====== Cerebrospinal Fluid (CSF) ======

Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds the brain and spinal cord. It plays critical roles in mechanical protection, metabolic support, and intracranial pressure regulation.

===== 🧪 Composition =====

^ Component         ^ Normal Value               ^
| Volume (adult)    | 140 – 270 mL                |
| Opening pressure  | 10 – 20 cmH₂O               |
| pH                | ~7.33                       |
| Glucose           | 45 – 80 mg/dL               |
| Protein           | 15 – 45 mg/dL               |
| WBC               | 0 – 5 cells/μL (lymphocytes)|

===== 🧠 Functions =====

  * Mechanical cushion: protects brain and spinal cord from trauma.
  * Buoyancy: reduces the effective weight of the brain.
  * Metabolic exchange: removes waste and delivers nutrients.
  * Intracranial pressure (ICP) buffer.
  * Immune surveillance.

===== 🔄 Circulation Pathway =====

  - Produced in the **choroid plexus** of the lateral, third, and fourth ventricles.
  - Flows:
    - Lateral ventricles → Foramina of Monro →
    - Third ventricle → Aqueduct of Sylvius →
    - Fourth ventricle → Foramina of Luschka and Magendie →
    - Subarachnoid space → Arachnoid villi → Superior sagittal sinus.

===== 🧬 Clinical Relevance =====

==== Lumbar Puncture (LP) ====
  * Diagnostic tool for infection, bleeding, or demyelinating disease.
  * Normal pressure: 10–20 cmH₂O in lateral decubitus position.
  * Contraindicated in patients with raised ICP and midline shift.

==== Hydrocephalus ====
  * Excess accumulation of CSF.
  * Classified as:
    - Communicating
    - Non-communicating (obstructive)
    - Normal pressure hydrocephalus

==== CSF Shunting ====
  * Types: Ventriculoperitoneal (VP), ventriculoatrial, lumboperitoneal
  * Indications: hydrocephalus, CSF pseudocysts, Dandy-Walker malformation

==== CSF Leak ====
  * Can be spontaneous or traumatic/post-surgical.
  * Clinical signs: rhinorrhea, otorrhea, low-pressure headache.
  * Diagnosed via beta-2 transferrin test and imaging (CT/MRI cisternography).

===== 🔗 Related Topics =====

  * [[intracranial_pressure_monitoring]]
  * [[hydrocephalus]]
  * [[lumbar_puncture]]
  * [[shunt_malfunction]]