Evaluation of injectate distribution after ultrasound-guided peribulbar injections in canine cadavers

ObjectiveTo describe a contrast medium distribution pattern after peribulbar injection in cadavers.Study designA cadaveric study.AnimalsA group of eight male dogs and four canine cadaver heads.MethodsIn phase 1, ultrasound-guided peribulbar injections (1.0 mL dye) were performed in four orbits using a subzygomatic approach. After dissection, the procedure was considered successful if 1) no dye was found in the retrobulbar space, 2) the peribulbar compartment was stained and 3) the dye reached the orbital fissure. In phase 2, using 16 orbits, the same technique was used to inject 0.1 mL kg^–1 contrast medium into (group A, n = 8) or outside (group B, n = 8) the peribulbar compartment. After freezing at –20°C, orbits were imaged using computed tomography, and the contrast medium distribution was analysed.ResultsIn phase 1, the procedure was successful in all four eyes. In phase 2, two orbits (one in each group) were removed from the study: one was not injected and the other was injected twice. The contrast medium was found inside the peribulbar compartment in six of seven (85.7%) group A orbits and two of seven (28.6%) group B orbits. In all of these cases, distribution to the orbital fissure, rostral alar foramen, mandibular foramen and inside the skull was observed. The oval foramen was reached in three of seven (42.9%) group A orbits and one of seven (14.3%) group B orbits. In one/seven (14.3%) group A orbits and five/seven (71.4%) group B orbits, the contrast medium was found inside the masseter and temporal muscles, and no distribution towards the aforementioned structures was observed.Conclusions and clinical relevanceUltrasound-guided peribulbar injection of 0.1 mL kg^–1 contrast medium in canine cadavers can lead to an extensive distribution of the injectate that reaches the orbital fissure, the rostral alar, oval, and mandibular foramina and can be found intra-cranially.     

Ultrasound‐guided retrobulbar nerve block in horses: a cadaveric study

Objective To develop an ultrasound‐guided technique for retrobulbar nerve block in horses, and to compare the distribution of three different volumes of injected contrast medium (CM) (4, 8 and 12 mL), with the hypothesis that successful placement of the needle within the retractor bulbi muscle cone would lead to the most effective dispersal of CM towards the nerves leaving the orbital fissure. Study design Prospective experimental cadaver study. Animals Twenty equine cadavers. Methods Ultrasound‐guided retrobulbar injections were performed in 40 cadaver orbits. Ultrasound visualization of needle placement within the retractor bulbi muscle cone and spread of injected CM towards the orbital fissure were scored. Needle position and destination of CM were then assessed using computerized tomography (CT), and comparisons performed between ultrasonographic visualization of orbital structures and success rate of injections (intraconal needle placement, CM reaching the orbital fissure). Results Higher scores for ultrasound visualization resulted in a higher success rate for intraconal CM injection, as documented on the CT images. Successful intraconal placement of the needle (22/34 orbits) resulted in CM always reaching the orbital fissure. CM also reached the orbital fissure in six orbits where needle placement was extraconal. With 4, 8 and 12 mL CM, the orbital fissure was reached in 16/34, 23/34 and 28/34 injections, respectively. Conclusion and clinical relevance The present study demonstrates the use of ultrasound for visualization of anatomical structures and needle placement during retrobulbar injections in equine orbits. However, this approach needs to be repeated in controlled clinical trials to assess practicability and effectiveness in clinical practice.     

Determining the Gestational Age of Crioulo Mares Based on a Fetal Ocular Measure

The practice of covering in herds is often used in Crioulo breeding farms, thus not allowing the determination of ovulation dates and the early detection of pregnancies. This fact complicates the estimation of gestational age after 70 days of conception. This study aimed to evaluate the diameter of the fetal orbits of Crioulo mares to develop a formula to estimate a gestational date. Measurements of 164 fetal ocular orbits were performed in 124 Crioulo mares with gestational ages ranging between 119 and 341 days. The current study observed a linear growth pattern of Crioulo fetal orbits up to 341 days of gestation. Thus, obtaining a suitable linear regression model to determine the gestational age of Crioulo mares based on fetal ocular orbit diameter measure is possible. The obtained model was y = 8.3756x + 11.90, where y represents the gestational age in days, and x represents the diameter of the fetal ocular orbit in millimeters. This formula had an r² of 0.985 (P < .001). We conclude that this model allows researchers and veterinarians to accurately estimate the gestational age of Crioulo mares between 4 and 11 months of pregnancy.     

Bilateral microphthalmos with cyst in a neonatal foal

A 1‐day–old miniature horse filly was presented to the University of Florida Veterinary Ophthalmology service for evaluation of multiple ocular anomalies which were present from birth. Protruding from the right orbit was a large, fluctuant, red, dry and variably ulcerated mass. A globe could not be appreciated clinically in the left orbit. Ocular ultrasound of both orbits was performed. This revealed a lobular, hypo‐echoic structure filling the right orbit, with multiple hyperechoic septations; normal ocular structures were not identified. Ultrasound of the left orbit revealed a microphthalmic eye, with a well‐defined, hyperechoic structure in the vitreous that was thought to be the lens. Due to irreversible blindness, the foal was humanely euthanized. Histopathology and immunohistochemistry of the orbital contents revealed bilateral microphthalmos with cyst, a congenital defect rarely reported in the veterinary literature.     

Bilateral orbital and nasal aspergillosis in a cat

A 12-year-old, 4 kg, castrated male Persian cat was referred with a 2-month history of sneezing and bilateral mucopurulent nasal discharge. Rhinoscopically acquired nasal biopsies at this time revealed bilateral lymphoplasmacytic rhinitis. A tapering dose of oral prednisone caused the complete remission of the clinical signs, but 2 months after discontinuation of the therapy, the rhinitis recurred and the OD became exophthalmic. Computed tomography showed a soft tissue mass in both sides of the nasal cavity, both frontal sinuses, the right orbit, and to a lesser extent the left orbit. A fine needle aspirate of the right orbit revealed pyogranulomatous inflammation and Aspergillus spp. hyphae. Repeat nasal biopsy demonstrated multi-focal necrosis and a mixed inflammatory cell process which now included macrophages and scattered septate fungal hyphae. A few days later the cat became bilaterally blind and a contrast enhancing lesion involving the optic chiasm was found on magnetic resonance imaging. Despite a poor prognosis, therapy consisted of exenteration of the right orbit and trephination of both frontal sinuses before the planned initiation of medical antifungal therapy. Unfortunately, the cat died of cardiac arrest intraoperatively. Aspergillus fumigatus was cultured from both orbits at necropsy. Orbital aspergillosis has been rarely reported in cats and its relationship with lymphoplasmacytic rhinitis is unclear. In this patient lymphoplasmacytic rhinitis or previous antibiotic/corticosteroid therapy may have allowed secondary fungal invasion of the nasal mucosa and subsequently both orbits and the brain. Alternatively, Aspergillus infection may have preceded the lymphoplasmacytic rhinitis.     

Retrobulbar pseudotumor of the orbit in a cat

Idiopathic nonspecific inflammatory disease of the orbit (orbital pseudotumor) was diagnosed detected in a cat. The cat had progressive lagophthalmia, keratitis, and decreased motion of the right eye. Four months later, the left eye was affected in a similar manner. Response to antibiotics and immunosuppressive agents was not detected. Computed tomography of the brain and orbits revealed bilateral thickening of the sclera and episcleral tissues. Bilateral exenteration of the eyes was required because of worsening clinical signs or corneal perforation. Histologic examination revealed proliferation of spindle cells and fibrovascular tissue within and adjacent to the sclera.     

Presumed canine trigemino‐abducens synkinesis in a dog

A ten‐year‐old male neutered Rhodesian ridgeback cross dog was presented for the investigation of abnormal bilateral protrusion of the third eyelid when chewing. Physical, ophthalmological, and neurological examinations were unremarkable. Thoracic radiographs, abdominal ultrasound, and magnetic resonance of the brain and orbits failed to reveal any abnormalities. Cerebrospinal fluid analysis revealed elevated protein, but the nucleated cell count was normal. trigemino‐abducens synkinesis was presumptively diagnosed. Aetiopathogenesis of this condition is discussed. To the authors' knowledge, this is the first report of presumed trigemino‐abducens synkinesis in a dog.     

Comparison of four peribulbar anaesthetic techniques: a preliminary study in equine cadavers

ObjectiveTo compare the peribulbar injectate distribution and probability of regional anaesthesia of four peribulbar anaesthetic techniques in equine cadavers.Study designProspective experimental cadaver study.AnimalsA total of 12 isolated equine cadaver heads and 24 eyes.MethodsThe 24 orbits underwent one of four injection techniques (six orbits each) with a mixture (1:4) of contrast medium and saline (CM): 20 mL ventrolateral peribulbar injection (V-20), 20 mL dorsolateral peribulbar injection (D-20), combined ventrolateral and dorsolateral peribulbar injections 10 mL each (VD-20) or 20 mL each (VD-40). To evaluate and score CM distribution at the base of, within the extraocular muscle cone (EOMC), and around the optic nerve (before and after pressure application to the periorbital area), computed tomography was performed. To assess the probability of achieving locoregional anaesthesia, two criteria were applied and both scored as ‘likely’, ‘possible’ or ‘unlikely’. To compare CM distribution scores between injection techniques, Kruskal-Wallis analysis of variance was used. Mann-Whitney U test was used for post hoc comparisons between groups when needed. A p value < 0.05 was considered significant.ResultsThe CM distribution within the EOMC and around the optic nerve circumference was detected as ‘possible’ only after pressure application in seven out of 24 orbits (V-20, 3; D-20, 1; VD-40, 3). It was never considered ‘likely’ either before or after pressure application. The CM distribution at the EOMC base was considered ‘likely’ to provide regional anaesthesia in 50% (V-20), 0% (D-20), 33% (VD-20), 100% (VD-40) and in 66% (V-20), 16% (D-20), 50% (VD-20), 100% (VD-40) before and after applying pressure, respectively.Conclusions and clinical relevanceComplete regional anaesthesia seems more likely using the VD-40 technique, although the authors advise caution due to the risk of potential complications. Future studies are necessary to evaluate the efficacy of the technique in vivo.     

Use of methyl methacrylate orbital prostheses in dogs and cats: 78 cases (1980-1986)

To prevent cosmetically undesirable orbital concavity after enucleation, methyl methacrylate spheres were implanted into the orbits of 73 dogs and 5 cats. In all cases, follow-up reports were obtained until suture removal 2 weeks after surgery, and for 58 animals (79%) until 6 months after surgery. Information was available for 46 animals (60%) 1 year after surgery, 28 animals (36%) 2 years after surgery, and 7 animals (9%) 3 years after surgery. Implants failed in 3 dogs and 2 cats. Complications were not detected in the remaining 73 animals (93%), and owners were pleased with the cosmetic results. The causes of implant failure in dogs varied; however, in cats, fluid accumulation was the consistent complication associated with failure. Orbital implantation of methyl methacrylate spheres was found to be a safe, practical, and inexpensive method of improving the cosmetic appearance of dogs requiring enucleation. Although the number of cats evaluated was limited, the accumulation of orbital fluid in a high percentage of those suggested that orbital implants may be less successful in this species.     

Partial facial duplication (diprosopus) in a goat kid

The anatomical and clinical features of a live-born diprosopic goat kid are described. The kid had two faces with two eyes each, two complete oral cavities and nostrils and two ears. Caudal to the neck, the kid grossly appeared normal. Both mouths of the kid showed synchronous suckling motions. Elevated respiratory and heart rates were recorded and the temperature was subnormal. Radiological examination showed a single trunk and vertebral column, normal limbs, two sets of jaws, three orbits, and contrast radiography revealed a single patent oesophagus. There was maxillary and mandibular duplication resulting in two faces. There was a cleft palate. The oropharyngeal regions of each face merged to form a single laryngopharynx and oesophagus. There was a single brain with hypoplasia of the cerebellum. The left and right cerebral hemispheres were fused rostrally, and there was duplication of the optic chiasma and the pituitary gland. The olfactory tract was absent and the superficial origins of most of the cranial nerves were not discernible.     

Geographical variation of skull morphology and its functional significances in the red-cheeked squirrel

Skulls of the red-cheeked squirrel (Dremomys rufigenis) from various geographical locations: Malaysia (peninsular area), Vietnam (south district)-Laos, and Thailand (north district) were osteometrically examined. The skull size of the squirrels in the southern (Malaysia) population was fundamentally larger than that in the northern (Vietnam, Laos and Thailand) populations. The proportion indices indicated that the splanchnocranium was relatively longer in the Malaysia population, and that the interorbital space was narrower in Vietnam-Laos, and Thailand populations. We suggest that the long nose and laterally-oriented orbits in the skull may be better adapted for terrestrial-insectivorous life in the Malaysia population and the binocular sense facilitated by rostrally-oriented eyes contributes to the arboreal-fruit eating behavior in the two northern populations. The Malaysia population was clearly distinguished from the other populations by the principal component analysis. We suggest that the geographical barrier of the Isthmus of Kra influences the morphological variation of the skull among the squirrel populations.     

First report of thelaziosis (Thelazia anolabiata) in an Andean Cock of the Rock (Rupicola peruviana) from Peru

Thelazia anolabiata is a spirurid nematode living in the orbits of birds which can cause lacrimation, keratitis, conjunctivitis, and corneal ulcers. This species is reported for the first time from an Andean Cock of the Rock, Rupicola peruviana (Passeriformes: Cotingidae), from a zoo in Lima, Peru. Clinical signs of keratoconjunctivitis were resolved with the treatment of ivermectin, ciprofloxacin, and an epithelium regenerator, and the host is presently in good health. The nematodes were identified using the primary characteristics used to differentiate the species of this genus as lengths of spicules and other morphologic characteristics.     

Cranioplasty by means of molded polymethylmethacrylate prosthetic reconstruction after radical excision of neoplasms of the skull in two dogs

Two dogs with osteoma or multilobulated tumor of bone of the skull were treated with large en bloc resections. The resections resulted in exposure of the brain above the horizon line of the remaining calvarium; in 1 dog, the removal of the dorsal orbital rims also exposed both orbits dorsally. Protection of the brain and exposed tissues and restoration of the cosmetic appearance of the skull were attempted by use of molded polymethylmethacrylate prosthetic reconstruction of the calvarium. The technique described involves cranioplasty by use of a preformed molded polymethylmethacrylate implant. Such prosthetic cranioplasty may benefit dogs undergoing radical excision of extensive tumors, and the usefulness and potential complications of its application are discussed.     

A comparison of retrobulbar and two peribulbar regional anesthetic techniques in dog cadavers

Objective

To compare injectate distribution and likelihood of regional anesthesia to the orbit following retrobulbar (RB) or peribulbar (PB) injections in dog cadavers.

Analysis of Mammalian Masticatory Mechanisms: Progress and Problems

Direct measurement of bone movements and muscle activation in mammalian mastication is now possible. Early results indicate that the patterns are quite variable and depart from the stereotyped versions sometimes reported. Most mammals masticate unilaterally; only a few chew simultaneously on both sides. Orbital movements are complex and three-dimensional. While most muscles are active during the reduction phase, it is difficult to define phases by sharp transitions of activity. The fascicles of pinnate muscles differ in fiber architecture and physiology; they tend to function at different times and with distinct mechanical advantages. Interspecific diversity and marked responses to food consistency and size, still preclude generalizations. Improved methods for comparisons among orbits, for correlation of forces and excursions, and automated correlations of movements, forces and electromyograms are beginning to be available and need to be more generallv applied to analysis.     

Direct and reconstructed multiplanar computed tomography of the orbits of healthy dogs

OBJECTIVE: To describe anatomy of the orbits as revealed by computed tomography (CT) in different scan planes, determine the most useful scan plane for imaging the eye, optic nerve, and extraocular muscles, and compare image quality of direct CT images with reconstructed images obtained from 2-mm-thick and 5-mm-thick transverse images. ANIMALS: 9 dogs with no ocular abnormalities. PROCEDURE: In 3 dogs, CT was combined with cisternography to facilitate imaging of the optic nerve and determine the scan plane that allowed optimum imaging of the optic nerve in a single image. In 6 dogs, CT images were made in transverse, dorsal oblique, and sagittal oblique scan directions. Dorsal and sagittal reconstructions were made from transverse images. RESULTS: In all dogs, scanning in different planes enabled identification of ocular structures, optic nerves, and orbital adnexa, as well as identification of the confines of the orbit. Imaging of optic nerve and extraocular muscles was optimal on dorsal oblique scans at an angle of 43 to 45 degrees to the skull base and on sagittal oblique images at an angle of 59 to 61 degrees to the midline of the skull. CONCLUSIONS AND CLINICAL RELEVANCE: All scan directions provided detailed images of orbital structures. Transverse images were convenient for survey examination, and dorsal oblique and sagittal oblique images were superior for imaging optic nerves and extraocular muscles. Image quality of reconstructed images obtained from the 2-mm-thick transverse images was superior to that obtained from the 5-mm-thick images. Optimum quality was achieved with direct multiplanar imaging.     

Pathological Findings in a Case of Equine T-Cell Lymphoma Associated with Ataxia

A 15-year-old Dutch Warmblood gelding suddenly developed incoordination and hindlimb stumbling. The horse had a history of eyelid lymphoma. Necropsy revealed yellow-white or dark reddish-brown masses adhering to the outer surface of the spinal dura mater from the first cervical vertebra to the seventh thoracic vertebra. The spinal cord close to the first cervical vertebra and the seventh thoracic vertebra was markedly compressed by the masses filling the epidural space. The masses were also observed in the larynx, eyelids, and adipose-rich tissues, including the joints and orbits. They appeared similar in shape. The mandibular, retropharyngeal, axillary, superficial inguinal, deep inguinal, and lateral iliac lymph nodes were solid and enlarged. Histologically, the masses were composed of small or medium-sized lymphocyte-like tumor cells, but atypical cells and mitotic figures were rare. There were moderate infiltrations of macrophages and multinucleated giant cells, which were occasionally ingesting the surrounding tumor cells. Immunohistochemically, the tumor cells were classified as T-cell-derived cells. Throughout the spinal cord, enlargement or loss of nerve axons, dilation of periaxonal spaces, and macrophage infiltration into periaxonal spaces were observed, mainly in the ventral funiculus. Spinal cord compression by the tumor mass was suggested as a cause of the locomotive dysfunction. This is the first report of equine lymphoma with ataxia located from the proximal cervical to middle thoracic dura mater and in joint cavities.     

Development of a retrobulbar injection technique for ocular surgery and analgesia in dogs

OBJECTIVE: To develop and compare 3 techniques for retrobulbar injection of local anesthetic agents for ocular surgery and analgesia in dogs. DESIGN: Prospective study. ANIMALS: 17 dogs (including 9 cadavers). PROCEDURES: Inferior-temporal palpebral (ITP), perimandibular, and combined superior-inferior peribulbar injection techniques were compared by assessing the distribution of latex after injection into the orbits of 5 canine cadavers; magnetic resonance imaging (MRI) evaluation of the distribution of contrast agent after injection in the retrobulbar space of 4 canine cadavers; and assessment of the efficacy and MRI evaluation of the anatomic distribution of injections of a lidocainecontrast agent mixture in 4 anesthetized, nonrecovery dogs. By use of the preferred technique (ITP), the ocular effects of lidocaine anesthesia were evaluated in 4 dogs; during a 2-week period after treatment, dogs underwent ophthalmic examination, Schirmer tear testing (STT), intraocular pressure (IOP) measurement, and Cochet-Bonnet esthesiometry. RESULTS: Of the 3 techniques, the ITP technique was the preferred method for retrobulbar administration of anesthetic agent in dogs because it was efficacious (pupil dilation and central rotation of the globe achieved in all eyes), easiest to perform, and provided thorough coverage of the intraconal retrobulbar space without complication. During the 2-week follow-up period, the ITP injection did not significantly affect STT, IOP, or Cochet-Bonnet esthesiometry values in dogs. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, retrobulbar administration of anesthetic agents via the ITP technique is a potential alternative to systemic administration of neuromuscular blocking agents for ophthalmic surgery and provides the additional benefit of local ocular analgesia.     

Clinical value of blood glucose measurement in pet rabbits

Blood glucose was measured with a portable glucose meter in 907 rabbits, including 238 clinically healthy ones. Blood glucose concentrations ranged from 1.2 to 30.1 mmol/l. Diabetes mellitus was not encountered. No significant effect of sex or sedation was found. Hypoglycaemia was seen in 16 rabbits including one with an insulinoma. There was a significant relationship between blood glucose, food intake, signs of stress and severity of clinical disease. Rabbits showing signs of stress had higher blood glucose than rabbits with no signs and rabbits that were totally anorexic had higher blood glucose values than those that were eating normally or those with reduced food intake. Severe hyperglycaemia (>20 mmol/l) was associated with conditions with a poor prognosis. Rabbits with confirmed intestinal obstruction had a mean blood glucose of 24.7 mmol/l (n=18). This was significantly higher than the rabbits with confirmed gut stasis, which had a mean value of 8.5 mmol/l (n=51). The conclusion of the study was that blood glucose is a measurable parameter that can be used to assess the severity of a rabbit's condition and help to differentiate between gut stasis and intestinal obstruction in rabbits that are anorexic.