Diagram representing pain sensitive areas in br ain

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Here is the diagram and a complete explanation of pain-sensitive areas in the brain/cranium.

Pain-Sensitive Areas in the Brain

Areas of headache resulting from different intracranial causes - Guyton & Hall Fig. 49.9

Figure 49.9 - Areas of referred headache from different intracranial structures (Guyton and Hall Textbook of Medical Physiology)

Key Concept: The Brain Parenchyma Is Insensitive to Pain

The brain tissue itself (parenchyma, ependyma, choroid plexuses, and most of the pia-arachnoid) is almost entirely insensitive to pain. Even cutting or electrically stimulating the sensory cortex produces only paresthesias, not pain. Intracranial mass lesions cause headache by deforming, displacing, or exerting traction on sensitive structures - not by directly stimulating brain tissue.

Pain-Sensitive Structures in the Cranial Vault

According to classic neurosurgical observations (Ray and Wolff) cited in Adams and Victor's Principles of Neurology and Guyton & Hall:

Structure	Pain Sensitivity
Skin, subcutaneous tissue, muscles, extracranial arteries, periosteum of skull	Sensitive
Eye, ear, nasal cavities, paranasal sinuses	Sensitive
Intracranial venous sinuses (sagittal, transverse) and their large tributaries	Sensitive
Dura at the base of the brain	Sensitive
Proximal portions of the anterior and middle cerebral arteries	Sensitive
Intracranial segment of the internal carotid artery	Sensitive
Middle meningeal artery (especially sensitive - anesthetized separately in awake craniotomies)	Sensitive
Superficial temporal artery	Sensitive
First 3 cervical nerves and cranial nerves as they pierce the dura	Sensitive
Brain parenchyma	Insensitive
Most of pia-arachnoid	Insensitive
Ependyma and choroid plexuses	Insensitive

How Pain Is Referred (as shown in the diagram)

The diagram shows three color-coded zones of referred headache:

Cerebral vault headaches (purple zone - frontal/parietal): Pain from structures above the tentorium cerebelli (supratentorial). Impulses travel via the trigeminal nerve (CN V, especially V1 and V2) - referred to the front half of the head.
Brain stem and cerebellar vault headaches (teal zone - occipital): Pain from structures below the tentorium (infratentorial/posterior fossa). Impulses travel via the glossopharyngeal (CN IX), vagus (CN X), and upper cervical nerves (C1-C3) - referred to the occiput and posterior head.
Nasal sinus and eye headaches (pink/red zone - periorbital/frontal): Pain from the nasoorbital region, transmitted by the sphenopalatine branches of the facial nerve (CN VII).

Clinical Relevance

Meningitis: Inflammation of the meninges (pain-sensitive) causes severe generalized headache.
Low CSF pressure (e.g., post-lumbar puncture): The brain sags, stretching pain-sensitive dural and vascular coverings.
Intracranial hemorrhage/hematoma: Stretches and tears pain-sensitive meninges and vessels.
Brain tumors: Cause headache by traction on vessels and dura - not from direct tumor-on-brain-tissue pressure.

Sources: Guyton and Hall Textbook of Medical Physiology, p. 49 (Headache of Intracranial Origin); Adams and Victor's Principles of Neurology, 12th Ed., p. 186 (Pain-Sensitive Cranial Structures)

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