Define Hydrocephalus?
Excess CSF in the intracranial space (specifically the intraventricular spaces) causing dilation of the ventricles and many symptoms
What are the major types of Hydrocephalus?
- 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 CoH present?
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
What causes Non-Communicating Hydrocephalus? (NCH)
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
Is NCH rapid or gradual onset?
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)
What is the earliest detectable sign of hydrocephalus?
Dilation of the Lateral Ventricle’s Temporal Horns on a radiograph
Usually they should be virtually invisible
What signs of hydrocephalus are there on a radiograph?
- Temporal horn dilation
- Ballooning of Lateral & 3rd ventricles
- Lateral sulci effaced (erased)
- Evans Ratio >30%
What is the Evans Ratio?
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
How do we treat hydrocephalus?
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)
What kinds of shunts are there for hydrocephalus?
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?
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
What is a 3rd ventriculostomy?
Treatment for NCH
Surgically open a hole in the floor of the 3rd ventricle
Allows CSF to bypass the cerebral aqueduct
How much do VP shunts fail?
40% in 1st yr (50% by 5 yrs)
- Infection
- Skin erosion
- Occlusion
- Disconnection
- Over/underdrainage
What is NPH?
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
How does NPH present?
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”)
How would you investigate a case of NPH?
- CT/MRI would appear as CoH
- LP would show normal opening pressure (symptoms improve as you remove CSF)
How do you treat NPH?
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.
