Fever + Headache: What You Need to Know

Key Principle

Red Flags - When Fever + Headache = Emergency

"Acute, severe headache with stiff neck and fever suggests meningitis. LP is mandatory. Meningitis can be easily mistaken for migraine in that the cardinal symptoms of pounding headache, photophobia, nausea, and vomiting are frequently present." - Harrison's Principles of Internal Medicine, 22e

Common Causes of Fever with Headache

1. Bacterial Meningitis

• Classic triad: fever, severe headache, neck stiffness
• May have photophobia, nausea/vomiting - easily confused with migraine
• Key differentiator: nuchal rigidity, Kernig's sign, Brudzinski's sign, altered consciousness
• Requires immediate LP and empiric antibiotics

2. Viral Meningitis (Aseptic Meningitis)

• Less fulminant than bacterial; usually self-limiting in 1-2 weeks
• Presents with headache, fever, lethargy, nuchal rigidity, photophobia
• CSF shows lymphocytosis; glucose is normal (unlike bacterial)
• Causes include enteroviruses, HSV-2, mumps

3. Viral Encephalitis

• Fever + headache + personality changes, cognitive dysfunction, seizures
• Arbovirus (Japanese encephalitis, West Nile), HSV most important
• HSV encephalitis requires urgent acyclovir

4. Mollaret's Meningitis

• Recurrent episodes of fever + headache + meningeal signs - can mimic recurrent migraine
• Often associated with HSV-2

5. Sinusitis

• Fever + headache with purulent nasal discharge, facial tenderness, simultaneous onset
• Often misdiagnosed as migraine; responds to antibiotics
• As per Swanson's Family Medicine: "Headache due to sinusitis would involve fever, purulent nasal discharge, simultaneous onset of sinus symptoms"

6. Influenza/Viral Illness

• Fever can trigger migraine attacks in susceptible individuals
• Systemic myalgia, fatigue help distinguish from pure meningitis

7. Fever as a Migraine Trigger

• Fever is a recognized migraine trigger (along with stress, sleep changes, head trauma)
• In known migraineurs, febrile illness may precipitate an attack
• Diagnosis of exclusion - must rule out meningitis first

8. Temporal Arteritis (Giant Cell Arteritis)

• Age >50, fever, malaise, weight loss + temporal headache
• Jaw claudication, scalp tenderness, elevated ESR
• Risk of sudden irreversible blindness; treat with prednisone urgently

Approach to the Patient

Fever + Headache
       |
       ├── Any red flags? (stiff neck, altered consciousness, 
       |   focal signs, rash, thunderclap onset)
       |         |
       |         YES → Emergency workup: CT head → LP
       |                Empiric antibiotics if meningitis suspected
       |
       └── No red flags?
                 |
                 ├── Sinusitis features? → Treat sinusitis
                 ├── Flu-like illness? → Symptomatic treatment
                 ├── Known migraineur + febrile illness → 
                 |   Treat underlying illness + migraine
                 └── Age >50, jaw claudication? → ESR, temporal artery biopsy

Treatment Principles

When to Seek Emergency Care

• Fever AND very severe, sudden-onset headache ("worst headache of my life")
• Fever + headache + stiff neck
• Fever + headache + confusion, seizures, or weakness
• Fever + headache + skin rash
• Fever + headache in someone immunocompromised (HIV, cancer, steroids)

Disclaimer: This is general medical information. If you or someone you know has fever with severe headache, especially with neck stiffness, altered consciousness, or rash, seek emergency medical care immediately.