What is the mechanism of pain in headaches related to elevated ICP?

• A. Inflammation of brain tissue
• B. Spinal nerve activation
• C. Direct cortical neuron firing
• D. Stretching of dura and arachnoid activates meningeal nociceptors

Answer: (D)

Rising intracranial pressure causes headaches mainly because it stretches the pain-sensitive meninges. The dura and arachnoid mater are innervated by meningeal nociceptors, so when ICP increases, these structures are distended and activated, sending pain signals through the trigeminal pathways to brainstem and onward to the cortex. The brain tissue itself has few if any pain receptors, so direct inflammation of brain parenchyma or direct firing of cortical neurons isn’t the primary source of the pain. Spinal nerves aren’t the main route for this intracranial pain since the sensory input from the meninges travels via the trigeminal system and upper cervical nerves.