Acute postretinal blindness: ophthalmologic,neurologic, and magnetic resonance imaging findings in dogs and cats (seven cases)

Objective To describe the ophthalmologic, neurologic, and magnetic resonance imaging (MRI) findings of seven animals with acute postretinal blindness as sole neurologic deficit. Methods Medical records were reviewed to identify dogs and cats with postretinal blindness of acute presentation, that had a cranial MRI performed as part of the diagnostic workup. Only animals lacking other neurologic signs at presentation were included. Complete physical, ophthalmic, and neurologic examinations, routine laboratory evaluations, thoracic radiographs, abdominal ultrasound, electroretinography, and brain MRI were performed in all animals. Cerebrospinal fluid analysis and postmortem histopathologic results were recorded when available. Results Four dogs and three cats met the inclusion criteria. Lesions affecting the visual pathways were observed on magnetic resonance (MR) images in six cases. Location, extension, and MRI features were described. Neuroanatomic localization included: olfactory region with involvement of the optic chiasm (n = 4), pituitary fossa with involvement of the optic chiasm and optic tracts (n = 1), and optic nerves (n = 1). Of all lesions detected, five were consistent with intracranial tumors (two meningiomas, one pituitary tumor, two nasal tumors with intracranial extension), and one with bilateral optic neuritis that was confirmed by cerebrospinal fluid analysis. Histologic diagnosis was obtained in four cases and included one meningioma, one pituitary carcinoma, one nasal osteosarcoma, and one nasal carcinoma. Conclusions Central nervous system (CNS) disease should be considered in dogs and cats with acute blindness, even when other neurologic deficits are absent. This study emphasizes the relevance of MRI as a diagnostic tool for detection and characterization of CNS lesions affecting the visual pathways.     

CT-GUIDED BRAIN BIOPSY USING A MODIFIED PELORUS MARK III STEREOTACTIC SYSTEM: EXPERIENCE WITH 50 DOGS

This report describes the results of CT-guided stereotactic brain biopsies performed on 50 consecutive dogs using a modified Pelorus Mark III Stereotactic System. Based on available histopathologic samples (stereotactic biopsy [n = 50], surgery [n = 17], necropsy [n = 9]) the patient population consisted of 34 dogs with primary brain tumors, 2 with invasive nasal adenocarcinomas, and 13 with non-neoplastic brain lesions. Brain tissue was not obtained from one dog. In 22 dogs a final diagnosis was made from tissue subsequently obtained from surgical resection or at necropsy. The final diagnosis was in agreement with the stereotactic biopsy diagnosis in 20 of these 22 dogs. In 17 other dogs without follow-up, stereotactic biopsy provided a diagnosis of a specific primary brain tumor subtype. Postoperative complications associated with the biopsy procedure were assessed in 41 dogs. The other 9 dogs either went directly to surgery (n = 7) or were killed (n = 2) immediately after the biopsy procedure. Thirty-six dogs recovered without apparent clinical complications. Postoperative clinical complications in the remaining 5 dogs included transient epistaxis (1 dog), transient exacerbation of cerebellar signs (1 dog), obtundation progressing to coma (1 dog), and medically uncontrollable seizures (2 dogs). The latter 3 dogs with severe neurologic complications all had large primary brain tumors and had been receiving high doses of phenobarbital and glucocorticoids to control seizures at the time of biopsy. These results suggest that this CT-guided biopsy procedure can provide an accurate pathologic diagnosis of brain lesions detected by CT and MR neuroimaging. Further refinement of both technique and case selection is expected to reduce the rate of clinical complications and to improve the accuracy of the procedure.     

Pituitary tumor size, neurologic signs, and relation to endocrine test results in dogs with pituitary-dependent hyperadrenocorticism: 43 cases (1980-1990).

Pituitary neoplasm was identified in 43 dogs with pituitary-dependent hyperadrenocorticism via necropsy (n = 33), diagnostic imaging with computerized tomography or magnetic resonance imaging (n = 5), or diagnostic imaging and necropsy (n = 5). All dogs had clinical signs and clinicopathologic test results typical of hyperadrenocorticism. Thirty-seven dogs had grossly visible pituitary tumors, and 6 dogs had microscopic pituitary tumors. Fifteen dogs had developed neurologic signs typical of those resulting from an enlarging pituitary mass. Twenty-three dogs had pituitary tumors greater than or equal to 1 cm in diameter. Provocative testing of the pituitary-adrenocortical axis was performed on all dogs. Dogs with grossly visible pituitary tumors and dogs with neurologic signs had significantly (P less than 0.05) higher mean plasma endogenous ACTH concentrations, compared with values from dogs with microscopic tumors and dogs without neurologic signs, respectively. Dogs with grossly visible pituitary tumors and dogs with tumors greater than or equal to 1 cm in diameter had significantly (P less than 0.05) lower adrenocortical responsiveness to exogenous ACTH, compared with dogs with microscopic pituitary tumors and dogs with tumors less than 1 cm in diameter, respectively. Despite these differences, there was overlap between test results among dogs. On the basis of endocrine test results, it would appear difficult to distinguish dogs with pituitary-dependent hyperadrenocorticism and large pituitary tumors from those with pituitary-dependent hyperadrenocorticism and microscopic pituitary tumors prior to onset of neurologic signs.     

MAGNETIC RESONANCE IMAGING FEATURES OF INTRACRANIAL ASTROCYTOMAS AND OLIGODENDROGLIOMAS IN DOGS

Astrocytomas and oligodendrogliomas represent one third of histologically confirmed canine brain tumors. Our purpose was to describe the magnetic resonance (MR) imaging features of histologically confirmed canine intracranial astrocytomas and oligodendrogliomas and to examine for MR features that differentiate these tumor types. Thirty animals with confirmed astrocytoma (14) or oligodendroglioma (16) were studied. All oligodendrogliomas and 12 astrocytomas were located in the cerebrum or thalamus, with the remainder of astrocytomas in the cerebellum or caudal brainstem. Most (27/30) tumors were associated with both gray and white matter. The signal characteristics of both tumor types were hypointense on T1‐weighted images (12 each) and hyperintense on T2‐weighted images (11/14 astrocytomas, 12/16 oligodendrogliomas). For astrocytomas and oligodendrogliomas, respectively, common findings were contrast enhancement (10/13, 11/15), ring‐like contrast enhancement (6/10, 9/11), cystic regions within the mass (7/14, 12/16), and hemorrhage (4/14, 6/16). Oligodendrogliomas were significantly more likely to contact the brain surface (meninges) than astrocytomas (14/16, 7/14, respectively, P=0.046). Contact with the lateral ventricle was the most common finding, occurring in 13/14 astrocytomas and 14/16 oligodendrogliomas. No MR features were identified that reliably distinguished between these two tumor types. Contrast enhancement was more common in high‐grade tumors (III or IV) than low‐grade tumors (II, P=0.008).     

Expression of vascular endothelial growth factor in tumors and plasma from dogs with primary intracranial neoplasms

OBJECTIVE: To quantitatively evaluate expression of vascular endothelial growth factor (VEGF) in intracranial tumors in dogs and determine whether relationships exist between circulating and intratumoral VEGF concentrations and tumor type and grade. ANIMALS: 27 dogs with primary intracranial neoplasms and 4 unaffected control dogs. PROCEDURES: Plasma and brain tumor samples were obtained from each dog, and plasma and intratumoral concentrations of VEGF were measured by use of an ELISA. RESULTS: Dogs with meningiomas (n = 11) were significantly older than dogs with oligodendrogliomas (7) or astrocytomas (9). Measurable VEGF was detected in all tumors, and a significant negative correlation between age and intratumoral VEGF concentration was detected. Age-adjusted comparisons identified significant differences in intratumoral VEGF concentrations among all tumor types; the highest VEGF concentrations were associated with astrocytomas. Within each tumor type, increasing tumor grade was significantly associated with increasing VEGF expression. Plasma VEGF concentrations were detectable in 9 of 27 dogs; the proportion of dogs with astrocytomas and a detectable circulating VEGF concentration (7/9 dogs) was significantly higher than the proportion of dogs with meningiomas (1/11 dogs) or oligodendrogliomas (1/7 dogs) with a detectable circulating VEGF concentration. CONCLUSIONS AND CLINICAL RELEVANCE: Overexpression of VEGF appears common in canine astrocytomas, oligodendrogliomas, and meningiomas. In the neoplasms examined, intratumoral VEGF concentrations correlated well with tumor malignancy. The VEGF expression patterns paralleled those of analogous human tumors, providing evidence that dogs are a suitable species in which to study angiogenesis and intracranial neoplasia for human application.     

MAGNETIC RESONANCE IMAGING OF ACQUIRED TRIGEMINAL NERVE DISORDERS IN SIX DOGS

The medical records and magnetic resonance (MR) images of dogs with an acquired trigeminal nerve disorder were reviewed retrospectively. Trigeminal nerve dysfunction was present in six dogs with histologic confirmation of etiology. A histopathologic diagnosis of neuritis (n=2) or nerve sheath tumor (n=4) was made. Dogs with trigeminal neuritis had diffuse enlargement of the nerve without a mass lesion. These nerves were isointense to brain parenchyma on T1-weighted (T1W) precontrast images and proton-density-weighted (PDW) images and either isointense or hyperintense on T2-weighted (T2W) images. Dogs with a nerve sheath tumor had a solitary or lobulated mass with displacement of adjacent neuropil. Nerve sheath tumors were isointense to the brain parenchyma on T1W, T2W, and PDW images. All trigeminal nerve lesions enhanced following contrast medium administration. Atrophy of the temporalis and masseter muscles, with a characteristic increase in signal intensity on T1W images, were present in all dogs.     

Canine intracranial primary neoplasia: 173 cases (1986-2003)

This study investigates the clinical and pathologic findings associated with 173 primary brain tumors in our hospital population of dogs that presented between the years 1986 and 2002. Of the 173 primary brain tumors, 78 (45%) were meningiomas, 29 (17%) were astrocytomas, 25 (14%) were oligodendrogliomas, 12 (7%) were choroid plexus tumors, and 7 (4%) were primary central nervous system lymphomas. Smaller numbers of glioblastomas (n = 5), primitive neuroectodermal tumors (n = 5), histiocytic sarcomas (n = 5), vascular hamartomas (n = 4), and unclassified gliomas (n = 3) were identified. One dog had both a meningioma and an astrocytoma. Most tumors were located within the telencephalon, and seizures were the most common clinical presenting complaint. Of 168 tumors for which a location in the brain was recorded at postmortem examination, 79 were found to involve more than 1 brain division. Other neoplasms unrelated to the primary brain tumor were identified on postmortem examination in 39 dogs (23%). Intrathoracic and intraabdominal neoplasms were present at necropsy in 13 and 24 cases, respectively. Based on the results of this study, thoracic radiographs and abdominal ultrasonography may be indicated to look for extracranial neoplasia prior to advanced imaging of the brain or intracranial surgery.     

INTRACRANIAL INTRA-ARACHNOID CYST WITH INTRACYSTIC HEMORRHAGE IN TWO DOGS

Clinical signs, magnetic resonance imaging (MRI) features, treatment, and outcome of two adult dogs with neurologic dysfunction resulting from hemorrhage into a quadrigeminal intracranial intra-arachnoid cyst are described. In dog 1, the cyst was hyperintense to cerebrospinal fluid (CSF) on T1-weighted MRI and hypointense to CSF on T2-weighted images. In dog 2, the cyst was isointense to CSF on T1- and T2-weighted images. Both dogs were treated with craniotomy and cyst fenestration. A large blood clot was removed from the lumen of the cyst in each dog. Dog 1 is clinically normal 3.5 years post-surgery and has a persistent cyst. Dog 2 had a good initial response to therapy but was euthanized 2.5 years post-operatively due to generalized seizures. The late onset of clinical signs in these dogs most likely resulted from hemorrhage into the cyst. Surgical fenestration and hematoma removal appear to provide a satisfactory treatment for adult dogs with an intracranial intra-arachnoid cyst and intracystic hemorrhage. Persistence of the cyst may occur in some dogs.     

MRI features of CNS lymphoma in dogs and cats

The magnetic resonance (MR) imaging features of central nervous system lymphoma in eight dogs and four cats are described. Intracranial lesions affected the rostrotentorial structures in six dogs and caudotentorial structures in two cats. Lesions affected the spinal cord in two dogs and in two cats. One dog and one cat with intracranial lymphoma had signs of local extracranial extension and lymphadenopathy. Lesions were considered extraparenchymal in four dogs and three cats, intraparenchymal in two dogs and one cat, and appeared to have both intra- and extraparenchymal components in two dogs. All lesions were hyperintense in T2-weighted images when compared to white matter, most were hypointense in T1-weighted images (7/12), and most were hyperintense in fluid-attenuated inversion recovery (FLAIR) images (5/9). When compared to grey matter, these lesions appear either isointense (5/12) or hyperintense (7/12) on T2-weighted images, half of them were hypointense in T1-weighted images (6/12), and most were isointense in FLAIR images (7/9). Lesion margins were usually indistinct in T2-weighted images (10/12) and had perilesional hyperintensity in FLAIR images (7/9). The majority of lesions (10/12) had abnormal meninges around the lesion and half (6/12) had generalized contrast enhancement. Mass effect was evident in all lesions. Although not specific, when combined with the history and neurologic signs, MR features aid presumptive diagnosis that should be confirmed by cytology or histopathology.     

Surgical technique, postoperative complications and outcome in 14 dogs treated for hydrocephalus by ventriculoperitoneal shunting

Objective: To report frequency and type of complications, and outcome in dogs with severe neurologic signs secondary to internal, suspected obstructive hydrocephalus treated by ventriculoperitoneal (VP) shunting. Study Design: Case series. Animals: Dogs (n=14). Methods: Medical records (2001–2006) was reviewed for dogs that had VP shunting. Inclusion criteria were complete medical record, progressive forebrain signs unresponsive to medical treatment, normal metabolic profile, negative antibody titers and/or cerebrospinal PCR for Toxoplasma gondii, Neospora caninum, and canine distemper virus, magnetic resonance images of the brain, confirmed diagnosis of VP shunting, and follow‐up information. Results: Hydrocephalus was idiopathic in 5 dogs and acquired (interventricular tumors, intraventricular hemorrhage, inflammatory disease) in 9 dogs. Four dogs developed complications 1 week to 18 months postoperatively, including ventricular catheter migration, infection, shunt under‐drainage, kinking of the peritoneal catheter, valve fracture, and abdominal skin necrosis. Three of these dogs had 1 or more successful revision surgeries and 1 dog was successfully treated with antibiotics. All, but 1 dog, were discharged within 1 week of surgery, and had substantial neurologic improvement. Median survival time for all dogs was 320 days (1–2340 days), for dogs with idiopathic hydrocephalus, 274 (60–420) days and for dogs with secondary hydrocephalus, 365 (1–2340) days. Conclusions: VP shunting was successful in relieving neurologic signs in most dogs and postoperative complications occurred in 29%, but were resolved medically or surgically.     

Clinical Signs of Tumors Affecting the Rostral Cerebrum in 43 Dogs

The clinical and pathologic features of 43 dogs with neoplasia of the rostral cerebrum were reviewed. Primary brain tumors included meningioma, astrocytoma, neuroblastoma, oligodendroglioma, and ependymoma. Other tumors that secondarily affected these areas included solitary hemangiosarcoma, nasal neuroendocrine carcinoma, nasal cell adenocarcinoma, nasal squamous cell carcinoma, and nasal neurofibrosarcoma. Older dogs were usually affected (mean, 10 years), and meningioma was the most frequent tumor type. Thirty-one dogs (72% of total) had a late-onset (greater than 5 years of age) of either generalized seizures or behavior abnormalities, or both, with an initially normal neurologic examination. In these 31 dogs, a mean time of 78 days (range, 2 to 400 days) elapsed from the onset of seizures or behavior change to the detection of a persistently abnormal neurologic examination. In all 43 dogs, the time from the detection of neurologic deficits to death or euthanasia and necropsy ranged from 1 to 63 days (mean, 13 days). On the basis of this review, it appears that dogs with late-onset seizures or behavior change, or both, should be suspected of having tumors involving the rostral cerebrum, despite the absence of persistent neurologic deficits commonly associated with cerebral tumors. Further, the onset of abnormalities in the neurologic examination and the time of death seem to occur within predictable time periods.     

Magnetic resonance imaging findings and clinical associations in 52 dogs with suspected ischemic myelopathy

BACKGROUND: The magnetic resonance imaging (MRI) features of ischemic myelopathy have been described in the human literature and in a small number of cases in the veterinary literature. HYPOTHESIS: The aims of this study were to identify associations among MRI findings, timing of imaging, and presenting neurologic deficits in a large series of dogs with a presumptive diagnosis of ischemic myelopathy. ANIMALS AND METHODS: The medical records and MR images of dogs with a presumptive diagnosis of ischemic myelopathy (2000-2006) were reviewed retrospectively. Inclusion criteria were acute onset of nonprogressive and nonpainful myelopathy, 1.5-tesla MRI of the spine performed within 7 days of onset, and complete medical records and follow-up information. Presumptive diagnosis was based on history, as well as clinical, MRI, and cerebrospinal fluid (CSF) findings. The extent of the lesion on MRI was assessed as the following: (1) the ratio between the length of the hyperintense area on sagittal T2-weighted images and the length of C6 or L2 vertebral body, and (2) the maximal cross-sectional area of the hyperintense area on transverse T2-weighted images as a percentage of cross-sectional area of the spinal cord. RESULTS: Fifty-two dogs met the inclusion criteria. MRI findings were abnormal in 41 dogs and normal in 11 dogs. The presence of MRI abnormalities was not significantly associated with the timing of imaging (P = .3) but was associated with ambulatory status on presentation (P = .04). Severity of signs on presentation was associated with extent of the lesion on MRI (P = .02). CONCLUSION AND CLINICAL IMPORTANCE: The severity of signs on presentation is associated with the presence and the extent of the lesion on MRI.     

Necrotizing meningoencephalitis in five Chihuahua dogs

An acute to chronic idiopathic necrotizing meningoencephalitis was diagnosed in 5 Chihuahua dogs aged between 1.5 and 10 years. Presenting neurologic signs included seizures, blindness, mentation changes, and postural deficits occurring from 5 days to 5.5 months prior to presentation. Cerebrospinal fluid analyses from 2 of 3 dogs sampled were consistent with an inflammatory disease. Magnetic resonance imaging of the brain of 2 dogs demonstrated multifocal loss or collapse of cortical gray/white matter demarcation hypointense on T1-weighted images, with T2-weighted hyperintensity and slight postcontrast enhancement. Multifocal asymmetrical areas of necrosis or collapse in both gray and white matter of the cerebral hemispheres was seen grossly in 4 brains. Microscopically in all dogs, there was a severe, asymmetrical, intensely cellular, nonsuppurative meningoencephalitis usually with cystic necrosis in subcortical white matter. There were no lesions in the mesencephalon or metencephalon except in 1 dog. Immunophenotyping defined populations of CD3, CD11d, CD18, CD20, CD45, CD45 RA, and CD79a immunoreactive inflammatory cells varying in density and location but common to acute and chronic lesions. In fresh frozen lesions, both CD1b,c and CD11c immunoreactive dendritic antigen-presenting cells were also identified. Immunoreactivity for canine distemper viral (CDV) antigen was negative in all dogs. The clinical signs, distribution pattern, and histologic type of lesions bear close similarities to necrotizing meningoencephalitis as described in series of both Pug and Maltese breed dogs and less commonly in other breeds.     

Clinical, morphologic, and morphometric features of cranial thoracic spinal stenosis in large and giant breed dogs

The clinical, morphologic, and morphometric features of cranial thoracic spinal stenosis were investigated in large and giant breed dogs. Seventy-nine magnetic resonance imaging studies of the cranial thoracic spine were assessed. Twenty-six were retrieved retrospectively and 53 were acquired prospectively using the same inclusion criteria. Images were evaluated using a modified compression scale as: no osseous stenosis (grade 0), osseous stenosis without spinal cord compression (grade 1), and osseous stenosis with spinal cord compression (grade 2). Morphometric analysis was performed and compared to the subjective grading system. Grades 1 and 2 cranial thoracic spinal stenosis were identified on 24 imaging studies in 23 dogs. Sixteen of 23 dogs had a conformation typified by Molosser breeds and 21/23 were male. The most common sites of stenosis were T2-3 and T3-4. The articular process joints were enlarged with abnormal oblique orientation. Stenosis was dorsolateral, lateralized, or dorsoventral. Concurrent osseous cervical spondylomyelopathy was recognized in six dogs and other neurologic disease in five dogs. Cranial thoracic spinal stenosis was the only finding in 12 dogs. In 9 of these 12 dogs (all grade 2) neurolocalization was to the T3-L3 spinal segment. The median age of these dogs was 9.5 months. In the remaining three dogs neurologic signs were not present. Stenosis ratios were of limited benefit in detecting stenotic sites. Grade 2 cranial thoracic spinal stenosis causing direct spinal cord compression may lead to neurologic signs, however milder stenosis (grade 1) is likely to be subclinical or incidental.     

Magnetic resonance imaging and histological classification of intracranial meningiomas in 112 dogs

BACKGROUND: Intracranial meningiomas are the most common primary brain tumors in dogs. Classification of meningiomas by tumor grade and subtype has not been reported, and the value of magnetic resonance imaging (MRI) characteristics for predicting tumor subtype and grade has not been investigated. HYPOTHESIS: Canine intracranial meningiomas are a heterogenous group of tumors with differing histological subtypes and grades. Prediction of histopathological classification is possible based on MRI characteristics. ANIMALS: One hundred and twelve dogs with a histological diagnosis of intracranial meningioma. METHODS: Retrospective observational study. RESULTS: Meningiomas were overrepresented in the Golden Retriever and Boxer breeds with no sex predilection. The incidence of specific tumor grades was 56% benign (Grade I), 43% atypical (Grade II), and 1% malignant (Grade III). Grade I histological subtypes included meningothelial (43%), transitional (40%), microcystic (8%), psammomatous (6%), and angiomatous (3%). No statistically significant (P < .05) associations were found among tumor subtype or grade and any of the MRI features studied. CONCLUSIONS AND CLINICAL IMPORTANCE: Meningiomas in dogs differ from their counterparts in humans mainly in their higher incidence of atypical (Grade II) tumors observed. MRI characteristics do not allow for prediction of meningioma subtype or grade, emphasizing the necessity of histopathology for antemortem diagnosis. The higher incidence of atypical tumors in dogs may contribute to the poorer therapeutic response in dogs with meningiomas as compared with the response in humans with meningiomas.     

Retrospective Review of 50 Canine Intracranial Tumors Evaluated by Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) was performed on 50 dogs with intracranial neoplasia. The following tumor features were assessed: axial origin, location, shape, growth pattern, MRI signal intensity, evidence for edema, and paramagnetic contrast enhancement. Histologic diagnoses included 5 intracranially invading nasal tumors, 7 pituitary tumors, 22 meningiomas, 6 choroid plexus tumors, 7 astrocytomas, 1 ependymoma, and 2 oligodendrogliomas. Axial origin, site, shape, and growth pattern were important diagnostic characteristics for tumor type. Signal intensity and contrast enhancement pattern allowed further differentiation. Characteristic MRI features that facilitate diagnosis and prognosis were identified. Accurate diagnosis of tumor type based on these features was not always possible because of similarities in MRI appearance for some tumors. Tissue biopsy remains necessary for definitive diagnosis of intracranial tumors.     

Changes of magnetic resonance imaging on the brain in beagle dogs with aging

Age-associated changes of magnetic resonance imaging (MRI) on the brain were evaluated in 19 beagle dogs aged from 8-month- to 16-year-old. A significant correlation of the volume of lateral ventricle space was observed in the dogs with age advanced, however, no correlation was found between hippocampus size and the aging. The hypo-intensity areas on T2-weighted MRI were detected in globus pallidus and substantia nigra with a significant correlation of both intensity ratios to lateral ventricle with age advanced. These areas were coincided with the accumulation of iron in the slice of the brain with Perls' staining. In addition, hyper-intensity area, suggesting perivascular demyelination with fluid-filled space, was also observed in white matter surrounding the lateral ventricle on T2-weighted MRI. These results suggested that age-associated changes of T2-weighted MRI were developed in the dog brain, especially in globus pallidus, substantia nigra, and white matter surrounding lateral ventricle, like as those reported in the human brain.     

A histologic and immunocytochemical study of choroid plexus tumors of the dog

Sixteen choroid plexus (CP) tumors in 12 male and four female adult dogs were analyzed microscopically. Tumors were in the lateral (six), third (six), and fourth (four) ventricles. The average age of the dogs was 6 years. Tumors were classified by the following criteria: 1) choroid plexus papilloma (CPP), which resembled normal choroid plexus and had low mitotic activity; 2) choroid plexus papilloma (CPP), which resembled normal choroid plexus and had low mitotic activity; 2) choroid plexus papilloma with atypical features (atypical CPP), which had increased cellular density, nuclear atypia, two to four mitoses per 40x microscopic field, necrosis, and infiltration of the brain parenchyma and/or leptomeninges; and 3) choroid plexus carcinoma (CPC), which had marked nuclear atypia, poorly formed papillae, greater than four mitoses per 40x microscopic field, abnormal mitotic figures, and/or extraneural metastasis. The 16 tumors were classified either as CPP or atypical CPP (none as CPC). Statistically significant associations between brain infiltration and necrosis and atypical CPP were identified. Immunohistochemical studies in 11 tumors demonstrated staining for keratin in three tumors, two of which also reacted with carcinoembryonic antigen (CEA). There was no immunoreactivity with glial fibrillary acidic protein or epithelial membrane antigen. Choroid plexus from one of three control dogs stained focally for cytokeratin only. It is concluded that normal choroid plexus and CP tumors in the dog express epithelial, but not glial differentiation.     

Magnetic resonance imaging of the femoral head of normal dogs and dogs with avascular necrosis.

The purpose of this study was to describe the appearance of the femoral head of normal, young, small breed dogs, and dogs with avascular necrosis using low-field (0.3 T) magnetic resonance (MR) imaging. Images of the femoral heads were obtained in the dorsal plane, and included T1-weighted spin-echo, T2-weighted fast spin-echo, fast spin echo-inversion recovery, and fluid attenuated inversion recovery pulse sequences. MR imaging features of the asymptomatic femoral heads and necks included uniform high signal intensity compared with muscle on T1- and T2-weighted images. There was either uniform enhancement or no enhancement on postcontrast T1-weighted images. The MR imaging findings of dogs affected with avascular necrosis differed from those of asymptomatic dogs. Typically, the affected dogs had inhomogeneous intermediate to low-signal intensity within the femoral head and neck compared with muscle on T1-weighted images, inhomogeneous enhancement of the femoral head and/or neck on postcontrast T1-weighted images, and inhomogeneous low- to high- signal intensity within the femoral head and neck on T2-weighted images.     

Imaging and surgical outcomes of spinal tumors in 18 dogs and one cat

Clinical and magnetic resonance imaging (MRI) findings, histological appearances and surgical outcomes of 18 dogs and one cat with spinal tumors are presented. Medical records of the cases admitted for spinal disorders were reviewed, and cases of spinal tumors that were diagnosed by MRI and confirmed by histological examination were included in this study. T1 weighted, T2 weighted and contrast enhanced T1 weighted images were taken and interpreted to evaluate the spinal tumors. The tumors were diagnosed as: meningioma (n = 6), ependymoma (n = 1), nerve sheath tumor (n = 4), metastatic spinal tumor (n = 3), osteosarcoma (n = 2), osteoma (n = 1), rhabdomyosarcoma (n = 1), and nephroblastoma (n = 1). Thirteen cases underwent surgical operation and the remaining six cases were euthanized at the request of the owners. The neurological status of the surgical cases did not deteriorate, except for one dog that showed ependymoma in the early period after the operation. These results indicate the potential for surgical gross total tumor removal of vertebral tumors to provide better quality of life and surgical collection of histological specimens for definitive diagnosis. For effective case management, dedicated MRI examination is important to accurate evaluation of the spinal tumors, and surgical treatment is useful for extradural and intradural-extramedullary spinal tumors.