Headaches can originate from either intracranial or extracranial structures. Intracranial headaches are caused by disturbances to pain-sensitive structures within the cranial vault like the meninges or blood vessels, and present with pain referred to specific areas of the head. Extracranial headaches arise from muscle tension, nasal/sinus irritation, or eye disorders, causing pain that is also referred to the head surface. The document outlines various headache types and their origins, as well as warning signs that could indicate an underlying secondary cause for the pain.

1. Causes & Mechanism of
Headache
TLester
MBBS 2
2023

2. Intro
 A headache is a type of pain by which originates from deep
head structures, is sent to the surface of the head.
 There are primary and secondary headaches. Primary
headaches are those by which the underlying cause of the pain
is unknown, whereas secondary headaches are symptomatic
and have a known underlying cause of pain.
 Warning Signs for Secondary Headaches:
Systematic symptoms & Secondary risk factors
Neurological symptoms
Onset in new (>40yrs)
Other associated conditions/features
Previous headache history (change in progression, position
or character)

3. Origins of Headaches
 INTRACRANIAL
oPain-sensitive areas in the Cranial Vault
- Brain tissues are almost insensitive to pain, therefore
headaches are least likely originating from the brain
itself.
- Causes paresthesis to the area controlled by the
stimulated portion of the sensory cortex
- Yet, disturbance to the venous sinus around the brain,
tentorium, dura at the base of the brain or blood vessels
of the meninges (i.e. meningeal artery) may cause
intense pain

4. oArea of the head to which Intracranial Headache is referred
- Pain impulse may be stimulated by pain receptors in the
cerebral vault or the upper and inner surface of the
tentorium
- This results in referred pain to the front half of the head,
specifically on sensory areas supplied by somatosensory
portion of Cranial Nerve V
- Pain impulses from beneath the tentorium enter the CNS
via glossopharyngeal, vagal and second cervical nerves
- This cause “occipital headaches” or pain referred to the
posterior portion of the head

5. Types of Intracranial Headache
- Headache of Meningitis
- Headache caused by low cerebrospinal fluid pressure
- Migraine headache
- Alcoholic headache

6.  EXTRACRANIAL
oHeadache resulting from Muscle Spasm
- Spastic muscles of the neck and scalp due to emotional
tension is suggested the most common cause of
headache
- This pain is referred to overlying areas of the head,
similar to intracranial lesion headaches
oHeadaches caused by Irritation of Nasal & Accessory
Nasal Structures
- Infection or irritation of the nasal structures (i.e. sinuses)
may result in headaches
- Referral to behind the eyes or frontal surfaces of the
forehead, scalp and face

7. oHeadache caused by Eye Disorders
- Focal difficulties in one eye may cause strain on the
other, resulting in the tonic contraction of eye ciliary
muscles or reflex spasm in various facial and extraocular
muscles, hence a retro-orbital headache
- Exposure to excessive irradiation light rays (i.e. UV rays)
may result in an “actinic” irritation of the conjunctivae,
and/or the intense light may also burn the retina
- This pain is referred to the surface of the head or retro-
orbitally

10. Reference
 Guyton and Hall Textbook of Medical Physiology. John E.
Hall and Michael E. Hall. Somatic Sensations: II. Pain,
Headache, and Thermal Sensations. 14th Edition. Chapter
49. p621-622
 Adam and Victor’s Principles of Neurology. Allan H Ropper
and Robert H Brown. Headache and other Cranial Facial
Pains. 8th Edition. Chapter 10. p144-165