Cerebrospinal Fluid (CSF)

Overview

Snapshot

• A 22-year-old male presents with altered mental status, fever, and headache. The patient is able to sluggishly answer questions. Passive flexion of the neck leads to spontaneous contraction of the hips. Pain is elicited when attempting to fully extend the knee while his hips are at a 90 degree angle. A skin finding is shown to the right.

Introduction

• Function
  • serves as a mechanical cushion for the CNS
    • protects the brain against concussive injury
  • removal of metabolites
    • CSF flow is one-way
  • hormone and hormone-releasing factor transportation
  • homeostasis
    • CSF pH affects ventilation and cerebral blood flow
• Production
  • produced by the choroid plexus epithelial cells within ventricles
    • found in lateral, third, and fourth ventricles
  • reabsorbed into circulation by arachnoid granulations
    • enters dural venous sinuses
    • entire volume of CSF is recycled 2-3 times per 24 hours
• Ventricular system communications 
  • lateral ventricle → 3rd ventricle
    • via the interventricular foramen of Monro 
  • 3rd ventricle → 4th ventricle
    • via the cerebral aqueduct (Aqueduct of Sylvius)
  • 4th ventricle → subarachnoid space via
    • foramina of Luschka (lateral)
    • foramen of Magendie (medial)
• Compared to the serum:
  • ↓↓ protein
  • ↓ glucose
  • ↓ pH
  • ↓ K⁺, HCO3^–, Ca²⁺
  • ↑ Cl-, Mg²⁺

Presentation

• Hydrocephalus
  • dilated ventricles via several types
    • communicating
      • ↓ reabsorption of CSF
        • scarring of arachnoid granulations following meningitis
      • ↑ production of CSF (rare)
        • choroid plexus papilloma
    • noncommunicating/obstructive
      • obstructed flow of CSF 
        • stenosis at narrow point along ventricular system
          • e.g., at the cerebral aqueduct, foramen of Monro
        • Chiari II malformation
        • Dandy-Walker syndrome
    • normal pressure (NPH)
      • ↓ reabsorbtion of CSF with chronic dilation of ventricles and normal CSF pressure 
      • distortion of corona radiata produces triad of 
        • urinary incontinence
        • dementia
        • apraxic gait
        • “wet, wacky, wobbly”
      • imaging
        • enlarged ventricles on CT/MRI
      • treatment 
        • peritoneal shunt
    • ex vacuo 
      • ↑ in CSF due to ↓ in brain size 
        • e.g., Alzheimer disease
      • ventricles appear large but CSF pressure is normal