William H. Adams

MRI of Brain Disease in Veterinary Patients Part 2: Acquired Brain Disorders

Magnetic resonance imaging (MRI) has revolutionized brain imaging in veterinary medicine, making possible improved characterization of intracranial pathologic processes. This article focuses on MRI features of acquired brain disorders, including infectious inflammatory, noninfectious inflammatory, cerebrovascular, metabolic, nutritional, toxic, degenerative, traumatic, and neoplastic causes. Congenital intracranial disorders are covered in a companion article.

Magnetic Resonance Imaging Susceptibility Artifacts Due to Metallic Foreign Bodies

Susceptibility artifacts due to metallic foreign bodies may interfere with interpretation of magnetic resonance (MR) imaging studies. Additionally, migration of metallic objects may pose a risk to patients undergoing MR imaging. Our purpose was to investigate prevalence, underlying cause, and diagnostic implications of susceptibility artifacts in small animal MR imaging and report associated adverse effects. MR imaging studies performed in dogs and cats between April 2008 and March 2010 were evaluated retrospectively for the presence of susceptibility artifacts associated with metallic foreign bodies. Studies were performed using a 1.0 T scanner. Severity of artifacts was graded as 0 (no interference with area of interest), 1 (extension of artifact to area of interest without impairment of diagnostic quality), 2 (impairment of diagnostic quality but diagnosis still possible), or 3 (severe involvement of area of interest resulting in nondiagnostic study). Medical records were evaluated retrospectively to identify adverse effects. Susceptibility artifacts were present in 99/754 (13.1%) of MR imaging studies and were most common in examinations of the brachial plexus, thorax, and cervical spine. Artifacts were caused by identification microchips, ballistic fragments, skin staples/suture material, hemoclips, an ameroid constrictor, and surgical hardware. Three studies were nondiagnostic due to the susceptibility artifact. Adverse effects were not documented.

Carcinoma ex Pleomorphic Adenoma with Sebaceous Differentiation in the Mandibular Salivary Gland of a Dog

A carcinoma ex pleomorphic adenoma was diagnosed in the left mandibular salivary gland of an 8-year-old female spayed dog. The animal presented with a large nonpainful swelling in the left submandibular region. A computed tomography scan detected an irregularly enhancing soft tissue mass that was closely associated with the left external ear canal and extended to the left wing of the atlas. On surgical exploration, the mass was intimately associated with the left mandibular salivary gland. Both the mass and the adjacent gland were removed, and the diagnosis was determined by histopathology. The tumor was comprised of basaloid and low columnar epithelial cells, many glandular units formed by well-differentiated sebocytes, and multifocal regions of necrosis, mineralization, and hemorrhage. Salivary gland tumors with sebaceous differentiation are very rare in animals, with one previously reported case in a cat.

Clinical and Imaging Findings in Five Dogs with Intracranial Blastomycosis (Blastomyces dermatiditis)

Fungal infections affecting the central nervous system are rare. The purpose of this study was to describe clinical and imaging findings in dogs with intracranial blastomycosis (Blastomyces dermatiditis). The radiology database was searched retrospectively for patients with a diagnosis of intracranial blastomycosis which had computed tomography performed as part of their diagnostic work-up. Medical records and imaging studies were reviewed. Five dogs met the inclusion criteria. Major presenting complaints were stertor/nasal discharge (n=2), exophthalmos (n=1), and seizures (n=2). Clinical and laboratory findings were variable. Computed tomographic examination revealed a single contrast-enhancing intra-axial mass (n=1), a nasal mass disrupting the cribriform plate (n=3), and an intracranial mass extending into the orbit and nasal cavity (n=1). Findings in intracranial blastomycosis in dogs are variable, and the disease may mimic other inflammatory disorders or neoplasia.

Radiation and intralesional chemotherapy for a fibrosarcoma in a boa constrictor, boa constrictor ortoni

ABSTRACT A 10-yr-old, female, boa constrictor, Boa constrictor ortoni, with a malignant subcutaneous fibrosarcoma of the body wall was treated with surgery and adjunctive radiation therapy. A total...

Radiotherapy-induced myelosuppression in dogs: 103 cases (2002-2006)

Definitive radiotherapy refers to delivery of large doses, typically 48-62 Gray, of ionizing radiation over several weeks using a daily or alternate-day fractionation schedule. The impact of definitive radiotherapy alone on haematopoiesis in tumour-bearing dogs is unknown. Medical records from 103 dogs receiving definitive (60) Cobalt teletherapy for cancer over a 5-year period were reviewed for signalment, tumour type and location, total radiotherapy dose and fractionation scheme. Complete blood count data were collected before, halfway through, and at the end of radiation treatment, and analysed for changes associated with patient variables. The results demonstrate significant reductions in haematocrit, total white blood cell count, neutrophils, eosinophils, monocytes, lymphocytes and platelets occurred during definitive radiotherapy but remained within laboratory reference intervals. These data are important for anticipation of toxicity associated with combinations of radiotherapy and chemotherapy in dogs but do not support the routine monitoring of haematology parameters during definitive radiotherapy.

Use of Contrast-Enhanced MR Angiography (CE-MRA) for the Diagnosis of a Vascular Ring Anomaly in a Dog

A 4-month-old female mixed breed dog was presented to the University of Tennessee College of Veterinary Medicine with a history of regurgitation and cachexia. Thoracic radiographs revealed focal megaesophagus cranial to the heart base. Magnetic resonance imaging (MRI) was performed. True fast imaging with steady-state precession (TrueFISP), fast low angle shot (FLASH), and short tau inversion recovery (STIR) sequences were acquired prior to contrast medium administration. Contrast-enhanced magnetic resonance angiography (CE-MRA) demonstrated focal megaesophagus and position of the aortic arch to the right of the esophagus. A small ductus diverticulum and an indistinct linear soft tissue band crossing the esophagus were also noted. Surgical exploration confirmed MR diagnosis of a persistent right aortic arch (PRAA) with left ligamentum arteriosum. The dog improved following surgery but was unable to be transitioned to dry food. To our knowledge this is the first report describing the use of CE-MRA for preoperative diagnosis and guided surgical treatment of a vascular ring anomaly in a dog.