Chapter 015. Headache (Part 1)

Harrisons Internal Medicine Chapter 15. HeadacheHeadache: Introduction Headache is among the most common reasons that patients seek medical attention. Diagnosis and management is based on a careful clinical approach that is augmented by an understanding of the anatomy, physiology, and pharmacology of the nervous system pathways that mediate the various headache syndromes.General Principles A classification system developed by the International Headache Society characterizes headache as primary or secondary (Table 15-1). Primary headaches are those in which headache and its associated features are the disorder in itself, whereas secondary headaches are those caused by exogenous disorders. Primaryheadache often results...
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Chapter 015. Headache (Part 1) Chapter 015. Headache (Part 1) Harrisons Internal Medicine > Chapter 15. Headache Headache: Introduction Headache is among the most common reasons that patients seek medicalattention. Diagnosis and management is based on a careful clinical approach thatis augmented by an understanding of the anatomy, physiology, and pharmacologyof the nervous system pathways that mediate the various headache syndromes. General Principles A classification system developed by the International Headache Societycharacterizes headache as primary or secondary (Table 15-1). Primary headachesare those in which headache and its associated features are the disorder in itself,whereas secondary headaches are those caused by exogenous disorders. Primaryheadache often results in considerable disability and a decrease in the patientsquality of life. Mild secondary headache, such as that seen in association withupper respiratory tract infections, is common but rarely worrisome. Life-threatening headache is relatively uncommon, but vigilance is required in order torecognize and appropriately treat patients with this category of head pain. Table 15-1 Common Causes of Headache Primary Headache Secondary Headache Type % Type % Migraine 16 Systemic infection 63 Tension-type 69 Head injury 4 Cluster 0.1 1 Vascular disorders Idiopathic stabbing 2 may originate from either or both mechanisms. Relatively few cranial structuresare pain-producing; these include the scalp, middle meningeal artery, duralsinuses, falx cerebri, and proximal segments of the large pial arteries. Theventricular ependyma, choroid plexus, pial veins, and much of the brainparenchyma are not pain-producing. The key structures involved in primary headache appear to be the large intracranial vessels and dura mater the peripheral terminals of the trigeminal nerve that innervate thesestructures the caudal portion of the trigeminal nucleus, which extends into thedorsal horns of the upper cervical spinal cord and receives input from the first andsecond cervical nerve roots (the trigeminocervical complex) the pain modulatory systems in the brain that receive input fromtrigeminal nociceptors The innervation of the large intracranial vessels and dura mater by thetrigeminal nerve is known as the trigeminovascular system. Autonomic symptoms,such as lacrimation and nasal congestion, are prominent in the trigeminalautonomic cephalalgias, including cluster headache and paroxysmal hemicrania,and may also be seen in migraine. These autonomic symptoms reflect activation ofcranial parasympathetic pathways, and functional imaging studies indicate thatvascular changes in migraine and cluster headache, when present, are similarlydriven by these cranial autonomic systems. Migraine and other primary headachetypes are not vascular headaches; these disorders do not reliably manifestvascular changes, and treatment outcomes cannot be predicted by vascular effects.