CNS Infections

Meningitis - Brain's Fiery Blanket

Meningeal inflammation: fever, headache, nuchal rigidity. Prompt Lumbar Puncture (LP) & treatment vital.

CSF Analysis: Key Differentiators

Empirical Antibiotics (Bacterial):

• Neonate (<1m): Ampicillin + Cefotaxime/Gentamicin.
• 1m-50y: Ceftriaxone + Vancomycin.

• 50y/ImmunoComp: Add Ampicillin.

⭐ Streptococcus pneumoniae: Most common bacterial cause in adults.

Complications: Hydrocephalus, cranial nerve palsies, seizures, hearing loss.

Encephalitis & Myelitis - Cord & Cortex Chaos

• Viral Encephalitis: Brain parenchyma inflammation.
  • HSV-1: Commonest sporadic fatal encephalitis.

    ⭐ Predilection for temporal lobes (hemorrhagic necrosis).

    • Rx: Acyclovir 10 mg/kg IV q8h for 14-21 days.
  • Japanese Encephalitis (JE): Flavivirus; rural Asia. Vector: Culex.
    • Features: Parkinsonism, dystonia, seizures, flaccid paralysis.
  • Rabies: Lyssavirus; animal bites.
    • Clinical: Hydrophobia, aerophobia, pharyngeal spasms.
    • Pathology: Negri bodies (intracytoplasmic inclusions).
• Acute Disseminated Encephalomyelitis (ADEM):
  • Immune-mediated demyelination, post-infectious/post-vaccinial.
  • Monophasic illness; encephalopathy common.
  • MRI: Multiple, bilateral, asymmetric, large (>1-2 cm) white matter lesions.
• Transverse Myelitis (TM):
  • Focal spinal cord segment inflammation.
  • Clinical triad:
    • Symmetric motor weakness (paraparesis).
    • Clear sensory level.
    • Sphincter dysfunction (urinary retention).
  • Causes: Idiopathic, post-infectious, MS, NMO. ​

Focal CNS Suppurations - Pus Pockets Peril

• Brain Abscess: Localized CNS pus.
  • Etiology: Direct spread (sinusitis, otitis, dental), hematogenous (lung, heart).
  • Organisms: Streptococci, Staphylococci, anaerobes. Nocardia (immunocompromised).
  • Imaging: Ring-enhancing lesion (CT/MRI).

  ⭐ Triad of brain abscess (fever, headache, focal neurological deficit) is seen in <50% cases.

• Subdural Empyema: Pus between dura & arachnoid. Rapid decline. Neurosurgical emergency.
• Epidural Abscess: Pus between dura & skull/vertebrae. Often spinal. Urgent.
• Management:
  • Antibiotics: Empirical (e.g., Ceftriaxone + Metronidazole ± Vancomycin), then targeted.
  • Surgical Drainage: Indicated if >2.5 cm, neurological compromise, or no improvement. 📌 Antibiotics, Brain imaging, Consult neurosurgery, Drainage if needed.

Chronic & Specific CNS Infections - Slow Burn Scourges

• Neurocysticercosis (NCC):

  • Etiology: Taenia solium larvae.
  • Stages: Vesicular → colloidal → granular → calcified.
  • Imaging: CT/MRI (cysts, edema, calcification).
  • Rx: Albendazole; Steroids for inflammation.

  ⭐ Neurocysticercosis: most common parasitic CNS infection globally.

• Neurosyphilis:

  • Etiology: Treponema pallidum.
  • Forms: Meningovascular (stroke-like), General Paresis (dementia), Tabes Dorsalis (sensory ataxia, Argyll Robertson pupil).
  • Dx: CSF VDRL (specific).

• Prion Diseases (e.g., CJD):

  • Patho: Misfolded PrP^Sc.
  • Features: Rapid dementia, myoclonus.
  • Dx: EEG (periodic sharp waves), CSF (14-3-3 protein), MRI (DWI/FLAIR hyperintensities).

• Progressive Multifocal Leukoencephalopathy (PML):

  • Etiology: JC virus (reactivation).
  • Risk: Immunocompromised (HIV, CD4 < 200/µL).
  • MRI: Asymmetric, non-enhancing white matter lesions_._

High‑Yield Points - ⚡ Biggest Takeaways

• Bacterial meningitis CSF: Shows ↑Protein, ↓Glucose, ↑Neutrophils, and ↑Opening Pressure.
• Tuberculous meningitis CSF: Features ↓↓Glucose, ↑↑Protein, ↑Lymphocytes, ↑ADA, and cobweb coagulum.
• Viral meningitis CSF: Presents with ↑Lymphocytes, Normal Glucose, and Normal/Slightly ↑Protein.
• Cryptococcal meningitis: Common in HIV patients; India ink positive; markedly ↑Opening Pressure.
• Herpes Simplex Encephalitis (HSE): Temporal lobe involvement characteristic; treat with IV Acyclovir.
• Neurocysticercosis (NCC): Most common parasitic CNS infection; causes seizures; shows ring-enhancing lesions or calcified granulomas.
• Japanese Encephalitis: Viral cause; presents with extrapyramidal symptoms (parkinsonism); endemic areas.