CSF, Hydrocephalus, Lumbar Puncture Flashcards
What is hydrocephalus?
Excess CSF in the intracranial space, more specifically the intraventricular spaces within the brain - causing dilation of the ventricles and a wide range of symptoms
Where is CSF produced?
Choroid plexus
What is the process by which CSF is produced?
It is a metabollically active process - requires ATP. Sodium is pumped into the subarachnoid space and water follows from the blood vessels.
Where is choroid plexus found?
Choroid plexus is primarily located in the lateral ventricles (temporal horn roofs, and floors of bodies), posterior 3rd ventricle roof, and caudal 4th ventricle roof.
How much CSF is produced in the average adult per day?
Between 450 and 600 cc’s every day
How much CSF is present in the average adult?
150 cc’s
Of this only 25 cc’s is within the brain ventricles
Normally what does production equal?
Resorption
How is CSF absorbed into the venous system?
Through numerous arachnoid granulations along the dural venous sinuses (especially the superior sagittal sinus)
Where are arachnoid villi and what do they do?
Arachnoid villi are found in arachnoid granulations - they function as pressure dependant one way valves that open when the ICP is 3-5cm H2O greater than the dural venous sinus pressure.
This opening of arachnoid villi is a passive process which is opposite to CSF formation which is an active process (requires ATP)
Resroption when ICP is greater than CVP (central venous pressure)
What are the twp types of hydrocephalus?
Communicating hydrocephalus (or non-obstructive hydrocephalus)
Non-communicating hydrocephalus (or obstructive hydrocephalus)
What is communicating hydrocephalus?
CSF travels freely from choroid plexus to the arachnoid granulations
(NO OBSTRUCTIONS)
What is meand by non-communicating hydrocephalus?
CSF can’t travel freely from start to finish - there is an obstruction
What is a common cause of communicating hydrocephalus?
CSF production is greater than resorption
Ventricular system dilates uniformly and ICP rises
Rarely it is because there is overproduction of CSF (rather than under - resorption) - this is rare but choroid plexus papillomas have been known to present this way
In infants the skull is still growing might not get a raised ICP – in adults however there will be raised ICP – skull is fused
What are the signs and symptoms of CoH?
◦In young children whose cranial sutures have not yet fused, you can see disproportional increase in head circumference compared to the rest of the face/body or failure to thrive
◦In children with fused sutures/adults, hydrocephalus manifests with symptoms of increased intracranial pressure;
Headache, Nausea and vomitting, papilledema, gait disturbance, 6th cranial nerve palsy, upgaze difficulty, etc.
What are the causes of communicating hydrocephalus?
Infection (e.g meningitis)
SAH - Blood and blood breakdown products can cause scarring of arachnoid granulations
Post - operative
Head trauma
Etc
What are the causes of non-communicating hydrocephalus?
Aqueductal stenosis
Tumours / cancers / masses
Cysts
Infection
Haemorrhage / haematoma
COngenital malformations / conditions
Give an exmaple of slow onset non - communicating hydrocephalus and fast onset
Slow onset - likely to be a mass
Fast onset - likely to be intraventricular bleed
What is the earliest consistent radiographical finding indicative of development of hydrocephalus?
Dilation of the temporal horns of the lateral ventricles (arrows). In most younger and middle-aged patients, these should be almost invisible.
What are the radiographical findings of hydrocephalus?
Third ventricle will become balloned
Lateral ventricle size will increase
Peipheral sulci effaced - means eraced
Evans ratio - greater than 0.3 indicates ventriculomegaly
What is the treatment for hydrocephalus?
Acute - Extraventricular drain - EVD
Catheter passed through the patients scalp and skull into the lateral ventricle - drains CSF to a collection system kept at the patients bedside
This treatment cannot be maintained indefinitely - permanent shunt may be required if the patient does not respond well to clamping of the EVD prior to removal
For communicating hydrocephalus, the mainstay of treatment is shunt placement what are the common shunts?
◦Ventriculo-peritoneal is most used.
◦Lumbar-peritoneal sometimes utilized, though overdrainage is a problem.
◦Ventriculo-atrial can also be considered in cases of peritoneal failure (if the shunt gets infected then the chances of endocarditis is high)
How can non-communicating hydrocephalus be treated surgically
Shunt can be avoided by removing the obstructing lesion
Give examples of obstructung lesions
Colloid cyst at anterior 3rd ventricle - obstruction of foramen of monro
Pineal region tumour causing compression of cerebral aqueduct
Ependymoma blocking 4th ventricular CSF outlets
What are the treatments for NCH?
Third ventriculostomy (often used in conjunction with Ventriculo peritoneal shunt placement)
Hole opened in the floor of the third ventricle so CSF flows out into the interpeduncular cistern and pre-pontine space (bypass the cerebral aqueduct)
What percentage of shunts fail within the first year?
40%
What are the reasons for shunt failure?
Occlusion
Disconnection
Migration
Overdrainage
Underdrainage
Infection
Skin erosion
What does treatment of normal pressure hydrocephalus prevent?
Dementia
Chance of outcome is improved if symptoms have been present for shorter period of time.
Dementia is unlikely to improve with shunt placement
Most likely to improve is gait > incontinence > memory
What is the classic triad for normal pressure hydrocephalus?
WET WOBBLY and WACKY
Urinary incontinence
Gait disturbance
Rather quickly progressive dementia
Communicating hydrocephalus on CT (Enlarged temporal horns of lateral ventricle, enlarged third ventricle, effaced peripheral sulci evans ratio is greater than 0.3)
Lumbar puncture - Normal opening pressure, symptoms improve with CSF removal
What is the treatment of choice for patients with NPH?
Programmable Ventriculo peritoneal shunt
Lumbar peritoneal shunt is often avoided because they tend to overdrain
What are the indications of a lumbr puncture?
◦Meningitis
◦Meningoencephalitis
◦Subarachnoid hemorrhage
◦Malignancy – diagnosis and treatment
◦Idiopathic Intracranial Hypertension
◦Other neurologic syndromes
◦Infusion of Drugs or contrast
What are contraindications to lumbar puncture?
Unstable patient with cardiovascular or respiratory instability
Localized skin /soft tissue infection over puncture site
Evidence of unstable bleeding disorder - (platelets are less than 50,000 or there is a cotting factor deficiency)
Increased intracranial pressure
Neurologic deterioration can occur if LP is done below the level of a complete spinal subarachnoid block
Caution in patients with Chiari malformations
What are the stages of lumbar puncture?
Topical anaesthetic about 30-45 mins before procedure
Puncture site is usually L3-L4 or L4-L5 (it is important to check!)
- Restrain patient in the lateral decubitus position
- Maximally flex spine without compressing the airway
- Position head to the left if right handed or vice versa
Insert needle - needle angle is upwards and not downwards
What causes the pop with sudden decrease in resistance indicate?
Indicates that the ligamentum flavum and dura are punctured
What is a method in which CSF pressure can be increased in low flow situations?
Jugular vein compression
What is used to determine opeining pressure?
Manometer - pressure can only be accurately measured in the lateral decubitis position and in the relaxed patient
Where is CSF sent to?
Collect 1ml of CSF in each of 3 vials for:
◦Tube 1: culture & gram stain
◦Tube 2: glucose, protein
◦Tube 3: cell count & differential
◦and extra CSF if desired for other lab tests
When would you use the sitting position for a lumbar puncture?
Infants
Obese patients where you cannot easily find their midline
Who is recommended the paramedian (lateral) aproach for lumbar puncture?
Use for patients who have calcifications from repeated LPs or anatomic abnormalities
What does the needle pass through in a paramedian approach?
Passes through erector spinae muscles and ligamentum flavum
Bypasses the supraspinal and interspinal ligaments
There is less chance of spinal headache
What are complications associated with lumbar puncture?
Headache - most common
Apnea
Back pain - disc herniation
Bleeding or fluid leak around the spinal cord
Infection, pain, hematoma
Subarachnoid epidermal cyst
Ocular muscle palsy
Nerve trauma
Brainstem herniation
Who is susceptible to spinal headache?
Risk factors: female, age 18-30, lower BMI, hx of HA, prior spinal HA
How can spinal headaches be improved?
Bilateral HA improves when supine
Hydration
Caffiene either PO or IV
Epidural blood pouch
How can spinal headache be avoided?
◦Passing needle bevel parallel to longitudinal fibers of dura
◦Replacing stylet before removing needle
◦Using small diameter needles
◦Using atraumatic needles
What are signs of nerve trauma / irritation during lumbar puncture?
Can feel electric shock or dysesthesias
Back pain can persist for months (consider disc herniation)
Rarely permanent
Motor weakness (if this is the case then start corticosteroids)
What should be done in response to nerve root trauma?
Withdraw needle immediately
If pain or motor weakness persists, start corticosteroids
Electromyogram/nerve conduction velocity studies should be scheduled if pain persists
What are the signs of herniation (brainstem)?
Altered mental status initially followed by cranial nerve abnormalities and cushing triad
What is the protocol if there is suspected braistem herniation?
Remove needle and raise the head of the bed to 30-45 degrees to improve venous return from the brain
Mannitol or 3% saline
Intubate patient and hyperventilate
Emergent neurosurgical consult
What causes an epidermal inclusion cyst?
Occurs when a core of skin is driven into spinal or paraspinal space with hollow needle -
Do not remove the stylet until you are through the skin
What are alternative methods of procedure for lumbar puncture?
Use anaesthesia
Bedside ultrasound for difficult LP’s
Radiographic guided procedure (fluroscopy, ultrasound, CT)
Cisterna magna tap
What are features of CSF?
Colour?
Opening pressure?
Protein level
Glucose level
Serum glucose
WCC
Appears Clear and Colourless
Opening Pressure 6-16 mm/H20
Protein level ~ 35 mg%
Glucose level ~ 60 mg %
(60% of serum glucose)
WCC <5 (Ratio WCC:RCC = 1/750)
How if csf transported?
Brown envelope ensures the sun doesn’t affect the sample. If sunlight gets on the sample, every sample will come back with positive test of subarachnoid haemorrhage
