Comparison of the effect of sedation and general anesthesia on pattern and flash visual evoked potentials in normal dogs.

BACKGROUND: Visual evoked potentials (VEPs) can provide objective functional assessment of the post-retinal visual pathway. This study compared the effects of sedation (butorphanol and dexmedetomidine) and general anesthesia (propofol and sevoflurane) on pattern and flash VEPs. Dogs (n = 13) underwent sedation or anesthesia and VEPs were obtained from 3 subcutaneous recording electrodes placed on the head (O1, Oz, O2). RESULTS: Pattern VEPs could only be recorded under sedation and a maximum of 3 peaks were identified (N75, P100, N135). Flash VEPs could be recorded under both sedation and anesthesia and a maximum of 5 peaks were identified (N1, P1, N2, P2, N3). The latency of the N1 peak and the baseline-N1 amplitude were significantly longer under general anesthesia. CONCLUSION: Visual evoked potentials should be preferentially recorded in dogs sedated with dexmedetomidine and butorphanol, regardless of the stimulus.

Effect of irrigation technique on the vertebral canal temperature during thoracolumbar hemilaminectomy in dogs: An ex vivo study.

OBJECTIVE: To determine the influence of continuous and intermittent bolus irrigation on vertebral canal temperature during thoracolumbar hemilaminectomy. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Ten canine cadavers. METHODS: Six consecutive thoracolumbar hemilaminectomies starting at T12-13 with alternating left- or right-side selection, and alternating continuous or intermittent bolus irrigation were performed in each dog resulting in 30 hemilaminectomies per irrigation technique. Drilling was performed for 15 s followed by a 10-s pause and resumed until completion of hemilaminectomy. Continuous irrigation consisted of saline delivered at 15 ml/min during drilling. Bolus irrigation consisted of manual delivery of 10 ml saline during the pause. Temperatures were recorded with two sensors placed within the vertebral canal adjacent to target hemilaminectomy site and compared between techniques with a linear mixed model. RESULTS: Intermittent bolus irrigation was associated with lower peak vertebral canal temperatures (mean 15.7°C; range 9.4-23.3°C) than continuous irrigation (mean 16.7°C; range 9.6-27.6°C, p = .003) (mean difference of 1.1°C, p = .006). Similarly, mean vertebral canal temperatures remained lower when hemilaminectomies were performed under intermittent rather than continuous irrigation (mean difference of 0.48°C, p = .006, linear mixed model). CONCLUSION: Lower vertebral canal temperatures were maintained during hemilaminectomy with intermittent bolus rather than continuous irrigation. CLINICAL SIGNIFICANCE: Both intermittent bolus and continuous irrigation are suitable to prevent elevations in canine vertebral canal temperature during hemilaminectomy.

Evaluation of intravenous T-61 as a euthanasia method for birds.

The use of T-61 as a sole euthanasia agent for birds was investigated. Nine broiler chickens (Gallus gallus domesticus) were euthanized by intravenous T-61 and assessed for insensibility [brainstem reflexes: nictitating membrane reflex (NIC), palpebral blink reflex (PAL)], brain death [isoelectric electroencephalogram activity (EEG)], cessation of audible heartbeat, and abnormal electrocardiogram. Birds were considered dead when the heart rate was less than 180 beats/minute with an isoelectric EEG. No vocalization or wing flapping occurred. Both NIC and PAL were lost 10.5 s from start of injection and audible heartbeat ceased at 24.5 s. Latency to isoelectric activity was 16.6 s. All but 1 bird died within 60 s. Rapid induction of insensibility meant birds did not experience pain and distress within 10.5 s from start of injection and birds were not conscious during cardiac and circulatory arrest. Intravenous injection of T-61 is an effective and efficient euthanasia method for birds.

Évaluation du T-61 intraveineux comme méthode d'euthanasie pour les espèces aviaires. La présente étude visait à évaluer l'utilisation du T-61 comme seul agent d'euthanasie pour les oiseaux. Neuf poulets de chair (Gallus gallus domesticus) ont été euthanasiés par injection intraveineuse de T-61 et évalués pour leur insensibilité [réflexes du tronc cérébral : réflexe de la membrane nictitante (NIC) et réflexe palpébral (PAL)], mort cérébrale [activité isoélectrique de l'électroencéphalogramme (EEG)], arrêt du rythme cardiaque audible et électrocardiogramme (ECG) anormal. Les oiseaux étaient considérés comme morts lorsque la fréquence cardiaque (ECG) était inférieure à 180 battements par minute avec un EEG isoélectrique. Aucune vocalisation ou battement d'aile ne s'est produit. Les réflexes NIC et PAL ont été perdus 10,5 s après l'injection et le rythme cardiaque audible a cessé à 24,5 s. La latence jusqu'à l'activité isoélectrique était de 16,6 s. Tous les oiseaux sauf un sont morts dans les 60 s. L'induction rapide de l'insensibilité signifiait que les oiseaux étaient incapables de ressentir de la douleur et de la détresse dans les 10,5 secondes suivant l'injection et que les oiseaux n'étaient pas conscients pendant un arrêt cardiaque et circulatoire. L'injection intraveineuse de T-61 est une méthode d'euthanasie efficace et efficiente pour les oiseaux.(Traduit par Dr Serge Messier).

Use of MRI increases interobserver agreement on gross tumor volume for imaging-diagnosed canine intracranial meningioma.

There is a lack of information regarding interobserver agreement on canine meningioma gross tumor volume (GTV) delineation, and on the impact of MRI on this agreement. The objectives of this retrospective, secondary analysis, observer agreement study were to describe agreement between veterinary radiation oncologists on GTV for canine intracranial meningioma, and to compare interobserver agreement between delineation based on CT alone and delineation based on fused CT-MRI. Eighteen radiation oncologists delineated GTV for 13 dogs with an imaging diagnosis of meningioma on pre- and postcontrast CT, pre- and postcontrast T1-weighted magnetic resonance, and T2-weighted magnetic resonance images. Dice similarity coefficient (DSC), concordance index (CI), and center of volume (COV) were used to quantify interobserver agreement. Multilevel mixed models were used to examine the difference in volume, DSC, CI and COV 3D distance between CT and CT-MR imaging. The mean volume for GTV contours delineated using fused CT-MRI was larger than when CT alone was used for delineation (mean difference CT-MR - CT = 0.89 cm3, 95% CI 0.66 to 1.12, P < .001). Interobserver agreement on GTV was improved when MRI was used; the mean DSC and CI were higher, and the mean COV 3D distance was lower, when fused CT-MRI was used than when CT alone was used (P < .001 for all differences). Based on our results, fused CT-MRI is recommended for radiation therapy planning of canine intracranial meningioma.

A review of Horner's syndrome in small animals.

Horner's syndrome arises from dysfunction of the oculosympathetic pathway and is characterized by miosis, enophthalmos, protrusion of the third eyelid, and ptosis. It has been recognized in a wide variety of breeds and ages in small animal patients. The oculosympathetic pathway is a 3-neuron pathway. The central/first order neuron arises from the hypothalamus and extends down the spinal cord. The preganglionic/second order neuron arises from the first 3 thoracic spinal cord segments and travels through the thorax and cervical region until it synapses at the cranial cervical ganglion. The postganglionic/third order neuron travels from this ganglion to the orbit. Topical application of cocaine is the gold standard for differentiating Horner's syndrome from other causes of miosis. Topical 1% phenylephrine allows for identification of a post-ganglion Horner's syndrome. Numerous etiologies have been reported for Horner's syndrome, but idiopathic disease is most common. Ancillary diagnostics include otoscopic examination, thoracic radiographs, or advanced imaging. Treatment and prognosis are determined by the etiology.

Examen du syndrome de Horner chez les petits animaux. Le syndrome de Horner provient d'une dysfonction de la voie oculo-sympathique et est caractérisée par la miose, l'enophtalmie, la protrusion de la troisième paupière et la ptose. Elle a été reconnue chez une grande variété de races et d'âges chez les patients petits animaux. La voie oculo-sympathique est une voie à trois neurones. Le neurone central/de premier ordre provient de l'hypothalamus et s'étend vers le bas sur la colonne vertébrale. Le neurone préganglionnaire/de deuxième ordre provient des trois premiers segments thoraciques de la colonne vertébrale et se déplace dans le thorax et la région cervicale jusqu'à la synapse au ganglion cervical crânien. Le neurone postganglionnaire/de troisième ordre se déplace de ce ganglion jusqu'à l'orbite. L'application topique de cocaïne est le test de référence pour la différenciation du syndrome de Horner des autres causes de miose. La phényléphrine topique 1 % permet l'identification d'un syndrome de Horner postganglionnaire. Plusieurs étiologies ont été signalées pour le syndrome de Horner, mais la maladie idiopathique est la plus commune. Les diagnostics auxiliaires incluent l'examen otoscopique, des radiographies thoraciques ou une imagerie avancée. Le traitement et le pronostic sont déterminés par l'étiologie.(Traduit par Isabelle Vallières).

Peripheral cranial neuropathies consistent with cavernous sinus syndrome caused by extracranial nasopharyngeal lymphoma in a cat.

Cavernous sinus syndrome is a unique constellation of cranial nerve deficits occurring typically as a result of pathologic infiltration of the cavernous sinus, which is located in the lateral sellar compartment of the calvarium. This case report describes a polyneuropathy consistent with cavernous sinus syndrome as a result of a lesion outside of the cavernous sinus. The cat was presented with right internal and external ophthalmoplegia, loss of right corneal sensation, inspiratory stridor, dysphagia, dysphonia, tongue weakness, and weight loss. Magnetic resonance imaging identified a large nasopharyngeal mass along the base of, but without extension into, the calvarium. The histologic diagnosis was nasopharyngeal lymphoma. Focal extracranial masses should be considered as differential diagnoses for multiple cranial nerve deficits, including the constellation of clinical signs recognized as cavernous sinus syndrome.

Neuropathies crâniales périphériques compatibles avec un syndrome du sinus caverneux causé par un lymphome nasopharyngé extra-crânial chez un chat. Le syndrome du sinus caverneux est une constellation unique de déficits des nerfs crâniens se produisant typiquement comme le résultat d'une infiltration pathologique du sinus caverneux, qui est situé dans le compartiment sellaire latéral du calvarium. Le présent rapport de cas décrit une polyneuropathie compatible avec un syndrome du sinus caverneux résultant d'une lésion à l'extérieur du sinus caverneux. Le chat fut présenté avec une ophtalmoplégie interne et externe droit, perte de sensation au niveau de la cornée droite, stridor inspiratoire, dysphagie, dysphonie, faiblesse de la langue, et perte de poids. Un examen d'imagerie par résonnance magnétique permis d'identifier une large masse nasopharyngée suivant la base du calvarium, mais sans extension à l'intérieur. Le diagnostic histologique en fut un de lymphome nasopharyngé. Les masses focales extra-crâniales devraient être considérées dans le diagnostic différentiel lors de déficits de plusieurs nerfs crâniens, incluant la multitude de signes cliniques reconnus comme le syndrome du sinus caverneux.(Traduit par Dr Serge Messier).

Wild hummingbirds rely on landmarks not geometry when learning an array of flowers.

Rats, birds or fish trained to find a reward in one corner of a small enclosure tend to learn the location of the reward using both nearby visual features and the geometric relationships of corners and walls. Because these studies are conducted under laboratory and thereby unnatural conditions, we sought to determine whether wild, free-living rufous hummingbirds (Selasphorus rufus) learning a single reward location within a rectangular array of flowers would similarly employ both nearby visual landmarks and the geometric relationships of the array. Once subjects had learned the location of the reward, we used test probes in which one or two experimental landmarks were moved or removed in order to reveal how the birds remembered the reward location. The hummingbirds showed no evidence that they used the geometry of the rectangular array of flowers to remember the reward. Rather, they used our experimental landmarks, and possibly nearby, natural landmarks, to orient and navigate to the reward. We believe this to be the first test of the use of rectangular geometry by wild animals, and we recommend further studies be conducted in ecologically relevant conditions in order to help determine how and when animals form complex geometric representations of their local environments.

Oral cytarabine ocfosfate pharmacokinetics and assessment of leukocyte biomarkers in normal dogs.

BACKGROUND: Cytosine arabinoside (Ara-C) is a nucleoside analog prodrug utilized for immunomodulatory effects mediated by its active metabolite Ara-CTP. Optimal dosing protocols for immunomodulation in dogs have not been defined. Cytarabine ocfosfate (CO) is a lipophilic prodrug of Ara-C that can be administered PO and provides prolonged serum concentrations of Ara-C. OBJECTIVES: Provide pharmacokinetic data for orally administered CO and determine accumulation and functional consequences of Ara-CTP within peripheral blood leukocytes. ANIMALS: Three healthy female hound dogs and 1 healthy male Beagle. METHODS: Prospective study. Dogs received 200 mg/m2 of CO PO q24h for 7 doses. Serum and cerebrospinal fluid (CSF) CO and Ara-C concentrations were measured by liquid chromatography-tandem mass spectroscopy (LC-MS/MS). Complete blood counts, flow cytometry, and leukocyte activation assays were done up to 21 days. Incorporation of Ara-CTP within leukocyte DNA was determined by LC-MS/MS. RESULTS: Maximum serum concentration (Cmax ) for Ara-C was 456.1-724.0 ng/mL (1.88-2.98 µM) and terminal half-life was 23.3 to 29.4 hours. Cerebrospinal fluid: serum Ara-C ratios ranged from 0.54 to 1.2. Peripheral blood lymphocyte concentrations remained within the reference range, but proliferation rates poststimulation were decreased at 6 days. Incorporation of Ara-CTP was not saturated and remained >25% of peak concentration at 13 days. CONCLUSIONS AND CLINICAL IMPORTANCE: Oral CO may produce prolonged serum Ara-C half-lives at concentrations sufficient to induce functional changes in peripheral leukocytes and is associated with prolonged retention of DNA-incorporated Ara-CTP. Application of functional and active metabolite assessment is feasible and may provide more relevant data to determine optimal dosing regimens for Ara-C-based treatments.

Congenital myasthenic syndrome in Golden Retrievers is associated with a novel COLQ mutation.

BACKGROUND: Congenital myasthenic syndromes (CMSs) are a group of inherited disorders of neuromuscular transmission that may be presynaptic, synaptic, or postsynaptic. Causative mutations have been identified in 4 breeds including the Labrador Retriever, Jack Russell Terrier, Heideterrier, and Danish Pointing Dog. HYPOTHESIS/OBJECTIVE: Clinical and genetic characterization of a neuromuscular disorder in Golden Retriever (GR) puppies. ANIMALS: Four GR puppies from California were evaluated for generalized muscle weakness beginning at weaning. Biological specimens were collected from the affected puppies, and familial information was obtained. Blood or buccal swabs were obtained from 63 unaffected GRs. METHODS: Complete physical, neurological, electrodiagnostic, and histological evaluations and biochemical quantification of muscle acetylcholine receptors were performed. Polymerase chain reaction was used to amplify the 17 exons of COLQ, and sequences were obtained by Sanger sequencing. Variant frequency was assessed in unrelated GRs and a public database. RESULTS: Clinical, neurological, and electrodiagnostic evaluations confirmed a disorder of neuromuscular transmission in a GR family. Sequencing of all exons and splice sites of a primary candidate gene, COLQ, identified a point mutation that predicts an amino acid substitution (G294R). The primary COLQ transcript was absent from affected muscle samples. All affected puppies were homozygous for the mutation, which was not detected outside this GR family or in other breeds. CONCLUSIONS AND CLINICAL IMPORTANCE: We confirmed the diagnosis of a CMS in GR puppies and identified a novel COLQ mutation. The COLQ gene encodes the collagenous tail of acetylcholinesterase, the enzyme responsible for termination of skeletal muscle contraction by clearing acetylcholine at the neuromuscular junction. Clinicians and breeders should be aware of this CMS in GR puppies with an early onset of weakness.