Abstract
The objective of this study is to describe the clinical features and computed tomography (CT) findings of dogs with retrobulbar disease. There are two facets to this study: a retrospective case series in which findings of dogs with primary vs. secondary retrobulbar disease are described, and a retrospective cross-sectional study in which computed tomography findings of dogs with retrobulbar neoplasia vs. infection/inflammation are described and compared. The medical records of 66 client-owned dogs diagnosed with retrobulbar disease between 2006 and 2016 were reviewed. Clinical information including signalment, the specialty service to which the dog was presented, clinical signs, physical examination findings, diagnostic results, treatment, and outcome were documented. Diagnostic imaging and histopathology were reviewed. Forty-one dogs (62.1%) were diagnosed with primary disease of the retrobulbar space; 25 dogs (37.9%) were considered to have secondary retrobulbar disease. Of the 41 dogs with primary retrobulbar disease, 19 were diagnosed with neoplasia, 19 with infectious/inflammatory disease, and 3 suffered traumatic insult to the retrobulbar space. Of the 25 dogs with secondary retrobulbar disease, 21 were diagnosed with neoplasia, 3 with infectious/inflammatory disease, and 1 with a cyst. Dogs had a combination of ocular, oral, and/or nasal clinical signs. CT findings of orbital osteolysis, orbital periosteal reaction, and presence of a retrobulbar mass were significantly associated with neoplasia, while zygomatic salivary gland enlargement, retrobulbar mass effect, and mandibular lymphadenopathy were more often associated with infectious/inflammatory disease. CT findings overlap among different retrobulbar diseases, but new bone formation and lysis are more often associated with neoplasia. Disease originating from the retrobulbar space was equally likely to be infectious/inflammatory (n = 19) or neoplastic (n = 19), based on definitive diagnostic results of dogs with primary retrobulbar disease. Due to the clinical ramifications of these disorders, the diagnosis and treatment of these cases should be managed with a multi-specialty approach.
Highlights
Retrobulbar disorders are challenging to diagnose and treat, due to the array of possible clinical presentations and anatomic complexity of the region
The purpose of the present study is to describe the clinical and computed tomography (CT) features of a large cohort of dogs with primary and secondary retrobulbar disorders, and to review treatments pursued and treatment outcomes
The main basis for inclusion in the study was pathology involving the retrobulbar space evident by CT; CT reports were searched for the keyword “retrobulbar.” Cases were included if an etiological diagnosis was achieved by cytology, biopsy, bacterial or fungal culture, exploratory surgery, necropsy and/or positive response to antibiotics or anti-inflammatory medications
Summary
Retrobulbar disorders are challenging to diagnose and treat, due to the array of possible clinical presentations and anatomic complexity of the region. Six bones contribute to the structure of the orbit: frontal, lacrimal, maxillary, zygomatic, palatine, and sphenoid [1, 2]. The retrobulbar tissues of the dog include extraocular muscles, the lacrimal gland, the zygomatic salivary gland, masticatory muscles, nerves, blood vessels, and the bones that form the orbit (Figure 1). The orbit contains a cone of eye-associated structures termed the periorbita, the apex of which points caudally. The periorbita is derived from the periosteum, encloses the caudal portion of the eyeball and the extrinsic muscles of the eye, and is surrounded by orbital fat. All of the extrinsic muscles of the eye except for the ventral oblique originate in the apex of the orbit [1, 4,5,6]. The orbit serves to position and protect the globe and house the retrobulbar tissues [2]
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