What is the differential diagnosis and treatment for a headache affecting the left half of the head and neck?

Unilateral Head and Neck Headache: Differential Diagnosis and Management

The differential diagnosis for left-sided head and neck pain includes migraine (most common primary cause), cluster headache, tension-type headache with cervical involvement, and critical secondary causes including temporal arteritis (if age >50), cervical artery dissection, intracranial hemorrhage, and meningitis that must be ruled out first. 1, 2

Immediate Red Flag Assessment

Before considering primary headache disorders, you must actively exclude life-threatening secondary causes:

Critical Red Flags Requiring Urgent Neuroimaging

• Thunderclap onset (maximum intensity within seconds to minutes) suggests subarachnoid hemorrhage 3
• "Worst headache of life" indicates possible vascular catastrophe 3
• New onset after age 50 raises concern for temporal arteritis or secondary pathology 3, 4
• Focal neurological signs on examination mandate immediate imaging 3
• Neck stiffness with fever suggests meningitis or subarachnoid hemorrhage 3
• Progressive worsening over time may indicate space-occupying lesion 3
• Recent head/neck trauma requires evaluation for dissection or hematoma 5
• Headache with exertion or Valsalva can indicate increased intracranial pressure 3, 5

Imaging Selection

• MRI is preferred for most secondary headache evaluation due to superior resolution 3
• Non-contrast CT is indicated when acute intracranial hemorrhage suspected, especially if presenting <6 hours from onset 3
• CT followed by lumbar puncture if presenting >6 hours from thunderclap onset with negative CT 3

Primary Headache Differential Diagnosis

Once red flags are excluded, distinguish between primary headache types based on specific clinical features:

Migraine (Most Likely)

Migraine is the most common cause of unilateral headache and should be your primary consideration when attacks last 4-72 hours with moderate-to-severe intensity. 2

Key diagnostic features:

• Duration: 4-72 hours per attack 2
• Quality: Pulsating, moderate-to-severe intensity 2
• Location: Often unilateral (can be bilateral) 1
• Associated symptoms: Photophobia, phonophobia, nausea, vomiting 2
• Aggravating factors: Routine physical activity worsens pain 2
• Aura: May have visual or sensory symptoms lasting 5-60 minutes before headache 2
• Neck involvement: Neck pain commonly accompanies migraine attacks 1

Cluster Headache

Suspect cluster headache if attacks are strictly unilateral, brief (15-180 minutes), and accompanied by ipsilateral autonomic symptoms. 2

Distinguishing features:

• Duration: 15-180 minutes (much shorter than migraine) 2
• Frequency: 1-8 attacks per day during cluster periods 2
• Location: Strictly unilateral, never switches sides during attack 1
• Intensity: Severe to very severe 1
• Autonomic symptoms: Ipsilateral conjunctival injection, lacrimation, nasal congestion, rhinorrhea, facial sweating, miosis, ptosis, or eyelid edema 2

Tension-Type Headache

Tension-type headache typically presents bilaterally but can have prominent neck involvement. 6

Characteristic features:

• Quality: Tightness, pressure, or dull ache (not pulsating) 6
• Location: Band-like distribution from forehead to occiput, often radiating to neck 6
• Intensity: Mild to moderate 1
• Absence of migraine features: No nausea, photophobia, or throbbing 6
• Not aggravated by routine physical activity 1

Treatment Approach

Acute Treatment for Migraine

First-line acute treatment consists of NSAIDs plus antiemetic if necessary, escalating to triptans for inadequate response. 1, 2

Stepped approach:

1. NSAIDs: Naproxen sodium 500-825 mg at onset, or combination aspirin + acetaminophen + caffeine 2
2. Add antiemetic if nausea present 1
3. Triptans if NSAIDs fail after three consecutive attacks, or for moderate-to-severe attacks 1, 2
4. Switch to different triptan if first triptan fails after three attacks 1
5. Consider ditans or gepants if all triptans fail 1

Critical caveat: Limit acute medication use to no more than 2 days per week to prevent medication-overuse headache 2

Acute Treatment for Cluster Headache

High-flow oxygen is the gold-standard first-line treatment for cluster headache. 2

• Oxygen therapy: 12-15 liters per minute via non-rebreather mask for 15-20 minutes provides rapid relief in 70-80% of patients 2

Preventive Therapy Indications

Consider preventive therapy if attacks occur ≥2 days per month causing disability despite optimized acute treatment. 1

First-line preventive medications:

• Beta blockers: Propranolol 80-160 mg daily, atenolol, bisoprolol, or metoprolol 1, 2
• Topiramate (particularly beneficial if obesity present) 1
• Candesartan 1

Second-line options:

• Amitriptyline (especially if depression or sleep disturbances present) 1
• Flunarizine 1
• Sodium valproate (contraindicated in women of childbearing potential) 1

Third-line options:

• CGRP monoclonal antibodies (erenumab, fremanezumab, galcanezumab, eptinezumab) after failure of other preventives 1

Common Pitfalls to Avoid

• Do not rely solely on neuroimaging without considering the complete clinical picture 3
• Avoid opioids for acute headache treatment due to poor effectiveness and high risk of medication-overuse headache 7
• Do not overlook temporal arteritis in patients >50 years with new-onset headache, even if ESR is normal (can be normal in 10-36% of cases) 4
• Recognize that neck pain is common in migraine and does not automatically indicate cervical pathology 1
• Monitor for medication-overuse headache: Non-opioid analgesics ≥15 days/month or other acute medications ≥10 days/month for ≥3 months 2

Follow-Up Strategy

Re-evaluate within 2-3 months to assess attack frequency, severity, disability, medication adverse effects, and adherence using headache calendars. 2