CSF, Hydrocephalus, Lumbar Puncture Flashcards by Callum Anderson

What is hydrocephalus?

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

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Where is CSF produced?

Choroid plexus

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What is the process by which CSF is produced?

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

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Where is choroid plexus found?

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.

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

Between 450 and 600 cc’s every day

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How much CSF is present in the average adult?

150 cc’s

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

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Normally what does production equal?

Resorption

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How is CSF absorbed into the venous system?

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

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Where are arachnoid villi and what do they do?

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)

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What are the twp types of hydrocephalus?

Communicating hydrocephalus (or non-obstructive hydrocephalus)

Non-communicating hydrocephalus (or obstructive hydrocephalus)

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What is communicating hydrocephalus?

CSF travels freely from choroid plexus to the arachnoid granulations

(NO OBSTRUCTIONS)

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What is meand by non-communicating hydrocephalus?

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

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What is a common cause of communicating hydrocephalus?

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

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What are the signs and symptoms of CoH?

◦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.

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What are the causes of communicating hydrocephalus?

Infection (e.g meningitis)

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

Post - operative

Head trauma

Etc

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What are the causes of non-communicating hydrocephalus?

Aqueductal stenosis

Tumours / cancers / masses

Cysts

Infection

Haemorrhage / haematoma

COngenital malformations / conditions

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

Slow onset - likely to be a mass

Fast onset - likely to be intraventricular bleed

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

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

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What are the radiographical findings of hydrocephalus?

Third ventricle will become balloned

Lateral ventricle size will increase

Peipheral sulci effaced - means eraced

Evans ratio - greater than 0.3 indicates ventriculomegaly

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What is the treatment for hydrocephalus?

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

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

◦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)

How can non-communicating hydrocephalus be treated surgically

Shunt can be avoided by removing the obstructing lesion

Give examples of obstructung lesions

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

What are the treatments for NCH?

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)

What percentage of shunts fail within the first year?

40%

What are the reasons for shunt failure?

Occlusion Disconnection Migration Overdrainage Underdrainage Infection Skin erosion

What does treatment of normal pressure hydrocephalus prevent?

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

What is the classic triad for normal pressure hydrocephalus?

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

What is the treatment of choice for patients with NPH?

Programmable Ventriculo peritoneal shunt Lumbar peritoneal shunt is often avoided because they tend to overdrain

What are the indications of a lumbr puncture?

◦Meningitis ◦Meningoencephalitis ◦Subarachnoid hemorrhage ◦Malignancy – diagnosis and treatment ◦Idiopathic Intracranial Hypertension ◦Other neurologic syndromes ◦Infusion of Drugs or contrast

What are contraindications to lumbar puncture?

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

What are the stages of lumbar puncture?

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

What causes the pop with sudden decrease in resistance indicate?

Indicates that the ligamentum flavum and dura are punctured

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

Jugular vein compression

What is used to determine opeining pressure?

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

Where is CSF sent to?

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

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

Infants Obese patients where you cannot easily find their midline

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

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

What does the needle pass through in a paramedian approach?

Passes through erector spinae muscles and ligamentum flavum Bypasses the supraspinal and interspinal ligaments There is less chance of spinal headache

What are complications associated with lumbar puncture?

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

Who is susceptible to spinal headache?

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

How can spinal headaches be improved?

Bilateral HA improves when supine Hydration Caffiene either PO or IV Epidural blood pouch

How can spinal headache be avoided?

◦Passing needle bevel parallel to longitudinal fibers of dura ◦Replacing stylet before removing needle ◦Using small diameter needles ◦Using atraumatic needles

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

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)

What should be done in response to nerve root trauma?

Withdraw needle immediately If pain or motor weakness persists, start corticosteroids Electromyogram/nerve conduction velocity studies should be scheduled if pain persists

What are the signs of herniation (brainstem)?

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

What is the protocol if there is suspected braistem herniation?

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

What causes an epidermal inclusion cyst?

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

What are alternative methods of procedure for lumbar puncture?

Use anaesthesia Bedside ultrasound for difficult LP's Radiographic guided procedure (fluroscopy, ultrasound, CT) Cisterna magna tap

What are features of CSF? Colour? Opening pressure? Protein level Glucose level Serum glucose WCC

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)

How if csf transported?

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