Analysis of aqueductal cerebrospinal fluid flow after endoscopic aqueductoplasty by using cine phase-contrast magnetic resonance imaging

Phase-contrast and three-dimensional driven equilibrium (3D-DRIVE) sequences in the assessment of paediatric obstructive hydrocephalus

BACKGROUND

Recently, most cases of hydrocephalus are related to obstruction. Accurate localization of the site of obstruction is crucial in determination of the treatment strategy.

PURPOSE

To describe the phase-contrast and 3D-DRIVE findings in cases of obstructive hydrocephalus in paediatric patients and to determine their functional and anatomical correlates.

MATERIAL AND METHODS

Brain MRIs of 25 patients (2 months to 11 years) with obstructive hydrocephalus were retrospectively reviewed. Phase-contrast and 3D-DRIVE were performed to assess cerebrospinal (CSF) pathways through the aqueduct of Sylvius and subarachnoid spaces. In addition to flow velocity measurement at the aqueduct of Sylvius, functional and anatomical correlation was analysed at the level of aqueduct of Sylvius, infracerebellar CSF space and at the third ventriculostomy using Spearman's rank test.

RESULTS

Aqueduct of Sylvius was the most common site of obstruction (19 patients) either secondary to focal, multifocal or tubular stenosis, adhesions, or secondary to extrinsic compression. Functional and anatomical correlation was analysed in 58 regions revealing strong correlation (ro = 0.8, p < .001). Functional anatomical mismatch was found in nine regions. Flow velocity measurements revealed diminished flow in most of the cases with obstruction at the aqueduct and normal velocity in cases with obstruction proximal to aqueductal level, while accelerated flow was seen in cases with infra-aqeuductal obstruction.

CONCLUSION

Phase-contrast and 3D-DRIVE sequences are essential sequences in the diagnosis of hydrocephalus enabling perfect localization of the site of obstruction. Both sequences should be interpreted in conjunction to avoid false results. Velocity measurements through the aqueduct can help understand CSF hydrodynamics.

Phase-contrast MRI and 3D-CISS versus contrast-enhanced MR cisternography on the evaluation of the aqueductal stenosis

INTRODUCTION

In the current study, we aimed to compare the diagnostic efficacies of phase-contrast magnetic resonance imaging (PC-MRI) and three-dimensional constructive interference in steady-state (3D-CISS) sequence over detection of aqueductal stenosis (AS) on the basis of contrast-enhanced magnetic resonance cisternography (MRC).

METHODS

Twenty-five patients with clinically and radiologically suspected AS were examined by PC-MRI, 3D-CISS, and MRC. Axial-sagittal PC-MRI and sagittal 3D-CISS were applied to view the cerebral aqueduct. Following injection of 0.5-1 ml intrathecal gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) injection, postcontrast MRC images were obtained in three planes in early and late phases. Aqueductal patency was scored as follows: grade 0, normal; grade 1, partial narrowing; and grade 2, complete obstruction. Results of PC-MRI and 3D-CISS were compared with the findings of MRC.

RESULTS

In PC-MRI, seven cases were assessed as grade 0, 16 cases grade 1, and two cases grade 2. As a result of 3D-CISS sequence, eight cases were evaluated as grade 0, 12 cases grade 1, and five cases grade 2. Based on MRC, nine cases were assessed as grade 0, whereas nine and seven cases were evaluated to be grades 1 and 2, respectively. Five cases that demonstrated partial patency in PC-MRI or 3D-CISS showed complete obstruction by MRC.

CONCLUSION

PC-MRI is helpful in confirming the AS. However, positive flow does not necessarily exclude the existence of AS. 3D-CISS sequence provides excellent cerebrospinal fluid-to-aqueduct contrast, allowing detailed study of the anatomic features of the aqueduct. MRC should be performed on patients who demonstrate suspected AS findings on PC-MRI and/or 3D-CISS sequences.