A headache experienced on only one side of the head is commonly referred to as a one-sided or unilateral headache. They can be quite painful, often making our heads feel like they are throbbing and possibly leading to additional symptoms of nausea, vomiting, and a visual sensitivity to light.
While there exist many reasons to why a headache may present themselves, being a one-sided headache often leads to the assumption it is a migraine, but there are in fact many types of a headache that can present in a similar fashion.
Health conditions that may cause a unilateral headache
Unilateral headaches usually do not alternate sides, and there are three observed types affecting people today. They include cluster headaches, chronic paroxysmal hemicrania (CPH), and cervicogenic headaches. However, cluster headaches are known for changing sides when going from one cycle to another and CPH possibly alternates sides while its occurring.
This type of headache is known for exclusively causing a headache on one side of the head and is technically caused by referred pain. This means that the originating source of pain does not begin primarily at the head but at another part of the body. In the case of cervicogenic headaches, the originating source of pain stems from the neck, or rather, the structures within it such ass the cervical spine and its components.
The neck region contains many pain-sensitive structures including the lining of the cervical spine, the joints, various ligaments, cervical nerve roots, and vertebral arteries that pass through cervical vertebral bodies. These areas can be affected by an excessive amount of stress to the neck on the spine area.
Those affected by cervicogenic headaches often present with a decreased range of motion of the neck, which can often worsen headaches with certain movements or when pressure is applied to the neck at certain spots. The condition may also cause a headache on one side extending behind the eye.
Occurring in bouts of frequent attacks or in clusters, they are considered one of the most painful types of headaches. They present with intense unilateral headaches accompanied by severe pain in or around the eye, often disrupting sleep and causing misery for sufferers. Cluster headaches can last for weeks to months but are usually followed by remission periods when a headache stops. Remission may last several months or even years.
Cluster headaches are more commonly seen in men and fortunately aren’t life-threatening. They can strike quickly and without warning, often leading to excessive tearing of the eyes and redness of the affected eye.
A rare primary headache disorder characterized by a severe unilateral headache typically affecting the areas around the eye. Episodes tend to occur multiple times in a single day, yet are short in duration. The condition is commonly seen in men more frequently as well. While it may bare many similarities to a migraine headache, paroxysmal hemicrania has no neurological symptoms associated with it. Fortunately, this type of a unilateral headache is completely treatable by taking indomethacin, a nonsteroidal anti-inflammatory medication.
A relatively uncommon type of unilateral headache that can cause severe pain and occurs primarily in women. Headaches tend to persist throughout the day, without pain-free periods that don’t shift to the alternate side of the head at any point. The condition generally presents with at least one of the following additional symptoms during exacerbations: conjunctival injection (eyes appearing red) or lacrimation (tears), nasal congestion or rhinorrhea (runny nose), and ptosis (drooping of the eyelid) or miosis (constriction of the pupil). While the cause for hemicrania continua is unknown, it can be treated using indomethacin, a nonsteroidal anti-inflammatory medication.
Does a one-sided headache always signal a migraine?
There are many different reasons for a unilateral headache, with one of them being a migraine. However, migraines tend to have a unique presentation that physicians look for when making a diagnosis. Migraines may present as a constant one-sided headache, but they may also occur on both sides (bilaterally). In addition to a headache, additional symptoms of a migraine may include:
- Auras: Described as a visual disturbance that appears as flashes of light or wavy, zigzag vision.
- Sensitivity to light (photosensitivity)
It is important for the doctor to know the differences between various types of headaches, as not all can be treated the same way. While a unilateral headache may present similarly to a migraine, looking a little deeper can reveal it as another type of a headache entirely.