Meningoencephalitis of unknown origin (MUO) is a frequent diagnosis for dogs with multifocal neurologic signs. The name should tip you off that we’re still figuring out this interesting disease amd do not know the underlying cause yet. It is thought to be immune mediated, and therefore treatment often includes an immunosuppressive dose of steroids +/- an additional immunosuppressive such as cytarabine, azathioprine or cyclosporine. Despite decades of awareness of this disease we are still working out the prognostic indicators. Back in my academic days, a resident of mine and I tried to sort out this question by evaluating brain MRI results, with little success. A recent study took another crack at the elusive prognostic indicators and published their findings in JVIM (Goncalves R, et al. JVIM 2024).
Materials and Methods
447 dogs were included in this retrospective study from 2 institutions. Did you see that giant number of included cases?? Go vet med, go! Anyhoo, the authors included dogs with signs of inflammation (brain MRI, spinal tap) and because it was a retrospective study, there were a number of different treatment protocols included. Perhaps this creates too much variability to carefully evaluate outcome or prognosis. I might argue that there is no other way to accrue a large number of cases of MUO. A neuro disability score (NDS) was assigned to these patients (score developed by the author and several others and published in 2023). Survival was reported.
Results
I’m going to list some of the key results below but if you wish to learn more about the results, please refer to the article. It is well written and comprehensive.
Median age at presentation was 48 months
The majority of breeds represented were small breeds, but a few Labs, spaniels, and larger dogs were also included.
The season of diagnosis was equal across all 4 seasons
Common presenting complaints were proprioceptive deficits (77%), ataxia (65%), obtunded mentation (62%), seizures (32%).
The most common neuroanatomic lesion localization was multifocal (43%), followed by forebrain (29%)
Median follow-up time was 11 months. 82% of dogs survived to discharge and 63% were alive at 6 months.
A significant difference in survival was noted for dogs WITH a NDS compared to those without and a score of greater than 7 resulted in a sensitivity of 61% and specificity of 67% for predicting death at 6 months after diagnosis.
Relapse occurred in 50% of dogs that survived to discharge
Of those that relapsed, incomplete resolution of neurologic disease during the 6 month follow-up period, a higher NDS and neurologic signs >7 days duration before intervention were statistically associated with relapse.
What should we do with this information?
The take home message should be that we should perform a NDS on patients with suspected or confirmed MUO to help provide a prognosis AND that a more rapid referral may provide a better long-term outcome.
Stay tuned next week for a review of the NDS! Thanks for reading and I Hope you have a great rest of your week!