should let the healthcare team know about all medications they take as part of the health history. Several medications, including estrogen and nitroglycerin, can cause symptoms that mimic hypnic headaches. After completing the health history, the doctor will perform a complete physical exam to rule out other conditions that could be causing the headaches. This will include checking the patient's blood pressure and cardiovascular health. Occasionally, high blood pressure at night or reduced blood flow in the carotid arteries could cause headaches, and doctors will want to rule this out, possibly with an ultrasound of the carotid arteries.

The physician will also perform a neurological exam to check the patient's coordination, sensation, and muscle tone. After finishing the exam, the patient may be asked to have further tests such as blood tests and imaging studies. These tests can help detect brain tumors, stroke, infection, and internal bleeding that could be contributing to the patient's symptoms. For example, blood glucose testing is performed to check for low blood sugar, a potential cause of nocturnal headaches. Sometimes, patients may need to have sleep studies at home or in a sleep laboratory. These studies measure the patient's oxygen levels, breathing, and brain activity during sleep, and they can detect sleep apnea, one of the major causes of nighttime headaches.

Treating Hypnic Headaches

High doses of caffeine are often the first option used in treating hypnic headaches. Doctors normally recommend patients take a caffeine supplement shortly before bed, and drinking a strong cup of caffeinated coffee may also help. Patients with hypnic headaches generally tolerate nighttime caffeine very well, and it does not seem to have adverse effects on sleep for the majority of these patients. Compared to other treatment options, caffeine carries the lowest risk of potential side effects. If the patient does not obtain enough relief with caffeine, another frequently used treatment option is lithium carbonate. This drug can be used to stop a hypnic headache that has already developed; however, it should be used with caution in patients with kidney or heart disorders. Some patients have been successfully treated with topiramate, an anti-seizure medicine, and individuals taking this medicine normally need to use it every day to successfully prevent hypnic headaches. Melatonin, flunarizine, and indomethacin may also be beneficial.