ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE HORSE USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY

Anatomy of the rabbit inner ear using computed tomography and magnetic resonance imaging

Anatomically, the inner ear is a highly complex organ of intricate design, composed of a bony labyrinth that encases the same-shaped membranous labyrinth. It is difficult to study the three-dimensional anatomy of the inner ear because the relevant structures are very small and embedded within the petrous temporal bone, one of the densest bones in the body. The current study aimed to provide a detailed anatomic reference for the normal anatomy of the rabbit's inner ear. As a study model, ten healthy adults New Zealand White rabbit heads were used. Six heads were used for macroscopic evaluation of the bony and membranous labyrinths. The remaining four heads were evaluated radiographically, where 3D images were generated of the bony and membranous labyrinths using data sets from computed tomography (CT) and magnetic resonance imaging (MRI), respectively. The anatomical structures were identified and labelled according to NominaAnatomicaVeterinaria (NAV). Our study revealed that CT and MRI are the optimal cross-sectional imaging modalities for investigating such tiny and often inaccessible inner ear structures. As high-quality scanners are not readily available to veterinarians, the CT and MRI images generated by this research were of lower quality; therefore, high-quality dissections were used to identify/support structures seen in these images. In conclusion, this study provides one of the first investigations that uses multislice CT scans and MRI to study the rabbit's inner ear and its correlation with the corresponding anatomical images. Both anatomical, CT and MRI images will serve as a reference for interpreting pathologies relative to the rabbit's inner ear.

Anatomical description of the skulls of peccaries (Tayassu tajacu, Linnaeus 1758) by computed tomography

ABSTRACT The aim of this study was to evaluate the anatomical structures of the skulls of peccaries to establish the basis for their clinical study and future preclinical research. Ten skulls of adult peccaries were subjected to tomographic examination. The data obtained were processed via three-dimensional image reconstruction software (3D images). The reconstructions obtained from the neurocranium of the studied specimens allowed the identification and description of the following structures: nasal bone, frontal bone, parietal bones, incisor bone, maxillary bone, zygomatic bone, temporal bone, palatal bone, occipital bone, vomer bone, pterygoid bone, sphenoid bone, paranasal sinuses and orbit. Computed tomography proved to be an important diagnostic tool in the investigation of the skull of this species, allowing the acquisition of anatomical values not yet documented for the species in the literature.

Pyogenic meningitis and trigeminal neuritis secondary to periodontogenic paranasal sinusitis in a red deer (Cervus elaphus)

An adult female red deer died of a severe seizure and dysbasia. Postmortem computed tomography (CT) and magnetic resonance imaging (MRI) were performed. On CT, deciduous right maxillary second and third premolar teeth were observed, and the right infraorbital canal was disrupted. MRI showed that the right trigeminal nerve was enlarged and the right subarachnoid cavity was occupied by fluid and gas. On gross examination, the right paranasal sinus, swollen muscles of the orbit and tonsils, right trigeminal nerve, and right cerebrum surface contained a yellowish-white, cheese-like pus. Based on these findings, the deer was believed to have developed pyogenic meningitis caused by a neuropathic infection secondary to periodontogenic paranasal sinusitis.

Facial nerve paralysis in 64 equids: Clinical variables, diagnosis, and outcome

BACKGROUND

Facial nerve paralysis (FNP) in equids is not well described in the veterinary literature.

OBJECTIVE

To investigate the causes of FNP and associations among clinical variables, diagnosis, and outcome.

ANIMALS

Sixty-four equids presenting with FNP between July 2000 and April 2019. Cases of postanesthetic FNP were excluded.

METHODS

Medical records were retrospectively reviewed. Variables were evaluated for associations with outcomes (diagnosis and case outcome) using logistic regression.

RESULTS

The most common cause of FNP was trauma (n = 20). Additional diagnoses included central nervous system (CNS) disease (n = 16), idiopathic (n = 12, 4 of which had adequate diagnostic investigation and were considered "true" idiopathic, and 8 of which were considered "not investigated" idiopathic), temporohyoid osteoarthropathy (n = 10), otitis media-interna (n = 3), lymphoma (n = 1), iatrogenic as a consequence of infiltration of local anesthetic (n = 1), and clostridial myositis (n = 1). Follow-up was available for 55 (86%) cases. Twenty-nine (53%) equids had full resolution of FNP, 14 (25%) were euthanized, 6 (11%) partially improved, and 6 (11%) were unchanged or worse.

CONCLUSIONS AND CLINICAL IMPORTANCE

If FNP is the consequence of CNS disease, successful treatment of the primary disease likely leads to resolution of FNP. Most cases of FNP in equids are traumatic in origin. True idiopathic cases are uncommon.

Morphological variations of the infraorbital canal during CT has limited association with headshaking in horses

Headshaking is a common problem in horses. The etiology is unknown but thought to involve sensory input from branches of the trigeminal nerve, some of which are within the infraorbital canal. The objective of this retrospective cross-sectional study was to describe the CT anatomy and variations of the infraorbital canal in horses with local disease processes and normal horses, and to examine associations between those findings and headshaking. Computed tomography scans were reviewed and morphological changes of the infraorbital canal were described. Presence of changes was then tested for association with headshaking prevalence, presence of disease processes in the region of the infraorbital canal, age, and sex. Nonparametric tests were used and a P-value of .05 was considered significant. A total of 218 horses were included, 9% of which had headshaking and 45% had CT lesions in the region of the infraorbital canal. Morphological changes to the bone of the infraorbital canal were found in 121 horses (56%) and included the following: increased mineralization 39 (18%), decreased mineralization 89 (41%), deformed shape 51 (23%), displaced position 43 (20%), and disruption 11 (5%). All changes of the infraorbital canal significantly increased in frequency with the presence of adjacent disease. Increased mineralization and disruption of the infraorbital canal were significantly associated with headshaking in horses with adjacent disease; the latter only reached significance after exclusion of dentally immature horses. No other changes were significantly associated with the presence of headshaking. No association was found between headshaking and the age or sex of the horse.

Agreement between transverse T2-weighted and three-dimensional constructive interference in steady state sequences in the evaluation of spinal cord disease in dogs

The constructive interference in steady state (CISS) sequence has been widely used in human neuroimaging. It has been shown to be advantageous in the evaluation of intra-axial and extra-axial cystic abnormalities, arteriovenous and dysraphic malformations and disturbances of cerebrospinal fluid circulation. To assess the utility of this technique in small animals, interpretations based on this sequence were compared with those based on T2-weighted (T2W) sequences in 145 dogs that underwent MRI of the spine for suspected spinal cord disease. Two sets of images (T2W and CISS) were reviewed separately by three observers in random order and intraobserver and interobserver agreements between both sequences were evaluated for several categorical variables. The overall agreement between T2W and CISS sequences was good. The highest agreement was observed for lesion diagnosis (0.739<k<0.928), treatment recommendation (0.715<k<0.833) and degree of spinal cord compression (0.772<k<0.952). The agreement for intramedullary intensity change (0.192<k<0.332) was lower compared with the other variables. Lesions that were predominantly characterised by focal hyperintense parenchymal changes on T2W were in some instances undetected on the CISS sequence while lesions consistent with spinal arachnoid diverticula on CISS sequences were occasionally missed on T2W. CISS enabled demonstration that lesions were directly affecting associated spinal nerves in some cases where T2W sequence was equivocal. Although CISS does not replace standard spin echo sequences, the results support inclusion of this sequence in small animal spinal MRI studies when subarachnoid diverticula or spinal nerve compression is suspected.