A Novel MRI/CT Fusion Segmentation Methodology for Safe and Consistent Percutaneous Transvenous Endovascular Transdural Access to the Cerebellopontine Angle Cistern

Introduction: The first endovascular CSF shunt (eShunt System; CereVasc, Inc.) placed using a percutaneous, transvenous Delivery Catheter successfully treated 31 patients of multiple hydrocephalus etiologies, resulting in swift and sustained symptom resolution. Longest follow-up of 32 months demonstrates a favorable safety profile. These encouraging initial results for hydrocephalus treatment suggest that minimally-invasive, vascular access to the brain could potentially treat other non-vascular neurological diseases. We describe pre- and peri-operative imaging protocols for safe and consistent cerebellopontine angle (CPA) cistern access.

Methods: Pre-operative screening involves axial thin-slice post-gadolinium MRI from C2 through the clivus, coupled with thin-slice head CT. MRI evaluation of the distance between CPA access site and adjacent arteries and brainstem uses multi-planar reconstruction. CT clarifies the extent of petrous bone overhang to confirm no access interference. Peri-operative venogram of the inferior petrosal and cavernous sinus immediately prior to the procedure further elucidates relevant venous anatomy. 3D subtracted rotational venography using cone-beam CT protocol acquired from the venogram for dual volume reconstruction of venous and bony anatomy provides visualization with high spatial resolution and wide dynamic range. This forms the basis for subsequent 3D road-mapping to ensure reliable Delivery Catheter navigation.

Results: Thirty-one patients (13 female; mean 71.0 +/- 27.0 years) underwent successful Implant placement following pre-operative screening. Twenty right-side and eleven left-side implantations occurred. All patients received heparin bolus throughout the procedure, maintaining target ACT 230-260. At the operator’s discretion, protamine was administered prior to CPA access (15 patients) for anticoagulation reversal. No observations of hemorrhage, dura damage, or contact with adjacent brainstem or arterial structures occurred.

Conclusion : The ubiquity of high-resolution imaging available to the neurovascular practitioner has enabled development of robust imaging protocols for safe and consistent percutaneous, transvenous CPA access. Further experience will facilitate broader usage of the CPA access technique for treatment of various other neurological disorders.