🎯 Pathology

• accumulation of excess cerebrospinal fluid (CSF) in the intracranial cavity

• this can permit the build-up of CSF within the ventricular system, increasing the pressure, which can consequently cause the ventricles to widen, exerting pressure on the brain tissue

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💡 Types

• communicating hydrocephalus

  • no obstruction within the ventricular system

  • causes

    • impaired CSF reabsorption via arachnoid granulations (e.g. due to subarachnoid haemorrhage)

    • excess CSF production (e.g. due to tumour of the choroid plexus)

    • normal pressure hydrocephalus

• non-communicating

  • there is an obstruction to the flow of CSF in the ventricular system

  • causes

    • tumour

    • congenital malformation (e.g. agenesis of the foramen of Monro, or stenosis of the cerbral aqueduct)

  • may occur anywhere within the ventricles but tends to occur at narrow areas such as the interventricular foramen of Monro, cerebral aqueduct or the fourth ventricle

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🩺 Clinical features

• signs and symptoms are due to raised intracranial pressure (the brain is being compressed)

  • headache that is worse in the morning, lying down and with Valsalva maneouvre

  • papilloedema (swelling of the optic disc)

  • abducens nerve compression leading to diplopia and impaired abduction of the eye

  • nausea and vomiting 

    • the area responsible for nausea and vomiting is called the area postrema, which constitutes a region called the "chemoreceptor zone" where the blood-brain barrier remains incomplete, allowing the entry of endogenous substances such as toxins and drugs which can potentially trigger nausea and vomiting​

  • Cushing’s triad:

    • wide pulse pressure

    • bradycardia

    • irregular respirations

    • raised intracranial pressure can lead to brain herniation which can result in comatose

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🕵️‍♂️ Investigations

• neuroimaging

  • 1st line: head CT

    • enlarged ventricles

    • may show a “Mickey Mouse” appearance (ballooning of the frontal horns of the lateral ventricles and the third ventricle) which may be indicative of cerebral aqueduct stenosis

  • best: MRI

    • can delineate soft tissues including tumours, and be manipulated to different sequences (such as T1, T2 and FLAIR)

• lumbar puncture (done for communicating hydrocephalus)

  • may be diagnostic and therapeutic (symptoms will be relieved temporarily)

  • contraindicated for non-communicating as removal of CSF from the lumbar can create a pressure gradient, increasing the risk of brain herniation

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💆‍♂️ Management

• if left untreated, permanent brain damage can ensue

• non-communicating hydrocephalus

  • initial: external ventricular drain

  • long-term: ventriculoperitoneal (VP) shunt

• communicating hydrocephalus

  • treat the underlying cause (usually via surgery)

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⚡️ Normal-pressure hydrocephalus

• typically seen in elderly patients

• the cause is unknown, although it has been postulated it may be the result of impaired absorption of CSF at the arachnoid granulations

• characterised by the triad:

  • gait disturbance

  • urinary incontinence

  • dementia

• symptoms may temporarily improve following a lumbar puncture​