Ch23 CSF

Question 1

What is the pH of CSF?

Answer 1

7.33-7.35

Question 2

What proportion of CSF is produced by the choroid plexus?

Answer 2

80% Most of the rest of intracranial production occurs in the interstitial space. CSF is also produced by the ependymal lining of the ventricles, and in the spine, in the dura of the nerve root sleeves.

Question 3

What is the total volume of CSF in the newborn?

Answer 3

5ml (150ml in Adults)

Question 4

What is the production rate of CSF in newborns?

Answer 4

25ml/day (450-750ml/day in adults - 0.3ml/min)

Question 5

Most accurate way to confirm CSF leak?

Answer 5

Beta transferrin

Question 6

Where is Rosenmullers fossa?

Answer 6

Potential site of CSF leak found behind the openingo of the Eustachian tube. It is inferior to cavernous sinus and can be exposed by drilling off anterior clinoids to access ophthalmic artery aneurysms.

Question 7

What proportion of head injury patients have a CSF leak?

Answer 7

2-3%

Question 8

What proportion of CSF leaks resolve spontaneously?

Answer 8

70% within 1 week, the rest usually by 6 months. in non-traumatic leaks only 33% resolve spontaneously

Question 9

How would you investigate a CSF leak?

Answer 9

Hx, test with Beta transferrin, if CSF +ve the water soluble CT cisternogram (Iohexol) or intraoperatively with fluorescein

Question 10

Would you treat CSF leaks with prophylactic antibiotics?

Answer 10

Not for traumatic causes, as likely to resolve spontaneously

Prophylactic abx for CSF leak controversial - There was no difference in the incidence or morbidity of meningitis between treated and untreated patients. (Klastersky 1976 Surg Neurol)

Furthermore, the risk of selecting resistant strains appears real and is therefore usually avoided. (Spetzler 1986)

Question 11

How would you treat a spontaneous CSF leak?

Answer 11

Conservative

• bed rest, avoid straining, blowing nose etc

Medical

• can give acetazolamide 250 mg QDS if due to raised ICP (not otherwise)

Surgical

• Lumbar drain
• repair

Question 12

What are the indications for surgical intervention in CSF leaks?

Answer 12

1. traumatic CSF leak that persists > 2 weeks in spite of non-surgical measures
2. spontaneous leaks and those of delayed onset following trauma or surgery: usually require surgery because of a high incidence of recurrence
3. leaks complicated by recurrent meningitis

Question 13

How does CSF protein vary with age?

Answer 13

Lowest at 1-2 years of age (15mg/dl) then increases preemie - 150 term - 80 young child 20 Young adult 30 senile 40

Question 14

What are the imaging findings seen in intracranial hypotension?

Answer 14

Remember ‘SEEPS’:

Sagging brain, pachymeningeal Enhancement, Engorged veins, Pituitary hyperaemia and Subdural collections

Question 15

How would you manage intracranial hypotension?

Answer 15

Identify site of leak: MRI head and whole spine, consider cisternogram if cranial or myleogram if spinal.

Conservative treatment options - bed rest, caffiene, hydration / IV fluids

Medical - Theophylline

Epidural blood patch

Surgical repair of CSF leak

Question 16

How can CSF leaks through the cribiform plate be repaired?

Answer 16

Extradural (endonasal)

Intradural (bifrontal bone flap)