Web-Vet TM Neurology Specialists
Low-Field Magnetic Resonance Imaging Findings in 18 Dogs With Presumed Optic Neuritis
Optic neuritis is an inflammation of the optic nerve and typically manifests as a visual deficit. Potential causes include granulomatous meningoencephalitis, canine distemper virus, cryptococcosis and histoplasmosis, although, often no underlying cause is identified and the disorder is presumed to be immune-mediated. MRI of the optic nerves can be indicated in cases of vision loss with lack of significant ocular lesions and a normal electroretinogram. The combination of lack of menace response and absent PLR in these cases indicates a lesion affecting the optic nerve(s) or optic chiasm with optic neuritis, neoplasia of the optic nerve (if unilateral blindness) or compressing the optic nerve and tumor of or in the vicinity of the optic chiasm (meningioma, pituitary macroadenoma) being the most likely causes.
In this study the authors look retrospectively at MRI abnormalities affecting the optic nerve sheath complex and optic chiasm in dogs with clinically suspected optic neuritis as a component of meningoencephalitis of unknown etiology or as an isolated form of optic neuritis.
The purpose of this study was to identify prognostic factors for recovery of vision in canine ON of unknown etiology. Clinical databases of three referral hospitals were searched for dogs with presumptive ON based on clinicopathologic, MRI/CT, and fundoscopic findings. Twenty-six dogs diagnosed with presumptive ON of unknown etiology, isolated (I-ON) and MUE-associated (MUE-ON), were included in the study.
Six of the 26 included dogs (23%) achieved complete recovery and 20 dogs (77%) incomplete or no recovery of vision. The presence of a reactive pupillary light reflex, the absence of fundoscopic lesions, a younger age, and a lower cerebrospinal fluid (CSF) total nucleated cell count (TNCC) were statistically associated with complete recovery of vision.
