Examination Of Cerebrospinal Fluid Flashcards
What is CSF
CSF is a clear colourless fluid formed in the ventricles of the brain mainly by the choroid plexus
It is mainly an ultra filtrate of plasma
Contained within the cerebral ventricles, the spinal canal and the subarachnoid space surrounding the brain and spinal cord
CSF is reabsorbed into the blood through the arachnoid villi of dural venous sinuses
What are the functions of CSF?
Protection of brain and spinal cord from injury by acting as a shock absorber
To serve as a medium between the blood and the brain for supply of nutrients to and removal of waste products.
Why do we need to examine CSF?
(Indications of CSF)
- For diagnosis of:
- CNS infections (e.g meningitis and encephalitis)
- CNS neoplasms
- Meningeal involvement by malignancy (e.g leukemia)
- subarachnoid hemorrhage (if CT scan is not available) - For administration of medications:
-anesthetic agents
-antibiotics
-anti cancer drugs
What is the site and position in which we obtain CSF?
Procedure: Lumbar puncture
Site: LP needle is inserted between the 3rd and 4th lumbar vertebrae into the subarachnoid space
Position:
- patient is in a side-lying (lateral recumbent) position with back vertical and at the edge of the bed, with the knees drawn up and the head flexed onto the chest
- this position increases the space between the lumbar vertebrae
-alternatively, the patient may be in a sitting position
What are the complications of obtaining CSF (lumbar puncture)?
Post-puncture headache: the most common side effect and results from leakage of CSF from puncture site at a rate faster than the rate of CSF production (use of a smaller bore needle and keeping the patient flat after the procedure for 2-3 hours reduces the risk)
Introduction of infection in spinal canal if aseptic precautions are not observed at the site of LP
Subdural hematoma with resultant neurological deficit in patients with bleeding tendency
Failure to obtain CSF (dry tap) which may be due to the incorrect positioning of the patient
What are the normal laboratory parameters of CSF examination?
Total volume: 100-150ml
Opening pressure: 60-180 mm of water
Appearance: clear, colourless, no clots
Cells:
Adults = 0-5cells/ cmm
Children will have slightly higher cell counts
Chemistry:
Glucose= 45-80 mg/dl (60% of blood glucose)
Protein= 15-45 mg/dl (1% of plasma proteins)
What are the causes of increased CSF pressure?
Tense and anxious patient
Intracranial mass lesion (e.g neoplasm, abscess and hemorrhage)
Meningitis
Cerebral oedema
Subarachnoid hemorrhage
What are the causes of decreased CSF pressure?
Leakage of spinal fluid following trauma or previous lumbar puncture
Obstruction of spinal subarachnoid space by tumor,abscess, herniated intervertebral disk and adhesions
What are the causes of abnormal CSF appearance?
Blood mixed CSF (e.g traumatic LP and subarachnoid haemorrhage):
-Clot formation does not occur in subarachnoid haemorrhage but occurs in traumatic LP
Turbid CSF (e.g meningitis, raised proteins and presence of cells)
What are the causes of increased cell count in CSF?
Increased neutrophils in bacterial meningitis
Increased RBCS in traumatic LP or hemorrhage
Meningeal infiltration by malignancy
What are the causes of decreased glucose in CSF? And why is immediate sample processing for glucose estimation done?
Meningitis (bacterial, fungal)
Glucose is normal in viral meningitis
Meningeal involvement by malignant tumour
Hypoglycaemia
Immediate sample processing for glucose estimation is done to avoid falsely low result due to glycolysis.
What are the causes of increased proteins in CSF?
Meningitis (increased capillary permeability of blood-brain barrier)
Malignancy
Hemorrhage in CSF: traumatic tap, subarachnoid hemorrhage
