Clinical, magnetic resonance imaging, and histological description of a choroid plexus papilloma with disseminated intraventricular and spinal cerebrospinal fluid drop metastases in a young adult dog: a case report.

A 2-year-old male entire Cane Corso was presented for investigations into a 1-week history of ambulatory paraparesis and pelvic limb ataxia gradually deteriorating. Magnetic resonance imaging (MRI) revealed intraventricular space-occupying lesions affecting the fourth ventricle and lateral apertures and intradural-extramedullary space-occupying lesions at the level of C7 vertebra, L4-L5, and L7-S1 intervertebral disk spaces. Due to poor quality of life, the patient was euthanized. A post-mortem examination revealed partially encapsulated, multifocally infiltrative, and moderately cellular neoplastic masses. The histological description was similar for all masses. The cells appeared cuboidal with round central nuclei and a moderate amount of eosinophilic cytoplasm and were arranged almost exclusively in single-layered papilliform patterns supported by a fibrovascular stroma. Mitoses were rarely observed (1/2.37 mm2). The primary neoplasm was morphologically most consistent with a choroid plexus papilloma despite drop metastases. This is the first report of a histologically confirmed primary ventricular choroid plexus papilloma causing disseminated MRI-apparent intraventricular and spinal drop metastases.

Correlative Magnetic Resonance Imaging and Histopathology in Small Ruminant Listeria Rhombencephalitis.

Background: Listeria rhombencephalitis, infection of the brainstem with Listeria monocytogenes, occurs mainly in humans and farmed ruminants and is associated with high fatality rates. Small ruminants (goats and sheep) are a large animal model due to neuropathological similarities. The purpose of this study was to define magnetic resonance imaging (MRI) features of listeria rhombencephalitis in naturally infected small ruminants and correlate them with histopathology. Secondly, the purpose of this study was to compare the results with MRI findings reported in humans. Methods: Twenty small ruminants (13 sheep and 7 goats) with listeria rhombencephalitis were prospectively enrolled and underwent in vivo MRI of the brain, including T2-weighted, fluid attenuation inversion recovery, and T1-weighted sequences pre- and post-contrast administration and postmortem histopathology. In MRI, lesions were characterized by location, extent, border definition, signal intensity, and contrast enhancement. In histopathology, the location, cell type, severity, and chronicity of inflammatory infiltrates and signs of vascular damage were recorded. In addition, histopathologic slides were matched to MRIs, and histopathologic and MRI features were compared. Results: Asymmetric T2-hyperintense lesions in the brainstem were observed in all animals and corresponded to the location and pattern of inflammatory infiltrates in histopathology. Contrast enhancement in the brainstem was observed in 10 animals and was associated with vessel wall damage and perivascular fibrin accumulation in 8 of 10 animals. MRI underestimated the extension into rostral brain parts and the involvement of trigeminal ganglia and meninges. Conclusion: Asymmetric T2-hyperintense lesions in the brainstem with or without contrast enhancement can be established as criteria for the diagnosis of listeria rhombencephalitis in small ruminants. Brainstem lesions were similar to human listeria rhombencephalitis in terms of signal intensity and location. Different from humans, contrast enhancement was a rare finding, and abscessation was not observed.

Clinical, radiographic, and magnetic resonance imaging findings of gastrocnemius musculotendinopathy in various dog breeds.

OBJECTIVES: To describe clinical, radiographic, and magnetic resonance imaging (MRI) findings in 16 dogs diagnosed with gastrocnemius musculotendinopathy. METHODS: Retrospective evaluation of medical records, radiographs, and MRI results, as well as follow-up completed by telephone questionnaire. RESULTS: Most dogs had chronic hindlimb lameness with no history of trauma or athletic activities. Clinical examination revealed signs of pain on palpation without stifle joint instability. Seven dogs had radiographic signs of osteophyte formation on the lateral fabella. Magnetic resonance imaging revealed T2 hyperintensity and uptake of contrast agent in the region of the origin of the gastrocnemius muscle. Changes were found in the lateral and medial heads of the gastrocnemius. Conservative treatment resulted in return to full function in 11 dogs. Two dogs showed partial restoration of normal function, one dog showed no improvement. Two dogs were lost to follow-up. CLINICAL SIGNIFICANCE: Gastrocnemius musculotendinopathy is a potential cause of chronic hindlimb lameness in medium to large breed dogs. A history of athletic activity must not necessarily be present. Magnetic resonance imaging shows signal changes and uptake of contrast agent in the region of the origin of the gastrocnemius muscle. A combination of T1 pre- and post-contrast administration and T2 weighted sequences completed by a fat-suppressed sequence in the sagittal plane are well-suited for diagnosis. Conservative treatment generally results in return to normal function.

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

BACKGROUND: Anatomical 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. RESULTS: A 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. CONCLUSIONS: The 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.