What is the diagnosis and management for a patient presenting with severe headache and altered mental status, with unknown past medical history?

Diagnosis: Bacterial Meningitis Until Proven Otherwise

A patient presenting with severe headache and altered mental status must be presumed to have bacterial meningitis and requires immediate empiric antibiotic therapy, aggressive resuscitation, and urgent diagnostic evaluation—delays in treatment significantly increase mortality. 1, 2

Immediate Management Algorithm

Step 1: Initiate Resuscitation (Within Minutes)

• Administer aggressive IV crystalloid boluses immediately to restore intravascular volume and correct any hypotension or tachycardia 2
• Target normalization of heart rate, blood pressure, capillary refill, urine output, and mental status 2
• Obtain IV access and draw blood cultures (at least 3 sets) but do not delay antibiotics beyond a few minutes 2

Step 2: Empiric Antibiotics (Before Any Imaging or LP)

Administer immediately after blood cultures are drawn:

• Ceftriaxone 2g IV PLUS Vancomycin 15-20 mg/kg IV 2
• Add Dexamethasone 10mg IV before or with the first antibiotic dose to reduce neurological complications 2
• Add Ampicillin 2g IV every 4 hours if patient is >50 years old, immunocompromised, or has risk factors for Listeria monocytogenes 2

This regimen covers Streptococcus pneumoniae (including resistant strains), Neisseria meningitidis, and other common bacterial pathogens 2

Step 3: Obtain CT Head Before Lumbar Puncture

• Non-contrast CT head is mandatory before lumbar puncture when altered mental status is present 1, 2
• CT evaluates for mass effect, hydrocephalus, or other contraindications to LP 1
• Do not delay antibiotics waiting for CT or LP—this significantly increases mortality 2

Step 4: Perform Lumbar Puncture

• Perform LP urgently once CT clears the patient, ideally within 4 hours of starting antibiotics to maximize culture yield 2
• CSF analysis should include: cell count with differential, glucose, protein, Gram stain, bacterial culture, and viral PCR panel 2
• Under contingency conditions (resource-limited), consider meningitis diagnosis if patient has two or more of: severe headache, altered mental status, meningeal signs, or other neurological symptoms 1

Clinical Reasoning and Evidence

Why This Presentation Demands Urgent Action

• The combination of severe headache and altered mental status strongly suggests meningitis 1, 2
• The classic triad of fever, neck stiffness, and altered consciousness is present in less than 50% of bacterial meningitis cases 1
• Absence of neck stiffness does NOT exclude meningitis—elderly patients and those with early disease frequently lack this finding 1, 2
• Patients with bacterial meningitis can deteriorate rapidly even if initially appearing stable 2

Diagnostic Considerations Beyond Meningitis

While meningitis is the primary concern, the differential includes:

• Encephalitis: Consider if viral PCR panel is available for CSF 2
• Subarachnoid hemorrhage: CT will identify this before LP 1
• Intracranial mass or abscess: CT or MRI will reveal structural lesions 1
• Cerebral venous thrombosis: May present with headache and altered mental status, particularly with risk factors 1
• Sepsis from other sources: Document presence of fever, rash (especially petechial), seizures, and signs of shock 1

Critical Pitfalls to Avoid

• Never delay antibiotics waiting for lumbar puncture or neuroimaging—every hour of delay increases mortality 2
• Do not rely on Kernig's sign or Brudzinski's sign—these have poor sensitivity and should not be used to rule out meningitis 1
• Do not underestimate severity based on initial vital signs—patients with sepsis and meningitis can deteriorate rapidly 2
• Do not assume "just a headache" in the presence of altered mental status—this combination requires exclusion of life-threatening causes 1, 3

Hospital Admission and Monitoring

• Arrange rapid emergency transport to ensure hospital arrival within 1 hour of initial assessment 1, 2
• Consider ICU admission if persistent hypotension despite fluid resuscitation, altered consciousness, or respiratory distress 2
• Monitor for clinical deterioration continuously during initial hours 2

Additional Diagnostic Studies

• CBC with differential to assess for leukopenia, thrombocytopenia, or leukocytosis 2
• Metabolic panel for hyponatremia, renal dysfunction, and electrolyte abnormalities 2
• Lactate level—lactate >4 mmol/L indicates high risk for fatal outcome 2
• Inflammatory markers (C-reactive protein, procalcitonin) to assess severity 2