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.     

IMAGING DIAGNOSIS—MALIGNANT PERIPHERAL NERVE SHEATH TUMOR PRESENTING AS AN INTRA‐AXIAL BRAIN MASS IN A YOUNG DOG

A 3‐year‐old Labrador retriever was presented with acute onset seizures. Magnetic resonance imaging demonstrated an intra‐axial mass affecting the right temporal lobe of the brain. Surgical resection and histopathological findings were most consistent with a malignant peripheral nerve sheath tumor. After initial recovery, deterioration 3 months post surgery prompted euthanasia. Post‐mortem revealed a mass protruding from the ventral surface of the temporal lobe, encroaching upon the optic chiasm and invading the brain. Histopathology findings were again consistent with malignant peripheral nerve sheath tumor. Although rare, this tumor should be included as a possible differential diagnosis for intra‐axial brain masses in dogs.     

Magnetic resonance imaging of a cerebral cavernous haemangioma in a dog

A 13-month-old, neutered, male Golden retriever presented with seizures and progressive depression. Clinical and neurological assessment was consistent with severe intracranial disease. The neurological condition progressively deteriorated and magnetic resonance imaging (MRI) revealed the presence of a large, contrast-enhancing, space-occupyingmass in the right cerebral hemisphere. Therapy with corticosteroids, mannitol and furosemide ameliorated the signs of depression and ataxia, but the owner elected euthanasia after 1 week. Post mortem examination of the brain confirmed the presence of a large haemorrhagic lesion in the right olfactory lobe, the histopathological appearance of which was consistent with cerebral cavernous haemangioma. This is the 1st case describing the MRI appearance of a cavernous haemangioma of the cerebrum in the veterinary literature.     

Magnetic resonance imaging of a giant frontal hemorrhagic mucocele with intracranial extension in a cat

A 6‐year‐old domestic short‐haired cat was presented with an acute onset of right cortical encephalopathy. Magnetic resonance imaging (MRI) performed 4 days after the onset of clinical signs revealed a lesion originating from the right frontal sinus with intracranial extension and compression of the right frontal lobe. The lesion was T1‐weighted hypointense and T2‐weighted and fluid‐attenuated inversion recovery hyperintense. Signal voids within the lesion were observed on T2* images, consistent with hemorrhage. Peripheral ring enhancement was visible on postcontrast sequences. These features were consistent with a giant hemorrhagic mucocele. To the authors’ knowledge, this is the first report of MRI characteristics of this lesion in a cat.     

MAGNETIC RESONANCE IMAGING CHARACTERISTICS IN FOUR DOGS WITH CENTRAL NERVOUS SYSTEM NEOSPOROSIS

Neosporosis is a polysystemic disease that can affect dogs of any age and can cause inflammation of the central nervous system. Antemortem diagnosis can be challenging, as clinical and conventional laboratory test findings are often nonspecific. A previous report described cerebellar lesions in brain MRI studies of seven dogs and proposed that these may be characteristic for central nervous system Neosporosis. The purpose of this retrospective study was to describe MRI characteristics in another group of dogs with confirmed central nervous system neosporosis and compare them with the previous report. The hospital's database was searched for dogs with confirmed central nervous system neosporosis and four observers recorded findings from each dog's MRI studies. A total of four dogs met inclusion criteria. Neurologic examination was indicative of a forebrain and cerebellar lesion in dog 2 and multifocal central nervous system disease in dogs 1, 3, and 4. Magnetic resonance imaging showed mild bilateral and symmetrical cerebellar atrophy in three of four dogs (dogs 2, 3, 4), intramedullary spinal cord changes in two dogs (dogs 3, 4) and a mesencephalic and metencephalic lesion in one dog (dog 2). Multifocal brain lesions were recognized in two dogs (dogs 1, 4) and were present in the thalamus, lentiform nucleus, centrum semiovale, internal capsule, brainstem and cortical gray matter of the frontal, parietal or temporal lobe. Findings indicated that central nervous system neosporosis may be characterized by multifocal MRI lesions as well as cerebellar involvement in dogs.     

Cerebral vascular hamartoma with thrombosis in a dog

A cerebral vascular hamartoma was identified in the frontal lobe, striatum and thalamus of the right side of the brain of a male, 7-year-old Shih Tzu. Histologically, the lesion consisted of thin-walled vessels, which showed various sizes and occasionally contained fibrin thrombi. These vascular walls were composed of a single layer of fibromuscular tissue lined by flat endothelium with various amount of collagen, but devoid of large coat of smooth muscles and elastic tissue. Immunohistochemically, the lining endothelial cells were positive for von Willebrand Factor antibody. Neuropil between the vessels was stained with Klüver-Barrera stain, and positive for synaptophysin and GFAP antibodies. Based on these findings, the lesion was diagnosed as vascular hamartoma, which might resemble venous malformation in humans.     

Intracranial epidural mucocele in a cat

An 18-month-old, spayed female, domestic shorthaired cat was presented with clinical signs of depression and reluctance to walk, which progressed to nonambulatory tetraparesis. Increased opacification of both frontal sinuses and a cyst-like abnormality causing compression and displacement of the right frontal lobe were seen on computed tomography. Bilateral frontal sinus trephination and right transfrontal craniotomy revealed clear, viscous fluid in the right frontal sinus and rostral fossa, compatible with an intracranial mucocele. At a 6-month follow-up examination, no signs of recurrence were appreciated.     

Photodynamic detection of a canine glioblastoma using 5-aminolevulinic acid

Photodynamic detection using 5-aminolevulinic acid has been used to identify the surgical margins during resection of human primary brain tumours. Although there are some reports on its use in malignant tumours in veterinary medicine, it has never been used for primary brain tumours. Here we describe a canine glioblastoma that was detected at autopsy with protoporphyrin IX fluorescence induced by orally administered 5-aminolevulinic acid. The fluorescence was strongest towards the centre of the lesion and was absent in normal brain tissue. Moreover, the fluorescence findings were consistent with MRI and histopathological findings. Our findings suggest that photodynamic detection using 5-aminolevulinic acid might be useful for intraoperative fluorescence-guided resection of malignant gliomas in dogs.     

DIFFUSION‐WEIGHTED MAGNETIC RESONANCE IMAGING OF THE NORMAL CANINE BRAIN

Diffusion‐weighted imaging (DWI) MRI has been primarily reported as a method for diagnosing cerebrovascular disease in veterinary patients. In humans, clinical applications for diffusion‐weighted MRI have also included epilepsy, Alzheimer's, and Creutzfeld–Jakob disease. Before these applications can be developed in veterinary patients, more data on brain diffusion characteristics are needed. Therefore, the aim of this study was to evaluate the distribution of diffusion in the normal canine brain. Magnetic resonance imaging of the brain was performed in ten, clinically normal, purpose‐bred beagle dogs. On apparent diffusion coefficient maps, regions of interest were drawn around the caudate nucleus, thalamus, piriform lobe, hippocampus, semioval center, and cerebral cortex. Statistically significant differences in mean apparent diffusion coefficient were found for the internal capsule, hippocampus, and thalamus. The highest apparent diffusion coefficient (1044.29 ± 165.21 μm²/s (mean ± SD (standard deviation)) was detected in the hippocampus. The lowest apparent diffusion coefficient was measured in the semioval center (721.39 ± 126.28 μm²/s (mean ± SD)). Significant differences in mean apparent diffusion coefficients of the caudate nucleus, thalamus, and piriform lobe were found by comparing right and left sides. Differences between brain regions may occur due to differences in myelination, neural density, or fiber orientation. The reason for the differences between right and left sides remains unclear. Data from the current study provide background for further studies of diffusion changes in dogs with brain disease.     

Primary meningeal T-cell lymphoma in a harbor seal (Phoca vitulina).

A 15-year-old female harbor seal (Phoca vitulina) was referred to the Nantes Veterinary School, Nantes, France, with a clinical history of anorexia, seizures, and left hemiplegia. Cerebrospinal fluid analysis revealed large numbers of neoplastic lymphoid cells. After injection of a contrast agent into the cerebrospinal space, radiographs demonstrated an asymmetry of the right lateral ventricle. Necropsy examination revealed a marked edema of the right frontal lobe, extending to the basal nuclei and thalamus in the brain. Histological examination of the brain revealed leptomeningeal lymphoma. Immunohistochemical labeling demonstrated that the neoplasm was of T-cell origin. No significant macroscopic or microscopic lesions were observed in the other organs examined, including lymphoid organs. This is the first report of primary leptomeningeal lymphoma in a harbor seal.     

Surgical treatment and radiation therapy of frontal lobe meningiomas in 7 dogs

The cases of 7 adult dogs with generalized seizures managed by surgical excision and radiation therapy for frontal lobe meningiomas were reviewed. The neurological examination was unremarkable in 6 of the 7 dogs. Five dogs were operated on using a bilateral transfrontal sinus approach and 2 using a unilateral sinotemporal approach to the frontal lobe. One dog was euthanized 14 d after surgery; radiation therapy was initiated 3 wk after surgery in the remaining 6 dogs. Long-term follow-up consisted of neurological examination and magnetic resonance imaging (MRI) and/or computed tomography (CT) scan after radiation therapy. The mean survival time for dogs that had surgery and radiation therapy was 18 mo after surgery. Frontal lobe meningiomas have been associated with poor prognosis. However, the surgical approaches used in these cases, combined with radiation therapy, allow a survival rate for frontal lobe meningiomas similar to that for meningiomas located over the cerebral convexities.     

Paraneoplastic polyneuropathy and subsequent recovery following tumor removal in a dog.

A 10-year-old, intact female Brittany spaniel was presented for evaluation of progressive tetraparesis. Physical examination and diagnostic testing revealed masses within the right mammary chain and left caudal lung lobe. Neuromuscular electrodiagnostic and histopathological findings were compatible with a peripheral polyneuropathy. Upon removal of the tumors, the dog's paresis disappeared. To the authors' knowledge, this is the first reported case in the veterinary literature of improvement following therapy of a suspected paraneoplastic neuropathy.     

Long-term chemotherapy with lomustine of intracranial meningioma occurring in a miniature schnauzer

A 14-year-old male miniature schnauzer was referred to us because it was circling to the right. A mass in the diencephalon was noted on brain magnetic resonance images. The dura was thickened with marked linear enhancement after contrast administration. Based on diagnostic image analysis, this lesion strongly suggested meningioma. The patient's symptoms were well controlled by a combination therapy of prednisolone and lomustine (CCNU), and survived for thirteen months after diagnosis. This case was diagnosed as a meningioma based on histopathological findings. This report describes the clinical findings, imaging characteristics, and pathologic features of a diencephalic and mesencephalic meningioma and long-term survival after lomustine and prednisolone therapy.     

Cerebral high-grade astrocytoma (glioblastoma) in a cat

A cerebral tumour was found in the right frontal lobe of a 7-year-old female mongrel cat. The mass showed infiltrative growth and caused deformation of the corpus callosum. Histopathologically, the tumour cells showed anaplasia, pleomorphism and mitotic figures. Necrosis and vascular proliferation were prominent. The neoplastic cells surrounded areas of necrosis, but as an indistinct pseudopalisade formation. Immunohistochemically, low numbers of tumour cells labelled positively for anti-glial fibrillary acidic protein and anti-S100 protein. Electron microscopically, the majority of tumour cells had no filaments and cytoplasmic processes, but the differentiated cells presented cytoplasmic filaments and glycogen granules. Based on these findings, the tumour was diagnosed as cerebral high-grade astrocytoma, glioblastoma.     

Patho-morphologic and histoenzymologic findings after VX (organophosphate) poisoning in sheep]

Sixty-one sheep were administered experimentally a VX chemical (organophosphate) at different rates. In the process of dissection, samples were taken for a histopathological examination. These were samples of brain, liver, kidneys, rumen wall, small intestine, muscles, myocardium, lungs and spleen. For another histochemical examination, samples of tongue, m. longissimus dorsi, jejunum, rumen, liver, kidneys and m. interconstalis were also taken. The activities of alkaline and acid phosphatase, nonspecific esterase, acetylcholinesterase and dehydrogenase of lactic acid were investigated. The most significant changes were found out in the lungs - in form of oedemas and acute catarrhal bronchopneumonias in those animals which died within three days after chemical administration. Sporadic haemorrhages or haemorrhages in form of vast spots were found out under the epicardium. Their range did not relate to the amount of the chemical administered. Rather dilated vessels were observed in the brain and also in the meninges. The histochemical examination showed different activities of enzymes in particular organs of sheep.     

Diagnosis and treatment of a cerebral infarct in a chimpanzee (Pan troglodytes).

A 29-yr-old chimpanzee (Pan troglodytes) presented after an acute onset of right facial and forearm paresis that progressed to paralysis within 24 hr, with subsequent development of right leg paresis. Magnetic resonance imaging (MRI) of the head revealed an abnormal region of increased signal intensity in the left frontal, parietal, and temporal cerebral hemispheres, corresponding to the vascular territory of the middle cerebral artery, with resultant compression of the left lateral ventricle. The findings were consistent with a cerebral infarct (stroke). MRI is the most sensitive test for early detection of cerebral changes due to ischemia and was essential in obtaining a diagnosis in this case. The chimpanzee responded well to treatment with long-term anticoagulant aspirin and a short, tapered course of prednisone and regained full gross motor function.     

Feline hippocampal and piriform lobe necrosis as a consequence of severe cluster seizures in two cats in Finland

Feline hippocampal and piriform lobe necrosis (FHN) has been reported from several countries worldwide and is considered an important aetiology for feline epileptic seizures. The aetiology of FHN remains unclear, however it is suspected that FHN might occur secondary to intense epileptic activity as described in humans and dogs although this has not yet been documented in cats. The purpose of our report is to describe the first cases of FHN in Finland diagnosed by magnetic resonance imaging (MRI) and histopathology. The two cases we describe had a well documented history of pre-existing seizures with normal brain MRI at the onset of cluster seizures but MRI done when the cats exhibited clinical deterioration secondary to severe seizure activity, revealed lesions in the hippocampus and piriform lobes typical of FHN. Our report confirms that feline hippocampus and piriform lobe necrosis does occur in the Finnish cat population and should therefore be considered as a differential diagnosis in cats with seizures. In addition, the presentation, clinical findings, results of MRI and/or histopathology shows that cats may develop FHN secondary to severe seizure activity.     

High‐field (3 Tesla) MRI of the navicular apparatus of sound horses shows good agreement to histopathology

Magnetic resonance imaging and the correlation to histopathological findings of the equine palmar foot of lame horses have been described previously, using 0.27 and 1.5 T systems. Compared to these, 3 T systems provide superior spatial resolution and imaging contrast. The aim of our prospective anatomic study was to characterize the imaging anatomy of the navicular region on 3 T MRI in comparison to histopathological findings. We hypothesized that 3 T MRI allows a good visualization of the entire navicular apparatus and reliable measurements of navicular cartilage and cortical bone thickness. Twenty front feet of sound horses were examined using a 3 T MRI system. For histopathological examination, sagittal tissue sections of the navicular bones and adjacent ligaments were prepared. Alterations in magnetic resonance signal were graded for each region and compared to corresponding histological slices. Overall, there was good visualization of the anatomical detail and a very good agreement between MRI and histology for compact bone and spongiosa, good agreement for the fibrocartilage and the distal sesamoidean impar ligament, but only moderate agreement for the hyaline cartilage and the collateral sesamoidean ligament. A comparative measurement of cartilage and cortical bone thickness on magnetic resonance images and histological sections was performed. In MRI, the hyaline cartilage of the articular surface appeared significantly thinner and the fibrocartilage of the flexor surface appeared significantly thicker compared to histology. Findings indicated that MRI at a field strength of 3 T allows reliable depiction of anatomic details of the navicular apparatus.