What is the recommended approach to taking a headache history, including red‑flag assessment, and what are the primary and secondary differential diagnoses?

History Taking for Headaches with Differential Diagnosis

Essential History Components

Begin by screening for red flags that mandate urgent evaluation, then systematically characterize the headache pattern to differentiate primary from secondary causes. 1, 2

Red Flag Assessment (Screen First)

Ask specifically about these danger signals that require emergency referral:

• Thunderclap onset: "Worst headache of life" with abrupt onset suggests subarachnoid hemorrhage 1, 2
• New headache after age 50: Raises concern for giant cell arteritis or space-occupying lesion 1, 3
• Progressive worsening: Headache that steadily worsens over weeks suggests tumor or increased intracranial pressure 1, 3
• Headache awakening from sleep: May indicate increased intracranial pressure or secondary causes 4, 1
• Valsalva/cough/exertion provocation: Suggests increased intracranial pressure 1, 3
• Fever with neck stiffness: Meningitis until proven otherwise 1, 2
• Focal neurological symptoms: Weakness, sensory changes, or atypical aura lasting >60 minutes 1, 2
• Recent head/neck trauma: Requires consideration of intracranial hemorrhage 3
• Altered consciousness, memory, or personality: Suggests serious intracranial pathology 1
• Orthostatic pattern: Absent/mild on waking, onset within 2 hours of standing, >50% improvement lying flat suggests spontaneous intracranial hypotension 1

Temporal Pattern Questions

• Age at onset: Migraine typically begins at/around puberty; new-onset headache in older adults is concerning 1, 5
• Duration of individual episodes: Migraine lasts 4-72 hours (2-72 hours in children <18 years); cluster headache 15-180 minutes; tension-type variable but often 30 minutes to 7 days 1, 5
• Frequency: Episodic versus chronic (≥15 days/month for >3 months) 1, 5
• Time of day: Document when headaches typically occur 4, 5
• Menstrual relationship: In women, ask if headaches occur during menstrual cycle 4, 5

Pain Characteristics

• Location: Unilateral (migraine, cluster) versus bilateral (tension-type) 1, 5
• Quality: Pulsating/throbbing (migraine) versus pressing/tightening (tension-type) versus severe unilateral (cluster) 4, 1, 5
• Severity: Moderate-to-severe (migraine, cluster) versus mild-to-moderate (tension-type) 1, 5
• Aggravating factors: Routine physical activity worsens migraine but not tension-type 1, 5
• Relieving factors: Lying flat improves orthostatic headache 1

Associated Symptoms

• Nausea/vomiting: Strongly suggests migraine 4, 1
• Photophobia AND phonophobia together: Characteristic of migraine 4, 1
• Aura symptoms: Visual disturbances (scintillations), hemisensory symptoms, speech difficulties lasting 5-60 minutes and preceding headache 1, 5
• Autonomic features: Lacrimation, conjunctival injection, nasal congestion, ptosis, miosis on same side as pain suggests cluster headache 4, 1
• Rhinorrhea and forehead/facial sweating: Cluster headache features 4

Medication History

• Current acute medications: Document frequency of use—≥15 days/month for non-opioid analgesics or ≥10 days/month for other acute medications for >3 months indicates medication-overuse headache 1, 2, 5
• Previous treatments: What has been tried, effectiveness, and adverse effects 4, 5
• Over-the-counter use: Many patients don't consider these "real" medications 4, 5

Screening Tools

• ID-Migraine questionnaire (3 items): Sensitivity 0.81, specificity 0.75, positive predictive value 0.93 1
• Migraine Screen Questionnaire (5 items): Sensitivity 0.93, specificity 0.81, positive predictive value 0.83 1
• Headache diary: Essential for documenting frequency, duration, character, triggers, accompanying symptoms, and medication use—reduces recall bias 1, 5

Primary Differential Diagnoses

Migraine Without Aura

Requires ≥5 lifetime attacks lasting 4-72 hours (2-72 hours in children <18 years) with ≥2 pain characteristics (unilateral, pulsating, moderate-to-severe intensity, or aggravation by routine activity) AND ≥1 associated symptom (nausea/vomiting OR both photophobia and phonophobia). 1, 2

Key distinguishing features:

• Photophobia together with nausea strongly supports migraine over tension-type 1
• Pulsating quality and aggravation by routine activity 1, 2
• Episodes last 4-72 hours if untreated 1

Migraine With Aura

Requires ≥2 attacks with ≥1 fully reversible aura symptom (visual, sensory, speech/language, motor, brainstem, or retinal) AND ≥3 of these six characteristics: 1, 2

1. Gradual spread over ≥5 minutes 1, 2
2. Two or more symptoms in succession 1, 2
3. Individual symptom duration 5-60 minutes 1, 2
4. At least one unilateral symptom 1, 2
5. At least one positive symptom (scintillations, pins-and-needles) 1, 2
6. Aura accompanied by or followed within 60 minutes by headache 1, 2

Critical caveat: Atypical aura with focal neurological symptoms or duration >60 minutes may indicate stroke/TIA and requires urgent neuroimaging 1, 2

Chronic Migraine

Defined as ≥15 headache days/month for >3 months with ≥8 days meeting migraine criteria. 1, 2

• This is a distinct entity requiring preventive therapy and neurology referral 1, 2
• Often coexists with medication-overuse headache 1, 2

Tension-Type Headache

Bilateral, pressing/tightening (non-pulsatile) pain of mild-to-moderate intensity with ≥2 of: bilateral location, pressing/tightening character, mild-moderate intensity, no aggravation with routine activity. 1, 2

Key distinguishing features:

• Lacks nausea/vomiting (anorexia may be present) 1, 2
• Lacks the combination of photophobia AND phonophobia (may have one or the other) 4, 1
• Not aggravated by routine physical activity 1, 2
• Duration highly variable: 30 minutes to 7 days 1
• Most common primary headache disorder, affecting 38% of population 1, 6

Cluster Headache

Strictly unilateral severe headache lasting 15-180 minutes with ipsilateral autonomic symptoms (lacrimation, conjunctival injection, nasal congestion, rhinorrhea, forehead/facial sweating, ptosis, miosis, eyelid edema). 4, 1

• Prevalence approximately 0.1% of population 1
• Pain is excruciating and patients are often restless/agitated during attacks 1
• No nausea/vomiting (may have anorexia) 4
• No photophobia and phonophobia together (may have one or the other) 4

Medication-Overuse Headache

Headache on ≥15 days/month with regular overuse of non-opioid analgesics on ≥15 days/month OR any other acute medication on ≥10 days/month for >3 months in someone with pre-existing headache disorder. 1, 2

• Often arises from excessive treatment of migraine attacks 1
• Requires withdrawal of overused medication and different management approach 1, 2

Secondary Differential Diagnoses (Red Flag Conditions)

Subarachnoid Hemorrhage

• Thunderclap headache: "worst headache of life" with abrupt onset 1
• May have altered taste sensation 1
• Requires non-contrast CT head if presenting <6 hours from onset (sensitivity 95% on day 0,74% on day 3,50% at 1 week) 1

Meningitis

• Headache with neck stiffness and unexplained fever 1, 2
• Life-threatening condition requiring immediate evaluation 1
• Altered mental status or confusion raises concern 2
• Kernig's and Brudzinski's signs have low sensitivity; absence does not rule out meningitis 2
• Elderly may present atypically without fever or neck stiffness 2

Brain Tumor/Space-Occupying Lesion

• Progressive headache that worsens over time 1, 3
• Awakens patient from sleep 1
• Worsens with Valsalva/cough 1
• MRI brain with and without contrast is preferred modality (higher resolution, no ionizing radiation) 1

Giant Cell Arteritis

• New-onset headache in patients >50 years 1
• Scalp tenderness, jaw claudication 1
• ESR/CRP indicated, but ESR can be normal in 10-36% of cases 1
• Requires urgent rheumatology referral 1

Spontaneous Intracranial Hypotension

• Orthostatic headache: absent/mild on waking, onset within 2 hours of upright posture, >50% improvement within 2 hours of lying flat 1
• Requires urgent neurology referral within 48 hours 1

Stroke/TIA

• Atypical aura with focal neurological symptoms lasting >60 minutes 1
• New focal neurological findings 2

Increased Intracranial Pressure

• Headache worsening with coughing, sneezing, exercise 1
• Headache awakening from sleep 1

Investigation Strategy

When Neuroimaging Is Indicated

Neuroimaging should be considered only in patients with atypical headache patterns, neurologic signs, or red flags. 4, 1

Specific indications include:

• Rapidly increasing frequency of headache 4
• History of uncoordination 4
• Focal neurologic signs or symptoms 4, 1
• Headache awakening from sleep 4, 1
• Abrupt onset of severe headache 4
• Marked change in headache pattern 4
• Persistent headache following head trauma 4
• New-onset headache after age 50 1, 3

Neuroimaging is NOT routinely indicated for patients with migraine who have normal neurological examination, even if first-line treatments fail. 1

Imaging Modality Selection

• MRI brain with and without contrast: Preferred for subacute presentations or suspected tumor/inflammatory process 1
• Non-contrast CT head: If presenting <6 hours from acute severe headache onset (subarachnoid hemorrhage) or acute trauma 1
• Dental panoramic radiographs: If dental pathology or sinusitis suspected 1

Laboratory Testing

• ESR/CRP: If temporal arteritis suspected (patients >50 years with new-onset headache) 1
• Morning TSH and free T4: If cold intolerance, lightheadedness present 1
• Thyroid peroxidase (TPO) antibodies: If biochemical hypothyroidism confirmed 1
• Blood cultures, complete blood count, inflammatory markers: For suspected meningitis 2
• Lumbar puncture: Mandatory when meningitis suspected, unless contraindicated by focal neuro signs or concern for raised intracranial pressure 2

Referral Pathways

Emergency Admission (Immediate)

Any red flag present or patient unable to self-care without help. 1, 2

• Thunderclap headache 1, 2
• Fever with neck stiffness or altered mental status 1, 2
• Focal neurological deficits 1, 2
• Progressive worsening with concerning features 1

Urgent Neurology Referral (Within 48 Hours)

• Suspected spontaneous intracranial hypotension 1
• Patient unable to self-care but has help 1

Routine Neurology Referral (2-4 Weeks)

• Suspected primary headache disorder with diagnosis uncertain 1
• First-line treatments fail 1, 2
• Cluster headaches 2
• Headache with motor weakness 2
• Migraine with persistent aura 2
• Chronic migraine 1, 2

Urgent Rheumatology Referral

• Suspected giant cell arteritis 1

Common Pitfalls to Avoid

• Do not dismiss headache in elderly patients: New-onset headache after age 50 requires thorough evaluation for secondary causes 1, 3
• Do not rely on absence of neck stiffness to rule out meningitis: Kernig's and Brudzinski's signs have low sensitivity 2
• Do not overlook medication-overuse headache: Always document frequency of acute medication use 1, 2, 5
• Do not order neuroimaging for typical migraine with normal exam: This increases cost without changing management 4, 1
• Do not assume aura is benign: Atypical aura lasting >60 minutes or with focal neurological symptoms may indicate stroke 1, 2
• Do not forget to use headache diaries: They reduce recall bias and increase diagnostic accuracy 1, 5
• Do not miss chronic migraine: ≥15 headache days/month for >3 months with ≥8 days meeting migraine criteria requires preventive therapy 1, 2