Unreliable sagittal T2-weighted flow void MRI in diagnosing third ventriculostomy: a case of long-standing obstructive hydrocephalus. Illustrative case

Abstract

Background: Aqueductal stenosis represents one of the most common causes of CSF intraventricular blockage and may lead to obstructive triventricular hydrocephalus. In rare cases, the spontaneous rupture of the third ventricular floor, known as spontaneous third ventriculostomy (STV), can occur.

Observations: The authors report an illustrative case of pseudo-STV in a 67-year-old man who presented with long-standing obstructive triventricular hydrocephalus. Despite the neuroimaging findings suggesting STV, endoscopic third ventriculostomy showed an intact floor of the third ventricle.

Lessons: The authors demonstrate the potential for imaging to be misleading in the diagnosis of STV. A flow void artifact on sagittal T2-weighted sequences of the floor of the third ventricle may reflect the fast motion of a thin third ventricular floor or CSF passage through the foramen of Monro rather than flow void through a patent stoma. Endoscopic exploration remains the gold standard for confirming the presence of a ventriculostomy, but other noninvasive tools may help differentiate real CSF intraventricular motion. Dimensional phase-contrast velocity mapping like time-SLIP (arterial spin labeling) MRI could allow the differentiation of flow artifacts caused by the rapid motion of the pulsating floor of the third ventricle from a true ventriculostomy. https://thejns.org/doi/10.3171/CASE2531.

Keywords: aqueductal stenosis; endoscopic third ventriculostomy; hydrocephalus; neuroendoscopy; neurosurgery; spontaneous third ventriculostomy.

FIG. 1.

T2-weighted sagittal midline MR image of the brain showing severe narrowing of the sylvian aqueduct at the level of the fourth ventricle junction and abnormal aspects of third ventricle floor thinning.

FIG. 2.

A: Sagittal magnified FIESTA MRI sequence showing septum formation at the level of the aqueduct junction with the fourth ventricle (arrow). B: Sagittal midline MR image showing a highly intense signal of CSF turbulent flow void throughout the interpeduncular cistern and third ventricle, interpreted as complete rupture of the third ventricle.

FIG. 3.

Endoscopic view of the floor of the third ventricle. The membrane appears to be thinning, but no stoma is present.

FIG. 4.

Endoscopic view after ETV is performed.

FIG. 5.

Sagittal midline T2-weighted flow MRI sequence showing patency of the third ventriculostomy.