1460 Scientific Reports: Clinical Report JAVMA, Vol 221, No. 10, November 15, 2002 EQUINE A 9-year-old Trakehner gelding was evaluated at the North Carolina State University Veterinary Teaching Hospital because of grade-3 lameness, on a scale from 1 to 4, of the left forelimb and exophthal- mus of the right eye. Three weeks previously, the horse had run to the right of a jump and sustained a lacera- tion of the proximal aspect of the left metacarpal region, resulting in mild stiffness and lameness. Signs of pain could also be elicited on abduction and exten- sion of the shoulder joint. The horse carried its head and neck to the right when trotting in a straight line, but signs of pain were not elicited when the neck was manipulated, and the range of motion was normal. The owner stated that the horse had appeared more sedate than normal and had been carrying its head lower than normal. Prior to examination at the teaching hospital, there had been mild swelling involving the lower lid of the right eye. An ophthalmologic examination by the referring veterinarian revealed exophthalmia and a mildly reduced menace response in the right eye. On initial examination at the veterinary teaching hospital, the horse was judged to be mildly to moder- ately lethargic. Rectal temperature, heart rate, and res- piratory rate were within reference limits. The menace response was absent in the right eye, and the direct right pupillary light reflex was sluggish. The consensu- al left pupillary light reflex was normal. Results of examinations of the posterior segments of each eye were normal. Results of scotopic electroretinography a were normal, and the dazzle response was normal in both eyes. There was no strabismus, and physiologic nystagmus could be elicited. The palpebral reflex was normal, as was sensation over the ears, eyes, and muz- zle bilaterally. There was no evidence of conscious pro- prioception deficits, sensory ataxia, or weakness. The horse leaned to the left at rest during the examination, indicating increased extensor tone on the right, but this was not evident when a blindfold was applied or when the horse walked. The neurologic examination findings indicated a lesion affecting the right optic nerve (cranial nerve II) and possibly the left vestibulo- cochlear nerve (cranial nerve VIII). 1 A vascular retrob- ulbar mass was identified during ultrasonographic examination of the right eye and orbit with a 7-MHz phased-array transducer b (Fig 1). The mass extended into the medial aspect of the sphenopalatine fossa. There was disruption of the bone surrounding the medial aspect of the orbit and lateral displacement of the globe. Results of a CBC and serum biochemical analyses were unremarkable. The owner elected to take the horse home and return later for further evaluation of the retrobulbar mass and lameness. The horse was re-examined 2 days later. Forebrain disease was suspected because of the horse’s profound lethargy. No conscious proprioception deficits were observed, indicating that the profound lethargy could not be explained by a lesion affecting the brainstem. 1 The right pupil was mydriatic. Right menace response and direct and consensual right pupillary light reflexes were absent. The dazzle reaction was normal. Ventrolateral deviation of the right eye was evident. The strabismus was unchanged when the head was moved, and there was no physiologic nystagmus on the right side. These findings were suggestive of a right- sided peripheral (retrobulbar) lesion affecting the ocu- lomotor nerve (cranial nerve III). 1 The lack of physio- logic nystagmus indicated possible retrobulbar involvement of the trochlear (cranial nerve IV) and abducens (cranial nerve VI) nerves in addition to the oculomotor nerve. A brainstem lesion affecting the vestibular nuclei could also have accounted for the lack of physiologic nystagmus. The palpebral reflex was asymmetrical, appearing more sluggish on the right than on the left, but the horse could close its eyes, indicating that the lack of a right menace response was a result of a lesion affecting the optic nerve. 1 Sensation over the ears, eyes, and muzzle was normal. There was an inconsistent head tilt to the left, leaning and circling to the left, a mild right-sided facial asymmetry with decreased flare of the right nostril, and a slight devia- tion of the muzzle to the left. These findings and the sluggish right palpebral reflex despite normal facial skin sensation were consistent with a deficit of the right facial nerve (cranial nerve VII) and the left vestibulocochlear nerve. Endoscopic c examination of Nasal adenocarcinoma with diffuse metastases involving the orbit, cerebrum, and multiple cranial nerves in a horse Jennifer L. Davis, DVM, MS; Brian C. Gilger, DVM, MS, DACVO; Kathy Spaulding, DVM, DACVR; Ian D. Robertson, BVSc, DACVR; Samuel L. Jones, DVM, PhD, DACVIM ' Metastatic adenocarcinomas in horses are rare, aggressive tumors with a grave prognosis. ' Involvement of multiple cranial nerves in horses with neoplasia without gross or histologic evi- dence of metastasis may be a result of an immune-mediated paraneoplastic syndrome. ' Computed tomography is a sensitive technique for diagnosis of neoplasia involving the head in horses. ' Thoracic radiographs should be obtained to rule out metastatic disease in all horses suspected to have neoplasia. From the Departments of Clinical Sciences (Davis, Gilger, Jones) and Anatomy, Physiological Sciences, and Radiology (Spaulding, Robertson), College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606. Address correspondence to Dr. Jones.