Intracranial nociception.

Area of Science:

• Neuroscience
• Anatomy
• Pain Research

Background:

• Headache pathophysiology understanding relies on intracranial nociceptive innervation knowledge.
• Current understanding stems from limited awake neurosurgery observations, anatomical studies, and animal research.
• Historically, dura mater and major cerebral vessels were considered the primary pain-sensitive intracranial structures.

Purpose of the Study:

• To review the anatomical and functional organization of intracranial nociceptive innervation.
• To highlight recent findings on pain sensitivity of smaller brain arteries and pia mater.
• To elucidate the trigeminal system's role in headache pathophysiology.

Main Methods:

• Review of existing anatomical and functional studies on intracranial nociception.
• Analysis of neurosurgical observations in awake patients.
• Examination of experimental data from animal studies.

Main Results:

• Intracranial nociception is primarily mediated by the trigeminal system, with the posterior fossa innervated by cervical roots.
• Evidence suggests smaller brain arteries and pia mater, in addition to dura mater and major vessels, are pain-sensitive.
• Nociceptive neurons project via the ophthalmic division (V1) to the trigeminal ganglion, storing neurotransmitters like glutamate, substance P, and CGRP.
• The trigeminal system exhibits somatotopy, and convergence in the trigemino-cervical complex may explain referred pain and treatment efficacy (e.g., occipital nerve stimulation).

Conclusions:

• The trigeminal system's specific anatomical organization, including the trigemino-cervical complex, is crucial for understanding headache characteristics.
• Convergence of nociceptive inputs from facial, intracranial, and occipital regions contributes to complex pain patterns.
• Further research into intracranial nociception can advance headache pathophysiology understanding and treatment strategies.