Cerebrospinal Fluid

Question 1

How much CSF is there at any one time?

Answer 1

Total around 125-150mL

Question 2

Where is most CSF produced?

Answer 2

• Choroid plexus in the lateral ventricles.
• Some may be filtered through entire ventricular lining.

Question 3

Where is CSF reabsorbed?

Answer 3

• Reabsorbed in arachnoid granulations in venous sinuses.
• Some may drain via nasal lymphatics.

Question 4

How much CSF is produced per day?

Answer 4

• ~1L per day
• ~25mL per hour

Question 5

How much protein, RBC, WBC and glucose is contained in CSF?

Answer 5

• Derived from plasma, but virtually protein free.
  
  • Protein <0.5mg/ml.
• No RBCs unless you do a traumatic tap.
• <5 WBCs/mL.
• Glucose 60-70% blood levels (2.5-5mmol).

Question 6

What are the functions of CSF?

Answer 6

• Buoyancy - brain effectively weighs less.
• Protection - “soft gel in hard box”.
• Waste clearance - in addition to arterial / venous system.
• Homeostasis - rapid signalling between cells.
• Intracranial pressure regulation to enable optimal brain perfusion.
• Immune surveillance.

Question 7

What level does the S.C. end?

What implication does this have for lumbar puncture?

Answer 7

• S.C. ends at the bottom of L1.
• You can safely put a needle in to L3/4 or L4/5 to do a lumbar puncture.

Question 8

Under which circumstances must a lumbar puncture NOT be done?

Answer 8

• DO NOT CONSIDER LP IS THERE IS ANY POSSIBILITY OF SPACE OCUPATION.
• Normal opening pressure = <20cm water.
• 21-29 = intermediate.
• >30cm wateris definitely elevated.
• Cannot estimate pressure if patient is sitting up during LP.
• If technically challenging, consider x-ray guidance =.

Question 9

What are the complications of lumbar puncture?

Answer 9

• Headache - typically low pressure headache, worse when standing up, eased by lying down, often with nausea and vomiting.
• Coning / death.
• Bleeding / bruising.
• Nerve damage.
• Infection.

Question 10

What happens when CSF circulation blocks?

Answer 10

• Depends on where in the system, and at what age, and at what speed.
• If sutures are not fused, hydrocephalus with expanded cranium results.
• If sutures are fused, and the CSF blockage occurs very slowly then this may result in normal.
• If it occurs fast, can cause symptoms of raised ICP, drowsiness and coma.
• Causes include congenital and acquired (infections, inflammation, tumours and vascular etc.).
• Idiopathic intracranial hypertension (IIH or BIH).

Question 11

Describe idiopathic intracranial hypertension.

Answer 11

• Occurs much more frequently in women than men.
  
  • Particularly in young females who are highly overweight.
• Present with symptoms of raised ICP, visual disturbances, diplopia.
• Papilloedema.
• May be associated with cerebral venous sinus thrombosis.
• Risk of blindness, so keep check on visual acuity and fields.
• Treatment is weight loss, a diuretic called acetazolamide (an old one), repeated lumbar puncture or the placement of a shunt.

Question 12

Describe the characteristics of a low pressure headache.

Answer 12

• Eased on lying down, worse standing up.
• Can occur spontaneously (this is very rare), usually occurs post-LP.

Question 13

What is a chiari malformation?

Answer 13

• A Chiari malformation, previously called an Arnold-Chiari malformation, is where the lower part of the brain pushes down into the spinal canal.
• Lesion can be at C8 or T1 or can be a peripheral nerve neuropathy.
• These are congenital malformations.