CSF, Hydrocephalus, Lumbar Puncture

Question 1

What is hydrocephalus?

Answer 1

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

an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull

Question 2

Where and how is CSF made?

Answer 2

The majority of CSF is produced by the choroid plexus within the brain through a metabolically active process (i.e. requires ATP) whereby sodium is pumped into the subarachnoid space, and water follows from the blood vessels

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 3

How much CSF is ther ein the brain every day?

Answer 3

The average adult brain produces between 450 and 600 cc’s of CSF every day

At any given moment, there is only ~150 cc’s of CSF present in the average adult; of this, only ~25 cc’s is within the brain ventricles

So, the CSF volume turns over three to four times 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

Question 4

The CSF ________/________system exists in a delicate balance under normal conditions

Answer 4

The CSF production/resorption system exists in a delicate balance under normal conditions

Question 5

Describe the CSF pathway

Answer 5

From the lateral ventricle, CSF travels through the foramen of Monro into the 3rd ventricle, then passes through the Cerebral Aqueduct [of Sylvius] into the 4th ventricle. Then exits the 4th ventricle through either of two Foramina of Luschka (“L” is for Lateral/Luschka) or the single Foramen of Magendie (“M” is for Midline/Magendie)

After exiting the 4th ventricle, the CSF flows through the subarachnoid space over and around the brain and spinal cord, and is eventually reabsorbed into the venous (blood) system through numerous arachnoid granulations along the dural venous sinuses (especially the superior sagittal sinus)

Question 6

How is CSF absorbed?

Answer 6

Arachnoid granulations contain arachnoid villi, which function as pressure-dependent one-way valves that open when the ICP is ~3 to 5 cm H20 greater than dural venous sinus pressure

Remember - CSF production is a metabolically active process which uses ATP, whereas CSF resorption is a passive process that is driven by the pressure gradient between the intracranial space (ICP) and the venous system (~CVP)

Question 7

What are the 2 types of hydrocephalus?

Answer 7

Communicating Hydrocephalus (CoH) - also known as “non-obstructive” hydrocephalus

Non-communicating Hydrocephalus (NCH) - also known as “obstructive” hydrocephalus

Question 8

What is the difference between “Communicating” and “Non-communicating” hydrocephalus?

Answer 8

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

If the CSF can’t travel freely from start to finish, then you’ve got an “obstruction” and non-communicating hydrocephalus

Question 9

What tends to be the reason for communicating hydrocephalus being caused?

Answer 9

In the vast, vast majority of cases, this represents a problem with CSF resorption; simply put, it cannot keep the pace with CSF production

Normal CSF production = resorption

Comm. Hydrocephalus CSF production > resorption

As a result, the ventricular system dilates uniformly, and ICP rises

Question 10

The normal CSF system exists in a dleicate balance, what can disrupt this?

Answer 10

A major insult is not required to upset this balance; sometimes, a very slight disturbance is enough to tip the scales such that, over time, communicating hydrocephalus results

Question 11

In communicating hydrocephalus, the main cause is the CSF not being absorbed fast enough but what may be the other rarer cause of communicating hydrocephalus?

Answer 11

Very rarely, there is overproduction of CSF (rather than under-absorption) which leads to disruption of this balance, and development of communicating hydrocephalus

This is rare, but Choroid Plexus Papillomas have been known to present this way

Do NOT say this as the first answer!

Question 12

What are the symptoms and signs of communicating hydrocephalus?

Answer 12

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; H/A, N/V, papilledema, gait disturbance, 6th cranial nerve palsy, upgaze difficulty, etc.

Question 13

What is the aetiology of communicating hydrocephalus?

Answer 13

Infection (incidence after bacterial meningitis can approach 30%)

Subarachnoid Hemorrhage (blood and blood breakdown products cause scarring of arachnoid granulations)

Post-operative

Head trauma

Etc.

Question 14

Although we usually think of Communicating Hydrocephalus as being a “gentle” disruption of the balance between CSF production and resorption that occurs over time, sometimes there can be a sizeable insult that causes an ______ disruption of the balance, and CSF resorption is suddenly (and dramatically) reduced

Answer 14

acute

Question 15

a dramatic decline in CSF resorption ability can represent an __________

Answer 15

emergency

Question 16

When may hydrocephalus develop rapidly?

Answer 16

If significant number of arachnoid granulations are impaired, say, by subarachnoid blood (from a ruptured aneurysm), hydrocephalus can develop very quickly

Neurological decline in such a situation can be rapid, with patients becoming sleepy, then obtunded, then requiring intubation

Question 17

When does non-communicating hydrocephalus occur?

Answer 17

Non-communicating hydrocephalus occurs whenever there is ANY physical obstruction to the normal flow of CSF before it leaves the ventricles

Question 18

What are the causes of non-communicating hydrcephalus?

Answer 18

Many causes:

Aqueductal stenosis

Tumors/Cancers/Masses

Cysts

Infection

Hemorrhage/hematoma

Congenital malformations/conditions

Etc.

Question 19

Non-communicating hydrocephalus can result from CSF flow obstruction at ________ along the intraventricular pathway

Answer 19

any point

Question 20

Processes that have developed over longer periods of time (i.e. masses, etc) usually cause _________ development of symptoms

Answer 20

gradual

Question 21

Acute processes (i.e. intraventricular bleed) can cause acute obstruction with ______ mental status decline (just like we discussed previously)

Answer 21

rapid

Question 22

The earliest consistent radiographical finding indicative of development of hydrocephalus?

Answer 22

dilation of the temporal horns of the lateral ventricles (arrows)

In most younger and middle-aged patients, these should be almost invisible

Question 23

What other changes can be seen on a radiograph in hydrocephalus?

Answer 23

The third ventricle will become ballooned

Lateral ventricle size increase

Peripheral sulci effaced

Evans Ratio ->30% /Ventricular index >50%

Question 24

What is the treatment of hydrcephalus?

Answer 24

Treatment for Hydrocephalus remains surgical

Acute hydrocephalus, whether communicating or not, usually necessitates urgent or emergent placement of an External Ventricular Drain (EVD - catheter passed through the patient’s scalp and skull into lateral ventricle, that drains CSF to a collection system kept at the patient’s bedside)

Question 25

What are the negatives of EVD

Answer 25

Common procedure but infection risk is high

EVD cannot be maintained indefinitely; usually, if the patient is unable to tolerate weaning/clamping of the EVD prior to removal, a permanent shunt will be required

Question 26

What is the treatment ofr communicating hydrocephalus?

Answer 26

For communicating hydrocephalus, the mainstay of treatment is shunt placement

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

Acute communicating hydrocephalus patients (i.e. SAH) can sometimes be managed with EVD with successful weaning and no shunt placement, but a significant number of these patients eventually need shunt placement weeks or months later

Question 27

What is the treatment of non-communicating hydrocephalus?

Answer 27

NCH treatment also surgical, but sometimes shunt can be avoided by removing the obstructing lesion:

Colloid cyst at anterior 3rd ventricle causing ball/valve obstruction of Foramen of Monro

Pineal region tumor causing compression of cerebral aqueduct

Ependymoma blocking 4th ventricular CSF outlets

Many, many more!

Question 28

When treating non-communicating hydrocephalus, in addition to surgical removal of obstructive lesion and shunt placement, what else may be done?

Answer 28

Third Ventriculostomy is an option for non-communicating hydrocephalus

Often performed in conjunction with VP shunt placement

Hole is surgically opened in floor of third ventricle so CSF flows out into the interpeduncular cistern and pre-pontine space (bypasses cerebral aqueduct)

Question 29

Every patient with a history of VP shunt placement who presents with a headache is NOT automatically having what?

Answer 29

a shunt malfunction/infection

Yes, you should consider that in your differential, but still work it up appropriately. After all, the vast majority of patients with headaches don’t have VP shunts

Question 30

Do VP shunts fail?

Answer 30

VP shunts can and do fail for any of a number of reasons

The incidence of shunt failure is as much as 40% the first year

Question 31

What is Normal Pressure Hydrocephalus (NPH)?

Answer 31

This is important and you MUST know it because it is one of the rare preventable and/or reversible causes of dementia

Under-recognition leads many patients with NPH to be diagnosed with Alzheimer’s or age-related dementia and they never seek (or receive) treatment

Question 32

What is the classic triad seen in NPH

Answer 32

Classic triad: “Wet, Wobbly, and Wacky!”

Question 33

What is seen on investigation of NPH?

Answer 33

Communicating hydrocephalus on CT/MRI

Lumbar Puncture (LP):

• Normal opening pressure
• Symptoms improve with CSF removal
• Gait assessment (time walk and turns) and MMSE

Question 34

What is the treatment of NPH?

Answer 34

Procedure of choice for patients felt to be suffering from NPH is Programmable VP shunt placement

Question 35

What is the prognosis of NPH?

Answer 35

Chance of outcome is improved if symptoms have been present for shorter period of time (meaning that failure to recognize these patients delays their treatment and lessens their chances!)

Least likely symptom to improve with shunting is dementia - It’s always a worse sign once mentation gets involved!

Most likely symptom to improve is gait>incontinence>memory

Question 36

Overall what is it you do with NPH patients?

Answer 36

Good history taking and time with patients and family is key to nailing this diagnosis. Just because they’ve got the classic triad doesn’t mean it may not be Alzheimer’s (it often will be); but if you keep NPH on your differential and consider it rather than writing off all dementia as Alzheimer’s, you will have the opportunity to make a fantastic difference in the lives of many patients

Question 37

What are the indications for doing a lumbar puncture?

Answer 37

To obtain CSF for the diagnosis of:

Meningitis

Meningoencephalitis

Subarachnoid hemorrhage

Malignancy - diagnosis and treatment

Idiopathic Intracranial Hypertension

Other neurologic syndromes

Infusion of Drugs or contrast

Question 38

What are the contraindications for a lumbar puncture?

Answer 38

Unstable patient with cardiovascular or respiratory instability

Localized skin/soft tissue infection over puncture site

Evidence of unstable bleeding disorder

Platelets < 50,000 or clotting factor deficiency

Increased intracranial pressure:

^{- Head CT before study if focal neurologic findings present to rule out impending cerebral mass herniation}

^{- Normal CT does not preclude intracranial HTN}

^{- Do not delay antibiotics to obtain imaging studies when bacterial meningitis is strongly suspected}

Neurologic deterioration can occur if LP is done below the level of a complete spinal subarachnoid block

Caution in patients with Chiari malformations

Question 39

What position is required for a LP?

Answer 39

Spinal cord usually ends at L1-L2(check!), so sites for puncture are located at L3-L4 or L4-L5

Restrain patient in lateral lying down position

Maximally flex spine without compromising airway

Keep alignment of feet, knees and hips

Position head to left if right handed or vice versa

Question 40

What is the procedure of alumbar puncture?

Answer 40

Cleanse skin with povidone iodine from puncture site radially out to 10 cm and ALLOW TO DRY

Drape below patient and around site with fenestrated drape

Anesthetize with lidocaine if topical not used by

–Careful not to inject into a blood vessel or spinal canal

Insert spinal needle with stylet with bevel up to keep cutting edge parallel with nerve and ligament fibers

Aim towards umbilicus directing needle slightly cephalad

Hold needle firmly

A “pop” of sudden decrease in resistance indicates that ligamentum flavum and dura are punctured

Remove stylet and check for flow of spinal fluid

If no fluid, then: Rotate needle 90°, Reinsert stylet and advance needle slowly checking frequently for CSF

Jugular vein compression can increase CSF pressure in low flow situations

If bony resistance is felt immediately then you are not in the spinal interspace

If bony resistance is felt deeply, then withdraw needle to the skin surface and redirect more cephalad and increase patient flexion

If bloody fluid that does not clear or that clots results, then withdraw needle and reattempt at a different interspace

Question 41

What is manometry used in a LP?

Answer 41

When CSF flows, attach manometer to obtain opening pressure if desired

Pressure can only be accurately measured in lateral decubitus position and in the relaxed patient

Attach manometer with a 3-way stopcock when free flow of CSF is obtained

Read column when highest level is achieved and respiratory variation is noted

Question 42

How do you end a LP?

Answer 42

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

Check closing pressure with manometer, if desired

Reinsert stylet and remove needle in one quick motion

Cleanse back and cover puncture site

Question 43

What posiiton is a LP done is a child

Answer 43

sitting