Physiology of Headache

Assalamualaikum w.b.t.

Someone asked me to post an entry about headache. So I did some homework about headache since we already learned Physiology of Headache during our 2nd year course. This post might relevant for the medical student rather than ordinary individuals. But I tried to simplify the words so that it wont sounds so0o medic.heheh. Enjoy the reading and may it benefits you alot!

Headache
source : 2nd year Physiology text book Mansoura U
What is headache?
Headache is a diffuse dull pain referred to the surface of the head. It results from pain signals that may arise from intracranial or extracranial sources.

Headache From Intracranial Sources

Sources:
This type of headache arises from stimulation of pain receptors in pain sensitive tissue inside the cranial cavity. These pain receptors are located in :

• The dural and intracerebral artery
• Large veins and venous sinuses
• The dura of the tentorium and at the base of the brain

In contrast, some areas of the intracranial have no pain receptors thus insensitive to pain stimulus. These areas are:

• Parenchyma of brain
• The lining of the ventricles
• The choroid plexus
• The most area of dura and pia

Stimuli:

The adequate stimuli that excite intracranial pian receptors include:

1. Pressure or traction upon the pain sensitives areas of dura
2. Inflammation or damage of these areas
3. Dilatation or distension of the dural and cerebral arteries
4. Distension of great venous sinuses
5. Inflammation or compression of cranial nerves containing pain fibres (5,7,9,10 cranial nerves)

Localization of Intracranial Headache:

1. Headache referred to the frontal,parietal and temporal region of head : caused by stimulation of pain receptors in the pain sensitive-tissues located within intracranial cavity above the tentorium including the upper surface of tentorium itself. It transmitted through the trigeminal nerve.
2. Headache referred to the occipital region : caused by stimulatin of pain receptors in the pain-sensitive tissues located within cranial cavity below the tentorium including its lower surface. It transmitted through the glossopharyngeal, vagus and the second cervical nerves.

Causes:

Clinically, the most important causes of intracranial headache are:

1. Head-Injury Headache - A post traumatic type of headache may follow head injuries. It is usually felt as a constant dull ache, which maybe localized or generalized in the head.
2. Headache of Meningitis - Inflammation of meninges including the sensitive areas of the dura and the walls of the venous sinuses, cause one of the most painful types of headache, which is commonly referred over the entire head.
3. Vascular Headache - Vascular headache could result from a variety of medical causes, including arterial hypertension. This type of headache is most probably evoked by excessive distension of intracranial arteries.
4. Migraine - Migraine is severe dull aching or throbbing headache. Attacks of classic migraine was found to be associated with dilatation of the cerebral vessels during the headache phase. It is thought that the excessive stretching of the walls of these arteries is the actual cause of pain in migraine headache.
5. Brain Tumour Headache - Intracranial tumours may cause headache owing to pressure or traction upon vascular structures or other pain-sensitive tissues inside the cranial cavity.
6. Lumbar Puncture Headache - Normally, the cerebrospinal fluid (CSF) provides a fluid cushion for suppport of the brain inside the cranium. Removing more than 20-30ml of CSF from the spinal canal by lumbar puncture, often cause intense headache. Removal such quantity of the CSF decreases the amount of CSF inside the cranial cavity, which emoves the floatation of the brain that is normally provided by CSF. Therefore, the weight of the brain pulls upon and stretches the dura and the vascular srtuctures.
7. Headache Caused by Constipation - Constipation causes headache in many people. It possibly results from the effect of absorbed toxic product on intracranial pain-eliciting mechanism.
8. Fever Headache - Headache is of frequent accurence in febrile diseases, and probably results from dilatation or distension of intracranial blood vessels.
   

Headache From Extracranial Sources

Sources :

Headache from extracranial pain receptors are arise mainly from the :

• Orbit and eyeballs
• Nasal mucosa
• Facial, scalp, and neck muscles
• Teeth
• Extraocular muscles
• Paranasal sinuses
• Extracranial ear and middle ear
  

Stimuli :

The adequate stimuli that can produce extracranial headache include :

• Ischemia
• Injury
• Irritation
• Inflammation

of the pain-sensitive somatic tissues in the face,head and neck.

Type of Headache From Extracranial Sources :

1. Tension Headache : Emotional tension often causes sustained spasm of many muscles of the head especially those of the scalp and the neck muscles that are attached to the occipital region.
2. Headache Caused by Inflammation of Nasal Mucosa and Paranasal Sinuses : Such inflammation can cause headache that is referred to the retro-orbital and frontal region of the head.
3. Headache Caused by Eye Disorders : Some visual disorders characterized by difficulty in focusing the eyes to gain clear vision, which causes excessive tonic contraction of the ciliary muscles in order to increase the diopteric power of the lens. The tonic contraction of there small intraocular muscles causes retro-orbital headache.