Pathology · Year 2 · from Pathology
Case 2: Bacterial Meningitis - Fibrinopurulent Inflammation
Patient Demographics
- Age: 19 years old
- Sex: Female
- Occupation: College freshman (lives in dormitory)
Chief Complaint
"Severe headache, stiff neck, and fever for 2 days"
History of Present Illness
A 19-year-old female college student presents with a 2-day history of severe headache, fever, and neck stiffness. The headache is described as the "worst of her life," diffuse, and constant. She reports photophobia and nausea with vomiting. Her roommate noted she has been increasingly confused over the past several hours. She had an upper respiratory infection one week ago that seemed to resolve. She lives in a college dormitory and recently attended several social gatherings. She is up to date on childhood vaccinations but did not receive the meningococcal booster before college.
Physical Examination
- Vital Signs: BP 90/58 mmHg, HR 118 bpm, RR 24/min, Temp 39.8°C (103.6°F), SpO2 95% on room air
- General: Ill-appearing young woman, eyes closed, responds to voice but confused
- HEENT: Photophobia, no papilledema
- Neck: Severe nuchal rigidity, positive Kernig's sign, positive Brudzinski's sign
- Skin: Several non-blanching petechiae on trunk and lower extremities
- Neurologic: GCS 13 (E3V4M6), no focal deficits
Diagnostic Workup
Laboratory Studies:
| Test | Result | Reference Range |
|---|---|---|
| WBC | 22,400/μL | 4,500-11,000/μL |
| Neutrophils | 88% | 40-70% |
| Bands | 15% | 0-3% |
| Platelets | 98,000/μL | 150,000-400,000/μL |
| Lactate | 4.1 mmol/L | 0.5-2.0 mmol/L |
Lumbar Puncture (CSF Analysis):
| Parameter | Result | Normal |
|---|---|---|
| Opening pressure | 32 cm H2O | 10-20 cm H2O |
| Appearance | Cloudy/turbid | Clear |
| WBC | 2,450/μL | <5/μL |
| Differential | 95% neutrophils | Lymphocyte predominant |
| Protein | 285 mg/dL | 15-45 mg/dL |
| Glucose | 18 mg/dL | 40-70 mg/dL |
| Serum glucose | 105 mg/dL | 70-100 mg/dL |
| CSF:serum glucose | 0.17 | >0.6 |
| Gram stain | Gram-negative diplococci | Negative |
Blood cultures: Gram-negative diplococci (Neisseria meningitidis confirmed)
Imaging:
- CT Head (prior to LP): No mass lesion, midline shift, or hydrocephalus
- MRI Brain: Leptomeningeal enhancement, particularly at skull base
Pathology Correlation
This case demonstrates fibrinopurulent meningitis:
- Cardinal Signs of Inflammation:
- Rubor/calor: Meningeal hyperemia
- Tumor: CSF accumulation with increased intracranial pressure
- Dolor: Severe headache from meningeal irritation
- Functio laesa: Altered mental status, neurologic dysfunction
- Exudate Formation:
- Fibrinopurulent exudate in subarachnoid space
- High protein content in CSF (fibrinogen leakage)
- Neutrophil predominance (acute inflammation)
- Low glucose (consumed by bacteria and neutrophils)
- Chemical Mediators:
- Bacterial LPS (endotoxin) activating complement and coagulation
- C3a and C5a promoting inflammation
- TNF-alpha and IL-1 causing fever and acute phase response
- Systemic Effects:
- Fever (endogenous pyrogens acting on hypothalamus)
- Leukocytosis with left shift
- Early DIC (thrombocytopenia, petechiae)
- Hypotension (early septic shock)
Clinical Image
Gross pathology of bacterial meningitis showing purulent exudate coating the leptomeninges at the base of the brain. The yellow-green fibrinopurulent material fills the subarachnoid space and obscures the normal sulci, representing intense acute inflammation with neutrophil accumulation.
Image Source: Wikimedia Commons - "Haemophilus influenzae Meningitis" License: Public Domain (CDC) URL: https://commons.wikimedia.org/wiki/File:Haemophilus_influenzae_Meningitis_5121_lores.jpg
Diagnosis
Acute Bacterial Meningitis due to Neisseria meningitidis (Meningococcal meningitis)
Treatment
- Immediate IV ceftriaxone (empiric, then continued after culture confirmation)
- IV dexamethasone (before or with first antibiotic dose to reduce inflammation)
- Aggressive IV fluid resuscitation
- ICU admission for monitoring
- Chemoprophylaxis for close contacts (rifampin or ciprofloxacin)
- Reported to public health department
Teaching Points
- Fibrinopurulent exudate forms when large molecules like fibrinogen escape inflamed vessels
- CSF neutrophilia indicates acute bacterial infection; lymphocyte predominance suggests viral or TB meningitis
- Low CSF glucose results from bacterial and neutrophil consumption
- Meningeal signs (Kernig's, Brudzinski's) result from meningeal inflammation and irritation
- The systemic inflammatory response can progress to septic shock through cytokine storm
- Complement activation by bacterial products generates C3a and C5a (anaphylatoxins), promoting further inflammation
- Petechiae indicate DIC from overwhelming activation of coagulation cascade