Meninges and Meningitis

Meninges Overview

• Refers to 3 membranes surrounding the brain and spinal cord:
  • Dura mater
  • Arachnoid mater
  • Pia mater
• Functions:
  • Protects the brain
  • Provides structural support
  • Contains cerebrospinal fluid (CSF)

Meningitis

• Definition: Inflammation of the meninges
• Causes:
  • Typically caused by infections
  • Non-infectious causes also exist
  • Common pathogens include bacteria (most severe cases)

Pathogenesis

• Central nervous system (CNS) is protected by:
  • Blood-brain barrier
  • Blood-cerebrospinal fluid barrier
• Meningitis occurs when pathogens evade these barriers and enter the meninges
• Immune response triggers inflammation:
  • Pathogens enter CSF
  • Increased permeability of blood-brain barrier
  • Influx of white blood cells and blood plasma constituents into CSF

Consequences of Meningitis

• Inflammation leads to:
  • Increased volume and viscosity of CSF
  • Cerebral edema (fluid accumulation in the brain)
  • Increased intracranial pressure
• Increased intracranial pressure can:
  • Disrupt cerebral blood flow
  • Result in brain tissue damage

Symptoms

• Common symptoms include:
  • Headache
  • Neck stiffness
  • Fever
  • Altered mental status
• Serious long-term complications or death may occur

Diagnosis and Treatment

• Diagnosis typically done via lumbar puncture (spinal tap)
• Treatment varies by cause:
  • Antibiotics often started immediately if bacterial meningitis is suspected
  • Bacterial meningitis is fatal if untreated