Q 1.31. Anatomy and Physiology of Cerebrospinal Fluid (CSF). CSF Syndromes.

1. Cerebrospinal Fluid (CSF):

• • CSF is a clear, colorless plasma-like fluid that bathes the central nervous system (CNS), including the brain and spinal cord.
  • It circulates through a system of cavities within the CNS:
    • Ventricles: These are interconnected spaces within the brain.
    • Subarachnoid space: The space between the arachnoid and pia mater layers of the meninges.
    • Central canal of the spinal cord.
  • The majority of CSF is secreted by specialized tissue called the choroid plexus, located in the lateral, third, and fourth ventricles.
  • CSF serves several essential functions:
    • Cushioning: It protects the brain and spinal cord from mechanical forces.
    • Immunological protection: Basic defense for the CNS.
    • Waste removal: Clears metabolic waste products.
    • Transport of neuromodulators and neurotransmitters.
    • Clinical diagnosis: CSF samples obtained via lumbar puncture aid in diagnosis.

2. Choroid Plexus:

• • The choroid plexus is responsible for CSF production.
  • It is found in the walls of the lateral ventricles and the roofs of the third and fourth ventricles.
  • Structural components of a choroid plexus villus:
    • Modified ependymal cells (choroid cells): These cells secrete CSF into the ventricles.
    • Pia mater layer (tela choroidea).
    • Fenestrated capillaries beneath the pia mater.
  • Choroid cells actively secrete CSF by taking up various chemicals from the underlying blood vessels.

3. Circulation of CSF:

• • CSF flows through the following path:
    • Lateral ventricle → third ventricle → fourth ventricle → central canal of spinal cord → subarachnoid space.
  • Arachnoid granulations and glymphatics are involved in CSF absorption.

4. Clinical Syndromes Involving CSF:

• Protein-Cell Dissociation refers to an abnormal finding in the CSF where the protein concentration is elevated, but the cell count (pleocytosis) remains normal.

• • • Clinical Significance:
      • This dissociation is often seen in chronic inflammatory conditions affecting the central nervous system (CNS).
      • Examples include neurosyphilis, subacute sclerosing panencephalitis (SSPE), and some cases of multiple sclerosis (MS).
      • In these conditions, the immune response leads to increased protein production without a significant increase in white blood cells (WBCs) in the CSF.
    • Diagnostic Clues:
      • When encountering protein-cell dissociation, consider the patient’s clinical history, neurological symptoms, and other laboratory findings.
      • Additional tests (such as serological tests for syphilis or oligoclonal band analysis) may help confirm the underlying cause.

• Cell-Protein Dissociation: refers to an abnormal finding in the CSF where the cell count (pleocytosis) is elevated, but the protein concentration remains normal.
• • • • • Clinical Significance:
          • This dissociation is typically observed in viral infections affecting the CNS.
          • Examples include viral encephalitis, aseptic meningitis, and certain herpes simplex virus (HSV) infections.
          • In these cases, the immune response leads to an influx of inflammatory cells (lymphocytes) into the CSF without a significant increase in total protein.
        • Diagnostic Clues:
          • Consider the patient’s symptoms (fever, headache, altered mental status), recent infections, and CSF cell count.
          • PCR testing for specific viruses (e.g., HSV, enteroviruses) can help confirm the diagnosis.

• Hydrocephalus: Abnormal accumulation of CSF due to impaired flow or absorption.
• Meningitis: Inflammation of the meninges affecting CSF composition.
• Subarachnoid hemorrhage: Bleeding into the subarachnoid space.
• Normal Pressure Hydrocephalus (NPH): Characterized by enlarged ventricles and normal CSF pressure.
• CSF leaks: Abnormal communication between CSF and external environment.

References:

1 kenhub.com

2 link.springer.com

3 academia.edu

4 link.springer.com

5 uptodate.com