MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF PERIPHERAL NERVE SHEATH TUMORS OF THE CANINE BRACHIAL PLEXUS IN 18 DOGS

Magnetic resonance imaging (MRI) examinations from 18 dogs with a histologically confirmed peripheral nerve sheath tumor (PNST) of the brachial plexus were assessed retrospectively. Almost half (8/18) had a diffuse thickening of the brachial plexus nerve(s), six of which extended into the vertebral canal. The other 10/18 dogs had a nodule or mass in the axilla (1.2-338 cm3). Seven of those 10 masses also had diffuse nerve sheath thickening, three of which extended into the vertebral canal. The majority of tumors were hyperintense to muscle on T2-weighted images and isointense on T1-weighted images. Eight of 18 PNSTs had only minimal to mild contrast enhancement and many (13/18) enhanced heterogeneously following gadolinium DTPA administration. Transverse plane images with a large enough field of view (FOV) to include both axillae and the vertebral canal were essential, allowing in-slice comparison to detect lesions by asymmetry of structures. Higher resolution, smaller FOV, multiplanar examination of the cervicothoracic spine was important for appreciating nerve root and foraminal involvement. Short tau inversion recovery, T2-weighted, pre and postcontrast T1-weighted pulse sequences were all useful. Contrast enhancement was critical to detecting subtle diffuse nerve sheath involvement or small isointense nodules, and for accurately identifying the full extent of disease. Some canine brachial plexus tumors can be challenging to detect, requiring a rigorous multiplanar multi-pulse sequence MRI examination.     

Clinical Effects of Longitudinal Division of the Corpus Callosum in Normal Dogs

Longitudinal division of the corpus callosum was performed in six normal beagles to determine surgical morbidity. The corpus callosum was divided sagittally on the midline and the effect on neurological function was determined. Five of six dogs were clinically normal within 14 days or less after surgery. One dog had persistent but improving clinical signs consistent with a forebrain disturbance at 30 days after surgery. Overall, minimal morbidity and no mortality was associated with this surgical procedure. Further study is indicated to determine the efficacy of this surgical treatment for seizure control in dogs with idiopathic epilepsy.     

Inflammatory Linear Verrucous Epidermal Nevus in Four Dogs

Abstract— A skin disease resembling inflammatory linear verrucous epidermal nevus is reported in four dogs. Three of the dogs were related cocker spaniels. Linear, pigmented verrucous lesions were noted most commonly on the lateral trunk, foot pads and ears. Histologic findings included focal areas of marked epidermal thickening by ortho-and parakeratotic hyperkeratosis and acanthosis, both in epidermis and follicular infundibular epithelium. This was associated with follicular distention and papillomatosis. Both hyper-and hypogranulosis were noted in association with parakeratosis. Improvement was noted in the three dogs administered isotretinoin and/or etretinate. Résumé— Une maladie cutanée ressemblant à un névus épidermique verruqueux linéaire inflammatoire est décrite chez quatre chiens. Trois de ces animaux sont des Cocker Spaniels. Les lesions verruqueuses, linéaires sont localisées le plus souvent sur les faces latérales du tronc, aux coussinets plantaires et aux oreilles. Les observations histologiques mettent en évidence des zones focales d'épaississement épidermique provoqué par une acanthose et une hyperkérathose ortho et parakératosique. Ceci est associéà une papillomatose et une distension folliculaire. On note à le fois une hyper et une hypogranulose associées à la parakératose. L'administration d'isotrétinoïne et/ou d'étritinate a entrainé une amélioration chez trois chiens. Zusammenfassung— Es wird über eine Hauterkrankung bei vier Hunden berichtet, die dem entzündlichen linearen vérrukösen epidermalen Naevus ähnelt. Drei der Hunde waren miteinander verwandte Cock-erspaniel. Lineare pigmentierte verruköse Hautveränderungen wurden am häufigsten lateral am Rumpf, an den Pfotenballen und an den Ohren festgestellt. Die histologischen Befunde beinhalten herdförmige Bezirke mit deutlicher Epidermisverdickung durch ortho-und parakeratotische Hyperkeratose und Akanthose, beides in der Epidermis und im Epithel des Haarbalginfundibulum. Letztere waren mit einer Ausweitung und Papillomatose der Haarbälge vergesellschaftet. In Verbindung mit der Parakératose wurden sowohl Hyperals auch Hypogranulose festgestellt. Nach Verabreichung von Isotretinoin und/oder Etretinate konnte bei den drei Hunden eine Verbesserung erzielt werden. Resumen El presente artículo trata de un caso dermatológico que asemeja a un nevus epidérmico infalmatorio linear verrucoso, reportado en cuatro perros. Tres de los perros eran cocker spaniels que estaban emparentados. En la región lateral del tronco, almohadillas plantares y orejas, se advirtieron lesiones verrucosas pigmentadas, de formal linear. Exámenes histológicos demostraron la presencia de foco de epidermis engrosada, asi como hiperqueratosis orto y paraqueratótica y acantosis, tanto en la epidermis, como en el infundíbulo folicular de la misma. Este hallazgo se asoció con distension folicular y papilomatosis. Tambien se encontró hiper e hipogranulosis en asociación con paraqueratosis. En los tres perros a los que se les administró isotretinoina/o etretinato, se advirtió una mejora considerable.     

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.     

Acute, Unilateral Transverse Sinus Occlusion During Craniectomy in Seven Dogs With Space-Occupying Intracranial Disease

Objective- The purpose of this study was to determine the effect of acute, unilateral transverse sinus occlusion on intracranial pressure (ICP) and postoperative mortality in dogs with structural intracranial disease.
Study Design- Affected dogs had a single transverse sinus occluded during craniectomy for intracranial mass biopsy or removal.
Animals- Seven dogs with space-occupying intracranial disease in the cerebellopontine angle area.
Methods- The ipsilateral transverse sinus was permanently occluded during the surgical approach to the intracranial lesion to increase surgical exposure by allowing a caudal lateral rostrotentorial craniectomy to be combined with a suboccipital craniectomy. In five dogs, intracranial pressure was monitored during surgery using a fiberoptic intracranial pressure monitoring device.
Results- Initial ICP varied among dogs, ranging from 7 to 21 mm Hg. Intracranial pressure, however, decreased in all dogs after craniectomy and durotomy ( P <.05). No increase in intracranial pressure occurred after transverse sinus occlusion ( P =.42). All dogs survived the surgical procedure.
Conclusions- Acute, unilateral transverse sinus occlusion during craniectomy in dogs with space-occupying intracranial lesions did not result in significant increases in ICP or intraoperative mortality.
Clinical Relevance- Acute, unilateral transverse sinus occlusion during craniectomy can be used to increased surgical exposure to the caudal fossa of the brain without increased risk of increasing ICP.     

The Effect of Acute, Unilateral Transverse Venous Sinus Occlusion on Intracranial Pressure in Normal Dogs

Lateral rostrotentorial and caudal suboccipital approaches to the brain were performed on six beagles. Intracranial pressure (ICP) was measured as the two craniectomies were connected by removing the bone of the nuchal crest and occluding the transverse venous sinus. Intracranial pressure remained constant after acute occlusion of the sinus with bone wax and there was no gross evidence of brain edema. All six dogs survived the surgery and five dogs survived for a minimum of 3 months. One dog died acutely during the postoperative period. The exact cause of the cerebellar hemorrhage and infarction found at necropsy in the latter dog was not evident. Anemia occurred in three of the six dogs as a result of intraoperative hemorrhage. All dogs surviving the perioperative period had mild, transient hypermetria and conscious proprioceptive deficits, but were neurologically normal 72 hours after surgery. Results of this study indicate that acute, unilateral transverse sinus occlusion is possible without an increase in ICP. The ability to do this allows access to the rostral aspect of the ipsilateral cerebellum and brain stem.