Equine Imaging: Computed Tomography Interpretation.

Computed tomography (CT) has revolutionized the veterinarian's ability to image the equine skull and led to improved diagnostic accuracy and clarity for surgical planning. The increased cost for this evaluation is offset by more accurate diagnosis and targeted therapy. As novel technology is developed that allows for increased availability of equine head, the price will continue to decrease and more examinations will be performed. New skills are needed for the veterinarian to accurately interpret this modality. This article reviews the normal CT appearance of the equine skull and presents examples and key features of several common diseases.

Signs consistent with syringobulbia may be detected in dogs undergoing MRI.

Syringobulbia is a pathologic condition characterized by one or more fluid-filled cavities within the brainstem. This retrospective case series describes observations in eight dogs with syringobulbia diagnosed during MRI. All dogs were adult, small-breed dogs with concurrent syringomyelia and neurologic deficits localized to sites rostral to the spinal cord, which cannot be explained by syringomyelia (eg, six dogs had vestibular signs). On MRI, the fluid-filled cavities had signal intensity characteristics like cerebrospinal fluid, were in the medulla oblongata, and were solitary in each dog. Initially, the shape of the cavity was a slit in five dogs and bulbous in two dogs. Magnetic resonance imaging was repeated in five dogs (6-55 months of age). One dog had progression of syringobulbia from slit-like to bulbous, and four dogs had unchanged slit-like syringobulbia. One dog developed slit-like syringobulbia after cranioplasty. A variety of medical and surgical treatments were performed with improvement of some but not all clinical signs. One dog died following surgery due to cardiopulmonary failure and the other seven dogs were alive at least 1 year after the initial diagnosis, which was the least time of follow-up. One surviving dog developed a unilateral hypoglossal nerve deficit 2 months after the initial diagnosis and megaesophagus 14 months later. In conclusion, detecting a fluid-filled cavity in the medulla oblongata consistent with syringobulbia is possible in dogs undergoing MRI. The cavity is likely acquired, slit-like or bulbous, progressive, or static, and might be associated with breed size and neurologic signs localized to the medulla oblongata.

Dogs with acute myeloid leukemia or lymphoid neoplasms (large cell lymphoma or acute lymphoblastic leukemia) may have indistinguishable mediastinal masses on radiographs.

Acute myeloid leukemia is an uncommon hematopoietic neoplasm of dogs that should be differentiated from lymphoid neoplasms, such as lymphoma, because of different treatment protocols and a worse prognosis. Thoracic radiography is performed frequently in dogs with suspected hematopoietic neoplasia, and detecting a mediastinal mass often prioritizes lymphoma as the most likely diagnosis. However, we have observed a mediastinal mass in several dogs with acute myeloid leukemia and hypothesized that (1) the frequency of a mediastinal mass was higher and (2) the size of the mass was larger in dogs with acute myeloid leukemia compared to dogs with lymphoid neoplasms. In this analytical study (observational, retrospective, and cross-sectional), the sample population included 238 dogs with hematopoietic neoplasia. These dogs were divided into lymphoid (large cell lymphoma, acute lymphoblastic leukemia) and myeloid groups based on standard phenotyping tests. A mediastinal mass was detected during thoracic radiography in 73/218 (33%) and nine of 20 (45%) dogs in the lymphoid and myeloid groups (P = 0.21), respectively. The median size ratio of mediastinal mass to cardiac silhouette was 0.20 and 0.23 in the lymphoid and myeloid groups (P = 0.96), respectively. Additionally, we observed normal thoracic radiographs in 111/218 (51%) dogs in the lymphoid group and nine of 20 (45%) dogs in the myeloid group. In conclusion, acute myeloid leukemia should be considered when a mediastinal mass is detected during radiography in dogs with suspected hematopoietic neoplasia-but the presence or size of a mediastinal mass does not differentiate between myeloid and lymphoid neoplasms.