Makindo Medical Notes

🧠 Central Nervous System (CNS) Infections

CNS infections are medical emergencies — delayed recognition or treatment can lead to death or permanent neurological damage. Empirical therapy depends on likely pathogen, patient age, immune status, and clinical context. Always involve microbiology early.

💉 Meningitis – Community Acquired

⚠️ Medical Emergency: Do not delay antibiotics for imaging or LP if contraindicated. Outcome correlates directly with time to antibiotic administration.

• Likely pathogens: Neisseria meningitidis and Streptococcus pneumoniae. Less common: Listeria monocytogenes in elderly, pregnant, or immunocompromised patients.
• Initial investigations:
  • CSF microscopy, culture, and PCR (if safe to perform LP).
  • Blood cultures ± EDTA sample for meningococcal PCR.
  • Throat swab for meningococcal carriage.
• Empirical therapy:
  • Ceftriaxone 2 g IV every 12 h.
  • If Listeria risk → add Amoxicillin 2 g IV every 4 h.
  • If sensitivities allow, step down to Benzylpenicillin 2.4 g IV every 4 h.
• Duration:
  • Meningococcal — 7 days
  • Pneumococcal — 10–14 days
  • Listeria — 14–21 days
• Public Health: Notify UKHSA Health Protection Team immediately — they arrange chemoprophylaxis for close contacts.
• Penicillin allergy: Seek microbiology advice; third-generation cephalosporins may still be safe if non-anaphylactic.

💡 Teaching Pearl: If meningococcal disease is suspected pre-hospital, give Benzylpenicillin 1.2 g IM/IV immediately — early treatment improves survival.

🧩 Meningitis after Head Injury / Neurosurgery & Brain Abscess

• Likely organisms: Gram-negative bacilli (e.g. Pseudomonas), Staphylococcus aureus, and anaerobes.
• Empirical therapy:
  • Meropenem 2 g IV every 8 h OR
  • Ceftriaxone 2 g IV every 12 h + Metronidazole 500 mg IV every 8 h
• Neurosurgical review: Essential — abscesses frequently require drainage.
• Obtain imaging prior to LP if raised ICP or focal neurological signs present.

🧬 Viral Encephalitis

⚠️ Key fact: HSV-1 is the commonest cause of sporadic viral encephalitis. Mortality exceeds 70% without treatment.

• First-line therapy: Aciclovir 10 mg/kg IV every 8 h (adjust for renal function).
• Duration: Typically 10–14 days; extend to 21 days in immunocompromised or severe cases.
• Investigations: CSF PCR for HSV, EEG, MRI (temporal lobe changes typical).
• Rationale: Early aciclovir markedly reduces death and long-term neurological sequelae.

📋 Adjunctive Measures & Key Notes

• Do not delay antibiotics/antivirals while awaiting imaging or LP in unstable patients.
• Consider Dexamethasone 10 mg IV every 6 h for 4 days in suspected pneumococcal meningitis (start before or with first antibiotic dose).
• Close liaison with Microbiology, Neurology, and Infectious Diseases for complex or resistant cases.
• Monitor for complications: seizures, hydrocephalus, cranial nerve palsies, SIADH.

🧠 Teaching Point

The key skill in CNS infection management is timing: a lumbar puncture should never delay antibiotics when the patient is unwell. Empiric therapy is guided by age and risk factors — Listeria coverage in the elderly, Pseudomonas coverage post-neurosurgery, and aciclovir for encephalitis are must-know distinctions for finals and MRCP.

📚 References

• NICE CG102: Bacterial Meningitis & Meningococcal Septicaemia
• UKHSA Guidance: Meningococcal Prophylaxis
• IDSA Guidelines: Bacterial Meningitis
• UK Viral Encephalitis Guidelines