Infections of the Nervous System: Meningitis & Encephalitis

Infections of the Nervous System: Meningitis and Encephalitis

• Account for approximately 4% of infections in ICUs, linked to high morbidity and mortality rates.
• Early identification and treatment are crucial for improving clinical outcomes.
• Urgent brain imaging recommended if there's evidence of increased intracranial pressure (ICP) before lumbar puncture; however, treatment with antibiotics should not be delayed.
• Causative organisms can vary by geographical location and patient immune status.

Causes of CNS Infections

• Autoimmune Encephalitis: Considered when microbiological tests yield negative results.
• Infectious agents include:
  • Parasites: Hydatid cysts, cysticercosis
  • Protozoa: Toxoplasmosis
  • Rickettsiae: Rocky Mountain spotted fever
  • Spirochetes: Syphilis, leptospirosis, Lyme disease
  • Fungi: Cryptococcus, Candida
  • Chronic Mycobacteria: Tuberculosis, leprosy
  • Bacteria: Meningococcus, Haemophilus influenzae
  • Viruses: Acute (e.g., HSV, H Zoster, Polio) and chronic (e.g., AIDS, SSPE)
  • Prions: Creutzfeldt-Jakob disease
  • Mycoplasma: Mycoplasma pneumoniae

Bacterial Meningitis

• Defined by inflammation of the meninges, typically affecting the pia and arachnoid mater; results from bacterial invasion into the subarachnoid space.
• Bacterial invasion often follows high-grade bacteremia, with entry points including highly vascular areas and direct access via sinusitis or traumatic defects.
• Symptoms include:
  • Classic signs: Kernig’s sign (pain upon knee extension with hip flexed) and Brudzinski’s sign (involuntary hip flexion when neck flexed).
  • Other symptoms: Headache, fever, neck stiffness, confusion, seizures, photophobia, vomiting, and potential purpuric rash in meningococcal infections.

Diagnosis and Treatment of Bacterial Meningitis

• CSF analysis via lumbar puncture is critical:
  • Characteristic findings: Elevated WBC count (predominantly neutrophils), elevated protein, low glucose.
• CT scans needed prior to lumbar puncture if papilledema or focal neurological signs are present to prevent brain herniation.
• Empirical antibiotic therapy is critical in life-threatening scenarios, usually involving:
  • IV Cefotaxime and Ampicillin for those at risk of Listeria.
• Meningococcal vaccination is a standard element of childhood immunization.

Tuberculous Meningitis

• Affects the basal meninges, potentially leading to cranial nerve palsies and complications like hydrocephalus.
• Presents insidiously with malaise and non-specific symptoms.
• CSF typically show lymphocytic pleocytosis and low glucose levels.

Brain Abscess and Spinal Epidural Abscess

• Brain abscesses may present with headaches, neurological signs, and raised ICP; often require imaging to differentiate from tumors.
• Spinal epidural abscess symptoms include neck or back pain, neurological signs of cord compression, and potential urinary dysfunction.
• Diagnosis typically confirmed by imaging; prolonged antibiotic treatment is required.

Viral Infections of the CNS

• Viral Meningitis: Often caused by enteroviruses; diagnostics reveal lymphocytic CSF profile with normal glucose levels.
• Viral Encephalitis: Symptoms include fever, altered consciousness, and seizures; often presents with you elevated RBC count in CSF and positive PCR for HSV.

Fungal and Parasitic Infections

• Fungal infections like Cryptococcus neoformans affect both immunocompetent and immunocompromised patients; treatments typically involve amphotericin.
• Toxoplasmosis in AIDS patients often results in ring-enhancing lesions on imaging.

Late Complications of HIV Infection

• Include HIV-associated dementia, vacuolar myelopathy, and progressive multifocal leukoencephalopathy.

Neurosyphilis

• Characterized by varying clinical manifestations, including:
  • Asymptomatic forms detected via serology.
  • Meningovascular syphilis causing subacute meningitis and cranial nerve palsies.

Transmissible Spongiform Encephalopathy

• Creutzfeldt-Jakob Disease presents with progressive dementia and spongiform changes in the brain; diagnosis through biopsy and electrophoresis.

Post-Infective Neurological Syndromes

• Acute Disseminated Encephalomyelitis: Follows infections or immunizations; characterized by multifocal neurological deficits.
• Guillain-Barre Syndrome: Post-infectious condition leading to progressive weakness and sensory loss, often fully recoverable.
• Reye’s Syndrome: Develops in children post-viral infection, linked to aspirin use; presents with severe symptoms including hepatic encephalopathy.
• Myalgic Encephalomyelitis: Associated with prolonged fatigue and muscle pain following viral infections.

This quiz focuses on the infections of the nervous system, specifically meningitis and encephalitis. It covers key aspects such as morbidity, mortality, and the importance of early recognition and treatment. Additionally, it discusses urgent brain imaging protocols and the impact of geographic location on these infections.