hydrocephalus Flashcards
definition of hydrocephalus
enlargement of the cerebral ventricular system because of excess CSF accumulation
subdivisible into obstructive and non-obstructive (or communication or non-communicating)
Hydrocephalus ex vacuo - apparent enlargement of ventricles but this is a compensatory change due to brain atrophy.
definition of normal pressure hydrocephalus
form of chronic communicating hydrocephalus
mainly affects elderly idnividuals >60ys
triad - urinary incontinence, dementia, ataxic gait
normal or episodic increase in ICP
aetiology of hydrocephalus
abnormal accumulation of CSF on the ventricles
aetiology of obstructive hydrocephalus
obstructive = impaired outflow - obstruction of the cerebral aqueduct of sylvius, the lateral foramen of Luschka, or the median foramen of Magendi:
lesions of 3rd, 4th ventricle or cerebral aqueduct
posterior fossa lesions eg tumour, blood, compressing the 4th ventricle
cerebral aqueduct stenosis
Subarachnoid hemorrhage or intraventricular hemorrhage → inflammatory response → fibrosis
Inflammation (e.g., following recovery from bacterial meningitis)
Arnold-Chiari malformation
Dandy-Walker malformation: A congenital malformation caused by failure of the fourth ventricle to close,= persistence of Blake’s pouch (cyst in the 4th ventricle) and cerebellar vermis hypoplasia = neurologic abnormalities and hydrocephalus, extracranial abnormalities
intrauterine infections - congenital toxoplasmosis
aetiology of non-obstructive hydrocephalus
impaired CSF resorption in the subarachnoid villi or increased CSF production:
tumours
meningitis - typically TB
inflammatory disease of CNS = inflamed arachnoid villi
Subarachnoidal or intraventricular hemorrhage → inflammatory response → fibrosis of villi
congenital absence of villi
choroid plexus papilloma - rare benign tumour of the choroid plexus - present with headache and symptoms if ICP due to hydrocephalus - secondary to CSF overproduction
choroid plexus carcinoma
inflammation of the choroid plexus
aetiology of normal pressure hydrocephalus
idiopathic chronic ventricular enlargement. possible secondary causes: inflammatory disease of CNS eg meningitis, intraventricular haemorrhage, subarachnoidal haemorrhage -> fibrosis:
The long white matter tracts (corona radiata, anterior commisure) are damaged causing gait and cognitive decline.
epidemiology of hydrocephalus
bimodal age distribution
congenital malformations and tumours in young
strokes and tumours in elderly
female more
NPH, a common form of acquired hydrocephalus, primarily affects individuals > 60 years
Prevalence: communicating hydrocephalus > noncommunicating hydrocephalus
sx of hydrocephalus
obstructive - a cute drop in conscious level, diplopia
NPH - chronic cognitive decline, falls, urinary incontinence
headache
nausea
vomiting
normal pressure hydrocephalus:
- urinary incontinency - increased urge and frequency then urgge incontinence, worsens as dementia does
- dementia
- ataxic gait
signs of obstructive hydrocephalus
impaired GCS
papilloedema
CNVI palsy - ‘false localising sign’ of increased ICP
abnormal gait
cushing triad - irregular breathing, widening pulse pressure, bradycardia
CN6 palsy
lower extremity spasiticty, hyperreflexia
Changes in vital signs resulting from brainstem compression due to herniation
In neonates, the head circumference may enlarge (macrocephaly), and ‘sunset sign’ (downward conjugate deviation of eyes), tense fontanelle - Because the fontanelles of infants are still open, the accumulation of CSF can lead to macrocephaly; this accommodation offsets the elevation in ICP, meaning that neurological symptoms often develop later than in older patients whose fontanelles are closed!
signs of normal pressure hydrocephalus
cognitive impairment
gait apraxia - shuffling
hyper-reflexia
ix for hydrocephalus
CT head
- first line investigation
- may detect cause eg tumour in brainstem
- enlarged ventricles (all in communicating, upstream of obstruction in non-communicating)
CSF
- from ventricular drains or LP - may indicate underlying pathology eg TB
- check MC&S, protein, glucose (CSF and plasma)
LP
- CI in obstructive - tonsilar herniation and death
- may be necessary in NPH as a therapeutic trial
US in neonate - enlarged lateral ventricles
Ix in normal pressure hydrocephalus
rule out other causes - cognitive assessment, B12 and TFT
MRI/CT - Ventriculomegaly without sulcal enlargement, Periventricular hypodensity due to periventricular edema
CSF tap - opening pressure normal/slightly elevated, symptom improvement is confirmatory
