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Aqueductal Stenosis


KEY FACTS

Terminology

  • Focal reduction of cerebral aqueduct diameter

Imaging

  • Ventriculomegaly of lateral and 3rd ventricles with normal-sized 4th ventricle

  • ± periventricular interstitial edema (uncompensated hydrocephalus)

  • Multiplanar MR with sagittal 3D-heavy T2WI sequences and sagittal cardiac-gated cine MR

Top Differential Diagnoses

  • Obstructing extraventricular pathology

    • Neoplasm

    • Vein of Galen malformation

    • Quadrigeminal cistern arachnoid cyst

  • Obstructing intraventricular (aqueductal) pathology

  • Postinflammatory gliosis (aqueductal gliosis)

  • Rhombencephalosynapsis

Pathology

  • Congenital aqueductal stenosis is common cause of fetal hydrocephalus

  • Aqueductal web and fork are pathological subsets

Clinical Issues

  • Symptoms depend on patient age at time of diagnosis

  • Onset often insidious, may occur at any time from birth to adulthood

  • Headache, papilledema, 6th nerve palsy, bulging fontanelle

  • Parinaud syndrome (sun-setting eyes, lid retraction, and tonic downgaze), convergence retraction nystagmus

Diagnostic Checklist

  • Consider postinflammatory gliosis (aqueductal gliosis), particularly if history of prematurity or meningitis

  • Carefully scrutinize posterior 3rd ventricle, tectum, and tegmentum for obstructing neoplastic mass

Sagittal graphic shows obstructive hydrocephalus with markedly enlarged lateral and 3rd ventricles
, stretched (thinned) corpus callosum
, and a funnel-shaped cerebral aqueduct
related to distal obstruction. Note the normal size of the 4th ventricle and herniation of the floor of the 3rd ventricle from the hydrocephalus.

Sagittal T1WI C+ MR demonstrates aqueductal web
causing dilation of the proximal cerebral aqueduct, 3rd
and lateral ventricles
. The 4th ventricle below the web is normal.

Sagittal T2 SPACE MR demonstrates a normal aqueduct with a “flow void”
due to cerebrospinal fluid flow from the 3rd ventricle into the 4th ventricle.

Sagittal T2 SPACE MR demonstrates classic findings of aqueductal stenosis. There is an enlarged, funnel-shaped cerebral aqueduct
and marked dilatation of the lateral
and 3rd ventricles
with thinning and upward bowing of the corpus callosum
. Note the normal size of the 4th ventricle.

TERMINOLOGY

Abbreviations

  • Aqueductal stenosis (AS)

Definitions

  • Focal reduction of cerebral aqueduct diameter with concomitant lateral and 3rd ventriculomegaly

IMAGING

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