How can I differentiate a thunderclap headache from a migraine and what are the appropriate acute and preventive management strategies for each?

Differentiating Thunderclap Headache from Migraine

Thunderclap headache is a medical emergency requiring immediate neuroimaging to exclude subarachnoid hemorrhage, while migraine develops more gradually and can be managed with outpatient therapy.

Critical Distinguishing Features

Thunderclap Headache Characteristics

• Onset to peak intensity occurs within 60 seconds, distinguishing it from all other headache types 1
• Pain severity is maximal at onset and described by 80% of alert patients as "worst headache of my life" 1
• Duration lasts at least 5 minutes and can persist up to 10 days 2
• Subarachnoid hemorrhage accounts for 10-25% of thunderclap presentations with 27-44% mortality, making immediate exclusion mandatory 1, 3

Migraine Characteristics

• Pain builds gradually over minutes to hours, not seconds 4
• Typically bilateral with pressing or tightening quality when mild, or unilateral and pulsating when moderate to severe 4
• Accompanied by photophobia, phonophobia, nausea, or vomiting 4
• Aggravated by routine physical activity 4
• May include aura symptoms (visual, sensory, or speech disturbances) preceding headache by 5-60 minutes 4

Immediate Diagnostic Algorithm for Thunderclap Headache

Within 6 Hours of Onset

• Perform non-contrast CT brain scan immediately with 98.7% sensitivity for detecting SAH when interpreted by board-certified neuroradiologist 1
• Apply Ottawa SAH Rule criteria: age ≥40 years, neck pain/stiffness, witnessed loss of consciousness, onset during exertion, or limited neck flexion on examination 1

After 6 Hours or Negative CT

• Never rely on CT alone after 6 hours as sensitivity drops significantly with time 1
• Lumbar puncture is mandatory at least 12 hours after headache onset when clinical suspicion remains high, as failure to identify SAH leads to nearly 4-fold higher likelihood of death or disability 1

If CT and LP Are Negative

• Obtain brain MRI with susceptibility-weighted imaging (SWI) plus vascular imaging (CTA or MRA) to evaluate for reversible cerebral vasoconstriction syndrome (RCVS), arterial dissection, cerebral venous thrombosis, and other vascular pathology 1
• RCVS accounts for 45% of thunderclap headache cases and presents with recurrent attacks 5
• Cervical artery dissection causes thunderclap headache in up to 20% of cases, though gradual onset is more typical 1, 3

Red Flags Requiring Immediate Investigation

Any of these features mandate neuroimaging and exclusion of secondary causes 4:

• Thunderclap onset (maximal intensity within 1 minute)
• Atypical aura symptoms
• Recent head trauma
• Unexplained fever
• Impaired memory or altered consciousness
• Focal neurological symptoms or signs
• Loss of consciousness at onset (carries 2.8-fold increased risk of death) 3

Acute Management of Migraine

First-Line Therapy

• NSAIDs are first-line treatment for all migraine attacks, including severe attacks that previously responded to NSAIDs 4
• Aspirin, ibuprofen, naproxen sodium, or combination acetaminophen plus aspirin plus caffeine have the most consistent evidence 4
• Acetaminophen alone is ineffective 4

Second-Line Therapy (Triptans)

• Oral triptans (naratriptan, rizatriptan, sumatriptan, zolmitriptan) have good evidence for effectiveness 4
• Subcutaneous sumatriptan provides very rapid onset and is an option for patients with nausea and vomiting 4
• Intranasal sumatriptan is also effective when oral route is compromised 4
• Contraindicated in patients with cardiovascular disease risk, basilar or hemiplegic migraine, or uncontrolled hypertension 4

Critical Pitfall: Medication Overuse Headache

• Limit acute therapy to no more than twice per week to prevent medication overuse headache 4, 6
• Frequent use of acute medications causes increasing headache frequency that can progress to daily headaches 6
• Ergotamine, opiates, triptans, and analgesics containing butalbital, caffeine, or isometheptene are most likely to cause this complication 4

Preventive Management of Migraine

Indications for Preventive Therapy

Preventive therapy should be initiated when 4, 6:

• Two or more attacks per month producing disability lasting 3+ days
• Use of abortive medication more than twice weekly
• Contraindication to or failure of acute treatments
• Presence of hemiplegic migraine, migraine with prolonged aura, or migrainous infarction

Implementation Considerations

• Clinical benefit requires 2-3 months to manifest, yet patients and clinicians often discontinue therapy prematurely 6
• Patient education about realistic expectations is essential, as migraine treatment aims to reduce attack frequency and severity, not eliminate attacks entirely 6

Special Populations Requiring Heightened Vigilance

• Patients with first-degree relatives with aneurysms should undergo neuroimaging even with atypical presentations 1
• Autosomal dominant polycystic kidney disease increases intracranial aneurysm risk 1
• Coexisting cardiovascular disease, pregnancy, or uncontrolled hypertension limit migraine treatment choices 4