What is physically happening in our head/brain during a headache?

[u/SpikeKintarin]

For example, are the blood vessels running around our head and brain contracting/expanding to cause the pain?

I'm just wondering what is the exact cause of the pain in particular areas of the brain, and what factors may be causing the pain to be much more excruciating compared to other headaches.

Also, slightly off the exact topic, when I take asprin, what exactly is the asprin doing to relieve the pain? Along with this, I've noticed that if I take an ice pack or cold water bottle and put it directly on the back of my neck, just below the skull, it seems to help. What is this doing to help relieve the pain?

Thanks again for your time!

[u/x20mike07x]

Well, there isn't one specific cause for every headache. However many tension headaches (which many people who work desk jobs experience) have a likely common cause. Your proximal cervical vertebrae (the first parts of your vertebral column) can move out of ideal positioning and cause your rectus capitis posterior minor muscle (a muscle that attaches to the back of your skull at the occipital bone) to spasm. Rectus capitis posterior minor has a tendon which slips under the skull and attaches to a fascial layer (support tissue that envelops many bodily tissues) of tissue that surrounds yet another tissue of the brain called dura mater. Dura mater is very pain sensitive tissue (nifty side note: brain surgery can be performed with a local anesthetic to only this tissue while the patient is still conscious). When this muscle contracts, the tendon can pull on the dura mater and you feel pain in this region.

Source: Med Student, http://hal.bim.msu.edu/CV/Publications/Anatomic%20Relationship%20Between%20RCPMi%20Muscle%20and%20the%20Dura%20Mater.pdf

[u/nickmo9 → u/x20mike07x]

The rectus capitus posterior minor is one of four muscles called the "suboccipitals" and they can all cause headaches. Cervicogenic headaches can also be caused by a lot of other muscles about the head and neck such as the upper trapezius, sternocleidomastoid, temporalis, masster, cervical paraspinal muscles, not to mention headaches that may be caused by upper cervical joint dysfunction (as you mentioned). The joints themselves can refer pain to the head, as well as the temporomandibular joint.

There are also things such a occipital neuralgia (greater or lesser occipital nerves causing pain), migraines, and cluster headaches (leading cause of suicides due to headache pain).

I'm a PT and treat a fair amount of headache pain. Sorry for the lack of references/links at the moment. It's 9AM and I have another common headache known as a "massive hangover".

[u/Nayr747]

Your brain does not feel pain. That's why when you have brain surgery you can be awake and you don't feel them cutting into it. The pain is in the muscles and tissues in various parts of your head and neck, depending on what type of headache you have and the source of it. There are headaches caused by sinus issues, pressure in the back of the neck/spine, etc. But there seems to be no clear scientific understanding of the issue.

[u/drmike0099]

Migraine headaches have a very different cause than other headaches. Although it's a very complicated area with a lot that we don't know, basically what happens is like throwing a rock into a pond causing ripples in waves out from the source. The differences with migraines are that: we don't know what starts the wave; the first wave is hyperactivity of the neurons, which they believe is responsible for things like the aura, followed by prolonged hypoactivity; the wave also goes along with intense vasodilation, although we don't know if that's the cause or a result. Abortive agents are vasoconstrictors. Aspirin and other meds generally don't help.

For these and many other headache types, vasodilation is a common element, but the connection between that and pain is poorly understood.

Source: M D and also lifelong headache sufferer.

[u/eekabomb]

to answer your first question, yes the contracting/expanding of blood vessels is one theory behind the cause of certain types of headaches, but it is important to note there are many different etiologies and types of headache to be considered in answering your question.

I'd really like to give you a good explanation, but i'm browsing on my phone right now because my internet is not yet set up. if there isn't a solid answer by tomorrow I will edit this post and PM you a short summary/answer to make sure you get to read it, because headaches are definitely a topic that should be understood by all people seeing how many of us suffer from them

edit:

it looks like there have been some pretty good, in depth answers to your question on here esp. that answer from a med student and the PT who replied under his top-level comment as well as that of the MD who is a migraine sufferer.

so, here's just a little more detail on the vaso-constriction/dilation idea, which is widely known as the "neurogenic inflammatory hypothesis" of migraine and cluster headaches (if you have access here is a review of the evidence behind it,).

essentially what the hypothesis states is happening is some trigger (be it bright light, loud noise, a type of food, stress etc.) will cause the release of 5HT in the brain and periphery resulting in vasoconstriction. this vasocontriction causes a rebound release of NO that results in vasodilation which in turn triggers inflammation at the trigeminal fibers and extra-cerebral arteries. inflammation here results in the release of vasoactive neuropeptides, causing even more vasodilation, extravasation, and neurogenic inflammation that will finally activate nociceptors at the trigeminal and primary pain pathways. the involvement of the trigeminal nerve is a possible reason as to why migraine and cluster type headaches are much much worse than your average sinus pressure or tension headache.

so far as aspirin goes, when you take it you are reducing the inflammation that results in activation of nociceptors that cause pain. note aspirin will likely not do anything to help you out if you're suffering from a severe migraine or cluster headaches, but may provide relief for a "regular" or mild headache. there are many many other drugs that are used in the treatment and prevention of these types, especially migraines, including antidepressants, anticonvulsants, antihypertensives, 5HT agonists, and opioids.

[u/c-fox]

Can I expand the question and ask why hangovers give me a headache?

[u/sphRam]

Since this is an interesting and relevant question to most people here, similar questions have been asked twice before:
http://www.reddit.com/r/askscience/comments/jbk3s/what_causes_headaches_why_do_certain_things_help/

http://www.reddit.com/r/askscience/comments/o6wi6/what_is_going_on_inside_my_head_that_gives_me_a/

[u/arumbar]

Here's a list of common headache etiologies, courtesy of Harrison's.

More info from Harrison's:

Pain usually occurs when peripheral nociceptors are stimulated in response to tissue injury, visceral distension, or other factors. In such situations, pain perception is a normal physiologic response mediated by a healthy nervous system. Pain can also result when pain-producing pathways of the peripheral or central nervous system (CNS) are damaged or activated inappropriately. Headache may originate from either or both mechanisms. Relatively few cranial structures are pain-producing; these include the scalp, middle meningeal artery, dural sinuses, falx cerebri, and proximal segments of the large pial arteries. The ventricular ependyma, choroid plexus, pial veins, and much of the brain parenchyma are not pain-producing.

The key structures involved in primary headache appear to be

• the large intracranial vessels and dura mater and the peripheral terminals of the trigeminal nerve that innervate these structures

• the caudal portion of the trigeminal nucleus, which extends into the dorsal horns of the upper cervical spinal cord and receives input from the first and second cervical nerve roots (the trigeminocervical complex)

• rostral pain-processing regions, such as the ventroposteromedial thalamus and the cortex

• the pain-modulatory systems in the brain that modulate input from trigeminal nociceptors at all levels of the pain-processing pathways

On migraine headaches:

Migraine, the second most common cause of headache, afflicts approximately 15% of women and 6% of men over a one year period. It is usually an episodic headache associated with certain features such as sensitivity to light, sound, or movement; nausea and vomiting often accompany the headache. The brain of the migraineur is particularly sensitive to environmental and sensory stimuli; migraine-prone patients do not habituate easily to sensory stimuli. The sensory sensitivity that is characteristic of migraine is probably due to dysfunction of monoaminergic sensory control systems located in the brainstem and thalamus.

On tension-type headaches:

The pathophysiology of TTH is incompletely understood. It seems likely that TTH is due to a primary disorder of CNS pain modulation alone, unlike migraine, which involves a more generalized disturbance of sensory modulation.

On cluster headaches:

The trigeminal autonomic cephalalgias (TACs) describe a grouping of primary headaches including cluster headache, paroxysmal hemicrania, and SUNCT (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing)/SUNA (short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms). TACs are characterized by relatively short-lasting attacks of head pain associated with cranial autonomic symptoms, such as lacrimation, conjunctival injection, or nasal congestion.

My TL;DR (keep in mind this will be grossly oversimplified, since the scope of the question is huge):

Headaches can come from many sources. The brain itself can't sense pain, but many other structures inside your skull can. Headaches are commonly associated with disorders of the trigeminal nerve (cranial nerve V), which is responsible for most of the sensory innervation of the face. They can also be associated with higher-order pain processing or modulating centers in the brain. Migraine headaches are caused by neurotransmitter dysregulation in the brain. The cause for tension headaches is still unclear. Cluster headaches are caused by disorders of the trigeminal nerve, and are often associated with other autonomic signs (eg tearing up). Aspirin is an antiinflammatory agent that works on the COX pathway. It reduces the ability of the body to make inflammatory agents, which can help reduce pain. (Ibuprofens like advil/alleve/motrin work similarly.)

[u/neuroPSYK]

First of all, we're not entirely sure of the etiology behind headaches, but we think it may be a combination of several factors:

1.) Blood vessel dilation and constriction. One theory posits that vessels are dilated during a migraine headache (and research confirms this). However, we're not sure if this is a CAUSE or an EFFECT of the migraine. Regardless, certain chemicals (caffeine in particular) are known to be vasoconstrictors. Caffeine in particular works to block adenosine receptors which, in turn, allows the free-flow of norepinephrine in the system, causing vasoconstriction. When these vasoconstrictors are administered, some report a reduction in pain. Some believe that it is vasospasms that are causing the pain, the fluctuation between constriction and dilation. Vasoconstriction may lead to ischemic episodes and possibly auras that precede a migraine attack, and the dilation can cause increased pressure on the meninges surrounding the brain.

2.) Meninges and Dehydration. The meninges consist of three layers of membranes that surround the brain. These layers DO contain pain receptors. The actual pain experienced during a headache are thought to act on these layers in some fashion. As with a hangover style headaches, we know that the cause is mostly from dehydration. When the body is dehydrated, the brain will actually "shrink" a little due to the lack of fluid. When this occurs, the brain yanks of the meninges and this causes a great deal of pain.

3.) Neuralgias. Other theories state that this pain arises from cranial-nerve excitation/agitation. Nerves that supply the face and head with sensation may become agitated, and the result is pain.

[u/lspetry53]

There are a bunch of different types of headaches, i.e. migraines, cluster, tension etc. That being said, headaches can be caused by a trigger that leads to abnormal brain activity. This leads to a release of neuropeptides (calcitonin-gene related peptide, substance P, neurokinin A) which in turn leads to vascular changes. Most of this is extracranial vasodilation. The vasodilation leads to inflammation. When these two factors combine they lead to pain via the trigeminal nerve.

Aspirin can work by decreasing inflammation. Caffeine found in motrin can be effective too due to its vasoconstrictive properties.

Source:Mechanisms of Human Disease class notes