CSF, Hydrocephalus and Lumbar Puncture

Question 1

What is hydrocephalus?

Answer 1

A general condition where there is excess CSF within the intracranial space, specifically the intraventricular spaces within the brain

Question 2

How is CSF produced?

Answer 2

Majority produced by choroid plexus that pumps sodium into the subarachnoid space with water following from the blood vessels

Question 3

Describe the pathway of CSF

Answer 3

From the lateral ventricles, CSF travels into the 3rd ventricle then into the cerebral aqueduct and into the fourth ventricle. It then exits the fourth ventricle and flows through the subarachnoid space over and around the brain and spinal cord. It is eventually reabsorbed into the venous system through numerous arachnoid granulations along the dural venous sinuses

Question 4

What are the two kinds of hydropcephalus?

Answer 4

Communicating/non-obstructive

Non-communicating/obstructive

Question 5

Describe the pathophysiology of communicating hydrocephalus

Answer 5

In most cases, CSF production is greater than CSF resorption, and so the ventricular system dilates and ICP rises
Rarely, there is overproduction of CSF and communicating hydrocephalus develops

Question 6

What are the signs and symptoms of communicating hydrocephalus?

Answer 6

In young children, disproportional increase in head circumference compared to the rest of the face and failure to thrive
In those who’s sutures have fused ie older children and up, present with symptoms of increased intracranial pressure: headache, N&V, papilloedema, gait, disturbance, 6th cranial nerve palsy, upgaze difficulty

Question 7

What are the causes of communicating hydrocephalus?

Answer 7

Infection
Subarachnoid haemorrhage
Post-operative
Head trauma

Question 8

When does non-communicating hydrocephalus occur?

Answer 8

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

Question 9

What are the causes of non-communicating hydrocephalus?

Answer 9

Aqueductal stenosis
Tumours/masses
Cysts
Infection
Haemorrhage/haematoma
Congenital malformations

Question 10

What is the first sign of development of hydrocephalus on MRI?

Answer 10

Dilation of the temporal horns of the lateral ventricles

Question 11

What signs of hydrocephalus can be seen on MRI?

Answer 11

Dilation of temporal horns of lateral ventricles
Third ventricle becomes ballooned
Lateral ventricle size increases
Peripheral sulci effaced

Question 12

How is acute hydrocephalus treated?

Answer 12

Surgically- placement of external ventricular drain (EVD- catheter passed into lateral ventricle through scalp)
Some patients may have successful weaning off EVD but many will need a shunt inserted

Question 13

What is the main complication of EVD?

Answer 13

High infection risk

Question 14

How is communicating hydrocephalus treated?

Answer 14

Surgical- shunt placement, ventriculo-peritoneal most used

Question 15

How is non-communicating hydrocephalus treated?

Answer 15

Surgical- shunt may be necessary but can be avoided if obstructing lesion is removed
Third ventriculostomy can also be used, often in conjunction with shunt

Question 16

What are the symptoms of normal pressure hydrocephalus?

Answer 16

Urinary incontinence
Gait disturbance
Quickly progressive dementia
(wet, wobbly and wacky)

Question 17

What condition can normal pressure hydrocephalus cause if left untreated?

Answer 17

Dementia

Question 18

What investigations can be useful in normal pressure hydrocephalus?

Answer 18

Looks like communicating hydrocephalus on CT/MRI

Lumbar puncture- normal opening pressure, symptoms improve with removal of CSF

Question 19

How is normal pressure hydrocephalus treated?

Answer 19

Surgically- programmable VP shunt placement

Question 20

What are the indications of lumbar puncture?

Answer 20

To obtain CSF for the diagnosis of:
Meningitis
Meningoencephalitis
Subarachnoid haemorrhage
Malignancy
Idiopathic intracranial hypertension
Infusion of drugs or contrast

Question 21

What are the contraindications to lumbar puncture?

Answer 21

Unstable patient with cardiovascular or respiratory instability
Localised skin/soft tissue infection over puncture site
Evidence of unstable bleeding disorder
Increased intracranial pressure
Neurologic deterioration can occur if LP done below the level of a complete spinal subarachnoid block
Caution in patient with Chiari malformations

Question 22

At what vertebral level should a lumbar puncture be done?

Answer 22

L3-L4 or L4-L5

Question 23

What should the different CSF samples from a lumbar puncture be tested for?

Answer 23

Culture and gram stain
Glucose and protein
Cell count and differential

Question 24

What are the complications of lumbar puncture?

Answer 24

Headache
Apnea
Back pain
Bleeding or fluid leak around spinal cord
Infection, pain, haematoma
Subarachnoid epidermal cyst
Ocular muscle palsy
Nerve trauma
Brainstem herniation

Question 25

What are the risk factors for a spinal headache as a complication of lumbar puncture?

Answer 25

Female
Aged 18-30
Lower BMI
History of headache
Prior spinal headache

Question 26

How is a spinal headache treated?

Answer 26

Supine position for at least two hours
Hydration
Caffeine either oral or IV
Epidural blood patch

Question 27

How does brainstem herniation present?

Answer 27

Altered mental status
Cranial nerve abnormalities
Cushing triad

Question 28

What is Cushing triad?

Answer 28

Bradycardia
Systolic hypertension
Irregular, decreased respirations

Question 29

What steps can be taken if a lumbar puncture fails and collection of CSF sample is critical?

Answer 29

Have someone else try- anaesthesia, neurology
Bedside ultrasound for difficult LP
Radiographic guided procedure
Cisterna Magna tap