Validation of a magnetic resonance imaging guided stereotactic access to the ovine brainstem

Abstract

BackgroundAnatomical differences between humans and domestic mammals preclude the use of reported stereotactic approaches to the brainstem in animals. In animals, brainstem biopsies are required both for histopathological diagnosis of neurological disorders and for research purposes. Sheep are used as a translational model for various types of brain disease and therefore a species-specific approach needs to be developed. The aim of the present study was to establish a minimally invasive, accurate and reproducible stereotactic approach to the brainstem of sheep, using the magnetic resonance imaging guided BrainsightTM frameless stereotactic system.ResultsA transoccipital transcerebellar approach with an entry point in the occipital bone above the vermis between the transverse sinus and the external occipital protuberance was chosen. This approach provided access to the target site in all heads. The overall mean needle placement error was 1.85 ± 1.22 mm.ConclusionsThe developed transoccipital transcerebellar route is short, provides accurate access to the ovine caudal cranial fossa and is a promising approach to be further assessed in live animals.

Review of Stereotactic and Neuronavigation Brain Biopsy Methods in the Dog

“…All studies that used neuronavigation to plan biopsies measured the needle accuracy dogs [20][21][22]. Despite using distinct species and different imaging techniques, this was the most homogenous group in terms of precision.…”

“…Only histopathological exams can identify the nature of the lesion seen in image studies [2]. Brain tissue biopsies are delicate procedures and different methods have been proposed: free-hand [6][7][8][9], ultrasound-guided [10] and, more recently, with the aid of stereotactic [11][12][13][14][15][16][17][18][19] and neuronavigational devices [20][21][22].…”

“…A more recent technique, neuronavigation, has also been tested in dogs [20,21] and sheep [22]. In this method, instead of af ixing a rigid stereotactic device to the head of the animal, either CT-scan or MR images are imported to a computer, and the animal is immobilized in front of a set of infrared cameras that capture the spatial location of speci ically developed instruments in real time, overlapping their position with previously imported images.…”

Computation of a high‐resolution MRI 3D stereotaxic atlas of the sheep brain

“…The utilization of the atlas presented herein will provide a precise framework to establish neuro‐navigation procedures between brain structures. Such approaches based on MRI are starting to be used in ex vivo sheep heads (Staudacher et al, ), but the current precision (error of 1.85 ± 1.22 mm) is variable and can most likely be increased with the use of our stereotaxic atlas, which incorporates interindividual variability (especially for small brain nuclei that are not easily discernable on individual MRI images). To this end, the stereotaxic frame should be combined with a fiducial marker system (see Staudacher et al, , for details).…”

“…The first reported preclinical study was performed by Opdam et al (2002), concerning the localization of epileptic foci by functional (f)MRI and EEG. Further studies used anatomical MR images to plan surgical interventions for translational stroke (Dreyer et al, 2012), to achieve a stereotactic access of the brainstem (Staudacher et al, 2014), and to guide micro-electrocorticography grid implantation for the mapping of the sensory cortex in the sheep brain (Gierthmuehlen et al, 2014). Recently, Lee et al (2015) utilized routine human fMRI and diffusion tensor imaging (DTI) protocols on sheep brain.…”