Hydrocephalus Flashcards
What are the three different ways of classifying hydrocephalus?
Infantile or childhood/adult, acute or chronic, obstructive or communicating
What are the three causes of hydrocephalus?
Something obstructing the flow of CSF, a problem absorbing CSF, too much production of CSF
Describe obstructive hydrocephalus?
Hydrocephalus caused by something obstructing the flow of CSF e.g. a blockage in the ventricular system or outflow from the ventricular system
Describe communicating hydrocephalus?
Hydrocephalus caused by impaired CSF absorption by the arachnoid granulations
What can obstructive hydrocephalus also be known as? Why is this?
Non-communicating hydrocephalus, the CSF in the ventricles does not communicate with the CSF in the subarachnoid space
Hydrocephalus leads to intracranial accumulation of CSF which causes what?
Increased ventricular size and raised ICP
How does acute hydrocephalus present?
With features of raised ICP: patients develop acute headache with N+V as well as a deterioration in conscious level
What are some extra features of acute hydrocephalus?
Irritability in young children and ‘sunsetting’ eyes
What causes a sunsetting gaze?
Impairment of upward gaze caused by pressure on the midbrain vertical gaze centres
How does chronic hydrocephalus usually present?
Progressive deterioration in higher neurological functions and persistent pressure headache
What are some examples of deterioration in higher neurological function seen in chronic hydrocephalus that may be seen in children?
Failure to thrive, developmental delay, worsening school performance
Occasionally, congenital hydrocephalus can be picked up before birth on what investigation?
US scan
How may congenital hydrocephalus present?
Large head, thin and shiny scalp with visible veins, bulging or tense fontanelle, downward looking eyes
Why does congenital hydrocephalus cause an increase in head circumference?
Children < 18 months have skull bones that are still unfused to increased ICP causes the skull to enlarge
As well as the signs on the head, what are some more behavioural features that may be seen in congenital hydrocephalus?
Poor feeding, irritability, sleepiness, vomiting, muscle stiffness and spasms in the lower limbs
Some babies have a large head but do not have congenital hydrocephalus. When should you be concerned about this?
When the head circumference starts increasing centiles
Does congenital hydrocephalus go away?
No, it is usually a lifelong condition
Give an example of a vascular cause of hydrocephalus which is a) obstructive? b) communicating?
a) intracerebral haemorrhage b) subarachnoid haemorrhage
Give an example of an infective cause of hydrocephalus which is a) obstructive? b) communicating?
a) infective space occupying lesion e.g. abscess b) meningitis
Give an example of a tumour cause of hydrocephalus which is a) obstructive? b) communicating?
a) any tumour within or outside the ventricular system b) carcinomatous infiltration of the meninges
Congenital hydrocephalus is usually caused by what? Is this obstructive or communicating?
Stenosis of a part of the ventricular system, this is obstructive
What is the first line investigation for hydrocephalus?
CT
What will a CT show in obstructive hydrocephalus?
Dilation of the ventricle proximal to the site of obstruction
What will a CT show in communicating hydrocephalus?
Generalised dilatation of all ventricles
After a CT, further imaging for hydrocephalus may be done with what?
MRI
In neonates and infants with an open anterior fontanelle, what investigation can you use to monitor ventricular size?
Ultrasound
What is a ventriculoperitoneal shunt?
A catheter inserted into the ventricle to drain excess CSF into the peritoneum
What % of valves on a VP shunt function well after insertion?
80%
80% of valves on a VP shunt are no longer functioning after how long?
12 years
What are 3 common complications of a VP shunt?
Overdrainage, underdrainage and infection
What is the most common treatment option for hydrocephalus (assuming there is not an underlying cause to be treated)?
VP shunt
Underdrainage of CSF from a shunt can be caused by what?
Blockage or a displaced catheter
What can be used to reduce the risk of infection of a VP shunt?
Use of an antibiotic, impregnate the shunt with silver, use iodine
What are some less common complications of a VP shunt?
Intracerebral haemorrhage, seizure, umbilical fistula, erosion into abdominal viscera, ascites, inguinal hernia
What features may a blocked VP shunt present with?
Features of acute hydrocephalus: headache, vomiting, sunsetting gaze in children/lack of upgaze in adults, blurred vision
Why is blurred vision a worrying sign of a blocked VP shunt?
Suggests papilloedema which precedes blindness and can be a rapid progression
How do you investigate a blockage of a VP shunt?
Tap of the shunt or LP to send CSF to microbiology, CT head to show hydrocephalus
How is an acute VP shunt blockage treated?
Urgent surgery to replace the shunt
Aside from a VP shunt, what is another treatment that can be used for hydrocephalus?
Endoscopic 3rd ventriculostomy
What is endoscopic 3rd ventriculostomy?
A minimally invasive technique where a hole is made in the floor of the 3rd ventricle, creating an alternative channel for CSF to flow through to reach the subarachnoid space to be absorbed
If endoscopic 3rd ventriculostomy is successful, is a VP shunt needed?
No
When is endoscopic 3rd ventriculostomy a useful treatment?
If there is an obstruction distal to the 3rd ventricle (e.g. aqueduct stenosis or compressing tumours)
Is endoscopic 3rd ventriculostomy used for obstructive or communicating hydrocephalus?
Obstructive
If the VP shunt is overdraining CSF this can lead to collapse of the ventricles and tearing of blood vessels. What can this lead to?
Headaches, haemorrhage (subdural haematoma) and slit ventricle syndrome (ventricles decrease in size until they are too small)
What are some clinical features of normal pressure hydrocephalus?
Enlarged ventricles, normal or intermittently raised ICP, triad of ataxia, memory decline and incontinence
Is there potential for NPH to respond to CSF diversion?
Yes, but this is not permanent
NPH is a condition seen mostly (but not exclusively) in who?
Older age groups
Why is the diagnosis of NPH especially important?
It is one of the few treatable causes of dementia
What are some causes of NPH?
Primary (idiopathic) or secondary (post-inflammation) after meningitis, SAH, trauma or craniotomy
What are some differentials of NPH?
Cerebellar pathology and myelopathy (ataxia) as well as Alzheimer’s and vascular dementia
How may dementia as a result of NPH present?
Delay in answering questions, loss of spontaneity
Dementia as a result of NPH may progress to what?
Akinetic mutism
Does the dementia as a result of NPH stay the same all the time?
No, it fluctuates in severity
What symptom of NPH is essential to the diagnosis and usually precedes all other symptoms?
Ataxia
How can ataxia as a result of NPH present?
Difficulty rising from a chair, tendency to fall backwards, difficulties initiating gait, broad based shuffling gait
When is suspicion of NPH raised?
When there is hydrocephalus in association with one or more of the classic triad
What are some investigations that should be performed on all patients with suspected NPH?
CT, MRI, LP, infusion studies
What is an infusion study?
Record baseline ICP for a period of time and then challenge absorptive mechanisms with an infusion of saline
What would happen in an infusion study of a normal person?
After 10 minutes or so of the infusion, a new plateau is reached (usually within 10mmHg of the opening pressure) with a modest increase in pulse pressure
What happens in an infusion study of someone with impaired CSF absorption?
Amplitude of the pressure wave and the mean pressure increase dramatically
What are the 3 treatment options for NPH and how is the treatment decided?
VP shunt, LP shunt, endoscopic ventriculostomy: based on radiological appearance and patient preference
What is the most likely treatment for NPH?
VP shunt
How long do shunts last in NPH?
About a year
How can you tell if a shunt is going to work for a patient with NPH?
‘Tap test’ or LP drain both pre and post CSF drainage - if there is an improvement these patients should be shunted
What are some predictors of a poor outcome of treatment for NPH?
Pronounced dementia, secondary NPH
What are some predictors of a good outcome of treatment for NPH?
Gait problems predominate, primary NPH
With NPH treatment, some specific safeguarding is needed against what? How is this done?
Overdrainage and subdural haematoma formation; can be avoided with anti-syphon/adjustable pressure valve
