Atlas of pathophysiology, 2 Edition

Part II - Disorders

Neurologic disorders

Headache

Headache, although usually benign, can be a serious and commonly disabling disorder. The International Headache Society (IHS) identified a comprehensive classification system that includes more than 100 types of headaches, which are divided into 13 categories. Various processes may cause headache, and they range from benign to life-threatening.

Causes

Primary headaches are classified based on their symptom profiles and account for 90% to 98% of headaches. Primary headaches include migraines, tension-type, and cluster.

Acute and progressive, secondary headaches are the result of an identifiable structural or physiologic cause, including:

·         head trauma

·         vascular disorders

·         nonvascular intracranial disorders

·         substance abuse and substance withdrawal

·         infections

·         metabolic disorders

·         disorders of the face and neck

·         cranial neuralgias.

Pathophysiology

Primary headaches occur when pain-sensitive structures of the head, including the cerebral vasculature, musculature, and cranial or cervical nerves, are irritated. Vascular changes occur as follows:

·         Stimulation of the trigeminal ganglion located in the midbrain causes releases of substance P and calcitonin gene-related peptide (CGRP).

·         The release of substance P causes degranulation of mast cells.

·         Mast cells release histamine, and platelets release serotonin.

·         Vasodilation, plasma extravasation, and inflammation occur.

·         Inflammation and release of substance P cause distention of cranial arteries and headache pain.

·         Triggers either directly act on the vasomotor tone or mediate the neurochemical release of vasoactive substances.

·         Vasoconstriction, platelet changes, and neurochemical mediators initiate cerebral ischemia and activate the trigeminal-vascular system.

Signs and symptoms

Migraine

·         Commonly preceded by temporary focal neurologic signs known as auras (auras are usually visual—scotomata, zigzag, flashing lights and colors, geometric shapes, jagged lines.)

·         Unilateral in onset but may become generalized

·         Begins as a dull ache that progressively worsens and develops into throbbing, pulsating pain

·         Commonly associated with photophobia, nausea and vomiting, phonophobia, and paresthesia

Tension-type

·         Gradual onset of bilateral bandlike pressure or tightening of mild to moderate intensity; usually doesn't prohibit daily activities

·         Not aggravated by physical activity or accompanied by associated symptoms; may have phonophobia or photophobia

·         May be triggered by stress, fatigue, loud noises, heat, or bright lights

·         Chronic form possibly resembles depression or fibromyalgia syndrome

Cluster

·         Acute onset of excruciating severe unilateral orbital pain lasting 15 to 180 minutes

·         Episodic clusters; one every other day to eight per day; commonly nocturnal

·         Accompanied by ipsilateral lacrimation, conjunctival injection, rhinorrhea, miosis, ptosis, and nasal congestion

Clinical Tip

The presence of one or more of these factors is an indication for further evaluation:

·         first-onset headache that begins after age 50

·         sudden-onset headache

·         accelerating pattern of headaches

·         new-onset headache in a patient with cancer or human immunodeficiency virus

·         headache with systemic illness (fever, stiff neck, or rash)

·         presence of focal neurologic symptoms (not typical aura)

·         papilledema.

Diagnostic test results

·         Skull X-rays identify skull fracture.

·         Computed tomography scan shows tumor or subarachnoid hemorrhage or other intracranial pathology; reveals pathology of sinuses.

·         Lumbar puncture shows increased intracranial pressure suggesting tumor, edema, or hemorrhage.

·         EEG shows alterations in the brain's electrical activity, suggesting intracranial lesion, head injury, meningitis, or encephalitis.

·         Sinus X-rays show sinusitis.

Treatment

·         Avoidance of trigger mechanisms

·         Over-the-counter analgesics or anti-inflammatory agents

·         Analgesics or combination analgesics

·         Vasoconstrictors, such as ergotamine tartrate and dihydroergotamine

·         Serotonin agonists, such as sumatriptan, naratriptan, rizatriptan, and zolmitriptan

·         Antiemetics

·         Opioid analgesics

·         Sedatives or tranquilizers

·         Intranasal lidocaine

·         Corticosteroids

·         Lithium carbonate

·         Preventive therapy with beta-adrenergic blockers, calcium antagonists, tricyclic antidepressants, selective serotonin reuptake inhibitors, serotonin antagonists, monoamine oxidase inhibitors, anticonvulsants, or nonsteroidal anti-inflammatories

P.139

VASCULAR CHANGES IN HEADACHE

image

image