Hydrocephalus and Lumbar Puncture

Question 1

what is hydrocephalus?

Answer 1

a conditions where there is excess cerebrospinal fluid within the intracranial space and the intra-ventricular spaces.

Question 2

where is the majority of CSF produced?

Answer 2

the choroid plexus:
> temporal horn roofs and body floors of lateral ventricles
> posterior 3rd ventricle roof
> caudal 4th ventricle roof

Question 3

describe the CSF production process

Answer 3

it is metabolically active, sodium is pumped into the subarachnoid pace and water follows from the blood vessels

Question 4

describe the CSF pathway

Answer 4

> 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

Question 5

how is CSF reabsorbed back into the venous system?

Answer 5

through numerous arachnoid granulations along the Dural venous sinuses which contain arachnoid villi.

Question 6

how do arachnoid villi function?

Answer 6

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

Question 7

what drives CSF reabsorption?

Answer 7

the pressure gradient between the intracranial space and the venous system

Question 8

name the two major distinctions of hydrocephalus

Answer 8

> communicating hydrocephalus

> non-communicating hydrocephalus

Question 9

describe communicating hydrocephalus

Answer 9

the CSF can travel from the choroid plexus to the arachnoid granulations

Question 10

what happens if CSF production is larger than CSF resorption?

Answer 10

there is communicating hydrocephalus

Question 11

what is the result of communicating hydrocephalus?

Answer 11

> ventricular system dilates uniformly

> intracranial pressure rises

Question 12

what rare condition could lead to overproduction of CSF?

Answer 12

choroid plexus papillomas

Question 13

how can communicating hydrocephalus present in children whose cranial sutures have not fused?

Answer 13

> disproportionate increase in head circumference compared to the rest of the face, prominent frontal bossing
venous scalp distension
failure to thrive

Question 14

what signs and symptoms can be seen in communicating hydrocephalus in a patient with fused sutures?

Answer 14

> papilledema
gait disturbance
6th cranial nerve palsy
upgaze difficulty

Question 15

what is the aetiology of communicating hydrocephalus?

Answer 15

> infection (bacterial meningitis)
subarachnoid haemorrhage
post operative
head trauma

Question 16

when can neurological decline due to communicating hydrocephalus be rapid?

Answer 16

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

Question 17

when does non-communicating hydrocephalus occur?

Answer 17

whenever there is any physical obstruction to the normal flow of CSF before it leaves the ventricles

Question 18

what can cause non-communicating hydrocephalus?

Answer 18

> aqueductal stenosis
> tumours
> cysts
> infection
> haemorrhage/haematoma
> congenital malformations/conditions

Question 19

what is the earliest radiographical indicative finding of the development of hydrocephalus?

Answer 19

dilation of the temporal horns of the lateral ventricles (in most young and middle aged patients these should normally be invisible)

Question 20

what is the treatment for acute hydrocephalus?

Answer 20

surgical: external ventricular drain. if this cannot be maintained indefinitely then a permanent shunt will be required.

Question 21

what different types of shut replacement is available for communicating hydrocephalus treatment?

Answer 21

> ventriculo-peritoneal
lumbar peritoneal
ventriculo-atrial (in peritoneal failure)

Question 22

what is the treatment for non-communicating hydrocephalus?

Answer 22

> surgical removal of the obstructing lesion can sometimes avoid shunt
third ventriculostomy

Question 23

describe third ventriculostomy

Answer 23

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)

Question 24

how many shunts fail in 5 years of placement?

Answer 24

50%

Question 25

why can shunts fail?

Answer 25

``` > mechanical failure > disconnection > migration > over drainage > underdrainage > infection > skin erosion ```

Question 26

what is a rare preventable/reversible cause of dementia?

Answer 26

normal pressure hydrocephalus

Question 27

what are the signs and symptoms of normal pressure hydrocephalus?

Answer 27

> urinary incontinence > gait disturbance: wide stance, short shuffling steps > quickly progressive dementia

Question 28

what would you see on CT/MRI in normal pressure hydrocephalus?

Answer 28

communicating hydrocephalus

Question 29

what is the treatment for normal pressure hydrocephalus?

Answer 29

programmable VP shunt replacement

Question 30

what is the prognosis of normal pressure hydrocephalus?

Answer 30

> 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

Question 31

what is lumbar puncture used to diagnose?

Answer 31

``` > meningitis > meinigoencephalitis > subarachnoid haemorrhage > malignancy > idiopathic intracranial hypertension > infusion of drugs ```

Question 32

what are the contraindications for a lumbar puncture?

Answer 32

> unstable patient with cardiovascular or respiratory instability > localised skin/soft tissue infection over the puncture site > evidence of unstable bleeding disorder > increased intracranial pressure

Question 33

when should you do a head CT before a lumbar puncture?

Answer 33

if focal neurological findings are present to rule out impending cerebral mass herniation

Question 34

when can neurological deterioration occur form a lumbar puncture?

Answer 34

if it is done below the level of a complete subarachnoid block

Question 35

in what patients should you be cautious about a lumbar puncture?

Answer 35

chiari malformations

Question 36

describe the lateral decubitus position

Answer 36

> minimally flexed spine without compromising airway > alignment of feet, knees and hips > position head to left if right handed or vice versa

Question 37

what level is a lumbar puncture usually carried out at in an adult?

Answer 37

L3-L4 or L4-L5

Question 38

describe the procedure of a lumbar puncture

Answer 38

> 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

Question 39

what does a pop of sudden decrease in resistance indicate in a lumbar puncture?

Answer 39

that the ligamentum flavum and dura are punctured

Question 40

what should you do if there is no fluid after the stylet is removed?

Answer 40

> rotate the needle | > reinsert the stylet and advance needle slowly checking frequently

Question 41

in low flow situations what can increase the CSF pressure during a lumbar puncture?

Answer 41

jugular vein compression

Question 42

what should you do if bony resistance is felt in a lumbar puncture?

Answer 42

> immediately: you are not in spinal interface | > deeply: withdraw the needle to skin surface and redirect more cephalad and increase patient flexion

Question 43

what should you do if bloody fluid does not clear or a clot results during a lumbar puncture?

Answer 43

withdraw the needle and reattempt at a different interspace

Question 44

describe manometry in a lumbar puncture

Answer 44

> 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

Question 45

what are the three different vials collected for?

Answer 45

> culture and gram stain > glucose and protein > cell count and differential

Question 46

what is the lumbar puncture position in an infant?

Answer 46

seated position with maximal spinal flexion: | > hold infants hands between flexed legs with one hand and flex head with the other

Question 47

when is the paramedian (lateral) approach used

Answer 47

patients who have calcifications from repeat lumbar puncture or anatomic abnormalities

Question 48

through what does the needle pass through in a lumbar puncture in the paramedian approach?

Answer 48

through erector spinae muscles and ligamentum flavum

Question 49

what complications can arise from a lumbar puncture?

Answer 49

``` > 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 ```

Question 50

describe a spinal headache

Answer 50

> bilateral > improves if supine > last hours to weeks > treat with hydration and caffeine or an epidural blood patch

Question 51

what are the risk factors for a spinal headache?

Answer 51

> female > 18-30 > low BMI > prior spinal headache

Question 52

how can you avoid a spinal headache?

Answer 52

> passing needle parallel to longitudinal fibres of dura > replacing stylet before removing the needle > small diameter needles > atraumatic needles

Question 53

describe nerve root trauma

Answer 53

> feels like electric shocks or dysthesias > back pain can persist for months > rarely permanent

Question 54

what should be done if pain from nerve root trauma persists?

Answer 54

> corticosteroids | > electromyogram/nerve conduction velocity studies

Question 55

how may herniation manifest?

Answer 55

altered mental status followed by cranial nerve abnormalities and cushing triad

Question 56

when does an epidermal inclusion cyst?

Answer 56

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

Question 57

what alternatives are available is CSF sample is critical?

Answer 57

> someone else do it > bedside ultrasound > radiographic guided procedures (fluoroscopy, ultrasound, CT) > cisterna magna tap