CSF, hydrocephalus & lumbar puncture Flashcards
What is CSF produced by
Choroid plexus
Is CSF production/resorption metabolically active/passive
Production - active (requires ATP for Na/K ATPase)
Resorption - passive
How much CSF do we make daily
450-600ml
At any given moment, there’s how much CSF in the body
150ml
How much CSF is in the ventricles at any given moment
25ml
CSF exits the 4th ventricle into the subarachnoid space via what 2 foramen
Formamen of luschka - lateral
Foramen of magendie - medial
Define hydrocephalus
Excess CSF in the brain
2 types of hydrocephalus
Communicating (non-obstructive)
Non-communicating (obstructive)
Describe communicating (non-obstructive) hydrocephalus
CSF pathway open from start to finish, i.e. can travel from choroid plexus to arachnoid villi to be resorbed
Pathophysiology of communicating hydrocephalus (2)
CSF resorption < production
(under-absorption)
Ventricles dilate –> ICP rises
In a RARE type of communicating, CSF production > resorption - what condition is this
Choroid plexus papilloma
Causes of communicating hydrocephalus (4)
Infection
Subarachnoid haemorrhage - blood in subarachnoid space impairs arachnoid granulations so resorption impaired
Post-op
Head trauma
Describe non-communicating hydrocephalus (obstructive hydrocephalus)
CSF can’t travel freely from start to finish due to a PHYSICAL obstruction
Causes of non-communicating hydrocephalus (6)
Aqueductal stenosis Tumours/masses - MOST COMMON Cysts, e.g. colloid cyst Infection Haemorrhage Congenital malformations
Symptoms/signs of hydrocephalus
- in babies (4)
- in children with fused sutures/adults (7)
Babies: Massive head Bulging fontanelle Failure to thrive Downward looking eyes
Children/adults: Headache Nausea Vomiting Sleepiness Gait disturbance (difficulty walking) Blurry vision Urinary incontinence
Investigations of hydrocephalus
CT - shows dilated inferior/ temporal horns of lateral ventricles
MRI
How is the Evans ratio used to diagnose hydrocephalus
Max width of anterior horns of lateral ventricles divided by max width of the skull at the same level
If ratio >30% = indicates ventriculomegaly and potentially hydrocephalus
Treatment of:
- communicating hydrocephalus (1)
- non-communicating hydrocephalus (3)
Communicating:
Shunt placement
Non-communicating:
Shunt placement
Endoscopic third ventriculostomy
Remove obstructing mass
How does shunt placement work
Shunt is implanted in the brain
. The excess cerebrospinal fluid (CSF) in the brain flows through the shunt to another part of the body, usually the chest or abdo cavity - from here, it’s absorbed into your bloodstream
How does endoscopic third ventriculostomy work
Hole made in the floor of the 3rd ventricle to allow the trapped CSF to bypass cerebral aqueduct and escape to the brain’s surface, where it can be absorbed
Most common type of shunt used for hydrocephalus
Ventriculo-peritoneal
Treatment of acute hydrocephalus
External ventricular drain
What is normal pressure hydrocephalus
Characterised by the clinical features of hydrocephalus (i.e., levodopa-unresponsive gait apraxia +/- urinary incontinence or cognitive impairment), but without significantly elevated CSF pressure
Despite this, the condition responds to a reduction in CSF pressure and/or a CSF diversion procedure
What condition is normal pressure hydrocephalus a reversible cause of
Dementia
Symptoms/signs of normal pressure hydrocephalus (3)
Wet, wobbly, wacky:
Urinary incontinence
Gait disturbance (unusual walking)
Cognitive impairment
Investigations of normal pressure hydrocephalus (3)
CT
MRI
Lumbar puncture + CSF tap (i.e. lumbar drain) - if LP doesn’t improve symptoms
Treatment of normal pressure hydrocephalus (1)
Surgery only if lumbar puncture/ lumbar drain was proven beneficial:
Shunt placement - ventriculoperitoneal shunt
Place the wet, wobbly and wacky symptoms in order of which will most likely improve
Gait > incontinence > memory
What vertebral level are LPs performed
Between L3 and L4
or L4 and L5
What position does the patient have to lie in when doing an LP
Lateral decubitus position - maximally flex spine with chin near chest and knees near chest
-usually lying on their left side
Indications of an LP (5)
Meningitis Encephalitis Subarachnoid haemorrhage Malignancy Idiopathic intracranial hypertension
Contra-indications of an LP (5)
Cardio or resp instability
Localised skin infection over puncture site
Evidence of unstable bleeding disorder
Increased ICP – as you can cause herniation syndrome
(HOWEVER, IS NOT A CONTRAINDICATION OF CoH as lumbar puncture would relieve the pressure)
Chiari malformation
When doing an LP, will hear 2 pops when inserting spinal needle - what is being punctured in the first and second pop
Ligamentum flavum
Then dura mater
Complications of an LP (7)
Post dural puncture headache – MOST COMMON
Apnoea – temporary stop of breathing
Back pain – maybe disc herniation
Bleeding or fluid leak around spinal cord
Infection
Nerve trauma
Brainstem herniation
Management of a post dural puncture headache (4)
Lie flat
Hydration
Caffeine
Epidural blood patch - injecting own blood into the puncture site, clotting factors of the blood patch up the hole
Prevention of a post dural puncture headache (spinal headache) (2)
Using smaller diameter or atraumatic needles
Passing spinal needle parallel to longitudinal fibres of dura
Management of nerve root trauma caused by LP (2)
Remove needle immediately
Steroids
Management of brainstem herniation caused by LP (4)
Remove needle ASAP
Raise head of head to improve venous return from brain to heart
Mannitol - diuretic
Intubate
What properties of CSF can be analysed in CSF analysis (6)
Colour Opening pressure Culture + gram stain CSF glucose CSF protein count CSF cell count
