What causes headaches?

What Causes Headaches

Headaches are primarily caused by either primary headache disorders (migraine, tension-type headache, trigeminal autonomic cephalalgias) that arise from dysfunction of pain-modulating neural networks, or secondary headache disorders resulting from underlying medical conditions such as vascular, neoplastic, infectious, or intracranial pressure abnormalities. 1, 2

Primary Headache Disorders

Primary headaches account for the vast majority of headache presentations and are not related to underlying medical conditions 2:

Migraine Pathophysiology

• Migraine results from disruption of normal neural networks of the head, causing activation of vascular networks that leads to meningeal vasodilation and inflammation perceived as head pain 3
• Calcitonin gene-related peptide (CGRP), a protein contributing to trigeminal nerve pain and inflammation, plays a critical role in migraine pathophysiology 1
• Affects 22.3% of adult females and 10.8% of adult males in the US 3
• Characterized by moderate to severe throbbing headache, typically unilateral, exacerbated by physical activity, and associated with photophobia, phonophobia, nausea, and vomiting 3
• Parasympathetic activation and neurogenic inflammation explain why nasal symptoms frequently accompany migraine, despite not being part of diagnostic criteria 4

Tension-Type Headache

• Affects 38% of the population, making it the most prevalent primary headache disorder 2
• Presents as symmetrical frontal or temporal headache, sometimes with occipital component 5
• Characterized by pressing, tightening, or nonpulsatile pain of mild to moderate intensity, bilateral location, and no aggravation with routine activity 1

Trigeminal Autonomic Cephalalgias

• Includes cluster headaches with severe unilateral pain lasting 15-180 minutes 1
• Associated with ipsilateral autonomic features: lacrimation, nasal congestion, rhinorrhea, facial sweating, ptosis, miosis, or eyelid edema 1

Secondary Headache Disorders

Secondary headaches arise from identifiable underlying medical conditions 1:

Structural/Vascular Causes

• Head or neck trauma 6
• Cranial or cervical vascular disorders including stroke, hemorrhage, or vascular malformations 1
• Intracranial tumors: Nearly all children with brain tumors have abnormal neurologic findings (94%) and many have papilledema (60%) 1
• Intracranial hypotension from CSF leakage through dural defects, leaking meningeal diverticulum, or CSF-venous fistula 1
• Increased intracranial pressure from pseudotumor cerebri (idiopathic intracranial hypertension), particularly in overweight females of childbearing age 1

Infectious/Inflammatory Causes

• Acute bacterial sinusitis: Genuine sinus headache is rare and confined to acute frontal sinusitis or sphenoiditis when sinus ostia are blocked, causing increased pressure from trapped pus 5
• Chronic sinusitis is NOT validated as a cause of headache unless relapsing into acute stage 5
• Meningitis or other CNS infections 1

Medication-Related Causes

• Medication overuse headache: Overuse of acute migraine drugs (ergotamine, triptans, opioids, or combinations) for 10 or more days per month leads to exacerbation of headache 7
• Substance withdrawal 1

Cervical Strain

• Head injury resulting in neck pain, stiffness, weakness, and persistent occipital/suboccipital headache 1
• Injury to cervical structures causes somatosensory dysfunction and aberrant signaling along cervical afferent pathways 1

Red Flag Features Requiring Investigation

The following features increase likelihood of secondary headache and necessitate diagnostic testing 6:

• Recent head or neck injury 6
• New, worse, worsening, or abrupt onset headache 6
• Headache brought on by Valsalva maneuver, cough, or exertion 6
• Age over 50 years at onset 1, 6
• Neurologic findings or symptoms 1, 6
• Systemic signs or symptoms including fever 6
• Cancer or immunosuppression 6
• Headache awakening patient from sleep 1
• Progressive worsening pattern 1

Common Diagnostic Pitfalls

"Sinus Headache" Misdiagnosis

• The vast majority of patients diagnosed with "sinus headache" actually have migraine 5, 4
• Nasal congestion in migraine results from vasodilation of nasal mucosa as part of the vascular event, not sinus infection 5
• Approximately 62% of pediatric migraineurs have cranial autonomic symptoms like rhinorrhea from trigeminal-autonomic reflex activation 1
• Chronic sinusitis does not cause headache unless experiencing acute bacterial exacerbation 5

Sleep Disturbance

• Sleep disturbance commonly accompanies concussion and other headache disorders but does not occur in isolation 1
• Nonrestorative sleep can cause fatigue and worsen headache-related disability 1