BackgroundCerebellar abiotrophy (CA) is a rare but significant disease in Arabian horses caused by progressive death of the Purkinje cells resulting in cerebellar ataxia characterized by a typical head tremor, jerky head movements and lack of menace response. The specific role of magnetic resonance imaging (MRI) to support clinical diagnosis has been discussed. However, as yet MR imaging has only been described in one equine CA case. The role of MR morphometry in this regard is currently unknown. Due to the hereditary nature of the disease, genetic testing can support the diagnosis of CA.Therefore, the objective of this study was to perform MR morphometric analysis and genetic testing in four CA-affected Arabian horses and one German Riding Pony with purebred Arabian bloodlines in the third generation.ResultsCA was diagnosed pathohistologically in the five affected horses (2 months - 3 years) supported by clinical signs, necropsy, and genetic testing which confirmed the TOE1:g.2171G>A SNP genotype A/A in all CA-affected horses.On MR images morphometric analysis of the relative cerebellar size and relative cerebellar cerebrospinal fluid (CSF) space were compared to control images of 15 unaffected horses. It was demonstrated that in MR morphometric analyses, CA affected horses displayed a relatively smaller cerebellum compared to the entire brain mass than control animals (P = 0.0088). The relative cerebellar CSF space was larger in affected horses (P = 0.0017). Using a cut off value of 11.0% for relative cerebellar CSF space, the parameter differentiated between CA-affected horses and controls with a sensitivity of 100% and a specificity of 93.3%.ConclusionsIn conclusion, morphometric MRI and genetic analysis could be helpful to support the diagnosis of CA in vivo.

Summary: For evaluating neurological diseases, magnetic resonance imaging (MRI) has been widely recommended as the method of choice in human medicine. It has been proposed as a valuable tool in clinical diagnostics and research projects in veterinary medicine as well. The aim of this study was to elaborate optimal settings appropriate for an examination of the equine brain in a 3-Tesla tomograph within an adequate examination time and with related optimal image quality. A key issue was the evaluation of those neuro-anatomical structures (formations of Grey and White Matter included) which were always clearly recognisable and, as such, were useful orientation landmarks. Furthermore, the average sizes of selected structures were measured in the magnetic resonance images in transversal views. MRI of 11 healthy horses was performed in general anaesthesia. After the examination the horses were euthanised, their heads were fixated by perfusion, the brain was removed and cut either in transversal, dorsal or sagittal slices (approximately 4 mm thick). Photographic images of these slices corresponded to the magnetic resonance images in the equivalent planes. In the anatomical slices, all visible neurological structures (gyri, nuclei, and formations of White Matter) were identified. In the corresponding magnetic resonance images, these structures were evaluated with regard to the image quality (intensity, delineation). Those best visible were proposed as landmarks for orientation. The evaluation of the image quality was performed using a score system. In general, the anatomical slices displayed more details compared to the magnetic resonance images. In the latter, large nuclei -like, e.g. Nucleus caudatus -could always be identified with certainty, whereas small nuclei -like those of the thalamic region or of the area of the Medulla oblongata -could not be identified. The relation between operational effort and benefit was discussed considering the parameters 'acquisition time' (and related duration of general anaesthesia) and 'image quality' (which depended on the selection of sectional planes and matrix sizes, as displayed in the proposed protocols).Keywords: MRI / horse / brain / 3 Tesla / orientation landmarks / diagnostic imaging 3-Tesla-magnetresonanztomographische Untersuchungen des Gehirns gesunder Pferde -Möglichkeiten und GrenzenDie Magnetresonanztomographie (MRT) wird in der Humanmedizin als Methode der Wahl zur Bewertung neurologischer Erkrankungen empfohlen und ist ebenso in der tiermedizinischen Diagnostik und Forschung etabliert. Ziel dieser Untersuchung am lebenden Pferd war es, optimale Einstellungen festzulegen, mit denen das Pferdegehirn in einem 3-Tesla-Gerät adäquat, d.h. in angemessener Untersuchungszeit bei optimaler Bildqualität, untersucht werden kann. Im Mittelpunkt stand dabei die Darstellung jener neuroanatomischen Strukturen einschließlich Formationen aus Grauer und Weißer Substanz, die stets sicher erkennbar und deshalb als Landmarks zur Orientierung im Pferdegehirn geeignet waren. Außerdem w...