Miscellaneous conditions of the equine head

Magnetic resonance dacryocystography in the horse: A feasibility study

OBJECTIVE

To provide a comprehensive anatomical description of the normal equine nasolacrimal duct using magnetic resonance imaging, and to develop a practical protocol for performing magnetic resonance dacryocystography (MRD) in horses.

ANIMAL STUDIED

The heads of ten fresh horse cadavers with no history of sinonasal or ophthalmologic disorders were used for this study.

PROCEDURE

An MRD technique was developed in this study, which consisted of two parts. In the first part, olive oil and gadolinium were compared as contrast medium, using five horses. Two concentrations of gadolinium were used: 0.25 mmol/mL and 0.5 mmol/mL. In the second part, the influence of different head recumbencies using olive oil as the sole contrast medium was studied in the remaining five horses.

RESULTS

Injection with olive oil resulted in better distention and a complete filling of the nasolacrimal duct (ND) in all horses. Injection of 0.25 mmol/mL of gadolinium resulted in incomplete filling of the ND, whereas injection of 0.5 mmol/mL of gadolinium resulted in slightly better filling of the duct. The nondependent duct showed better distention compared to the dependent duct when scanning in lateral recumbency. No differences were observed between ducts in a dorsal recumbency. The degree of distention in dorsal recumbency was slightly less than the degree of distention observed in the nondependent ND in lateral recumbency.

CONCLUSIONS

Magnetic resonance dacryocystography is a suitable technique for evaluating the nasolacrimal duct and can be performed during a normal magnetic resonance examination.

Fluoroscopically guided neocanalization for treatment of nasolacrimal atresia in two horses

CASE DESCRIPTION

A yearling Thoroughbred stallion and an 8-year-old Saddlebred mare were evaluated for persistent mucoid ocular discharge.

CLINICAL FINDINGS

Examination of both horses revealed copious yellow-tan mucoid ocular discharge with a negative Jones I test, absent nasal punctum, and unsuccessful anterograde nasolacrimal duct (NLD) irrigation. Clinical abnormalities were present on the right side only in one horse and bilaterally in the other. Computed tomography (CT) with contrast confirmed nasolacrimal duct atresia in both horses.

TREATMENT AND OUTCOME

Under general anesthesia, the affected NLD was catheterized anterograde and contrast injected. Using fluoroscopic guidance, retrograde access to the distal NLD was obtained for through-and-through wire access. Over the wire, the stoma was dilated and a temporary stent placed for 4-8 weeks. After the procedure, both horses were comfortable and free of ocular discharge at the minimum time of last follow-up, 9 months postoperatively.

CLINICAL RELEVANCE

Fluoroscopically guided neocanalization is a viable alternative to traditional surgical approaches for NLD atresia, especially when access to the site of obstruction is limited.

Mucocele in a spectacled owl (Pusilatrix perspicillata)

A 6-year-old breeding female spectacled owl (Pusilatrix perspicillata) was presented for a soft, fluid-filled, spherical mass under the neck that had been increasing in size over the previous 3 days. Results of a fine-needle aspirate of the mass showed clear, pale-yellow fluid with a total protein of 12.6 g/L. Cytologic examination revealed erythrocytes, moderate numbers of heterophils, and numerous foamy mononuclear cells against a mucoid background. Macroscopically, the mass appeared to be attached firmly to the esophagus. The mass was excised surgically and submitted for histopathologic examination. The lesion comprised a circumscribed, fibrous-encapsulated multilocular cyst, lined by plump, goblet-type, cuboidal epithelial cells lying in abundant mucinous matrix. Findings were consistent with a mucocele of the esophageal mucosal gland. Excision was considered curative based on follow-up 6 months after initial presentation. To our knowledge, this is the first report of this condition in Strigiformes and indicates that mucocele should be included in the differential diagnosis of cervical masses in birds.