Hydrocephalus

Question 1

Define Hydrocephalus?

Answer 1

Excess CSF in the intracranial space (specifically the intraventricular spaces) causing dilation of the ventricles and many symptoms

Question 2

What are the major types of Hydrocephalus?

Answer 2

• Communicating Hydrocephalus (CoH), CSF can travel all the way from the choroid plexus to the arachnoid granulations
• Non-communicating Hydrocephalus (NCH), also known as obstructive hydrocephalus
• Normal Pressure Hydrocephalus (NPH), its own clinical entity

Question 3

What are the causes for CoH?

Answer 3

Production > Reabsorption

Mostly its due to a reduction in reabsorption:

• Infection (e.g. bacterial meningitis)
• Subarachnoid Haemorrhage (Scars Arachnoid villi)
• Post-op
• Head Traums

Very Rarely it can be caused by a choroid plexus papilloma increasing CSF production

Question 4

How does CoH present?

Answer 4

Symptoms of raised ICP:

• N&V
• Headache
• Papilledema
• Gait Disturbance
• 6th Cranial Nerve Palsy
• Upgaze difficulty

In infants the skull will get excessively big too as sutures havent yet fused

Question 5

What causes Non-Communicating Hydrocephalus? (NCH)

Answer 5

In order of likelihood:

• Aqueductal Stenosis
• Tumours/Masses (E.g. pineal tumour or Ependymoma)
• Cysts (e.g. colloid cyst at foramen of monro)
• Infection
• Haemorrhage or Haematoma
• Some very rare Congenital Malformations

Question 6

Is NCH rapid or gradual onset?

Answer 6

Depends on the cause:

• A tumour will show a gradual increase in symptoms
• An intraventricular bleed blocking flow will cause rapid mental status decline (Sleepy -> Obtunded -> Needed Intubated)

Question 7

What is the earliest detectable sign of hydrocephalus?

Answer 7

Dilation of the Lateral Ventricle’s Temporal Horns on a radiograph

Usually they should be virtually invisible

Question 8

What signs of hydrocephalus are there on a radiograph?

Answer 8

• Temporal horn dilation
• Ballooning of Lateral & 3rd ventricles
• Lateral sulci effaced (erased)
• Evans Ratio >30%

Question 9

What is the Evans Ratio?

Answer 9

Ratio of Max width of ant horns of lateral ventricles – Max width of skullcap at level of foramen of monro

A ratio over 0.3 indicates ventriculomegaly

Question 10

How do we treat hydrocephalus?

Answer 10

Acutely:
- External Ventricular Drain (EVD)

CoH:
A shunt must be emplaced long term (often preceded by an EVD acutely)

NCH:

• Surgical removal of obstruction
• If not possible then a shunt
• Third Ventriculostomy (often combined with VP shunt)

Question 11

What kinds of shunts are there for hydrocephalus?

Answer 11

Ventriculo-Peritoneal (VP)

• Most common
• Drains CSF to peritoneal cavity where its absorped

Lumbar-Peritoneal (LP)
- Can overdrain

Ventriculo-Atrial (VA):
- Dangerous

Question 12

How does an EVD work?

Answer 12

Catheter placed through scalp into lateral ventricle draining CSF to the patients bedside

Allows you to adjust the amount drained and measure the current ICP

Question 13

What is a 3rd ventriculostomy?

Answer 13

Treatment for NCH
Surgically open a hole in the floor of the 3rd ventricle
Allows CSF to bypass the cerebral aqueduct

Question 14

How much do VP shunts fail?

Answer 14

40% in 1st yr (50% by 5 yrs)

• Infection
• Skin erosion
• Occlusion
• Disconnection
• Over/underdrainage

Question 15

What is NPH?

Answer 15

Normal Pressure Hydrocephalus

Its its own clinical entity

Important as its a preventable cause of dementia and is often mistaken for Alzheimer’s or aging

Question 16

How does NPH present?

Answer 16

Hakin-Adam’s Triad:

• Urinary Incontinence (“wet”
• Gait Disturbance (“Wobbly”) i.e. a wise stance with short shuffling steps and slow turning
• Quickly progressing dememtia (“Whacky”)

Question 17

How would you investigate a case of NPH?

Answer 17

• CT/MRI would appear as CoH

- LP would show normal opening pressure (symptoms improve as you remove CSF)

Question 18

How do you treat NPH?

Answer 18

Programmable VP shunt to remove CSF.

The earlier you treat it the better the prognosis with gait most likely to improve, then incontinence then memory.