CSF

Question 1

Steps in CSF production

Answer 1

Location: Choroid plexuses in ventricles + blood supply from anterior and posteror choroidal arteries (tight junctions maintain Blood-CSF Barrier)

1. ultrafiltration of plasma across fenestrated capillary walls
2. choroid epithelial cells (ependymal cells) secrete/transport components into the ventricle

Question 2

Components of CSF (compared to Plasma)

Answer 2

• Lower in protein (30 mg/dL)
• 2/3 of serum glucose (~60mg/dL)
• Same osmolality
• Less K+
• Same Na+, Ca2+, Cl-

Question 3

Circulation of CSF

Answer 3

Lateral ventricle –> 3rd –> 4th –> subarachnoid space –> bathe brain/spinal cord –> subarachnoid granulations –> venous sinuses (via transcytosis vesicles)

Question 4

Functions of CSF (4)

Answer 4

• Buoyancy –> reduces effective weight (physical support)
• Shock absorption (protection)
• Path for waste excretion
• Protects metabolic functions – suitable extracellular environment (homeostasis)

Question 5

Barriers into the brain (2)

Answer 5

1. Blood-CSF Barrier: @ choroid plexuses - capillary junction –> allows influx of Ca2+ into brain but not gases
2. Blood-Brain Barrier: @ brain capillaries –> diffusion of O2, CO2 and glucose

** 2 routes into the CNS

Question 6

Blood Brain Barrier – structure and function

Answer 6

Excludes:

• Large, charged molecules (fibrinogen, prealbumin)

Includes:

• Uncharged, lipid soluble molecules (O2, caffeine, nicotine, ethanol, heroin)
• Endotelial transporters for glucose, amino acids, nucleic acid precursors

** Exceptions exist w/ leakier capillaries –> to sense/monitor changes in osmolality, body temp; allows pituitary to release hormones into blood

Question 7

Indications to sample CSF

Answer 7

1. CNS infection
2. Subarachnoid hemorrhage
3. CNS malignancy
4. Demyelinating disease

Question 8

Lumbar puncture - complications

Answer 8

Headache

• Decreased physical support/protection due to less CSF –> stimulates pain sensitive structures in CNS
• Can last multiple days
• Can be exacerbated by positional changes
• 10-30% of pts

Question 9

Gross examination - CSF

Answer 9

Normal = clear, colorless, watery

Cloudy = >WBC from infection

Bloody = >RBC from hemorrhage (e.g. SAH) or trauma (if 1st tube is bloody)

Xanthochromia =

• Yellow: billirubin from RBC breakdown
• Orange: > beta carotene ingestion
• Brown: metastatic melanoma

**Viscous: **e.g. metastatic mucinous adenocarcinoma

Question 10

Microscopic Examination - CSF

Answer 10

Normal = few WBC, no RBC

Pleocytosis: elevation of total cell counts in CSF

Neutrophil predominance = bacterial

Lymphocyte predominance = viral, fungal

Question 11

Chemical workup - CSF

Answer 11

• Low glucose = increased anaerobic glycolysis in brain tissue and WBCs
  
  • ** often seen in bacterial or fungal infections
• High protein
  
  • increased permeability of BBB and/or B-CSF barrier
  • decreased reabsorption @ arachnoid granulations
  • increased synthesis of Ig in CNS
  • ** infections (bacterial, viral), neoplasm, inflammatory/auto-immune