Hydrocephalus Flashcards
Define Hydrocephalus [2]
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]
What are the major types of Hydrocephalus? [3]
Define each one.
- 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
What are the causes for CoH?
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
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]
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
What causes Non-Communicating Hydrocephalus? (NCH) [3]
State 3 congenital causes of NCH
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
Is NCH rapid or gradual onset? Give 2 examples
Give 3 causes of communicating hydrocephalus
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:
- Thickening of leptominengies secondary to infection, hemorrhage, carcinoma
- Increased viscosity of CSF
- Excessive CSF production (choroid plexus papilloma)
First line investigation [1]
What is the earliest detectable radiological sign of hydrocephalus?
Give 2 other investigation options for hydrocephalus [3]
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
What signs of hydrocephalus are there on a radiograph? [4]
- Temporal horn dilation
- Ballooning of Lateral & 3rd ventricles
- Lateral sulci effaced (erased)
- Evans Ratio >30%
What is the Evans Ratio? [2]
Clinical significance? [1]
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
Hydrocephalus treatment based on:
Acute [1]
Communicating hydrocephalus [1]
NCH [1]
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)
What kinds of shunts are there for hydrocephalus [3]
Ventriculo-Peritoneal (VP)
- Most common
- Drains CSF to peritoneal cavity where its absorped
Lumbar-Peritoneal (LP)
- Can overdrain
Ventriculo-Atrial (VA):
- Dangerous
How does an EVD work?
Pros [1]
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
What is a 3rd ventriculostomy [2]
Treatment for NCH
Surgically open a hole in the floor of the 3rd ventricle [1]
Allows CSF to bypass the cerebral aqueduct [1]
How much do VP shunts fail?
Complications [5]
40% in 1st yr (50% by 5 yrs)
- Infection
- Skin erosion
- Occlusion
- Disconnection
- Over/underdrainage
What is NPH? [2]
Sequelae if untreated [1]
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
