Abby Caine

CLINICAL AND LOW‐FIELD MRI CHARACTERISTICS OF INJECTION SITE SARCOMA IN 19 CATS

Magnetic resonance imaging (MRI) has been recommended for staging and surgical planning in cats with injection site sarcomas (ISS). The purpose of this retrospective study was to describe low-field MRI characteristics of confirmed injection site sarcomas in a group of cats. Low-field MR images, thoracic radiographs, histopathology findings, and medical records of cats that fulfilled histological criteria of injection site sarcoma were retrieved and reviewed retrospectively. Presence or absence of tumor mineralization and pulmonary metastases were recorded from thoracic radiographs. Characteristics recorded from low-field MRI studies included tumor number, volume (ellipsoid method), intensity relative to surrounding musculature, homogeneity, regions of signal void (mineralization) or cavitation, degree and pattern of contrast enhancement, tumor margination, presence of a peripheral T2W hyperintense zone, and bone contact. A total of 19 cats met inclusion criteria. Cats with multiple tumors were more likely to have had previous excisional biopsy, and were less likely to undergo definitive surgery. All tumors were hyperintense relative to surrounding musculature on T1W and T2W images. Larger tumors were more likely to exhibit mineralization (P < 0.05). Tumor volume could not predict tumor-free margins at definitive surgery. The majority of tumors showed moderate to marked heterogeneous contrast enhancement. Infiltrative margins and the presence of a peripheral T2W hyperintense zone were more prevalent following excisional biopsy, while cavitation was more prevalent following incisional biopsy. Findings indicated that low-field MRI characteristics of injection site sarcoma may vary widely and may be affected by prior incisional or excisional biopsy.

IMAGING DIAGNOSIS—MAGNETIC RESONANCE IMAGING FINDINGS IN A DOG WITH SEQUENTIAL BRAIN INFARCTION

An adult greyhound was evaluated on three occasions for acute, intracranial neurologic signs. Based on magnetic resonance (MR) imaging, there were T2-hyperintense and T1-hypointense, noncontrast enhancing lesions in the cerebellum, and brain stem. Using diffusion-weighted imaging (DWI), the lesions were characterized initially by restricted water diffusion. The presumptive diagnosis on each occasion was acute ischemic cerebrovascular accident leading to infarction. This allowed us to characterize the changes in appearance of infarcted neural tissue on the standard MR sequences over time, and to confirm that the DWI could be successfully used in low-field imaging.

Prognostic significance of specific magnetic resonance imaging features in canine nasal tumours treated by radiotherapy

OBJECTIVES To investigate the prognostic significance of the magnetic resonance (MR) findings of meningeal hyperintensity of the olfactory bulbs and tumour extension into the caudal nasal recess (CNR) in dogs with nasal tumours treated by radiotherapy. METHODS MR images of 41 dogs with nasal tumours treated with radiotherapy were reviewed. The occurrence of neurological signs and survival of patients with and without meningeal hyperintensity of the olfactory bulbs and tumour extension into the CNR were analysed together with possible confounding factors including intracranial extension and patient age. RESULTS There was no significant association between the presence of meningeal hyperintensity or CNR involvement and the occurrence of neurological signs. Although there was a tendency towards shorter survival in dogs with tumour extension into the CNR, multivariable analysis showed no significant difference in survival between dogs with/without CNR involvement, meningeal hyperintensity or intracranial tumour extension (P=0.12, 0.50 and 0.57, respectively). CLINICAL SIGNIFICANCE In dogs with nasal tumours treated with radiotherapy, tumour extension into the cranium is not necessarily associated with shorter survival in patients without neurological signs at time of diagnosis. Although a definite influence of CNR involvement on case outcome could not be demonstrated, studies with a larger population are warranted.

MRI characteristics of fourth ventricle arachnoid diverticula in five dogs.

Intracranial arachnoid diverticula (cysts) are rare accumulations of cerebrospinal fluid (CSF) within the arachnoid membrane. The purpose of this retrospective study was to describe magnetic resonance imaging (MRI) characteristics of fourth ventricle arachnoid diverticula in a group of dogs. The hospitals medical records were searched for dogs with MRI studies of the brain and a diagnosis of fourth ventricle arachnoid diverticulum. Clinical characteristics were recorded from medical records and MRI studies were reinterpreted by a board-certified veterinary radiologist. Five pediatric dogs fulfilled inclusion criteria. Clinical signs included cervical hyperaesthesia, obtundation, tetraparesis, and/or central vestibular syndrome. In all five dogs, MRI findings were consistent with obstructive hydrocephalus, based on dilation of all ventricles and compression of the cerebellum and brainstem. All five dogs also had cervical syringohydromyelia, with T2-weighted hyperintensity of the gray matter of the cord adjacent to the syringohydromyelia. A signal void, interpreted as flow disturbance, was observed at the mesencephalic aqueduct in all dogs. Four dogs underwent surgical treatment with occipitalectomy and durotomy. A cystic lesion emerging from the fourth ventricle was detected in all four dogs during surgery and histopathology confirmed the diagnosis of arachnoid diverticula. Three dogs made excellent recovery but deteriorated shortly after surgery and were euthanized. Repeat MRI in two dogs revealed improved hydrocephalus but worsening of the syringohydromyelia. Findings from the current study supported theories that fourth ventricle arachnoid diverticula are secondary to partial obstruction of the central canal or lateral apertures and that arachnoid diverticula are developmental lesions in dogs.

Feline ischemic myelopathy and encephalopathy secondary to hyaline arteriopathy in five cats

Five cats presented with acute-onset neurological signs. Magnetic resonance imaging in four cats showed a T2-weighted hyperintense spinal cord lesion that was mildly contrast-enhancing in three cats. Owing to inflammatory cerebrospinal fluid changes three cats were treated with immunosuppression. One cat was treated with antibiotics. All cats improved initially, but were eventually euthanased owing to the recurrence of neurological signs. Histopathology in all cats showed hyaline degeneration of the ventral spinal artery, basilar artery or associated branches with aneurysmal dilation, thrombosis and ischemic degeneration and necrosis of the spinal cord and brain. Two cats also had similar vascular changes in meningeal vessels. Vascular hyaline degeneration resulting in vascular aneurysmal dilation and thrombosis should be a differential diagnosis in cats presenting with acute central nervous system signs.

IMAGING DIAGNOSIS—MAGNETIC RESONANCE IMAGING FEATURES OF CRANIOMANDIBULAR OSTEOPATHY IN AN AIREDALE TERRIER

An Airedale Terrier was presented for evaluation of depression and reluctance to be touched on the head. Magnetic resonance (MR) imaging of the head was performed. The images revealed bone lesions affecting the calvarium at the level of the coronal suture and left mandibular ramus, with focal cortical destruction, expansion, and reactive new bone formation. Skull lesions were hypointense on T1-weighted sequences, hyperintense on T2-weighted sequences, and showed an intense and homogeneous enhancement after gadolinium administration. Reactive new bone formation and periosteal proliferation were confirmed histopathologically. The clinical signs, imaging findings, and histopathological examination were consistent with craniomandibular osteopathy.

RADIOGRAPHIC CHARACTERIZATION OF THE OS PENIS IN THE CAT

The os penis in the cat has not been described radiographically, as compared with the dog. However, a small linear bony radiopacity is sometimes detected in the perineal area of male cats. We hypothesized that the feline os penis might be visible on survey radiographs of the pelvis, and we aimed to investigate the frequency of its visualization using analog and computed radiography (CR) system. One hundred radiographs of the pelvis of 99 male cats were reviewed retrospectively (50 were obtained with a CR system and 50 with an analog system). Age, breed, neutering status, and reason for presentation were recorded, as well as the visualization of the os penis. An os penis was detected in 19/50 (38%) cats with CR and in eight of 50 (16%) cats with analog radiography; this difference was statistically significant. With CR, the median age of cats with a visible os penis was significantly higher than in cats where the os penis was not seen. In one cat with a visible os penis examined with CR and analog radiography, the os penis was only visible on CR images. The penile tissues were examined histopathologically in one cat and well-differentiated bone was found but there were no pathologic findings detected in surrounding tissues. Thus, the os penis can be detected on radiographs of cats and this should not be mistaken for a pathologic finding such as urolithiasis or dystrophic mineralization.

Malignant melanoma with central nervous system involvement in a dog treated with surgery, radiotherapy and chemotherapy

A five-year-old female entire cocker spaniel was admitted for acute obtundation and non-ambulatory tetraparesis. MRI of the brain revealed a mass lesion in the right olfactory and frontal lobe area and in the right frontal sinus. Transfrontal craniotomy was performed for surgical excision, with intraoperative application of cytarabine and methotrexate. At discharge, the dog was ambulatory with mild generalised ataxia. Histopathology and immunohistochemistry revealed a malignant melanoma. Lomustine was initiated. Six months after surgery the dog was readmitted for right exophthalmos, due to a right retrobulbar mass that was surgically excised. Histopathology confirmed melanoma, and a course of radiotherapy was added and lomustine restarted. The dog was euthanased after further 17 months for relapsing neurological signs secondary to recurrent CNS melanoma. This treatment of a melanoma with CNS involvement showed encouraging results, achieving a total survival time of 23 months.

Repeated arterial chemoembolisation in a dog with an unresectable hepatocellular carcinoma

An 11-year-old male neutered Staffordshire bull terrier presented for investigation of inappetence and intermittent postprandial abdominal pain. An 8 cm diameter mass was documented within the right lateral lobe of the liver. An exploratory laparotomy was performed and removal attempted however the mass was unresectable. Biopsy confirmed a low-grade hepatocellular carcinoma. Arterial chemoembolisation was performed and the patient discharged three days later. The mass was documented to gradually reduce in size before slowly regrowing, then to remain stable until 10 months postchemoembolisation, when the patient again became inappetent. At this time the mass was 11.5 cm diameter. Repeat chemoembolisation was performed as previously. The patient developed pancreatitis following the procedure and remained hospitalised for 10 days. Five weeks after the second procedure, the mass had reduced to 8 cm in diameter. Signs of pancreatitis returned and the dog was euthanased nine weeks after the second procedure; 14 months after the first.

IMAGING DIAGNOSIS - MAGNETIC RESONANCE IMAGING OF INTRACRANIAL INFLAMMATORY FIBROSARCOMA IN A MIXED BREED DOG.

An 8-year-old mixed-breed dog presented with progressive behavioral changes and altered mentation. Magnetic resonance imaging (MRI) of the brain revealed an olfactory and frontal lobe extra-axial mass. The mass exhibited the following MRI signal intensity characteristics: T2W mixed, T1W iso- to hypointense, FLAIR hyperintense, and strong contrast enhancement. The mass was removed with cavitronic ultrasonic surgical aspirator (CUSA) assisted neurosurgery. Based on histopathological appearance and immunohistochemistry, the diagnosis of inflammatory fibrosarcoma was made. To our knowledge, this is the first report describing MRI characteristics of intracranial inflammatory fibrosarcoma in the veterinary literature.