Relevance of magnetic resonance imaging for ventricular endoscopy

Endoscopic procedures may represent an alternative to microsurgery or shunt operations in intra- or paraventricular pathologies. However, the operative results mainly depend on the selection of suitable patients. In the present study of 30 patients with occlusive hydrocephalus, the relevance of differentiated magnetic resonance (MR) imaging for evaluation of the pathophysiological and anatomic prerequisites was investigated.

Apart from conventional axial T(2) -weighted turbo spin echo (TSE) sequences (TR/TE 2126/100 ms) and T(1) -weighted spin echo (SE) sequences (TR/TE 450/15 ms) with and without the administration of Gd-DTPA, the MR protocol included sagittal and coronal thin-sliced T(2) -weighted TSE sequences, cardiac-triggered (TR/TE > 2700/120 ms, slice thickness 3.0 mm) or in volume technique (TR/TE 4000/180 ms, slice thickness 1.4 mm). For the visualization of CSF flow, a sagittal and axial phase-contrast-multi-heart-phase (PCMHP) measurement with 16 phases per cardiac cycle and flow sensitivity in the cranio-caudal direction (TR/TE 18/9.5 ms and 14/9.5 ms) was performed.

The combination of imaging and flow sequences provided most information about the extent and the etiology of hydrocephalus. An obstruction of CSF pathways could be detected by the absence of flow voids in T(2) -weighted TSE sequences or of flow signals in PCMHP sequences. The size of the foramen of Monro and of the third ventricle could be evaluated in thin-sliced T(2) -weighted TSE sequences, for the foramen of Monro in coronal and sagittal and for the third ventricle in coronal and axial slice direction, respectively. The basal structures of the third ventricle, including its floor, the infundibular recess, the mamillary bodies, and the basilar artery, could be best identified in sagittal thin-sliced T(2) -weighted TSE scans, cardiac-triggered or in volume technique.

In occlusive hydrocephalus, a differentiated MR protocol with thin-sliced T(2) -weighted TSE sequences and phase-contrast sequences allows a very precise estimation of the pathophysiological and the anatomic prerequisites for endoscopic procedures. Furthermore, MR imaging can be used for the follow-up documentation of ventriculo-cisternostomies, -cytostomies, or openings of other membranes.