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.

Extradural spinal synovial cysts in nine dogs.

Nine dogs presenting for investigation of cervical or thoracolumbar myelopathies were diagnosed with extradural spinal synovial cysts. Degenerative disease affecting the articular facets or intervertebral discs was present on plain spinal radiographs in all cases. Myelography was consistent with dorsolateral, extradural spinal cord compression. Two groups of dogs were identified: (1) young, giant breed dogs with multiple cysts involving one or more levels of the cervical spinal cord; and (2) older, large breed dogs with solitary cysts involving the thoracolumbar spinal cord. The synovial cysts constituted the major compressive lesions in four of the dogs. Analysis of lumbar cerebrospinal fluid demonstrated albuminocytological dissociation, consistent with chronic compressive myelopathy, in six dogs. All dogs underwent decompressive surgery and the diagnosis of synovial cysts was confirmed histologically. The mean follow-up period was 17 months (range four to 36 months). At the time of follow-up, all dogs were fully ambulatory with improved neurological function compared with that at initial presentation.

Primary canine and feline nervous system tumors: intraoperative diagnosis using the smear technique.

The recent application of neuroimaging techniques in veterinary neurology has led to the accurate localization of many types of intracranial lesions but has also created a clinical need, particularly with brain tumors, for a specific intraoperative diagnosis. For human brain tumors, a smear technique has been used successfully for many years to provide an extremely rapid, highly accurate intraoperative diagnosis. In similar smear preparations of intracranial lesions, obtained either by computed tomography (CT)-guided stereobiopsy or from a craniotomy, we have described distinguishing cytologic features of some primary spontaneous nervous system tumors in 80 dogs and 13 cats. A final diagnosis was confirmed by evaluation of paraffin-embedded sections from the same sample and, when appropriate, by immunocytochemical staining. Preliminary findings indicate that, in dogs and cats, this procedure is useful for rapid, accurate intraoperative diagnosis of many primary nervous system tumors. The distinguishing features of the canine and feline tumors bear a remarkably close resemblance to their human counterparts.

Prevalence of pituitary tumors among diabetic cats with insulin resistance.

OBJECTIVE: To determine prevalence of pituitary tumors, detectable by means of computed tomography or magnetic resonance imaging, in cats with insulin resistance suspected to have acromegaly or hyperadrenocorticism versus cats with well-controlled diabetes mellitus. DESIGN: Case series. ANIMALS: 16 cats with insulin resistance that were also suspected to have acromegaly (n = 12) or pituitary-dependent hyperadrenocorticism (4) and 8 cats with well-controlled diabetes mellitus. PROCEDURE: Computed tomography was performed on all 16 cats with insulin resistance and 2 cats in which diabetes mellitus was well-controlled. The remaining 6 cats in which diabetes mellitus was well-controlled underwent magnetic resonance imaging. Images were obtained before and immediately after i.v. administration of contrast medium. RESULTS: Computed tomography revealed a mass in the region of the pituitary gland in all 16 cats with insulin resistance. Maximum width of the masses ranged from 4.4 to 12.7 mm; maximum height ranged from 3.1 to 12.6 mm. Results of computed tomography performed on 2 cats with well-controlled diabetes and magnetic resonance imaging performed on the remaining 6 cats were considered normal. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cats with insulin resistance suspected to have acromegaly or pituitary-dependent hyperadrenocorticism are likely to have a pituitary mass detectable by means of computed tomography or magnetic resonance imaging.

Samarium 153-labeled hydroxyapatite microspheres for radiation synovectomy in the horse: a study of the biokinetics, dosimetry, clinical, and morphologic response in normal metacarpophalangeal and metatarsophalangeal joints.

OBJECTIVE: To determine the effects of Samarium-153 bound to hydroxyapatite microspheres (153SmM) when injected into the metacarpophalangeal and metatarsophalangeal joints of horses. STUDY DESIGN: - Horses were injected with 153SmM in metacarpophalangeal and metatarsophalangeal joints with the diagonal contralateral joints used as untreated controls. ANIMALS OR SAMPLE POPULATION: Twelve adult horses without pre-existing disease involving the metacarpo/metatarsophalangeal joints. METHODS: Horses were divided into three groups: high-dose Samarium-153 (12.5 to 17.0 millicurie [mCi]), intermediate dose (6.5 to 12.0 mCi), and low dose (3.5 to 6.0 mCi). Horses were examined daily for 7 days postinjection for clinical abnormalities, lameness, and surface and systemic radiation levels. One horse from each group was euthanatized at 14, 30, and 60 days postinjection and the effects of the 153SmM examined microscopically in the cartilage and synovial membrane. RESULTS: Intraarticular(153)SmM caused inflammation characterized by lameness, effusion, and regional edema for 48 to 72 hours. Minimal levels of active 153SmM were identified in the blood or urine and were well below the maximal tolerance of 1 mCi. Microscopically the radiation caused no effects on the articular cartilage. The synovectomy created was good but not ideal in that some areas did have necrosis into the subintimal regions and a few islands of intact intimal cells persisted. CONCLUSIONS: The use of 153SmM is an effective means of targeting the synovial intimal cells with minimal extrasynovial leakage of radiation. CLINICAL RELEVANCE: The metacarpophalangeal and metatarsophalangeal joints of the horse can be safely treated with 153SmM without damage to the cartilage or significant extracapsular leakage.

Clinical and pathologic features of oligodendrogliomas in two cats.

Two oligodendrogliomas in two domestic cats involved mainly the rostral brain stem, midbrain, fourth ventricle, and cerebellum. Both cats were aged neutered males presenting with clinical neurologic deficits suggestive of a brain stem lesion. Magnetic resonance imaging of both tumors demonstrated lesions with a pattern of heterogeneous contrast enhancement and multifocal lesions in one cat. Routine cerebrospinal fluid analysis was normal in one cat and suggestive of an inflammatory disease in the other. Oligodendroglioma cells were seen in cytospin preparations of cerebrospinal fluid from both cats. In each cat, the tumors occurred intraventricularly in the midbrain and fourth ventricle with aggressive intraparenchymal infiltration. There was extensive growth into the basilar subarachnoid space of the midbrain and brain stem in one cat. One tumor was well differentiated, and the other was an anaplastic subtype. Immunostaining for several myelin- and oligodendroglia-specific antigens was negative with formalin-fixed tumors and with unfixed frozen samples from one cat. In both tumors, component cells of the intratumoral vascular proliferations were positive for human von Willebrand factor VIII antigen or smooth muscle actin. Immunocytochemical reactivity for glial fibrillary acidic protein identified both reactive astrocytes and a subpopulation of minigemistocytes in both tumors. Ultrastructurally, the tumor cells were unremarkable except for their prominent desmosomal junctions and paucity of microtubules.

Contrast radiographic findings in canine bacterial discospondylitis: a multicenter, retrospective study of 27 cases.

A multicenter, retrospective study was undertaken to evaluate contrast radiographic findings in canine bacterial discospondylitis. Records and myelograms or epidurograms of 27 patients were obtained from five colleges of veterinary medicine. Fifteen cases (56%) were evaluated as having some degree of spinal cord compression. The majority (73.3%) of the cases had only soft tissue as the compressive mass. The median compression for all cases was 5% of the vertebral canal. No difference was noted for compression based on anatomical site (i.e., cervical versus thoracolumbar versus lumbosacral). No significant correlation between degree of lesion compression and clinical outcome was noted, but there was a trend toward increased mortality with greater compression. There was no correlation between the ambulatory status and the ultimate outcome. Three of the 15 (20%) cases showed vertebral subluxation. Results of this study indicate that static spinal cord compression is not a significant component of the neurological dysfunction associated with bacterial discospondylitis. Identification of vertebral subluxation in some patients may indicate a dynamic lesion that should be evaluated with stress radiography.

Reversible magnetic resonance imaging abnormalities in dogs following seizures.

Reversible magnetic resonance (MR) imaging lesions have been described in humans following seizures. This condition has not yet been reported in animals. This paper describes reversible abnormalities identified in 3 dogs using MR imaging that was performed initially within 14 days of the last seizure and follow-up imaging that was performed after 10 to 16 weeks of anticonvulsant therapy. All three dogs had lesions in the piriform/temporal lobes, characterized by varying degrees of hyperintensity on T2-weighted images and hypointensity on T1-weighted images. In one dog, contrast enhancement was evident. On reevaluation, partial resolution occurred in all 3 dogs. In a fourth animal with an olfactory meningioma, similar appearing lesions in the temporal cortex and right and left piriform lobes were identified after seizure activity. A surgical biopsy of the temporal cortex and hippocampus was performed and edema, neovascularization, reactive astrocytosis, and acute neuronal necrosis were evident. These histologic findings are similar to those reported in humans with seizures. Recognizing the potential occurrence of reversible abnormalities in MR images is important in developing a diagnostic and therapeutic plan in canine patients with seizures. Repeat imaging after seizure control may help differentiate between seizure-induced changes and primary multifocal parenchymal abnormalities.

Ultrasonographic evaluation of biliary cystadenomas in cats.

The purpose of this study was to describe the ultrasonographic appearance of biliary cystadenomas in cats and compare the findings to a similar rare form of liver tumor in humans. Biliary cystadenomas are uncommon, benign liver tumors of older cats that may occur as focal or multifocal cystic lesions within the liver. The records of 10 cats which had abdominal ultrasonography and histologic diagnosis of biliary cystadenoma were reviewed. The average age of affected cats was 13.3 years (range 10-16 years). Eight cats were neutered males and two were neutered females. In three cats, the tumors were not seen ultrasonographically due to their small size or from being obscured by near-field reverberation echoes. The remaining seven cats had solitary (4 cats) or multifocal (3 cats) masses corresponding to variable ultrasonographic patterns: multilocular masses containing thin-walled cysts, hyperechoic masses with cystic components, or masses of mixed echogenicity with cystic components. The masses had variable ultrasonographic patterns when multifocal disease was present. Recognizable cysts were evident somewhere within the tumors seen ultrasonographically, although sometimes the cysts appeared very small. The biliary cystadenomas were thought to be clinically silent. Although liver enlargement or a cranial abdominal mass was palpable in 4 cats, no consistent trend of clinical signs, CBC or serum biochemical abnormalities could be directly attributed to biliary cystadenoma. The treatment of choice is surgical resection of the tumor, as continued growth may compress adjacent vital structures within the liver. The differential diagnosis of biliary cystadenomas from other cystic liver lesions such as hepatic cysts, hematomas, abscesses, parasitic cysts, or other liver tumors is discussed.

Modification and application of a Pelorus Mark III stereotactic system for CT-guided brain biopsy in 50 dogs.

The Pelorus Mark III Stereotactic System is a commercially available device for CT-guided stereotactic brain biopsy in people. With relatively minor modifications, this device was used to safely and accurately perform CT-guided stereotactic brain biopsies in 50 dogs with intracranial lesions. Modifications were necessary to accommodate a 90 degree shift in orientation of the canine head compared to the human head during the imaging phase of the procedure, and to facilitate other phases of the biopsy procedure that are affected by the uneven and variable topography of the canine skull. Description of a typical CT-guided brain biopsy procedure in dogs using the modified Pelorus Mark III Stereotactic System is provided. Accuracy of biopsy needle placement was determined by comparing the x, y and z coordinates of the biopsy target site with the actual coordinates of the needle tip on CT images. Mean needle placement error was 3.5 +/- 1.6 mm. Needle placement error was not significantly related to operator experience, dog size (body weight), or needle path length, however, needle placement error was significantly affected by lesion location.

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.

Magnetic resonance imaging of the normal feline abdomen: an anatomic reference.

Magnetic resonance images of two adult domestic short-haired cats were obtained with a whole body scanner. Images of the abdomen were compared with cross-sectional anatomy cadaver specimens from the same two cats. Anatomic structures were first identified on the cadaver specimens with the aid of anatomy texts and references and were then identified and labeled on the magnetic resonance images. Results from this project provide an atlas of normal cross-sectional MRI anatomy of the feline abdomen.

Percutaneous ultrasound-guided trans-splenic catheterization of the portal vein in the dog.

The purpose of this investigation was to develop a safe and reliable technique for percutaneous catheterization of the portal vein via a major splenic vein using ultrasound guidance. Three separate catheter systems were evaluated on five anesthetized dogs. At least five attempts at catheterization of the splenic vein and subsequently the portal vein were attempted on each animal. Following the procedure the dogs were necropsied to assess for intrasplenic and intraabdominal hemorrhage. A technique using an introducer system and a large catheter was not successful on seven attempts. A technique using an over the needle catheter was successful in gaining access to the splenic vein on two out of five attempts; however the catheter could not be advanced into the portal vein. A technique utilizing 19 or 17 gauge needles with 22 or 19 catheter through-the-needle-catheters was successful in catheterization of the splenic vein and advancement to the portal vein on twelve of fifteen attempts. The smaller gauge needle and catheter system provided for easier access to the splenic vein and subsequent catheter manipulation facilitating access to the portal circulation.

Development of an automated 12-8 bit conversion algorithm for displaying and archiving scanned radiographs.

The lossless capture of the entire range of optical densities encountered in a radiograph can require up to 4000 individual shades of gray. Most inexpensive computer displays, and most grayscale image formats contain only 256 gray shades. To use these systems, a look up table must be generated to display the scanned image, which maps the approximately 4000 gray shades in the digitized radiograph to the 256 gray shades on the monitor. However, if this conversion is inappropriately performed, much of the information contained in the original image could be lost. This study was undertaken to develop an histogram equalization algorithm that would automatically convert the 4000 gray shade digitized radiograph into a 256 gray shade image file, without perceptable loss of diagnostic information or image quality.

Normal cross-sectional anatomy of the feline thorax and abdomen: comparison of computed tomography and cadaver anatomy.

Computed tomographic images of two adult domestic short-haired cats were obtained with a whole body scanner. Images of the thorax and abdomen were compared with cross-sectional anatomy cadaver specimens from the same two cats. Anatomic structures were first identified on the cadaver specimens with the aid of numerous anatomy texts and references and were then identified and labeled on the computed tomographic images. Results from this project provide an atlas of normal cross-sectional gross and CT anatomy of the feline thorax and abdomen that can be used in the interpretation of any cross-sectional imaging modality.

Cobalt 60 irradiation of pituitary gland tumors in three cats with acromegaly.

Acromegaly was diagnosed in 3 cats with insulin-resistant diabetes mellitus (DM) on the basis of history and physical examination findings, which ruled out other causes of insulin-resistant DM, and by documenting high plasma concentrations of growth hormone. Computed tomography revealed a mass in the area of the pituitary gland in each cat. Pituitary gland tumors were irradiated with cobalt 60, and none of the cats developed complications to radiotherapy. Each cat received a total dose of 48 Gy of cobalt 60 during 12 treatments. After completion of radiotherapy, insulin requirements were less for all cats, although in 1 cat, this improvement was transient. Diabetes mellitus resolved in 2 of 3 cats. After treatment, decreases in insulin requirements correlated with decreases in plasma growth hormone concentrations in 2 of 3 cats in which DM resolved. On the basis of these findings, irradiation of pituitary gland tumors appears to be a treatment option for cats with acromegaly.

Comparison of topical administration of clotrimazole through surgically placed versus nonsurgically placed catheters for treatment of nasal aspergillosis in dogs: 60 cases (1990-1996).

OBJECTIVE: To examine the clinical response to topical administration of clotrimazole in dogs with nasal aspergillosis, to compare effect of surgically placed versus nonsurgically placed catheters used for administration on outcome, and to examine whether subjective scoring of computed tomographic images can predict outcome. DESIGN: Retrospective case series. ANIMALS: 60 dogs with nasal aspergillosis. PROCEDURE: Information including signalment, history, diagnostics, treatment method, and outcome was retrieved from medical records of dogs with nasal aspergillosis treated between 1990 and 1996 at the University of California School of Veterinary Medicine or cooperating referral practices. Final outcome was determined by telephone conversations with owners and referring veterinarians. Images obtained before treatment were subjectively assessed to develop an algorithm for predicting outcome. RESULTS: Clotrimazole solution (1%) was infused during a 1-hour period via catheters surgically placed in the frontal sinus and nose (27 dogs) and via nonsurgically placed catheters in the nose (18). An additional 15 dogs received 2 to 4 infusions by either route. Topical administration of clotrimazole resulted in resolution of clinical disease in 65% of dogs after 1 treatment and 87% of dogs after one or more treatments. The scoring system correctly classified dogs with unfavorable and favorable responses 71 to 78% and 79 to 93% of the time, respectively. CLINICAL IMPLICATIONS: Topical administration of clotrimazole, using either technique, was an effective treatment for nasal aspergillosis in dogs. Use of non-invasive intranasal infusion of clotrimazole eliminated the need for surgical trephination of frontal sinuses in many dogs and was associated with fewer complications.

Efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadrenocorticism.

OBJECTIVE: To determine efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadrenocorticism (PDH) that have detectable tumors but no neurologic abnormalities. DESIGN: Case series. ANIMALS: 6 dogs with PDH that had a detectable pituitary mass on magnetic resonance images. PROCEDURE: Radiation was delivered in 11 fractions during a 3.5-week period for a total dose of 44 Gy. Clinical signs were evaluated, a urinalysis and ACTH stimulation test were performed, and urine cortisol-to-creatinine ratio and plasma endogenous ACTH concentration were measured before, immediately after, and 1, 3, 6, 9, and 12 months after radiotherapy. Magnetic resonance imaging was repeated 1 year after radiotherapy. RESULTS: Clinical signs of hyperadrenocorticism resolved in 3 dogs but recurred in 2 of the 3. Clinical condition of 2 dogs improved but did not return to normal. One dog did not improve. Results of ACTH stimulation tests and urine cortisol-to-creatinine ratios correlated with clinical signs. Plasma endogenous ACTH concentration transiently decreased in all 6 dogs. One year after radiotherapy, size of tumors was decreased by 25% in 2 dogs; in the other 4 dogs, tumors could no longer be detected. None of the dogs developed neurologic abnormalities. Adverse effects of radiotherapy were mild. CLINICAL IMPLICATIONS: Radiotherapy did not result in adequate control of clinical signs of hyperadrenocorticism in 5 of 6 dogs, but size of pituitary tumors was dramatically reduced. Thus, it may be reasonable to recommend radiotherapy in dogs with PDH that have pituitary tumors for which greatest vertical height is 8 mm or more.

Scintigraphic biodistribution and plasma kinetics of indium 111-labeled transferrin in dogs.

OBJECTIVE: To determine plasma clearance kinetics and imaging biodistribution of indium 111-labeled transferrin (111In-TF) in dogs. ANIMALS: 7 adult dogs. PROCEDURE: After 30 minutes' incubation of 18.5 MBq (0.5 mCi) of 111InCl3 with 1 ml of serum (n = 3) or 1 ml of plasma (n = 4) at 37 C, dogs were given autologous 111In-TF i.v., and serial blood samples and right lateral and dorsal scintigraphic images were obtained immediately and 1, 3, 5, 9, 22, and 48 hours later. Blood and plasma clearance kinetics were determined from a least-squares, nonlinear fit of the sample radioactivity data. Blood radioactivity was compared with plasma radioactivity to determine the extent of cellular labeling. Imaging biodistribution was characterized by subjective and objective assessment of blood pool, liver, gastrointestinal (abdomen) tract, kidney, and bone marrow activity. RESULTS: 111In-TF plasma clearance was best described by a biexponential fit, with early and late clearance half-times of 6 and 49 hours, respectively. The 111In was not redistributed between transferrin (plasma proteins) and blood cells. Imaging studies documented progressive liver and bone marrow uptake of the 111In-TF over 48 hours. Some radioactivity was evident in the colon of 1 dog on 48-hour images. Decay-corrected count rates (counts/pixel/mCi/kg/min) within the abdominal region of interest increased over the 48-hour imaging period and exceeded the blood pool (cardiac) activity at 20 hours after injection. CONCLUSION: 111In-TF has a biexponential plasma clearance in clinically normal dogs, with early and late clearance half-time of 6 and 49 hours, respectively. Scintigraphically, 111In-TF localizes to sites of iron storage (bone marrow and liver) over time. Some loss of 111In-TF via the gastrointestinal tract may be seen on late 48-hour images. CLINICAL RELEVANCE: 111In-TF appears to be a viable radiopharmaceutical for use in dogs, with specific application for identifying those with protein-losing enteropathy.