Is all "communicating" hydrocephalus really communicating? Prospective study on the value of 3D-constructive interference in steady state sequence at 3T

Abstract

Background and purpose: 3D-constructive interference in steady state (3D-CISS) sequence has been used to assess the CSF pathways. The aim of this study was to investigate the additive value of 3D-CISS compared with conventional sequences in the diagnosis of obstructive membranes in hydrocephalus.

Materials and methods: A total of 134 patients with hydrocephalus underwent MR imaging examination with a 3T unit consisting of turbo spin-echo, 3D-CISS, and cine phase-contrast (cine PC) sequences. 3D-CISS was used to assess obstructive membranes in CSF pathways compared with other sequences. Cine PC, follow-up imaging, and surgical findings were used to confirm obstructive membranes.

Results: Comparing the number of noncommunicating cases by using the conventional and 3D-CISS images, we found 26 new cases (19.4%) of 134 cases that were previously misdiagnosed as communicating hydrocephalus by conventional images. 3D-CISS sequence identified obstructive membranes invisible in other sequences, which facilitated selection of neuroendoscopy in the treatment of 31 patients (23.1%) in total who would have been otherwise treated with shunt insertion. These patients included 26 newly diagnosed noncommunicating cases after demonstration of intraventricular and/or fourth ventricular outlet membranes and 5 cases of communicating hydrocephalus with obstructing cisternal membranes. There were obstructions of the foramina of Luschka in 22 of 26 newly found noncommunicating cases.

Conclusions: Conventional sequences are insensitive to obstructive membranes in CSF pathways, especially in the fourth ventricular exit foramina and the basal cisterns. 3D-CISS sequence, revealing these obstructive membranes, can alter patient treatment and prognosis.

Fig 1.

Case 1. A, Sagittal TSE T2 image shows third ventricle enlargement with downward displacement of the floor of the third ventricle consistent with hydrocephalus. The cerebral aqueduct and foramen of Magendie are open widely, showing extensive flow void phenomenon. There is a mild enlargement in the fourth ventricle. There is no sign of obstructive membrane in the prepontine cistern. B, Left parasagittal TSE T2 images through the left lateral ventricular exit show no direct or indirect sign of membrane. C, Axial TSE T2 image through the fourth ventricular exits demonstrates prominent signal intensity void in the fourth ventricle, but there is no direct or indirect sign of obstructive membrane at the foramina of Luschka. D, Left parasagittal 3D-CISS image clearly points out the membrane itself in the foramen of Luschka. There is extensive intensity difference between the fourth ventricle and the neighboring cistern. E, Sagittal 3D-CISS image clearly demonstrates prepontine membranes extending from the clivus to the basilar artery. F, Left parasagittal follow-up 3D-CISS image indicates persistent membrane in the fourth ventricle exit foramen, though the intensity differences between cistern and ventricle have disappeared.

Fig 2.

Case 2. A, Axial TSE T2 image through the posterior fossa shows left cerebellar hypoplasia and enlargement of the bilateral cerebellomedullary cistern without any evidence of membrane at the fourth ventricle exit foramina. B, Axial oblique reformatted image of sagittal 3D-CISS reveals obstructing membranes of foramina of Luschka, bulging into the cerebellomedullary cisterns.

Fig 3.

Case 3. A, Sagittal TSE T2 image shows an enlarged third ventricle. The cerebral aqueduct seems to be open. B, Sagittal 3D-CISS demonstrates superior medullary velum synechia, causing triventricular hydrocephalus. There is a spontaneous third ventriculostomy at the floor of the ventricle, just behind the tip of the basilar artery. Sagittal CISS revealed the anatomic defect, whereas cine PC did not detect any flow through the defect.

Fig 4.

Case 4. A, Sagittal TSE T2 image demonstrates enlarged third ventricle, extensive flow void phenomenon in the cerebral aqueduct, the fourth ventricle, and prepontine/interpeduncular cisterns compatible with communicating hydrocephalus. B, Sagittal 3D-CISS image shows Liliequist membrane just below the downward bulging floor of the third ventricle. In addition to this, there is a thin membrane extending from the clivus to the basilar artery, dividing the prepontine cistern into upper and lower parts. The signal intensity difference between 2 parts with a sharp, linear zone of transition was seen. C, Coronal oblique reformatted image of 3D-CISS through the cisterns demonstrates lateral extension of the prepontine membrane, trapping CSF between the Liliequist membrane and the prepontine membrane. D, During ETV, after the floor of the third ventricle through the Liliequist membrane is opened, a complete membrane without any aperture is seen. E, The same view after the membrane is opened and removed, the cisternal part of the left abducens nerve is seen partly. F, On the follow-up sagittal 3D-CISS image, there is free communication between the third ventricle and the prepontine cistern through the interpeduncular cistern. G, Follow-up coronal oblique reformatted image of 3D-CISS after ETV through the cisterns (same view as in C) reveals nearly complete removal of the prepontine membrane. The difference in signal intensity between the 2 parts of the cisterns has almost completely disappeared.

Fig 5.

Case 4. A, Axial TSE T2 image through the lateral ventricle demonstrates unilateral right lateral ventriculomegaly. B, Coronal TSE T2 image through the foramen of Monro falsely demonstrates a free communication between the right lateral ventricle and the third ventricle. C, Coronal reformatted sagittal 3D-CISS image points out a complete membranous obstruction in the right foramen of Monro. D, Follow-up axial-oblique reformatted image revealing complete removal of obstructing membrane and normal-appearing lateral ventricles.