Convergence Retraction Nystagmus Secondary to Central Nervous System Disseminated Coccidioides Immitis Infection in a Dog.

This report describes a Belgian Malinois dog residing in metropolitan Phoenix, Arizona that was presented to a veterinary neurology center with abnormal eye movements as his only clinical sign. On examination, clinical signs were isolated to convergence-retraction nystagmus. A brain MRI was performed which identified two well-demarcated, T2-hypointense and T1-isointense, avidly contrast enhancing mass lesions with moderate to severe perilesional T2 and FLAIR hyperintensity within the left frontal lobe and left dorsal midbrain. Imaging characteristics were most consistent with Coccidioides immitis fungal granulomas and serology was supportive of Coccidioidomycosis infection. The patient's clinical signs resolved quickly with antifungal and anti-inflammatory therapies, and brain granulomas were resolved or resolving on repeat imaging 10 months after initial diagnosis. To the authors' knowledge, this is the first report of convergence-retraction nystagmus secondary to an infectious etiology described in a canine patient.