Beyond Conventional Stereotaxic Targeting: Using Multiplanar Computed Tomography, Optical Coherence Tomography and Intracranial/Extravascular Ultrasound of the Subarachnoid Space to Locate the Rhesus Vestibular Nerve for Single Unit Recording
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Date
2016-08-16
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Johns Hopkins University
Abstract
Single-neuron electrophysiologic recording of activity in the vestibular nerve and vestibular nuclei of alert rhesus monkeys is a uniquely informative technique in the arsenal of neurophysiologists who seek to elucidate adaptive neuronal signal processing that mediate learning within vestibulo-ocular and vestibulo-spinal reflex pathways. The traditional approach to targeting these structures with a recording microelectrode - stereotactic guidance based on atlas coordinates - has changed little over the past half century and is made difficult by the vestibular nerve’s mobility, mechanical compliance, small caliber and relatively long distance from where a microelectrode enters the cranium (typically at the base of a recording chamber surgically affixed to the parietal aspect of the skull). The goal of the present study was to determine whether imaging techniques that have recently gained prominence in clinical care might augment or replace the traditional neurophysiologic method. Toward that end, we evaluated 3D multiplanar computed tomography (3DCT), optical coherence tomography (OCT) and an intracranial/cisternal adaptation of intravascular ultrasound (IVUS) as adjuncts to facilitate targeting the rhesus vestibular nerve. Image guidance using CT scans acquired after recording chamber implantation proved to be a simple and useful complement to traditional atlas-based stereotaxis; however, atlas-based stereotaxis, 3DCT, OCT and IVUS offer complementary advantages and disadvantages for targeting cranial nerves. Although OCT and IVUS ultimately proved needlessly complex for our application, adaptation of those techniques for intracranial/cisternal or intracranial imaging of cranial nerves, spinal nerves and other structures adjacent to cerebrospinal fluid spaces may hold promise for intraoperative guidance during minimal-access rhizotomy, biopsy and other neurosurgical procedures.
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CT-guidance, vestibular nerve, stereotactic surgery, OCT, ultrasound