Fact-sheet: Obstructive hydrocephalus


Updated on 01/17/2025 at 10:39 AM

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Definition

Hydrocephalus is a ventriculomegaly related to an imbalance between production and resorption of cerebrospinal fluid (CSF).

Obstructive, or non-communicating, hydrocephalus results from an obstruction within the ventricular system preventing normal CSF flow, causing ventricular dilatation upstream of the obstacle.

Clinical features

The circumstances leading to the discovery of hydrocephalus depend mainly on two factors: the patient's age and the rate of onset of the hydrocephalus.

Acute hydrocephalus:

  • Florid clinical presentation
  • Headaches
  • Vomiting
  • Intracranial hypertension syndrome.
  • +/- altered consciousness (ranging from simple drowsiness to coma)
  • In infants: bulging anterior fontanelle, described as "clown's hat" shaped, dilated scalp veins, "sunset" eyes

Chronic hydrocephalus: sometimes a paucisymptomatic presentation despite significant ventricular dilatation

CT

Absence of communication between the ventricular cavities and the pericerebral subarachnoid spaces, related to an obstacle within the ventricular pathway.

  • Bicaudate index > 95th percentile in children
  • Axial width of the temporal horn of the lateral ventricle >= 5 mm
  • Rounding of the temporal horn of the lateral ventricle
  • Effacement of the pericerebral spaces
  • Distension of the third ventricle cavity/bulging of the third ventricle floor
  • Stretching of the corpus callosum. Excessive stretching may lead to detachment of the fornix from the splenium of the corpus callosum.
  • Stretching of the septum pellucidum
  • Effacement of the basal cisterns in cases of intraventricular obstruction
  • Dilatation of the basal cisterns in cases of intracisternal obstruction
  • Signs of transependymal CSF resorption

MRI

Acute hydrocephalus:

  • ventriculomegaly (starts with the occipital horns and the V3)
  • transependymal resorption of CSF, hypointense on T1 and hyperintense on periventricular T2 FLAIR
  • + signs of severity: cerebral edema
  • herniation signs

Non-communicating hydrocephalus:

  • Direct signs: obstacle along the ventricular pathway unilateral ventricular dilatation
    astrocytoma related to Tuberous sclerosis of Bourneville
  • Colloid cyst
  • biventricular dilatation Colloid cyst of the V3++
  • triventricular dilatation: stenosis of the aqueduct of Sylvius
  • extrinsic compression (cyst, Hematoma, tectal glioma or Other tumor...)
  • Indirect signs: dilatation of the recesses
  • diffuse effacement of the subarachnoid spaces
  • absence of motion of the lamina terminalis of the third ventricle
  • transependymal resorption of CSF

Management

Acute non-communicating hydrocephalus:

  • urgent neurosurgical consultation
  • CSF diversion
  • ventriculocisternostomy (fenestration of the floor of the V3)

Differential diagnosis

  • Communicating hydrocephalus absence of obstruction to CSF flow between the ventricular cavities and the pericerebral subarachnoid spaces with no identifiable obstacle visible along the ventricular pathway
  • Non-progressive ventriculomegaly ex-vacuo enlargement following stroke
  • periventricular leukomalacia
  • cavum septum pellucidum
  • subcortical atrophy
  • CSF is hypointense on T1 and hyperintense on T2. Beware of flow artifacts! Slice entry phenomenon (flow hyperintense on T1 and hyperintense on T2 FLAIR)
  • Slice exit phenomenon (T2 hypointensity)
  • Turbulent flow (T2 hypointensity)