CSF, hydrocephalus and lumbar puncture Flashcards
What is Hydrocephalus?
A general condition whereby there is excess Cerebro-Spinal Fluid (CSF) within the intracranial space and, specifically, the intraventricular spaces within the brain…causing dilation of the ventricles, and a wide range of symptoms.
What produces the majority of CSF?
Choroid plexus
Mechanism behind CSF production
metabolically active process (i.e. requires ATP) whereby sodium is pumped into the subarachnoid space, and water follows from the blood vessels.
Where is the choroid plexus located?
lateral ventricles (temporal horn roofs, and floors of bodies)
posterior 3rd ventricle roof
4th ventricle roof
How much CSF does the average adult produce?
450 and 600 cubic centimeters of CSF every day
normally, production = resorption
CSF vol turns over 3-4 x every day, with only a very small fraction of the CSF being in the ventricles at any given time, even though the majority of it is produced there
Describe the CSF pathway
From the 2 lateral ventricles the CSF travels through the foramen of monro into the 3rd ventricle
it then passes through the cerebral acqueduct into the 4th ventricle
It exits the 4th ventricle through either of two Foramina of Luschka or Foramen of Magendie
After exiting 4th ventricle - CSF flows through subarachnoid space over and around the brain and spinal cord and is eventually reabsorbed into venous system through arachnoid granulations in the dural venous sinuses
What is special about the arachnoid villi within the granulations?
They function as pressure-dependent one-way valves that open when the ICP is greater than dural venous sinus pressure.
Describe CSF resorption
passive process driven by the pressure gradient between the intracranial space (ICP) and the venous system (CVP)
What are the 2 major distinctions of hydrocephalus
Communicating Hydrocephalus (CoH) - Also known as “non-obstructive” hydrocephalus
Non-communicating Hydrocephalus (NCH)
Also known as “obstructive” hydrocephalus
What is communicating hydrocephalus?
If the CSF pathway is “open from start to finish,” meaning CSF can travel freely from the choroid plexus to the arachnoid granulations, then you have “no obstruction” and a communicating hydrocephalus.
In the vast majority of cases this represents a problem with CSF resorption; simply put, it cannot keep the pace with CSF production.
Pro>res
as a result the ventricular system dilates uniformly and ICP rises
What is non-communicating hydrocephalus?
If the CSF can’t travel freely from start to finish, then you’ve got an “obstruction” and non-communicating hydrocephalus.
Any physical obstruction to the normal flow
What is a rare cause of communicating hydrocephalus
Very rarely, there is overproduction of CSF (rather than under-absorption) which leads to disruption of this balance, and development of communicating hydrocephalus.
Choroid plexus papillomas can present this way
Signs/symptoms of communicating hydrocephalus in young children whose cranial sutures have not yet fused
Disproportional increase in head circumference compared to the rest of the face/body
Failure to thrive
Signs/symptoms of communicating hydrocephalus in children with fused sutures/adults
hydrocephalus manifests with symptoms of increased ICP;
Headache Nause and vomiting Papilloedema - O.D swelling Gait disturbance 6th cranial nerve palsy upgaze difficulty.
Aetiologies of communicating hydrocephalus (4)
Infection (incidence after bacterial meningitis can approach 30%)
Subarachnoid haemorrhage (blood and blood breakdown products cause scarring of arachnoid granulations)
Post-operative
Head trauma
What can happen if a significant number of arachnoid granulations are impaired?
Hydrocephalus can develop very quickly and it can become an emergency.
Neurological decline in such a situation can be rapid, with patients becoming sleepy, then obtunded (like lethargy), then requiring intubation.
Causes of non-communicating hydrocephalus (6)
Aqueductal stenosis
Tumors/Cancers/Masses
Cysts
Infection
Hemorrhage/hematoma
Congenital malformations/conditions
Acute processes causing NCH
Like intraventricular bleed
can cause acute obstruction with rapid mental status decline
What is the earliest consistent radiographical finding indicative of development of hydrocephalus?
dilation of the temporal horns of the lateral ventricles
in most younger and middle-aged patients, these should be almost invisible
What are other signs you can see on a CT scan that suggest hydrocephalus
III ventricle balloons
lateral ventricle size increase
peripheral sulci effaced - gyri pushed together so CSF is displaced from sulcus
What is surgical treatment for hydrocephalus
Acute hydrocephalus (comm and non-comm) usually requires urgent or emergent placement of an External ventricular Drain - this is not permanent
How is an External ventricular drain inserted?
A catheter is passed through the patient’s scalp and skull into lateral ventricle, that drains CSF to a collection system kept at the patient’s bedside
high infection risk
What is the main treatment for communicating hydrocephalus?
shunt placement
Ventriculo-peritoneal is the most used.
Lumbar-peritoneal sometimes utilized, though overdrainage is a problem.
Acute communicating hydrocephalus patients can sometimes be managed with EVD with no shunt placement but majority then need shunt placement weeks or months later
Treatment for NCH
Surgical removal of obstructive lesion
shunt placememt
Third Ventriculostomy - often performed in conjunction with VP shunt placement
What happens in Third Ventriculostomy procedure
Hole is surgically opened in floor of third ventricle so CSF flows out into the interpeduncular cistern and pre-pontine space (bypasses cerebral aqueduct).
Failure rate of VP shunts
as much as 40% the first year (most in the first few months), and then 5% per year after the first year.
50% of shunts fail by 5 years from placement.
What is normal pressure hydrocephalus (must know)
A rare preventable and/or reversible cause of dementia
what is the classic triad of Normal pressure hydrocephalus
‘Wet, Wobbly and Wacky.’
urinary incontinence
gait disturbance
rather quickly - progressive dementia
What is the procedure of choice for patients felt to be suffering from normal pressure hydrocephalus?
programmable VP shunt placement
It drains excess fluid from the ventricle. This is achieved by placing a tube into the ventricle which drains the fluid to the abdomen. A programmable shunt has an adjustable valve which prevents the fluid from moving in the wrong direction and only lets fluid drain when the pressure is too high.
What symptoms does a shunt improve/ not improve?
least likely to improve dementia
most likely to improve gait>incontinence>memory
Why might you need to do a Lumbar puncture to obtain CSF? (7)
Meningitis
Meningoencephalitis
Subarachnoid hemorrhage
Malignancy – diagnosis and treatment
Idiopathic Intracranial Hypertension
Other neurologic syndromes
Infusion of Drugs or contrast
Contraindications to lumbar puncture
Unstable patient with cardiovascular or respiratory instability
Localised skin/soft tissue infection over puncture site
Evidence of unstable bleeding disorder
Raised ICP - do head CT first
How much CSF do you collect during procedure?
1ml of CSF in each of 3 vials
tube 1 - culture and gram stain
2 - glucose, protein
3- cell count and differential
Complications of lumbar puncture
Headache
Apnea - central or obstructive (stop breathing)
Back pain
Bleeding or fluid leak around spinal cord
infection, pain, haematoma
subarachnoid epidermal cyst
nerve trauma
brainstem herniation
Spinal headache
Most common complication
Risk factors: female, age 18-30, lower BMI, hx of HA, prior spinal HA
Bilateral HA, improves when supine
Can last hours to weeks
Prevention of spinal headache
Can avoid by:-
Passing needle bevel parallel to longitudinal fibers of dura
Replacing stylet before removing needle
Using small diameter needles
Using atraumatic needles
Bed rest or PO intake after LP does not reduce incidence of headache
Nerve root trauma
Can feel electric shocks or dysesthesias
Back pain can persist for months
Rarely permanent
Electromyogram/nerve conduction velocity studies should be scheduled if pain persists
Herniation
Manifests initially as altered mental status, followed by cranial nerve abnormalities and Cushing triad
May be rapidly fatal
Immediately remove needle and raise the head of bed to 30-45° improve venous return from the brain.
Intubate and hyperventilate
If lumbar puncture fails then what are the other alternatives?
Have someone else try
- Anesthesia
- Neurology
Bedside ultrasound for difficult LPs
Radiographic guided procedure
- Fluoroscopy
- Ultrasound
- CT
Cisterna Magna tap
