What is the differential diagnosis for a unilateral retro‑orbital headache in a 40‑year‑old woman?

Differential Diagnosis: Unilateral Retro-Orbital Headache in a 40-Year-Old Woman

The most likely diagnosis is migraine without aura, given the unilateral retro-orbital location and the patient's age and sex, though cluster headache and trigeminal autonomic cephalalgias must be systematically excluded based on attack duration, frequency, and presence of autonomic symptoms 1.

Primary Differential Diagnoses

1. Migraine Without Aura (Most Likely)

Migraine characteristically presents with unilateral headache in approximately 60% of cases, though bilateral pain occurs in ~40% 1. Key features to assess:

• Attack duration: 4-72 hours when untreated 1
• Pain quality: Pulsating, moderate to severe intensity
• Aggravating factors: Worsened by routine physical activity (walking, climbing stairs)
• Associated symptoms: Nausea/vomiting, photophobia, phonophobia 1
• Prodrome: Depression, yawning, fatigue, food cravings may precede pain
• Family history: Often positive for migraine 1

The retro-orbital location is entirely consistent with migraine, and the "always same side" pattern (side-locked) occurs in a subset of migraine patients.

2. Cluster Headache (Critical to Exclude)

This diagnosis is less likely given the patient's sex (affects ~0.1% of population, male predominance), but must be ruled out based on these distinguishing features 1:

• Attack duration: 15-180 minutes (much shorter than migraine) 2
• Frequency: 1-8 attacks daily during cluster periods
• Pain intensity: Severe to very severe (often described as "worst pain imaginable")
• Ipsilateral autonomic symptoms (essential for diagnosis):
  • Conjunctival injection and lacrimation
  • Nasal congestion or rhinorrhea
  • Eyelid edema
  • Facial sweating
  • Miosis/ptosis 1, 3
• Restlessness: Patients typically cannot lie still during attacks

Critical pitfall: Cluster headache can initially be misdiagnosed as sinusitis or dental pain due to autonomic symptoms 4. The absence of prominent autonomic features makes this diagnosis unlikely.

3. Trigeminal Autonomic Cephalalgias (SUNCT/SUNA)

Consider if attacks are very brief with autonomic features 5:

• Short-lasting attacks (seconds to minutes)
• Unilateral tearing, nasal symptoms, facial sweating
• Multiple daily attacks

4. Chronic Migraine

If headaches occur ≥15 days/month for >3 months, with ≥8 days meeting migraine criteria 1. This may coexist with medication overuse headache if the patient uses acute medications ≥10-15 days/month.

Secondary Causes to Exclude (Red Flags)

You must actively screen for these potentially serious conditions 1:

Immediate Red Flags Requiring Urgent Investigation:

• Thunderclap onset: Subarachnoid hemorrhage
• New onset after age 50: Giant cell arteritis (check ESR, CRP) 5
• Progressive worsening: Space-occupying lesion
• Atypical aura: TIA or stroke
• Recent head trauma: Subdural hematoma
• Fever, neck stiffness: Meningitis
• Focal neurological deficits: Structural lesion

Orbital/Cavernous Sinus Pathology:

If accompanied by diplopia, ophthalmoplegia, or proptosis, consider 6, 7:

• Tolosa-Hunt syndrome: Painful ophthalmoplegia with cranial nerve palsies (III, IV, VI)
• Orbital apex syndrome: Similar presentation
• Cavernous sinus thrombosis: Requires urgent imaging

Other Considerations:

• Trigeminal neuralgia: Brief, electric shock-like pain (seconds), triggered by touch/eating 5
• Glossopharyngeal neuralgia: Posterior tongue/ear pain 5
• Sinusitis: Usually accompanied by purulent discharge, facial tenderness
• Glaucoma: Check intraocular pressure if eye appears injected

Diagnostic Approach

Step 1: Characterize the headache systematically 1:

• Duration of individual attacks
• Frequency (attacks per week/month)
• Time of day pattern (cluster often nocturnal)
• Presence/absence of autonomic symptoms
• Triggers identified
• Response to previous treatments

Step 2: Physical examination 1:

• Neurological exam (must be normal in primary headache)
• Fundoscopy (papilledema suggests raised intracranial pressure)
• Temporal artery palpation if age >50
• Cranial nerve examination
• Check for neck stiffness

Step 3: Neuroimaging is NOT routinely indicated 1 unless:

• Red flags present on history or examination
• Atypical features
• Abnormal neurological examination
• New onset in patient >50 years
• If needed, MRI preferred over CT (higher sensitivity, no radiation) 1

Step 4: Use validated screening tools:

• ID-Migraine questionnaire (3 questions: nausea, photophobia, disability) - sensitivity 81%, specificity 75% 1
• Headache diary for 4 weeks minimum 1

Most Likely Clinical Scenario

For a 40-year-old woman with unilateral retro-orbital headache on the same side, migraine without aura is the leading diagnosis if:

• Attacks last 4-72 hours
• Pain is moderate-severe, pulsating
• Associated with nausea and/or photophobia/phonophobia
• No prominent autonomic symptoms (tearing, nasal congestion)
• Normal neurological examination

The side-locked pattern does not exclude migraine and is seen in a subset of patients 1. The retro-orbital location is classic for migraine.

If attacks are brief (15-180 min), extremely severe, with ipsilateral tearing and nasal congestion, cluster headache becomes the primary diagnosis despite female sex 1, 2.