Gregg D. Kortz

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.

Glioblastoma Multiforme: Clinical Findings, Magnetic Resonance Imaging, and Pathology in Five Dogs:

Although glioblastoma multiforme (GBM), a World Health Organization grade IV astrocytoma, is the most common primary brain tumor in humans, in dogs GBM is relatively rare, accounting for only about 5% of all astrocytomas. This study presents combined clinical, neuroimaging, and neuropathologic findings in five dogs with GBM. The five dogs, aged from 5 to 12 years, were presented with progressive neurologic deficits that subsequent clinical neurologic examination and neuroimaging studies by magnetic resonance imaging (MRI), localized to space occupying lesions in the brain. MRI features of the tumors included consistent peritumoral edema (n = 5), sharp borders (n = 4), ring enhancement (n = 3), heterogenous T2-weighted signal intensity (n = 3), iso- to hypointense T1-weighted images (n = 5), necrosis (n = 5), and cyst formation (n = 2). Two tumors were diagnosed clinically using a computed tomography-guided stereotactic biopsy procedure. At necropsy all the tumors resulted in, on transverse sections, a prominent midline shift and had a variegated appearance due to intratumoral necrosis and hemorrhage. Histologically, they had serpentine necrosis with glial cell pseudopalisading and microvascular proliferation, features which distinguish human GBM from grade III astrocytomas. Immunoreactivity of tumor cells for glial fibrillary acidic protein was strongly positive in all cases, whereas 60% and 40% of the tumors also expressed epidermal growth factor receptor and vascular endothelial growth factor, respectively. These canine GBMs shared many diagnostic neuroimaging, gross, microcopic, and immunoreactivity features similar to those of human GBMs.

Clinical Signs, Magnetic Resonance Imaging Features, and Outcome After Surgical and Medical Treatment of Otogenic Intracranial Infection in 11 Cats and 4 Dogs

Brainstem dysfunction resulting from central extension of infection is a life-threatening complication of otitis media/interna (OMI) that has been described infrequently in dogs and cats. We review the clinical signs of disease, diagnostic findings, and results of surgical and medical treatments of brainstem disease attributable to otogenic intracranial infection in cats and dogs. Eleven cats and 4 dogs were examined because of acute, subacute, or chronic clinical signs of brain disease including central vestibular signs, altered mentation, abnormal posture/gait, cranial nerve deficits, and seizures. Results of a minimal database (CBC, serum biochemical panel, urinalysis, thoracic radiographs, and abdominal ultrasonographic images or radiographs) were within reference intervals in all animals. Magnetic resonance (MR) images of the head were acquired for all animals, and cisternal cerebrospinal fluid (CSF) from 9 of 11 cats and 3 of 4 dogs was examined. Surgical exploration and ventral bulla osteotomy were done for 12 of 15 animals, followed by 1-3 months of antibiotic therapy; the remaining animals were euthanized before treatment. In all animals, MR imaging was effective in characterizing the location and extent of the pathologic changes intracranially as well as within middle/inner ear structures. Results of CSF analysis were characteristic of bacterial infection in most of the animals with acute or subacute disease. Since long-term outcome in all treated animals was very good to excellent, it was concluded that dogs and cats with intracranial disease secondary to extension of otitis media/interna have a good-to-excellent prognosis when the condition was diagnosed and was treated by surgical exploration and appropriate antibiotic therapy.

Levetiracetam as an adjunct to phenobarbital treatment in cats with suspected idiopathic epilepsy.

OBJECTIVE To assess pharmacokinetics, efficacy, and tolerability of oral levetiracetam administered as an adjunct to phenobarbital treatment in cats with poorly controlled suspected idiopathic epilepsy. DESIGN-Open-label, noncomparative clinical trial. ANIMALS 12 cats suspected to have idiopathic epilepsy that was poorly controlled with phenobarbital or that had unacceptable adverse effects when treated with phenobarbital. PROCEDURES Cats were treated with levetiracetam (20 mg/kg [9.1 mg/lb], PO, q 8 h). After a minimum of 1 week of treatment, serum levetiracetam concentrations were measured before and 2, 4, and 6 hours after drug administration, and maximum and minimum serum concentrations and elimination half-life were calculated. Seizure frequencies before and after initiation of levetiracetam treatment were compared, and adverse effects were recorded. RESULTS Median maximum serum levetiracetam concentration was 25.5 microg/mL, median minimum serum levetiracetam concentration was 8.3 microg/mL, and median elimination half-life was 2.9 hours. Median seizure frequency prior to treatment with levetiracetam (2.1 seizures/mo) was significantly higher than median seizure frequency after initiation of levetiracetam treatment (0.42 seizures/mo), and 7 of 10 cats were classified as having responded to levetiracetam treatment (ie, reduction in seizure frequency of >or=50%). Two cats had transient lethargy and inappetence. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that levetiracetam is well tolerated in cats and may be useful as an adjunct to phenobarbital treatment in cats with idiopathic epilepsy.

Intravascular malignant T-cell lymphoma (malignant angioendotheliomatosis) in a cat.

A 7-year-old spayed female Siamese cat was presented with a 7-day history of ataxia, circling to the right, and involuntary micturition and defecation. Cerebrospinal fluid analysis showed increased protein content and relative eosinophilia. At necropsy, there was flattening of the cerebral cortical gyri of the right frontal and parietal lobes, and both kidneys had multiple wedge-shaped cortical indentations. Histologically, the cerebral cortex contained several extensive malacic foci, and the kidneys had multifocal parenchymal degeneration and atrophy. There was multifocal partial to complete thrombosis of renal interlobar arteries and of the right middle cerebral artery and meningeal branches; these thrombi contained large anaplastic round cells, which often invaded the arterial wall. Many smaller vessels within the kidneys and brain were occluded with clusters of similar cells, without thrombosis or vascular wall invasion. The neoplastic round cells had immunohistochemical staining properties of T lymphocytes.

Deficit of inhibitory glycine receptors in spinal cord from Peruvian Pasos: evidence for an equine form of inherited myoclonus

Inherited myoclonus in Poll Hereford calves and spasticity in the spastic mouse (spa/spa) are characterized by myoclonic jerks of the skeletal musculature which occur spontaneously and in response to sensory stimuli, symptoms resembling those in subconvulsive strychnine poisoning. The primary, biochemical defect in these myoclonic animals is a deficit of inhibitory glycine receptors in the central nervous system. We now report the occurrence of similar stimulus-induced myoclonus in individual, pure-bred Peruvian Paso horses and an associated, specific deficiency in the density of [3H]strychnine binding to inhibitory glycine receptors sites in spinal cord of these animals. Specificity of the deficit was confirmed by a demonstrated lack of change in the density of several other receptor types in affected spinal cord, including muscarinic receptors and GABAA/benzodiazepine receptors. In light of the existence of genetically-inherited myoclonus in other species, these results suggest the occurrence of an equine form of the disorder.