CSF Flashcards
Where does CSF originate?
Choroid plexus of the intracranial ventricles
What spaces does the fluid occupy?
-Ventricles
-Subarachnoid space
(around the brain and spinal cord)
The composition of CSF is derived from these 3 things…
- Filtration
- Differential absorption
- Active secretion
What are the functions of CSF?
- Enhance nutrition of the brain
- Remove metabolic biproducts
- Protect against mechanical injury
The composition of electrolytes in CSF varies with the changes in _______ levels
Plasma
Most constituents in CSF are present in ______ or ______ concentration than the plasma
Equal or lower
Pathological conditions cause inflammation, this causes leaky vessels, this leads to…
Elements that are typically restrained entering the blood brain barrier getting into the CSF and causing high concentrations
Are proteins and lipids found in CSF?
Nope
Are RBC and WBC in the CSF?
Nope- only enter if there is a ruptured blood vessel of inflammation of the meninges
Is bilirubin in CSF
No- seen in intracranial hemorrhage (xanthochromia)
What color should the CSF be?
Clear
How is normal pressure maintained in the brain
By absorption of CSF through the arachnoid villi in equal amounts to its production by the choroid plexus
What are the steps for determining if you need a lumbar puncture
-Determine the diagnostic objective
When is a lumbar puncture normally used
- Suspected meningitis
- Subarachnoid hemorrhage
- Other intracranial bleed
What are 2 tests that replaced some need for lumbar punctures
- CT
- MRI
Do you have to consider the possibility of intracranial pressure?
Yes- if there is a pressure difference and you release it in a lumbar puncture you can pull the brainstem through the foramen magnum
When is a fundoscopy used?
To rule out the presence of papilledema (swelling of the optic disk)
What can be given to decrease the cranial pressures
Solute diuretic
What are 2 things to do before a lumbar puncture
- explain procedure
- provide reassurance
When is the pop sound heard?
When the needle punctures the dura
What are 2 things that can occur after a LP?
- Temporary parasthesias
- Post puncture headache
Describe the post puncture headache
- occurs in 25% of patients
- bilateral occipital or frontal
- occurs only in the upright position
- lying suprine relieves the pain quickly
How should the patient be positioned?
- Knees to chest with the chin flexed towards the knees
- Breath slowly and naturally
Where should the needle be inserted?
Between the 3rd, 4th, or 5th lumbar intervertebral spaces
Should the opening pressure be recorded?
Yes
What does turbitity signify
Leukocytes
What does yellow discoloration mean?
Previous bleeding
What is the pH of CSF compared to blood?
CSF= 7.31 Blood= 7.41
How do you know if the blood is due to puncture of a vessel on the way into do the LP
The tube will get lighter by the 3rd tube
What does brown CSF mean?
-Presence of methemalbumin (which is associated with subdural hematoma)
When can spontaneous clotting occur?
-Whenever protein content is high
What is the mean CSF pressure
120 mmHg
What happens when a patient holds their breath or tenses muscles
Increase in CSF pressure
What causes a person to have decrease in CSF pressure
Dehydration
These three things cause increase in CSF
- Intracranial tumors
- Purulent meningitis
- Encephalitis
- Neurosyphillis
What is the average drop in CSF pressure
5-10 mm drop in pressure for every mL of fluid removed
What kind of bloody tap does not clot
-subarachnoid hemorrhage
What is the correction factor?
Allow 1-2 WBC for every 1000 RBC= anything greater is indicative of preexisting leukocytes
10-200 cells=
Primarily lymphocytosis
- viral meningitis
- late neurosyphillis
- MS
- Tumor
200-500 mixed cell type=
- TB meningitis
- Herpes infection of CSF
Over 500 granulocytes
-Acute bacterial meningitis
Immature cells=
Meningeal leukemia
Normal blood concentrations of protein are less than __%
1%
What 2 things increase protein levels
- Purulent meningitis
- Multiple sclerosis
What do you suspect if you have elevated protein levels without cells
-Degenerative disease of CNS
(MS, neurosyphillis)
-Subarachnoid blockage
What are the levels of blood glucose in the CSF
50-80% of the normal blood glucose levels
How long is the lag period for glucose
30-40 minutes
In purulent meningitis, you get a ____ in CSF glucose
Drop
What do lactic acid levels reflect?
Local glycolysis
An isolated increase in CSF lactate indicates….
-Increased glucose metabolism
Are smears used?
Yes- if there is any question of meningitis or CNS infection - use a gram stain or acid fast stain
