Primary vs Secondary Headaches

As a general term, headache is a descriptor tied to hundreds of clinical entities. A headache is one of the most common reasons people present for medical attention. All headaches fall into 1 of 2 classification systems; primary and secondary headache syndromes. The presentation, degree of severity, underlying pathogenesis, potential clinical sequelae, management, and prognosis are as variable as the underlying headache entities.

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Overview

Definitions

  • Primary headaches: a headache (or headache disorder) not attributable to another disorder:
    • Generally benign; may be severe, recurrent, and potentially disabling
    • No dangerous underlying cause is identified. 
    • The pathophysiology is generally incompletely understood.
    • The pathophysiologic mechanisms generally involve overactivity of intracranial and extracranial nociceptors and/or related vascular structures.
  • Secondary headaches: a headache (or headache disorder) attributable to an underlying disorder:
    • May be a manifestation of an underlying systemic, vascular, or neurologic disorder
    • A potentially life-threatening etiology generally underlies the headache disorder.
    • The pathophysiology of the headache is generally related to 1 of the following:
      • Identifiable structural lesion
      • Metabolic abnormality
      • Infectious/inflammatory process

Epidemiology

  • Primary headaches: 50% of the adult population worldwide meets the clinical criteria for at least 1 primary headache disorder:
    • tension headache: approximately 40%
    • migraine headache: approximately 10%
    • cluster headache: approximately 1%
  • Secondary headaches: Prevalence and incidence is difficult to classify due to inconsistent documentation and coding practices among clinicians and institutions. 

Etiology

  • Primary headaches: The pathophysiologic mechanisms generally involve overactivity of intracranial and extracranial nociceptors and a complex interplay between neural and vascular structures.
  • Secondary headaches: The pathophysiologic mechanisms are generally related to an identifiable structural lesion, metabolic abnormality, or infectious/inflammatory process. 

Classification

All headaches can be classified as either primary or secondary and subclassified into a variety of classification schemes developed for clinical, epidemiologic, research, and coding purposes. The most common and clinically significant will be covered in detail here:

Primary headaches

Subtypes:

  • Migraine
  • Tension-type headache
  • Cluster headache

Frequency:

Primary headache disorders may be subclassified based on frequency of occurrence:

  • Low-frequency episodic: < 10 headache days per month
  • High-frequency episodic: 10–14 headache days per month
  • Chronic: ≥ 15 headache days per month

Secondary headaches

Subtypes:

  • Headache attributed to any of the following:
    • Head and/or cervical spine trauma
    • Cranial or cervical vascular abnormality
    • Severe hypertension
    • Intracranial structural lesion
    • Substance use or withdrawal
    • Infection
    • Disturbance of homeostasis
    • Psychiatric disorder 
  • Headache or facial pain attributed to: 
    • Disorder of cranial structure
    • Disorder of cervical spinal structure
    • Eyes
    • Ears
    • Nose
    • Sinuses
    • Teeth
    • Mouth
    • Other facial or cranial structures

Etiology:

Secondary headache disorders may be subclassified based on underlying etiology:

  • Vascular
  • Infectious
  • Neoplastic
  • Metabolic
  • Other

Clinical Presentation and Diagnosis

Features of primary headaches

Features warranting a conservative clinical evaluation:

  • Known history of a primary headache syndrome
  • Similar to previous headaches
  • Absence of focal neurologic signs and symptoms
  • If present, neurologic signs/symptoms are familiar to the individual:
    • Autonomic symptoms are typical of a cluster headache.
    • Reversible neurologic deficits are common in a migraine headache.

“Red flag” signs and symptoms

Signs and symptoms warranting immediate workup and/or intervention:

  • Severe hypertension
  • Focal neurologic findings
  • Papilledema
  • Neck stiffness
  • Immunocompromised state
  • Cancer/malignancy
  • 1st headache of the kind
  • Sudden (“thunderclap”) onset 
  • Mental status changes
  • Headache after trauma
  • Headache with visual changes
  • New-onset seizure
  • Exertional headache

Comparison of primary headaches

Table: Primary headache entities
Clinical entityHistorical clues/risk factorsClinical features
Tension headache
  • Bilateral location
  • Mild-to-moderate intensity
  • Tight or squeezing quality
  • Associated with extracranial muscle tenderness, trigger points
  • Affects almost everyone at some point in a lifetime
  • Often self-diagnosed and self-managed
  • Generally responds to simple and compound analgesics
  • Can be managed by primary care
Migraine headache
  • Unilateral > bilateral
  • Moderate-to-severe intensity
  • Women > men
  • Pulsatile quality
  • Associated with prodrome, aura, and postdrome
  • Associated with nausea, photophobia, and phonophobia
  • Associated with triggers
  • May present with transient neurologic and/or visual symptoms
  • May cause significant quality of life impairment and work-related disability
  • Onset during childhood or puberty (women), wanes during pregnancy, and persists until menopause
  • May need consultation by a specialist to formulate an effective abortive and preventative strategy
Cluster headache
  • Unilateral location
  • Severe intensity
  • Men > women
  • Associated with smoking/alcohol abuse
  • Accompanied by ipsilateral autonomic symptoms
  • May experience several severe episodes per day
  • May cause significant quality of life impairment and work-related disability
  • Also known as “suicide headaches” due to the increased risk of suicidal thoughts during an attack
  • May need consultation by a specialist to formulate an effective abortive and preventative strategy

Comparison of common secondary headaches

 The following tables outline the most important secondary headaches based on their etiology.

Table: Vascular etiologies of high risk headaches
Clinical entityHistorical clues/risk factorsClinical features
Subarachnoid hemorrhage (SAH)
  • Sudden onset
  • Severe intensity at onset
  • Syncope/near syncope
  • Neck pain/stiffness
  • Diplopia
  • Meningeal signs
  • Nausea and vomiting
Reversible cerebral vasoconstriction syndrome (RCVS)
  • Sudden onset
  • Severe intensity at onset
  • Short duration
  • Recurrent
  • Associated with triggers
  • Transient neurologic deficits from vasospasm
  • Neurologic deficits may persist (if vasospasm persists)
Cervical artery dissection/vertebral artery dissection
  • Associated with head and/or neck trauma
  • Prominent neck pain
  • New-onset dizziness
  • New-onset tinnitus
  • Cranial nerve palsy:
    • Nystagmus
    • Horner syndrome
  • Cervical artery bruit
  • Presents with cerebrovascular accident/transient ischemic attack (TIA)
Cerebral vein thrombosis/dural sinus thrombosis
  • Hypercoagulable state/risk factors
  • Pregnancy
  • Postpartum
  • Neurologic deficits inconsistent with arterial ischemia
  • Associated with seizure
  • Papilledema on fundoscopy
  • Encephalopathy
Subdural hematoma/epidural hematoma
  • Associated with head trauma
  • Anticoagulant therapy
  • Gradual progression of neurologic deficit and/or mental status
  • Posterior fossa hematoma →
    • Nausea/vomiting
    • Visual changes
    • Ataxia
    • Dysphagia
    • Anisocoria
    • Nuchal rigidity
Intraparenchymal hemorrhage (IPH)
  • Sudden onset
  • Associated with severe hypertension
  • Anticoagulant therapy
Variable presentation depending on site of bleed (much like cerebrovascular accident/TIA)
Idiopathic intracranial hypertension
  • Overweight/obese women
  • Childbearing age
  • Transient/intermittent visual symptoms
  • Papilledema on fundoscopy
  • Abducens nerve palsy
  • Other cranial nerve palsies
  • Visual deficit
  • Tinnitus
Spontaneous intracranial hypotension
  • Severe headache in upright position
  • Headache improves with caffeine and while lying flat
  • Headache worsens with Valsalva maneuver
  • Common after dural puncture
  • Neurologic findings may be absent or widely variable
  • Tinnitus
  • Cervical pain
  • Nausea and vomiting
Giant-cell arteritis
  • Age > 50 years
  • Sudden-onset visual disturbances (often monocular)
  • Jaw claudication
  • Palpable or nodular temporal arteries
  • Fever
  • Elevated acute-phase reactants:
    • CRP
    • Erythrocyte sedimentation rate (ESR)
Hypertensive encephalopathy
  • Gradual-onset headache in the setting of severe hypertension
  • Seizures
  • Altered mental status
  • Severe hypertension
  • Papilledema and retinal hemorrhage on fundoscopy
  • Hematuria and proteinuria on urinalysis
  • Encephalopathy
Posterior reversible encephalopathy syndrome
  • Gradual-onset headache inconsistently associated with severe hypertension
  • Seizures
  • Nausea and vomiting
  • Visual changes
  • Pregnancy or postpartum period
  • Hypertension may or may not be present
  • Papilledema and retinal hemorrhage on fundoscopy
  • Hematuria and proteinuria on urinalysis
  • Encephalopathy
Table: Infectious etiologies of high-risk headaches
Clinical entityHistorical clues/risk factorsClinical features
Meningitis and/or encephalitis
  • Toxic-appearing
  • Fever
  • Neck pain/stiffness
  • Altered mental status/level of consciousness
  • Fever
  • Meningism
  • Altered mental status/level of consciousness
  • Seizure
  • Cranial nerve palsies
  • Petechiae or purpura
Brain abscess
  • Onset of headache may be sudden or gradual
  • Recent history of infection:
    • Direct spread (sinusitis, otitis)
    • Distant spread (endocarditis, bacteremia)
  • Fever may be variable
  • Neck pain/stiffness may be variable
  • Papilledema on fundoscopy
  • Insidious onset of focal neurologic deficits or cranial nerve palsies
Table: Neoplastic etiologies of high-risk headaches
Clinical entityHistorical clues/risk factorsClinical features
Brain tumor
  • Cancer
  • Headache worsens with cough, Valsalva maneuver
  • Insidious headache onset, but may be sudden if tumor bleeds
  • Nausea and vomiting
  • Papilledema on fundoscopy
  • Seizure
  • Altered mental status/level of consciousness
  • Neurologic deficits corresponding to tumor location
Colloid cyst of 3rd ventricle
  • Headache worsens in upright position, improves with lying flat
  • Altered mental status
  • Symptoms may fluctuate
  • Altered mental status
  • Diplopia
  • Memory issues
  • Vertigo
Pituitary apoplexy
  • Associated with pituitary tumors (most often benign)
  • Sudden-onset headache associated with infarction/bleeding into tumor
  • Nausea and vomiting
  • Altered mental status
  • Visual/oculomotor defect
  • Endocrine dysfunction
Table: Other etiologies of high-risk headaches
Clinical entityHistorical clues/risk factorsClinical features
Acute narrow-angle glaucoma
  • Ocular pain
  • Ocular injection
  • Loss of vision
  • Nausea and vomiting
  • Conjunctival injection
  • Corneal clouding; fixed
  • Pupillary dilation with lack of constriction
  • Elevated intraocular pressure
CO toxicity
  • Acute CO exposure
  • Headache improves with separation from CO
  • Nausea/vomiting
  • Light-headedness/dizziness
  • Fatigue/malaise
  • Seizure
  • Coma
  • Red macula on fundoscopy
Preeclampsia/eclampsia
  • Pregnant woman at > 20 weeks
  • Sudden-onset headache associated with blood pressure > 140/90 mm Hg
  • Tinnitus
  • Visual disturbance
  • Seizure
  • Proteinuria
  • Brisk deep tendon reflexes (DTRs)
  • Placental abruption
  • Symptoms abate on delivery of the fetus

Diagnosis

Laboratory evaluation

  • Basic lab studies may be warranted with the initial headache workup:
    • CBC
    • Basic metabolic panel (BMP) or comprehensive metabolic panel (CMP)
    • Coagulation studies: PT, INR, PTT
  • Basic and specific lab studies may be indicated for secondary headache evaluation:
    • CRP
    • Erythrocyte sedimentation rate (ESR)
    • Hormone levels
    • CSF studies:
      • Cell count
      • Protein
      • Glucose
      • Gram stain
      • Opening pressure

Neuroimaging evaluation

  • Primary headache syndromes generally do not require neuroimaging for diagnosis; however, neuroimaging may be useful to:
    • Rule out secondary causes of headache at the initial evaluation
    • Evaluate headache severity or clinical features atypical of the individual
    • Evaluate neurologic signs or symptoms present with primary headaches (e.g., autonomic phenomena of cluster headache or focal neurologic phenomena of migraine headache)
  • Head CT without contrast is generally recommended as the initial imaging test of choice if “red flag” signs or symptoms are present.

Management

A wide range of management strategies exist for the various primary and secondary headache disorders. Only a broad overview is presented:

Primary headaches

Pharmacological management:

Most primary headache episodes and/or disorders are managed conservatively:

  • Simple or compound oral analgesics to abort isolated headache attacks:
    • Simple analgesics (single ingredient, nonspecific mechanism of action):
      • Acetaminophen
      • NSAIDs
    • Compound analgesics (more than 1 ingredient, nonspecific mechanism of action):
      • Aspirin + butalbital + caffeine
      • Acetaminophen + NSAID +/- caffeine, butalbital, or codeine
  • Specialized-mechanism or disease-specific analgesics to abort isolated headache attacks:
    • Triptans for migraine and cluster headaches
    • Calcitonin gene-related peptide (CGRP) inhibitors for migraines
    • O₂ delivery at 100% for cluster headaches

Prevention:

Multiple preventative headache regimens exist for primary headache syndromes:

  • Antihypertensives
  • Antidepressants
  • Anticonvulsants
  • Botulinum toxin
  • Specialized-mechanism or disease-specific interventions to prevent/reduce headache attack frequency:
    • Monoclonal antibody regimens
    • CGRP inhibitors for migraines
    • Interventional nerve blocks/ablations to targeted nerve structures

Secondary headaches

Secondary headache syndromes may require emergent evaluation and management strategies by consultation from 1 or more specialists:

  • Neurosurgical consultation
  • Interventional radiology/vascular intervention consultation
  • Neurology consultation
  • Ophthalmology consultation
  • HEENT surgical consultation
  • Infectious disease consultation
  • Medical/surgical oncology consultation

The clinician should look for the “hidden” cause of secondary headache (medication-overuse headache):

  • The individual generally has a primary headache disorder.
  • The primary headache attack frequency generally qualifies as frequent or chronic.
  • The individual has developed a pattern of overuse, misuse, or abuse of abortive medications.
  • A 2nd, “rebound” headache entity (or disorder) has developed and is difficult to distinguish from the primary headache.

References

  1. Hainer, B., Matheson, E. (2013). Approach to Acute Headache in Adults. American Family Physician. 87(10), 682–687. Retrieved August 15, 2021, from https://www.aafp.org/afp/2013/0515/p682.html
  2. Beck, E. (2013). Hard-to-Diagnose Headache: Practical Tips for Diagnosis and Treatment. American Family Physician. 87(10), 672–673. Retrieved August 15, 2021, from https://www.aafp.org/afp/2013/0515/p672.html
  3. Headache Classification Committee of the International Headache Society (IHS). (2013). The International Classification of Headache Disorders, 3rd edition (beta version). Cephalalgia. 33(9), 629–808. Retrieved August 15, 2021, from https://doi.org/10.1177/0333102413485658

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