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EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014


topical phenylephrine (Phenylephrine HCl 1%)12, dimethyl sulfoxide gel (DMSO)9, and triamcinolone acetonide cream (Triamcinolone acetonide cream 0.1%)13 were applied twice to the periocular region to reduce periocular inflammation.


Further clinical findings, diagnostics and treatment


On the morning of Day 3, the horse became acutely neurological and depressed. Abnormal clinical findings included leaning against the stall wall on his right side, head pressing and intermittent episodes of seizure-like activity characterised by rapid spastic movements of the left hindlimb. These episodes were preceded by periods of marked tachypnoea that resolved following the activity. Attempts to guide the horse away from the wall were unsuccessful, although he was able to ambulate using the wall for support. He was able to eat, but unable to locate feed placed in front of him, typically moving to the left of the food. Prehension, mastication and deglutition were otherwise normal. A complete blood count revealed a marked leucocytosis (22.3 ¥ 109 cells/l, reference range [rr] 5.0–11.0 ¥ 109 cells/l) consisting of a neutrophilia (21.2 ¥ 109 cells/l, rr 2.1–6.7 ¥ 109 cells/l) with a left shift (0.45 ¥ 109 cells/l band neutrophils, rr 0.0–0.20 ¥ 109 cells/l) and a moderate lymphopenia (0.22 ¥ 109 cells/l, rr 1.3–4.5 ¥ 109 cells/l). Hyperfibrinogenaemia (8 g/L, rr 1–4 g/l) and mild anaemia (packed cell volume 28.3%, rr 34–45%; erythrocytes 6.19 ¥ 1012 cells/l, rr 7.0–11.0 ¥ 1012 cells/l) were present. Serum chemistry panel was unremarkable. Radiographs (right lateral and right oblique) of the more caudal aspect of the skull revealed no evidence of fracture within the guttural pouches, basisphenoid bone or temporohyoid regions. The horse was able to move freely away from the wall by evening, but only moved to the left. Dysphagia was noted that evening when the horse prehended hay and made no attempts at mastication, keeping the jaw clamped. Periocular swelling remained unchanged since the previous day and the tarsorrhaphy was removed at this time in the event that increased pressure on the globe was exacerbating neurological signs. A 2 cm round mass was noted for the first time on the floor of the right naris, but was considered an incidental finding at that time. Menace response and pupillary light reflex (PLR) were present in the right eye. At this time, neurological evaluation was suggestive of diffuse forebrain disease with primary differentials including bacterial meningitis, trauma, equine protozoal myeloencephalitis secondary to stress and glucocorticoid administration, or viral encephalitis. Due to high suspicion of bacterial meningitis, antimicrobial therapy consisting of ceftiofur sodium (Naxcel3 4 mg/kg bwt i.v. b.i.d.) was initiated. On Day 4, the horse was placed under general anaesthesia and cerebrospinal fluid (CSF) was collected from the atlanto-occipital site; a sub-palpebral lavage system was also placed to facilitate ocular treatments. Computed tomography of the skull was recommended to further evaluate for skull fractures and to assess the nasal mass, but was declined by the owner. The CSF was xanthochromic and revealed a high nucleated cell count (5.38 ¥ 109 white blood cells/l, rr<0.005 ¥ 109 white blood cells/l), elevated total protein (2.75 g/l, rr 0.32–0.48 g/l) and an elevated red blood cell count (2.2 ¥ 107 erythrocytes/l). Cytology revealed a neutrophilic pleocytosis (99% neutrophils, primarily nondegenerate to slightly degenerate, and 1% lymphocytes) and a small number of neutrophils containing intracellular


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Fig 1: Cytology of cerebrospinal fluid. Modified Wright’s stain, 100 ¥ magnification. Numerous nondegenerate to mildly degenerate neutrophils. Arrowheads show a nondegenerate neutrophil containing intracellular bacterial rods and cocci. Image courtesy of Dr H. Flaherty, Department of Veterinary Clinical Pathology, Iowa State University, Ames, Iowa.


bacterial rods and cocci (Fig 1). Based on the neutrophilic pleocytosis and presence of bacteria within the CSF, a diagnosis of bacterial meningitis was established, and samples were submitted for anaerobic and aerobic bacterial culture. Gentamicin (GentaVed 1002 6.6 mg/kg bwt i.v. s.i.d.) was added to antimicrobial therapy following the identification of Gram-negative rods on CSF cytology. Despite the cytological evidence of polymicrobial infection, culture results of the CSF indicated a low pure growth of Escherichia coli that was susceptible to ceftiofur, gentamicin and enrofloxacin. A combination of ceftiofur and gentamicin were utilised as broad spectrum coverage until Day 11. A complete ophthalmic examination revealed multiple superficial ulcers in the cornea along with marked chemosis and a tear in the ventral palpebral conjunctiva. Topical ocular treatments in the left eye were changed to solutions of atropine (Atropine sulfate ophthalmic solution)8 used to effect and Neomycin Polymyxin B Gramicidin (Neo-Poly-Gramicidin ophthalmic solution)8 q.i.d. The mass in the right nostril had increased in size to approximately 3 cm, and a fine needle aspirate yielded a small quantity of serous fluid containing scant neutrophils. The horse remained quiet but responsive on Day 5, and


displayed propulsive circling to the right overnight. The horse was interested in food, but had difficulty prehending. The right nasal mass progressed to approximately 4 cm in size, and remained firm but did not appear hot or painful. Ultrasonographic examination of the mass via the rostral nasal passage revealed a honeycomb appearance, but no flocculent material was appreciated. Topical application of ichthammol (Ichthammol ointment)10 and application of hot compresses was instituted twice daily on the nasal mass. Right-sided facial hyperaesthesia, ptosis, ear droop and a head tilt developed in addition to muzzle deviation to the left, and an incomplete blink reflex was present. These findings were consistent with dysfunction of cranial nerves V, VII and VIII on the right side. The horse remained relatively stable on Days 6 and 7, but continued to have difficulty prehending food and masticating. He began moving to the left, and the circling decreased.


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