Devoted readers of my TidBit Tuesdays may recall our recent discussion about meningoencephalitis of unknown origin (MUO). As you likely recall, it is diagnosed antemortem through a combination of MRI, CSF analysis and negative infectious disease testing. We treat with immunosuppressive protocols - varying a bit by neurologist - and report modest response to treatment. Many of us a still left scratching our heads and wondering "what triggered the immune system in the first place?"
A study, conducted at the University of Georgia recently reported findings pertaining to viral DNA in CSF in dogs with MUO. (Alphabet soup, anyone?) They evaluated 172 dogs with neurologic dysfunction and CSF pleocytosis. Viral particles from adenovirus, bunyavirus, coronavirus, enterovirus, flavivirus, herpesvirus, paramyxovirus and parechovirus were screened. No viral nucleic acids were detected in the CSF samples save 4 dogs from Georgia with La Crosse virus particles. Two dogs were considered to have a subclinical infection, the other two had an unknown relationship with the virus.
What does this mean? It means that we still don't know what triggers MUO in dogs. It means that researchers are still working on it, and that we, as "field vets" can contribute cases to the Universities studying this disease when asked and that we must continue to face clients and tell them that we're still trying to figure it out.
How does this change what you do? It shouldn't! If you have a dog with multifocal neurologic signs, referral for diagnostic testing is strongly recommended. If they cannot refer, initiation of treatment is recommended. If you have a patient with focal CNS signs, don't forget about MUO! Focal CNS lesions are frequently inflammatory, not just vascular or neoplastic, so refer whenever possible for advanced imaging and CSF tap. (Did you know I do outpatient MRIs in Madison and Waukesha? Set up a neurology consultation first, and we'll schedule the MRI ASAP.)
I hope you have a wonderful week and enjoy the last of the Fall weather. Please reach out if you need assistance with a case; I'm here to help!
Reference: Barber RM, Li Q, Levine JM, Ruone SJ, Levine GJ, Kenny P, Tong S, Schatzberg SJ. Screening for Viral Nucleic Acids in the Cerebrospinal Fluid of Dogs With Central Nervous System Inflammation. Front Vet Sci. 2022 Mar 24;9:850510. doi: 10.3389/fvets.2022.850510. PMID: 35400093; PMCID: PMC8987525.