Recanalization of Obstructed Cerebrospinal Fluid Ventricular Catheters Using Ultrasonic Cavitation

Abstract

Fifty percent of implanted cerebrospinal fluid (CSF) shunts fail within 2 years, primarily because of obstruction of the proximal catheter. Percutaneous techniques to reduce the morbidity of shunt revision are being developed. The authors describe the development of a device that uses ultrasonic cavitation to unblock ventricular catheters. In collaboration with Cybersonics, Inc. (Erie, PA), we designed, built, and tested a system that produces low-frequency ultrasound (20-28 kHz). Extensional ultrasonic waves are transmitted along a tapered wire (final diameter, approximately 0.8 mm) to the tip, where cavitation is produced in a highly localized region. An in vitro model of sheep choroid plexus occluding typical ventricular catheters was developed. The device was safety tested in vivo in rat and pig brains by introducing the device into shunt catheters inserted during simulated shunt surgery. A clinical safety trial using the device to attempt to remove blocked and adherent ventricular catheters has commenced. In the sheep choroid plexus model, at least 90% of the occluded holes were unblocked in a few minutes, restoring normal flow. There was no adverse effect of the device within shunt catheters inserted into live animal brains. Four patients have undergone treatment with the device at open CSF shunt surgery without adverse effect, and the device seems effective at unblocking and freeing the occluded catheters. Ultrasonic cavitation produced at the end of a fine wire that is introduced percutaneously into a CSF shunt promises to be a useful technique for minimally invasive proximal ventricular CSF shunt catheter revision.