Amanda R. Taylor

Application and machine accuracy of a new frameless computed tomography-guided stereotactic brain biopsy system in dogs.

The purpose of this study was to describe application and machine accuracy for a new computed tomography (CT) guided, frameless, stereotactic brain biopsy system in dogs. Heads from ten canine cadavers were secured to a bite-plate with six attached fiducial markers and imaged using CT. Fiducialized CT images were imported into stereotactic software and spherical phantom lesions between 3.9 and 5.5 mm in diameter were created in six locations. Infrared cameras and reflective markers were used to register fiducials to the reconstructed image set. Coordinates in the X, Y, and Z planes were identified for each lesion center. Iohexol (1.5 μl of 240 mgI/ml) was injected into the center of each lesion and CT scans were repeated. Pre- and postinjection CT images for each cadaver were fused using the system software. Application accuracy was calculated using the center of each phantom lesion and the center of each injected contrast material location. Machine accuracy was calculated using a phantom with known distances between four fixed points in the X, Y, and Z planes. Mean application accuracy in the first 5 cadavers was 4.3 mm (95% confidence interval [CI] 2.9-4.3 mm) and in the second 5 cadavers was 2.9 mm (95% CI 2-3.9 mm). The more superficial lesions were targeted significantly less accurately than the deeper lesions (P = 0.0183). Median machine accuracy was 0.1 mm and the range was 0.1-0.2 mm. Findings supported use of the new biopsy system for canine brain lesions >3.9 mm in diameter.

Frequency of Resistance in Obligate Anaerobic Bacteria Isolated from Dogs, Cats, and Horses to Antimicrobial Agents

ABSTRACT Clinical specimens from dogs, cats, and horses were examined for the presence of obligate anaerobic bacteria. Of 4,018 specimens cultured, 368 yielded 606 isolates of obligate anaerobic bacteria (248 from dogs, 50 from cats, and 308 from horses). There were 100 specimens from 94 animals from which only anaerobes were isolated (25 dogs, 8 cats, and 61 horses). The most common sites tested were abdominal fluid (dogs and cats) and intestinal contents (horses). The most common microorganism isolated from dogs, cats, and horses was Clostridium perfringens (75, 13, and101 isolates, respectively). The MICs of amoxicillin with clavulanate, ampicillin, chloramphenicol, metronidazole, and penicillin were determined using a gradient endpoint method for anaerobes. Isolates collected at necropsy were not tested for antimicrobial susceptibility unless so requested by the clinician. There were 1/145 isolates tested that were resistant to amoxicillin-clavulanate (resistance breakpoint ≥ 16/8 μg/ml), 7/77 isolates tested were resistant to ampicillin (resistance breakpoint ≥ 2 μg/ml), 4/242 isolates tested were resistant to chloramphenicol (resistance breakpoint ≥ 32 μg/ml), 12/158 isolates tested were resistant to clindamycin (resistance breakpoint ≥ 8 μg/ml), 10/247 isolates tested were resistant to metronidazole (resistance breakpoint ≥ 32 μg/ml), and 54/243 isolates tested were resistant to penicillin (resistance breakpoint ≥ 2 μg/ml). These data suggest that anaerobes are generally susceptible to antimicrobial drugs in vitro.

Clinical Features and Magnetic Resonance Imaging Findings in 7 Dogs with Central Nervous System Aspergillosis.

Background Systemic aspergillosis is a manifestation of Aspergillus sp. infection that can result in central nervous system (CNS) involvement with marked alterations in CNS function. Information regarding the clinical presentation and magnetic resonance imaging (MRI) findings in cases of aspergillosis with CNS involvement is lacking, resulting in a need for better understanding of this disease. Hypothesis/Objectives The primary objectives were to describe the clinical features and MRI findings in dogs with CNS aspergillosis. The secondary objectives were to describe clinicopathologic findings and case outcome. Animals Seven dogs with CNS aspergillosis. Methods Archived records from 6 institutions were reviewed to identify cases with MRI of CNS aspergillosis confirmed with serum galactomannan enzyme immunoassay (EIA) testing, culture, or supported by histopathology. Signalment, clinical, MRI, clinicopathologic, histopathologic, and microbiologic findings were recorded and evaluated. Results Aspergillosis of the CNS was identified in 7 dogs from 3 institutions. The median age was 3 years and six were German Shepherd dogs. Five dogs had signs of vestibular dysfunction as a component of multifocal neurological abnormalities. The MRI findings ranged from normal to abnormal, including hemorrhagic infarction and mass lesions. Conclusions and Clinical Importance Until now, all reported MRI findings in dogs with CNS aspergillosis have been abnormal. We document that CNS aspergillosis in dogs, particularly German Shepherd dogs, can be suspected based on neurologic signs, whether MRI findings are normal or abnormal. Confirmatory testing with galactomannan EIA, urine, cerebrospinal fluid (CSF) or tissue culture should be performed in cases where aspergillosis is a differential diagnosis.

IMAGING DIAGNOSIS—SPINAL CORD HISTIOCYTIC SARCOMA IN A DOG

A 12-year-old mixed breed dog was presented for evaluation of progressive paraparesis and ataxia. Magnetic resonance (MR) imaging was performed and identified multifocal intradural spinal cord mass lesions. The lesions were hyperintense in T2-weighted sequences, isointense to mildly hyperintense in T1-weighted sequences with strong contrast enhancement of the intradural lesions and spinal cord meninges. Spinal cord neoplasia was suspected. A diagnosis of intramedullary spinal cord histiocytic sarcoma, confined to the central nervous system, was confirmed histopathologically. Spinal cord histiocytic sarcoma is a rare neoplasm, but should be included in the differential diagnosis for dogs with clinical signs of myelopathy.

Lipidomic Evaluation of Feline Neurologic Disease after AAV Gene Therapy

GM1 gangliosidosis is a fatal lysosomal disorder, for which there is no effective treatment. Adeno-associated virus (AAV) gene therapy in GM1 cats has resulted in a greater than 6-fold increase in lifespan, with many cats remaining alive at >5.7 years of age, with minimal clinical signs. Glycolipids are the principal storage product in GM1 gangliosidosis whose pathogenic mechanism is not completely understood. Targeted lipidomics analysis was performed to better define disease mechanisms and identify markers of disease progression for upcoming clinical trials in humans. 36 sphingolipids and subspecies associated with ganglioside biosynthesis were tested in the cerebrospinal fluid of untreated GM1 cats at a humane endpoint (∼8 months), AAV-treated GM1 cats (∼5 years old), and normal adult controls. In untreated GM1 cats, significant alterations were noted in 16 sphingolipid species, including gangliosides (GM1 and GM3), lactosylceramides, ceramides, sphingomyelins, monohexosylceramides, and sulfatides. Variable degrees of correction in many lipid metabolites reflected the efficacy of AAV gene therapy. Sphingolipid levels were highly predictive of neurologic disease progression, with 11 metabolites having a coefficient of determination (R2) > 0.75. Also, a specific detergent additive significantly increased the recovery of certain lipid species in cerebrospinal fluid samples. This report demonstrates the methodology and utility of targeted lipidomics to examine the pathophysiology of lipid storage disorders.

Fungal Infections of the Central Nervous System in Small Animals: Clinical Features, Diagnosis, and Management

Small animal mycoses vary geographically. Different clinical presentations are seen in animals with infection of the central nervous system (CNS), including multifocal meningoencephalomyelitis, intracranial lesions that accompany sinonasal lesions, rapidly progressive ventriculitis, or solitary granuloma of the brain or spinal cord. Systemic, nasal, or extraneural clinical signs are common but, especially in granuloma cases, do not always occur. Surgery may have a diagnostic and therapeutic role in CNS granuloma. There have been recent advancements in serology. Fluconazole, voriconazole, and posaconazole cross the blood-brain barrier, but voriconazole is neurotoxic to cats. Liposomal and lipid-encapsulated formulations of amphotericin B are preferred.

Use of a frameless computed tomography–guided stereotactic biopsy system for nasal biopsy in five dogs

CASE DESCRIPTION 5 dogs (median age, 9 years; median body weight, 31 kg [68.2 lb]) with undefined nasal masses were examined after undergoing CT of the head and nasal biopsy via a rostral rhinoscopic or unaided (blind) approach because histologic results for collected biopsy specimens (inflammatory, necrotic, or hemorrhagic disease) suggested the specimens were nonrepresentative of the underlying disease process identified via CT (aggressive or malignant disease). CLINICAL FINDINGS Clinical signs at the time dogs were evaluated included open-mouth breathing, sneezing, or unilateral epistaxis. Histologic findings pertaining to the original biopsy specimens were suggestive of benign processes such as inflammation. In an attempt to obtain better representative specimens, a frameless CT-guided stereotactic biopsy system (CTSBS) was used to collect additional biopsy specimens from masses within the nasal and sinus passages of the dogs. The second set of biopsy specimens was histologically evaluated. TREATMENT AND OUTCOME Histologic evaluation of biopsy specimens collected via the CTSBS revealed results suggestive of malignant neoplasia (specifically, chondrosarcoma, hemangiopericytoma, or undifferentiated sarcoma) for 3 dogs, mild mixed-cell inflammation for 1 dog, and hamartoma for 1 dog. No complications were reported. These findings resulted in a change in treatment recommendations for 3 dogs and confirmed that no additional treatment was required for 1 dog (with hamartoma). For the remaining dog, in which CT findings and clinical history were strongly suggestive of neoplasia, the final diagnosis was rhinitis. CLINICAL RELEVANCE Biopsy specimens were safely collected from masses within the nasal and sinus passages of dogs by use of a frameless CTSBS, allowing a definitive diagnosis that was unachievable with other biopsy approaches.

Clinical Evaluation of the Feline Neurologic Patient

Efficient, gentle, and safe handling of cats can result in complete neurologic evaluations and accurate neuroanatomic localizations. The clinic environment should facilitate the examination by providing a quiet and secure environment for the cat. When direct examination of a cat is not possible, the practitioner should fully use indirect methods of examination and video recordings of cat behavior or clinical signs. Direct examination of a cat should proceed in a logical order, where the most useful tests are performed early on in the examination.

Diagnostic Imaging of Discospondylitis

Discospondylitis can affect dogs of any age and breed and may be seen in cats. Although radiography remains the gold standard, advanced imaging, such as CT and MRI, has benefits and likely allows earlier diagnosis and identification of concurrent disease. Because discospondylitis may affect multiple disk spaces, imaging of the entire spine should be considered. There is a lengthening list of causative etiologic agents, and successful treatment hinges on correct identification. Image-guided biopsy should be considered in addition to blood and urine cultures and Brucella canis screening and as an alternative to surgical biopsy in some cases.

A serious adverse event secondary to rapid intravenous levetiracetam injection in a dog: Adverse event following levetiracetam injection

OBJECTIVE To describe a serious adverse event as a result of rapid intravenous injection of undiluted levetiracetam in a dog. CASE SUMMARY An 8-year-old female spayed Chihuahua was evaluated for cluster seizures and tachypnea. The patient was administered an intravenous dose of undiluted levetiracetam (60 mg/kg) and immediately developed tachycardia, hyperglycemia, hypotension, and a dull mentation. The patients blood pressure and mentation did not respond to intravenous fluid boluses but improved immediately after administration of epinephrine intravenously. The patient subsequently developed respiratory failure necessitating mechanical ventilation, prior to cardiac arrest. Necropsy examination noted a pulmonary inflammatory cell infiltrate, pulmonary edema, and interstitial pneumonia. NEW OR UNIQUE INFORMATION PROVIDED This report documents a serious adverse event associated with intravenous levetiracetam administration to a dog.