Hydrocephalus

Question 1

Define Hydrocephalus [2]

Answer 1

Hydrocephalus is defined as a condition in which there is an excessive volume of cerebrospinal (CSF) fluid within the ventricular system of the brain [1] and is caused by an imbalance between CSF production and absorption [1]

Question 2

What are the major types of Hydrocephalus? [3]

Define each one.

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 hydrocephalus with acute onset present in adults? [6]
How does hydrocephalus present in infants? [3]

What might you see on examination of an infant with hydrocephalus? [5]

Answer 4

Adults: symptoms of raised ICP:

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

Infants:

• Irritability
• Impaired conscious level
• Vomiting

Signs OE:

• Tense anterior fontanelle
• Cracked pot sound on skull percussion
• Increased skull circumference
• ‘Setting sun appearance’ - Lid retraction + impaired up gaze
• Thin scalp with dilated veins

Question 5

What causes Non-Communicating Hydrocephalus? (NCH) [3]

State 3 congenital causes of NCH

Answer 5

In order of likelihood:

• Aqueduct Stenosis caused by adhesions from infection/hemorrhage
• Tumours/Masses (E.g. pineal tumour or Ependymoma)
• Cysts (e.g. colloid cyst at foramen of monro)

Congenital causes:

• Congenital aqueduct stenosis
• Dandy walker syndrome
• Chiari malformation

Question 6

Is NCH rapid or gradual onset? Give 2 examples

Give 3 causes of communicating hydrocephalus

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)

CoH causes:

1. Thickening of leptominengies secondary to infection, hemorrhage, carcinoma
2. Increased viscosity of CSF
3. Excessive CSF production (choroid plexus papilloma)

Question 7

First line investigation [1]
What is the earliest detectable radiological sign of hydrocephalus?

Give 2 other investigation options for hydrocephalus [3]

Answer 7

Computed Tomography Head San
Dilation of the Lateral Ventricle’s Temporal Horns

MRI
LP (therapeutic and diagnostic) ONLY for communicating hydrocephalus will cause herniation in obstructive

Question 8

What signs of hydrocephalus are there on a radiograph? [4]

Answer 8

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

Question 9

What is the Evans Ratio? [2]

Clinical significance? [1]

Answer 9

Ratio of maximum 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

Hydrocephalus treatment based on:
Acute [1]
Communicating hydrocephalus [1]
NCH [1]

Answer 10

Acutely:
- External Ventricular Drain (EVD)

CoH:
A shunt must be in place 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 [3]

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?

Pros [1]

Answer 12

Catheter placed through scalp into lateral ventricle draining CSF to the patients bedside [1]

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

Question 13

What is a 3rd ventriculostomy [2]

Answer 13

Treatment for NCH
Surgically open a hole in the floor of the 3rd ventricle [1]
Allows CSF to bypass the cerebral aqueduct [1]

Question 14

How much do VP shunts fail?

Complications [5]

Answer 14

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

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

Question 15

What is NPH? [2]

Sequelae if untreated [1]

Answer 15

Normal Pressure Hydrocephalus is a unique form of non-obstructive hydrocephalus characterised by large ventricles [1] but normal intracranial pressure [1]

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

Question 16

How does NPH present? [3]

Answer 16

Hakin-Adam’s Triad:

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

Question 17

How would you investigate a case of NPH? [2]

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 [1]

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