What are the possible causes of a chronic headache in a healthy adult without red‑flag features (normal neurological exam, no sudden onset, no focal deficits, no systemic symptoms, no recent trauma, age under 50)?

Differential Diagnosis for Chronic Headache in Healthy Adults Without Red Flags

In a healthy adult under 50 with chronic headache, normal neurological examination, and no red-flag features, the differential diagnosis is limited to primary headache disorders, with tension-type headache being most common, followed by chronic migraine, new daily persistent headache, and less commonly, hemicrania continua or cluster headache. 1, 2, 3

Primary Headache Disorders to Consider

Tension-Type Headache

• Most common primary headache disorder, affecting up to 42% of the adult population globally 3
• Characterized by at least two of the following: pressing/tightening (non-pulsatile) character, mild-to-moderate intensity, bilateral location, and no aggravation with routine activity 1
• Must have both: no nausea/vomiting (anorexia acceptable) and no photophobia AND phonophobia together (may have one or the other) 1

Chronic Migraine

• Leading diagnosis if headaches occur ≥15 days per month for >3 months, with ≥8 days per month meeting migraine criteria or responding to triptan/ergot treatment 2
• Migraine features include at least two of: unilateral location, throbbing character, worsening with routine activity, moderate-to-severe intensity 1, 2
• Must have at least one of: nausea/vomiting OR photophobia and phonophobia together 1
• May include aura (visual distortions, scotomas) or prodromal symptoms (food cravings, heightened sensory perceptions, mood alterations) 1

Medication-Overuse Headache

• Critical to actively screen for this in any chronic headache patient, as it occurs in patients with ≥15 headache days/month who regularly overuse acute medications for >3 months 2
• Assess overuse of triptans, ergots, combination analgesics, NSAIDs, and acetaminophen 2
• Preventive therapy will not be effective until medication overuse is addressed 2

New Daily Persistent Headache

• Sudden onset of daily headache that becomes persistent, with patients often able to recall the exact date of onset 4, 3
• Requires exclusion of secondary causes despite absence of red flags 4

Cluster Headache

• Less common (prevalence 0.1% or 1 in 1000 persons) but has the highest pre-test probability (5%) for significant intracranial abnormalities among primary headaches 3
• Requires five attacks with frequency of one to eight attacks per day 1
• Severe unilateral orbital/supraorbital/temporal pain lasting 15-180 minutes untreated 1
• Must have at least one ipsilateral autonomic feature: lacrimation, nasal congestion, rhinorrhea, facial sweating, ptosis, miosis, or eyelid edema 1

Hemicrania Continua

• Continuous unilateral headache that varies in intensity 4, 3
• Responds absolutely to indomethacin (diagnostic criterion) 4

Essential Diagnostic Approach

History Documentation

• Implement a headache diary documenting attack frequency, duration, intensity, associated symptoms, and acute medication use over 4 weeks 2
• Apply validated screening instruments such as ID-Migraine to identify patients meeting migraine criteria 2
• Document specific triggers: hormonal changes, certain foods, sensory stimuli (light, smells), missed meals, or relief of tension after stressful events 1

Physical Examination Requirements

• Thorough neurologic examination is mandatory to confirm absence of focal signs 1, 4, 5
• General physical examination to exclude systemic disease 1, 6
• In your specified scenario (normal exam, no red flags, age under 50), this examination has already excluded concerning features 3, 5

When Neuroimaging Is NOT Indicated

Neuroimaging is not recommended in this specific population (chronic headache, normal neurological exam, no red flags, age under 50) as the pre-test probability of significant intracranial abnormalities is only 0.9% (95% CI 0.5-1.4%) 3

• The yield of neuroimaging in patients with headache and normal neurological examination is quite low: brain tumors 0.8%, arteriovenous malformations 0.2%, aneurysm 0.1% 7
• Primary headache disorders without red flags or abnormal examination findings do not need neuroimaging 5
• Neuroimaging should only be considered with atypical headache patterns or neurologic signs 1

Critical Pitfalls to Avoid

• Do not miss medication-overuse headache: This is the most commonly overlooked diagnosis and prevents response to preventive therapy 2
• Do not assume "just tension headache" without proper characterization: Many patients with chronic migraine are misdiagnosed as having tension-type headache 2
• Do not order unnecessary neuroimaging: In the absence of red flags and with normal examination, imaging does not reduce patient anxiety and has extremely low yield 3, 5
• The incidental finding rate (0.75%) means imaging may create more problems than it solves in this low-risk population 3