Hydrocephalus and Lumbar Puncture Flashcards
what is hydrocephalus?
a conditions where there is excess cerebrospinal fluid within the intracranial space and the intra-ventricular spaces.
where is the majority of CSF produced?
the choroid plexus:
> temporal horn roofs and body floors of lateral ventricles
> posterior 3rd ventricle roof
> caudal 4th ventricle roof
describe the CSF production process
it is metabolically active, sodium is pumped into the subarachnoid pace and water follows from the blood vessels
describe the CSF pathway
> from the 2 lateral ventricles
through the foramen of monro into the 3rd ventricle
through the cerebral aqueduct into the 4th ventricle
through either the foramen luschka (paired) or foramen magendie (midline)
subarachnoid space around the brain and spinal cord
reabsorption into venous sinuses
how is CSF reabsorbed back into the venous system?
through numerous arachnoid granulations along the Dural venous sinuses which contain arachnoid villi.
how do arachnoid villi function?
they are a pressure dependent one way valves that open when the intracranial pressure is 3 to 5cm h2o greater than dural venous sinus pressure
what drives CSF reabsorption?
the pressure gradient between the intracranial space and the venous system
name the two major distinctions of hydrocephalus
> communicating hydrocephalus
> non-communicating hydrocephalus
describe communicating hydrocephalus
the CSF can travel from the choroid plexus to the arachnoid granulations
what happens if CSF production is larger than CSF resorption?
there is communicating hydrocephalus
what is the result of communicating hydrocephalus?
> ventricular system dilates uniformly
> intracranial pressure rises
what rare condition could lead to overproduction of CSF?
choroid plexus papillomas
how can communicating hydrocephalus present in children whose cranial sutures have not fused?
> disproportionate increase in head circumference compared to the rest of the face, prominent frontal bossing
venous scalp distension
failure to thrive
what signs and symptoms can be seen in communicating hydrocephalus in a patient with fused sutures?
> papilledema
gait disturbance
6th cranial nerve palsy
upgaze difficulty
what is the aetiology of communicating hydrocephalus?
> infection (bacterial meningitis)
subarachnoid haemorrhage
post operative
head trauma
when can neurological decline due to communicating hydrocephalus be rapid?
if a significant number of arachnoid granulations are impaired there will be a rapid decline in CSF reabsorption due to high turnover is a normal individual
when does non-communicating hydrocephalus occur?
whenever there is any physical obstruction to the normal flow of CSF before it leaves the ventricles
what can cause non-communicating hydrocephalus?
> aqueductal stenosis > tumours > cysts > infection > haemorrhage/haematoma > congenital malformations/conditions
what is the earliest radiographical indicative finding of the development of hydrocephalus?
dilation of the temporal horns of the lateral ventricles (in most young and middle aged patients these should normally be invisible)
what is the treatment for acute hydrocephalus?
surgical: external ventricular drain. if this cannot be maintained indefinitely then a permanent shunt will be required.
what different types of shut replacement is available for communicating hydrocephalus treatment?
> ventriculo-peritoneal
lumbar peritoneal
ventriculo-atrial (in peritoneal failure)
what is the treatment for non-communicating hydrocephalus?
> surgical removal of the obstructing lesion can sometimes avoid shunt
third ventriculostomy
describe third ventriculostomy
a hole is surgically opened in the floor of the third ventricle so CSF flows out into the inter-peduncular cistern and pre-pontine space (bypassing the cerebral aqueduct)
how many shunts fail in 5 years of placement?
50%
why can shunts fail?
> mechanical failure > disconnection > migration > over drainage > underdrainage > infection > skin erosion
what is a rare preventable/reversible cause of dementia?
normal pressure hydrocephalus
what are the signs and symptoms of normal pressure hydrocephalus?
> urinary incontinence
gait disturbance: wide stance, short shuffling steps
quickly progressive dementia
what would you see on CT/MRI in normal pressure hydrocephalus?
communicating hydrocephalus
what is the treatment for normal pressure hydrocephalus?
programmable VP shunt replacement
what is the prognosis of normal pressure hydrocephalus?
> outcome is improved if the symptoms have been present for a shorter period of time
dementia is the least likely signs to improve with shunting
gait is the most likely to improve with shunting
what is lumbar puncture used to diagnose?
> meningitis > meinigoencephalitis > subarachnoid haemorrhage > malignancy > idiopathic intracranial hypertension > infusion of drugs
what are the contraindications for a lumbar puncture?
> unstable patient with cardiovascular or respiratory instability
localised skin/soft tissue infection over the puncture site
evidence of unstable bleeding disorder
increased intracranial pressure
when should you do a head CT before a lumbar puncture?
if focal neurological findings are present to rule out impending cerebral mass herniation
when can neurological deterioration occur form a lumbar puncture?
if it is done below the level of a complete subarachnoid block
in what patients should you be cautious about a lumbar puncture?
chiari malformations
describe the lateral decubitus position
> minimally flexed spine without compromising airway
alignment of feet, knees and hips
position head to left if right handed or vice versa
what level is a lumbar puncture usually carried out at in an adult?
L3-L4 or L4-L5
describe the procedure of a lumbar puncture
> cleanse the skin with provadine iodine radially to 10cm and ALLOW TO DRY
drape with fenestrated drape around site
anesthetise with lidocaine if topical not used
insert the spinal needle with stylet with bevel up to keep the cutting edge parallel with the nerve and ligament fibres, aim towards the umbilicus
when the pop is felt remove the stylet, checking for CSF
what does a pop of sudden decrease in resistance indicate in a lumbar puncture?
that the ligamentum flavum and dura are punctured
what should you do if there is no fluid after the stylet is removed?
> rotate the needle
> reinsert the stylet and advance needle slowly checking frequently
in low flow situations what can increase the CSF pressure during a lumbar puncture?
jugular vein compression
what should you do if bony resistance is felt in a lumbar puncture?
> immediately: you are not in spinal interface
> deeply: withdraw the needle to skin surface and redirect more cephalad and increase patient flexion
what should you do if bloody fluid does not clear or a clot results during a lumbar puncture?
withdraw the needle and reattempt at a different interspace
describe manometry in a lumbar puncture
> when CSF flows attach the manometer with a 3-way stopclock
read column when highest level is achieved and respiratory variation is noted
pressure can only be accurately measured in lateral decubitus position in the relaxed patient
check closing pressure with manometer
reinsert stylet and remove needle in one motion
cleanse back and cover puncture site
what are the three different vials collected for?
> culture and gram stain
glucose and protein
cell count and differential
what is the lumbar puncture position in an infant?
seated position with maximal spinal flexion:
> hold infants hands between flexed legs with one hand and flex head with the other
when is the paramedian (lateral) approach used
patients who have calcifications from repeat lumbar puncture or anatomic abnormalities
through what does the needle pass through in a lumbar puncture in the paramedian approach?
through erector spinae muscles and ligamentum flavum
what complications can arise from a lumbar puncture?
> headache > apnea > back pain (occasionally with short lived referred limp) > blleding/fluid leak > infection, pain > haematoma > subarachnoid epidermal cyst > ocular nerve palsy > nerve trauma > brainstem herniation
describe a spinal headache
> bilateral
improves if supine
last hours to weeks
treat with hydration and caffeine or an epidural blood patch
what are the risk factors for a spinal headache?
> female
18-30
low BMI
prior spinal headache
how can you avoid a spinal headache?
> passing needle parallel to longitudinal fibres of dura
replacing stylet before removing the needle
small diameter needles
atraumatic needles
describe nerve root trauma
> feels like electric shocks or dysthesias
back pain can persist for months
rarely permanent
what should be done if pain from nerve root trauma persists?
> corticosteroids
> electromyogram/nerve conduction velocity studies
how may herniation manifest?
altered mental status followed by cranial nerve abnormalities and cushing triad
when does an epidermal inclusion cyst?
rare, occurring when a core of skin is driven into spinal or paraspinal space with hollow needle. it is due to use of stylet so don’t remove it until through the skin
what alternatives are available is CSF sample is critical?
> someone else do it
bedside ultrasound
radiographic guided procedures (fluoroscopy, ultrasound, CT)
cisterna magna tap
