Four Cases of the Melanotic Variant of Malignant Nerve Sheath Tumour: a Rare, Aggressive Neoplasm in Young Dogs with a Predilection for the Spinal Cord.

Four cases of a rare melanotic variant of malignant nerve sheath tumour (MNST) in dogs are described. All four cases presented with neurological clinical signs due to multicentric, intradural, intra- and extraparenchymal neoplasms that surrounded the spinal and cranial nerves and infiltrated the adjacent spinal cord and brain. The dogs were young (3 months to 3 years of age), all were female and four different breeds were represented. Characteristic histological features were interweaving fascicles of spindle-shaped cells, sometimes with an architecture reminiscent of Antoni A and B patterns. Some spindle cells showed prominent cytoplasmic melanin pigmentation and such cells were positive by Masson-Fontana stain. Immunohistochemistry performed in three cases was positive for S100 and vimentin, strongly positive for melan A in the melanized cells and negative for glial fibrillary acidic protein and periaxin. Non-melanized cells did not express melan A. Transmission electron microscopy findings in one case were consistent with a peripheral nerve sheath tumour and demonstrated cytoplasmic pre-melanosomes and melanosomes. Melanotic variants of MNSTs are rare in animals with only a solitary report of two previous canine cases in the literature.

Hemifacial Microsomia in a Cat.

A 7-month-old domestic medium hair cat presented with facial asymmetry affecting the bony and soft tissue structures of the right side of the head including the maxilla, nose, eye and pinna of the ear. Additionally, neurological dysfunction of the facial and vestibulocochlear nerves on the affected side was present. A congenital malformation affecting the first and second embryologic pharyngeal arches was suspected. This is the first case of hemifacial microsomia of likely congenital origin reported in a cat.

Neuroendodermal cyst in the fourth ventricle of a dog.

CASE REPORT: We describe the MRI appearance and surgical outcome of a rare neuroendodermal cyst in the fourth ventricle of a German Shorthaired Pointer. The dog presented with uncoordinated gait and occasional falling that increased when she became excited. The MRI appearance is shown and the surgical treatment described. Recurrence occurred on two occasions and the dog was euthanased. CONCLUSION: Recurrence of these cysts is highly likely unless there is complete surgical resection.

A novel idiopathic superficial neocortical degeneration and atrophy in young adult dogs.

A diffuse, chronic, superficial neocortical degeneration that resulted in atrophy was detected in five 1 to 2-year-old-dogs. Presenting neurologic signs included ataxia, dysphagia, blindness, and mentation changes. Magnetic resonance imaging on brains from 2 dogs demonstrated severe bilateral cerebrocortical atrophy and enlarged lateral and third ventricles. Grossly, multifocal, bilaterally symmetrical, extensive areas of neocortical brownish discoloration associated with atrophy of gyri and sulcal widening were recorded in the dorsal and lateral cerebral hemispheres in 3 dogs. Microscopically, in all dogs there was subacute to chronic superficial neocortical degeneration affecting all cerebral lobes, ranging from loss of the molecular layer to less frequent larger and deeper cavitations of variable size. Clinical signs probably resulted from a combination of primary neocortical degeneration and secondary degeneration in the corticobulbar and corticospinal tracts. The distribution pattern of gross and histologic cerebrocortical lesions suggests that this is a novel degenerative canine cerebral disease.

Late-onset cerebellar abiotrophy in a Labrador Retriever.

CASE REPORT: A 5-year-old female spayed Labrador Retriever was examined for a hindlimb gait abnormality. Initial neurological examination was consistent with vestibular dysfunction. Over the course of 1 year, signs progressed to reflect cerebellar ataxia, vertical nystagmus and delayed postural reactions in all limbs. At the initial examination, subjective evaluation of magnetic resonance imaging scan of the brain was considered normal. Repeat imaging at 1 year after initial examination revealed a reduction in the size of the cerebellum. Retrospectively, the size of the cerebellum on the initial MRI was small when assessed using an objective measurement algorithm. Postmortem histopathological evaluation of the brain showed diffuse degeneration of Purkinje cell neurones with secondary granule cell loss in the cerebellum, in addition to pigment inclusions in brainstem neurones. CONCLUSION: The clinical history and clinicopathological data are consistent with late-onset cerebellar abiotrophy, which has not previously been described in this breed.

Leukoencephalomyelopathy of mature captive cheetahs and other large felids: a novel neurodegenerative disease that came and went?

A novel leukoencephalomyelopathy was identified in 73 mature male and female large captive felids between 1994 and 2005. While the majority of identified cases occurred in cheetahs (Acinonyx jubatus), the disease was also found in members of 2 other subfamilies of Felidae: 1 generic tiger (Panthera tigris) and 2 Florida panthers (Puma concolor coryi). The median age at time of death was 12 years, and all but 1 cheetah were housed in the United States. Characteristic clinical history included progressive loss of vision leading to blindness, disorientation, and/or difficulty eating. Neurologic deficits progressed at a variable rate over days to years. Mild to severe bilateral degenerative lesions were present in the cerebral white matter and variably and to a lesser degree in the white matter of the brain stem and spinal cord. Astrocytosis and swelling of myelin sheaths progressed to total white matter degeneration and cavitation. Large, bizarre reactive astrocytes are a consistent histopathologic feature of this condition. The cause of the severe white matter degeneration in these captive felids remains unknown; the lesions were not typical of any known neurotoxicoses, direct effects of or reactions to infectious diseases, or nutritional deficiencies. Leukoencephalomyelopathy was identified in 70 cheetahs, 1 tiger, and 2 panthers over an 11-year period, and to our knowledge, cases have ceased without planned intervention. Given what is known about the epidemiology of the disease and morphology of the lesions, an environmental or husbandry-associated source of neurotoxicity is suspected.

Prevalence of effusion in the tympanic cavity in dogs with dysfunction of the trigeminal nerve: 18 cases (2004-2013).

BACKGROUND: Animals with disorders involving the trigeminal nerve or its nuclei in the brainstem can have effusion in the tympanic cavity ipsilateral to the side of the neurological deficits. The tensor veli palatini muscle (TVP), innervated by the mandibular branch of the trigeminal nerve, opens the pharyngeal orifice of the auditory tube. With denervation of the TVP, dysfunction of the auditory tube may occur, which could lead to effusion. HYPOTHESIS/OBJECTIVES: To determine the prevalence of effusion in the tympanic cavity in dogs with disorders involving the trigeminal nerve. ANIMALS: Eighteen client-owned dogs were evaluated retrospectively. METHODS: Retrospective study. RESULTS: Diagnostic imaging databases were searched for dogs having undergone magnetic resonance imaging (MRI) evaluation for signs referable to dysfunction of the trigeminal nerve. Signalment and neurological examination findings were recorded. The MRI study was evaluated for the presence or absence of effusion. MRI characteristics of the affected trigeminal nerve and the muscles of mastication were recorded. Based on the location of the trigeminal nerve lesion, dogs were divided into three categories: brainstem, trigeminal canal, or extracranial. Eighteen dogs met the inclusion criteria. Six of 18 dogs (33%) had effusion in the tympanic cavity ipsilateral to the affected trigeminal nerve. CONCLUSION AND CLINICAL IMPORTANCE: A substantial proportion of dogs with a lesion affecting the trigeminal nerve had effusion in the tympanic cavity. This finding likely represents denervation of the TVP muscle, which may have led to dysfunction of the auditory tube.

Unusual features in four canine meningiomas.

Several subtypes of canine meningioma are recognized. This report describes four canine meningiomas with previously unreported features. The four affected dogs were of different breeds. Three of the affected dogs were male and aged 7-10 years. In one dog, age and gender were not recorded. Meningiomas were located intracranially (three dogs) or within the vertebral canal (one dog). Two meningiomas resembled gemistocytic astrocytomas, while one had focal features of a rhabdoid tumour; these three meningiomas also contained amyloid deposits. The fourth tumour, a secretory meningioma, was rich in amianthoid fibres (i.e. unusual collagen deposits containing giant collagen fibres). All of these features are also described in human meningiomas.

Ventricular and extraventricular ependymal tumors in 18 cats.

Ependymal tumors are reported rarely in domestic animals. The aims of this study were to examine the clinical and pathologic features of ventricular and extraventricular ependymomas and subependymomas in 18 domestic cats examined between 1978 and 2011. Parameters examined included age, sex, breed, clinical signs, and macroscopic and histopathologic features. The mean age of affected cats was 9 years, 4 months; median age, 8.5 years. There were 8 female and 4 male cats, and 6 cats for which sex was not recorded. Breeds included 10 domestic shorthaired, 2 domestic longhaired, 1 Persian, and 1 Siamese. Clinical signs included altered mentation or behavior, seizures, circling, propulsive gait, generalized discomfort, and loss of condition. The tumors often formed intraventricular masses and usually arose from the lining of the lateral or third ventricles, followed by the fourth ventricle, mesencephalic aqueduct, and spinal cord central canal. Three tumors were extraventricular, forming masses within the cerebrum and adjacent subarachnoid space. Histologically, 15 tumors were classified as variants of ependymomas (classic, papillary, tanycytic, or clear cell) and 3 as subependymomas. Tumors were generally well demarcated; however, 6 ependymomas focally or extensively infiltrated the adjacent neural parenchyma. Characteristic perivascular pseudorosettes were observed in all ependymomas; true rosettes were less common. Some tumors had areas of necrosis, mineralization, cholesterol clefts, and/or hemorrhage. This cohort study of feline ependymal tumors includes subependymoma and primary extraventricular ependymoma, variants not previously described in the veterinary literature but well recognized in humans.

Porencephaly and hydranencephaly in six dogs.

A retrospective study was performed to identify dogs with cerebrospinal fluid-filled cavitatory lesions on MRI. Six dogs were included and the lesions were classified. In the three dogs in the present study with hydranencephaly, unilateral but complete loss of the temporal and parietal lobes was noted and had almost complete loss of the occipital and frontal lobes of a cerebral hemisphere. In the three dogs with porencephaly, there was unilateral incomplete loss of the parietal lobe and one dog had additional partial loss of the temporal and frontal lobes. Two of the dogs with porencephaly had seizures; the third showed no associated clinical signs. The dogs with hydranencephaly had mentation changes and circled compulsively. The two porencephalic dogs with seizures were treated with phenobarbitone. One of the dogs with hydranencephaly showed increased frequency and duration of circling; one dog's clinical signs did not progress and the third dog was euthanased due to increasing aggression. The dog with increased circling had ventriculoperitoneal shunt placement and the circling frequency reduced.

Mapping of Purkinje neuron loss and polyglucosan body accumulation in hereditary cerebellar degeneration in Scottish terriers.

A hereditary cerebellar degenerative disorder has emerged in Scottish Terriers. The aims of this study were to describe and quantify polyglucosan body accumulation and quantify Purkinje neurons in the cerebellum of affected and control dogs. The brains of 6 affected Scottish Terriers ranging in age from 8 to 15 years and 8 age-matched control dogs were examined histopathologically. Counts of Purkinje neurons and polyglucosan bodies were performed in control and affected dogs on cerebellar sections stained with periodic acid-Schiff. Affected dogs showed a significant loss of Purkinje neurons compared with control dogs (vermis: P < .0001; hemisphere: P = .0104). The degeneration was significantly more pronounced dorsally than ventrally (P < .0001). There were significantly more polyglucosan bodies in the ventral half of the vermis when compared with the dorsal half (P < .0001) in affected dogs. In addition, there were more polyglucosan bodies in the ventral half of the vermis in affected dogs than in control dogs (P = .0005). Polyglucosan bodies in all affected dogs stained positively with toluidine blue and alcian blue. Immunohistochemically, polyglucosan bodies in affected dogs were positive for neurofilament 200 kD and ubiquitin and negative for glial fibrillary acidic protein, synaptophysin, neurospecific enolase, vimentin, and S100; the bodies were negative for all antigens in control dogs. Ultrastructurally, polyglucosan bodies in 1 affected dog were non-membrane-bound, amorphous structures with a dense core. This study demonstrates significant Purkinje cell loss and increased polyglucosan bodies in the cerebellum of affected Scottish Terriers.

Hereditary cerebellar degeneration in Scottish terriers.

BACKGROUND: Hereditary cerebellar degeneration is described in several dog breeds. This heterogeneous group of diseases causes cerebellar ataxia associated with cerebellar cortical degeneration. OBJECTIVE: To report the clinical and histopathological features, and describe the mode of inheritance of hereditary cerebellar degeneration in Scottish Terriers. ANIMALS: Sixty-two affected dogs recruited through the Scottish Terrier Club of America. MATERIALS AND METHODS: Prospective, observational study: Owners of affected dogs were contacted for a description of clinical signs, age of onset, and disease progression. Medical records, videotapes of gait, and brain imaging were evaluated. When possible, necropsy was performed and the brain examined histopathologically. Prevalence of the disease was estimated and a pedigree analysis was performed to determine mode of inheritance. RESULTS: Gait abnormalities were noted in the 1st year of life in 76% of dogs, and progressed slowly; only 1 of 27 dogs dead at time of writing was euthanized because of cerebellar degeneration. Clinical signs included wide based stance, dysmetria, intention tremor, and difficulty negotiating stairs and running. Cerebellar atrophy was detected on magnetic resonance imaging. On histopathological examination, there was segmental loss of Purkinje neurons, thinning of molecular and granular layers, and polyglucosan bodies in the molecular layer. Prevalence of disease was estimated at 1 in 1,335 American Kennel Club registered Scottish Terriers. Genetic analysis results are consistent with an autosomal recessive mode of inheritance. CONCLUSION AND CLINICAL IMPORTANCE: A hereditary cerebellar degenerative disorder with a relatively mild phenotype has emerged in the Scottish Terrier. Genetic studies are needed.

Hereditary encephalomyelopathy and polyneuropathy in an Alaskan husky.

An Alaskan husky puppy was examined for a neurologic disease which began at six weeks of age with generalised paresis that progressed resulting in recumbency by 18 weeks. Thoracic limbs primarily exhibited lower motor neuron signs that included distal muscle atrophy and persistent elbow and carpal flexion that resisted manual extension. Pelvic limb signs primarily exhibited upper motor neuron and general proprioceptive deficits, but also included lower motor neuron signs. Abnormal vocalisation suggested a laryngeal paresis. Histopathologic lesions included a diffuse axonopathy and secondary demyelination in the nerves of the limbs and larynx and a similar bilaterally symmetrical degeneration in the spinal cord white matter suggestive of a dying back axonopathy. In addition, a degenerative process was present in nuclei in the brain stem and cerebellum. Recognition of this disease through clinical and pathologic examination in other related Alaskan Huskies suggested an autosomal recessive inherited disorder.

Magnetic resonance imaging characteristics of necrotizing meningoencephalitis in Pug dogs.

BACKGROUND: The magnetic resonance imaging (MRI) characteristics of necrotizing meningoencephalitis (NME) are not well documented. OBJECTIVES: To describe common MRI features of NME, to compare the MRI features to histopathologic findings, and to determine whether or not MRI lesions are predictive of survival time. ANIMALS: Eighteen Pugs with NME. METHODS: Retrospective MRI case study of Pugs identified by a search of medical records at 6 veterinary institutions. Eighteen dogs met inclusion criteria of histopathologically confirmed NME and antemortem MRI exam. MRI lesions were characterized and compared with histopathology with the kappa statistic. Survival times were compared with MRI findings by use of Mann-Whitney U-tests and Spearman's rho. RESULTS: Twelve of 18 lesions were indistinctly marginated with mild parenchymal contrast enhancement. Prosencephalic (17/18) lesion distribution included the parietal (16/18), temporal (16/18), and occipital (16/18) lobes. There were cerebellar (4/18) and brainstem (3/18) lesions. Asymmetric lesions were present in both gray and white matter in all dogs. Falx cerebri shift was common (11/18), and 6 dogs had brain herniation. Leptomeningeal enhancement was present in 9/18 dogs. A moderate positive association was found between parenchymal contrast enhancement and both necrosis (kappa= 0.45; P= .045) and monocytic inflammation (kappa= 0.48; P= .025). Higher MRI lesion burden was correlated with longer time from disease onset to MRI (P= .045). MRI lesion burden did not correlate to survival time. CONCLUSIONS AND CLINICAL IMPORTANCE: Asymmetric prosencephalic grey and white matter lesions with variable contrast enhancement were consistent MRI changes in Pugs with confirmed NME. While not pathognomonic for NME, these MRI characteristics should increase confidence in a presumptive diagnosis of NME in young Pugs with acute signs of neurologic disease.

Encephalomyelopathy and polyneuropathy associated with neuronal vacuolation in two Boxer littermates.

Neuronal vacuolation and spinocerebellar degeneration is a rare, presumably inherited condition that is reported only in Rottweilers and in crossbred dogs with known or potential Rottweiler heritage. Gross and histopathologic findings include laryngeal muscle atrophy, neuronal vacuolation, and a combined central and peripheral axonopathy. Two 6-month-old Boxer puppies from the same litter were referred for evaluation of progressive pelvic limb paresis and ataxia, upper airway stridor, and visual deficits. Examination of each dog suggested a combined myelopathy and peripheral neuropathy, as well as congenital ocular disease. Gross lesions were limited to atrophy of the intrinsic laryngeal muscles. Histopathologically, there was diffuse loss of axons and myelin in the dorsolateral and ventral funiculi throughout the spinal cord and extending into the caudal aspect of the brain stem. Vacuolation of scattered neuronal cell bodies was present in the spinal cord and selected brain stem nuclei. Multifocal axonal degeneration and demyelination was observed in the recurrent laryngeal nerve, sciatic nerve, and brachial plexus and was most severe in the recurrent laryngeal nerve. Ocular abnormalities included microphthalmia, cataracts, and retinal dysplasia. The findings in these Boxer dogs, unrelated to the Rottweiler breed, are analogous to the syndrome of neuronal vacuolation and spinocerebellar degeneration reported in Rottweilers.