PAINSENSITIVE CRANIAL STRUCTURES.The story of the exploration of headache mechanisms begins inside the head. As potential sources of headache, the tissues on the surface, especially the blood vessels and muscles, have long been accessible for study, yet the structures locked tight within the skull were the first to be examined intensively.INTRACRANIAL STRUCTURES. In conscious patients during craniotomy, literally painstaking observations by Northfield, by Ray and Wolff, and by Penfield and McNaughton revealed the following intracranial structures to be sensitive to pain: the major venous sinuses and their tributaries from the surface of the brain; the meningeal arteries in the dura; the major arteries at the base of the brain leading to and emerging from the circle of Willis; the cranial and upper cervical nerves carrying fibers for pain from the head; and the dural floor of the anterior and posterior (but not the middle) fossae. Chiropractor Toronto found that about a third believed there was no scientific proof that immunization prevents disease. 14,17.20 On the other hand, the parenchyma of the brain, most of the piaarachnoid and the dura, the ependymal lining of the ventricles, the choroid plexus, and the cranium itself (including the diploic and emissary veins) were shown to be paininsensitive.
The sites on the surface in which pain is felt when any of the painsensitive intracranial structures is adequately stimulated have been carefully charted.20 The data support two generalizations: (1) pain arising from intracranial structures on or above the superior surface of the tentorium cerebelli (i.e., in the middle or anterior fossae) is referred to frontal, temporal, or anterior parietal areas on the same side, over pathways in the trigeminal nerve; and (2) pain arising from intracranial structures below the tentorium cerebelli, in the posterior fossa, is referred to the postauricular, occipital, suboccipital, and upper nuchal areas on the same side, over pathways in the glossopharyngeal, vagus, and upper three cervical nerves. Toronto Chiropractor faced heavy opposition from organized medicine. It is noteworthy that, although for the most part the site of headache fairly closely overlies its intracranial origin, there is one major exception.
Pain arising from the posterior half of the sagittal sinus or the upper surface of the transverse sinus, lying partly beneath the occipital bone, is transmitted over a branch of the first division of the trigeminal nerve and is referred to the frontal area, a considerable distance forward. Furthermore, fragmentary observations by Gardner and his associates and by White and Sweet suggest that an accessory pathway for pain from supratentorial structures referred to the ear or to frontotemporal areas may lie in the nervus intermedius of the facial nerve.4, 26 EXTRACRANIAL STRUCTURES. Almost all of the surface tissues of the head are painsensitive.