CSF, Hydrocephalus, Lumbar Puncture

Question 1

What is hydrocephalus?

Answer 1

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

Question 2

Where is CSF produced?

Answer 2

Choroid plexus

Question 3

What is the process by which CSF is produced?

Answer 3

It is a metabollically active process - requires ATP. Sodium is pumped into the subarachnoid space and water follows from the blood vessels.

Question 4

Where is choroid plexus found?

Answer 4

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.

Question 5

How much CSF is produced in the average adult per day?

Answer 5

Between 450 and 600 cc’s every day

Question 6

How much CSF is present in the average adult?

Answer 6

150 cc’s

Of this only 25 cc’s is within the brain ventricles

Question 7

Normally what does production equal?

Answer 7

Resorption

Question 8

How is CSF absorbed into the venous system?

Answer 8

Through numerous arachnoid granulations along the dural venous sinuses (especially the superior sagittal sinus)

Question 9

Where are arachnoid villi and what do they do?

Answer 9

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)

Question 10

What are the twp types of hydrocephalus?

Answer 10

Communicating hydrocephalus (or non-obstructive hydrocephalus)

Non-communicating hydrocephalus (or obstructive hydrocephalus)

Question 11

What is communicating hydrocephalus?

Answer 11

CSF travels freely from choroid plexus to the arachnoid granulations

(NO OBSTRUCTIONS)

Question 12

What is meand by non-communicating hydrocephalus?

Answer 12

CSF can’t travel freely from start to finish - there is an obstruction

Question 13

What is a common cause of communicating hydrocephalus?

Answer 13

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

Question 14

What are the signs and symptoms of CoH?

Answer 14

◦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.

Question 15

What are the causes of communicating hydrocephalus?

Answer 15

Infection (e.g meningitis)

SAH - Blood and blood breakdown products can cause scarring of arachnoid granulations

Post - operative

Head trauma

Etc

Question 16

What are the causes of non-communicating hydrocephalus?

Answer 16

Aqueductal stenosis

Tumours / cancers / masses

Cysts

Infection

Haemorrhage / haematoma

COngenital malformations / conditions

Question 17

Give an exmaple of slow onset non - communicating hydrocephalus and fast onset

Answer 17

Slow onset - likely to be a mass

Fast onset - likely to be intraventricular bleed

Question 18

What is the earliest consistent radiographical finding indicative of development of hydrocephalus?

Answer 18

Dilation of the temporal horns of the lateral ventricles (arrows). In most younger and middle-aged patients, these should be almost invisible.

Question 19

What are the radiographical findings of hydrocephalus?

Answer 19

Third ventricle will become balloned

Lateral ventricle size will increase

Peipheral sulci effaced - means eraced

Evans ratio - greater than 0.3 indicates ventriculomegaly

Question 20

What is the treatment for hydrocephalus?

Answer 20

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

Question 21

For communicating hydrocephalus, the mainstay of treatment is shunt placement what are the common shunts?

Answer 21

◦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)

Question 22

How can non-communicating hydrocephalus be treated surgically

Answer 22

Shunt can be avoided by removing the obstructing lesion

Question 23

Give examples of obstructung lesions

Answer 23

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

Question 24

What are the treatments for NCH?

Answer 24

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)

Question 25

What percentage of shunts fail within the first year?

Answer 25

40%

Question 26

What are the reasons for shunt failure?

Answer 26

Occlusion

Disconnection

Migration

Overdrainage

Underdrainage

Infection

Skin erosion

Question 27

What does treatment of normal pressure hydrocephalus prevent?

Answer 27

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

Question 28

What is the classic triad for normal pressure hydrocephalus?

Answer 28

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

Question 29

What is the treatment of choice for patients with NPH?

Answer 29

Programmable Ventriculo peritoneal shunt

Lumbar peritoneal shunt is often avoided because they tend to overdrain

Question 30

What are the indications of a lumbr puncture?

Answer 30

◦Meningitis

◦Meningoencephalitis

◦Subarachnoid hemorrhage

◦Malignancy – diagnosis and treatment

◦Idiopathic Intracranial Hypertension

◦Other neurologic syndromes

◦Infusion of Drugs or contrast

Question 31

What are contraindications to lumbar puncture?

Answer 31

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

Question 32

What are the stages of lumbar puncture?

Answer 32

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

Question 33

What causes the pop with sudden decrease in resistance indicate?

Answer 33

Indicates that the ligamentum flavum and dura are punctured

Question 34

What is a method in which CSF pressure can be increased in low flow situations?

Answer 34

Jugular vein compression

Question 35

What is used to determine opeining pressure?

Answer 35

Manometer - pressure can only be accurately measured in the lateral decubitis position and in the relaxed patient

Question 36

Where is CSF sent to?

Answer 36

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

Question 37

When would you use the sitting position for a lumbar puncture?

Answer 37

Infants

Obese patients where you cannot easily find their midline

Question 38

Who is recommended the paramedian (lateral) aproach for lumbar puncture?

Answer 38

Use for patients who have calcifications from repeated LPs or anatomic abnormalities

Question 39

What does the needle pass through in a paramedian approach?

Answer 39

Passes through erector spinae muscles and ligamentum flavum

Bypasses the supraspinal and interspinal ligaments

There is less chance of spinal headache

Question 40

What are complications associated with lumbar puncture?

Answer 40

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

Question 41

Who is susceptible to spinal headache?

Answer 41

Risk factors: female, age 18-30, lower BMI, hx of HA, prior spinal HA

Question 42

How can spinal headaches be improved?

Answer 42

Bilateral HA improves when supine

Hydration

Caffiene either PO or IV

Epidural blood pouch

Question 43

How can spinal headache be avoided?

Answer 43

◦Passing needle bevel parallel to longitudinal fibers of dura

◦Replacing stylet before removing needle

◦Using small diameter needles

◦Using atraumatic needles

Question 44

What are signs of nerve trauma / irritation during lumbar puncture?

Answer 44

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)

Question 45

What should be done in response to nerve root trauma?

Answer 45

Withdraw needle immediately

If pain or motor weakness persists, start corticosteroids

Electromyogram/nerve conduction velocity studies should be scheduled if pain persists

Question 46

What are the signs of herniation (brainstem)?

Answer 46

Altered mental status initially followed by cranial nerve abnormalities and cushing triad

Question 47

What is the protocol if there is suspected braistem herniation?

Answer 47

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

Question 48

What causes an epidermal inclusion cyst?

Answer 48

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

Question 49

What are alternative methods of procedure for lumbar puncture?

Answer 49

Use anaesthesia

Bedside ultrasound for difficult LP’s

Radiographic guided procedure (fluroscopy, ultrasound, CT)

Cisterna magna tap

Question 50

What are features of CSF?

Colour?

Opening pressure?

Protein level

Glucose level

Serum glucose

WCC

Answer 50

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)

Question 51

How if csf transported?

Answer 51

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