How can a wave in the cortex lead to a headache, if the brain itself feels no pain? · Grey Matter

The pain comes from the meninges and their blood vessels, which are innervated by sensory fibres of the trigeminal nerve, mostly its ophthalmic (V1) division.

How can a wave in the cortex lead to a headache, if the brain itself feels no pain?

The pain comes from the meninges and their blood vessels, which are innervated by sensory fibres of the trigeminal nerve, mostly its ophthalmic (V1) division. In animal models, the potassium, glutamate and other substances released by spreading depression reach these trigeminovascular fibres and activate them; the fibres release peptides such as CGRP, the meninges become sensitised, and the signal passes through the brainstem and thalamus to the cortex as throbbing pain. Spreading depression is therefore a plausible trigger for attacks with aura. Most attacks have no aura, however, and they share the same trigeminovascular pain pathway, so how those attacks begin is still studied.