How do MRI lesions affect survival for MUE?

 
A study was published this week that looked at the survival times between dogs with and dogs without MRI lesions and diagnosed with meningoencephalomyelitis of unknown etiology (MUE). MUE is diagnosed if a dog has evidence of CNS inflammation (meningitis, encephalitis, myelitis or a combination of these) without evidence of infectious etiology. Signs can be focal or multifocal, and age is irrelevant. To make this diagnosis an MRI, CSF tap, and infectious disease testing are performed. There is a subset of dogs that are diagnosed with immune mediated CNS disease that do not show evidence of disease on MRI but have all of the other markers of MUE. The purpose of this paper was to determine if there is a difference in survival between the two groups of dogs.
Results
A total of 73 dogs with MUE were included in the study. This included 19 dogs with a normal MRI and 54 with an abnormal MRI. The survival time was >107 months in both groups with a significantly longer survival in the normal MRI group. Neither group reached median survival in Kaplan-Meier survival, however. Death was secondary to MUE in 1/19 dogs with a normal MRI, and 18/54 in dogs with an abnormal MRI.
Below is the breakdown comparison between the two groups:

• Remission – 68% of the normal MRI group; 53% of the abnormal MRI group.

• Death within 3 months due to disease – 5% in the normal MRI group and 13% in the abnormal MRI group.

No difference was found between dog groups regarding remission, disease-free interval, or relapse while on prednisone. The two groups received similar treatment protocol, for which corticosteroids were included in all dogs and a variation of additional immunosuppression. The total nucleated cell count (TNCC) was higher in the dogs with the abnormal MRI however this did not correlate with higher rates of death after multivariate analysis. The only significant factor associated with death was the presence of an abnormal MRI.

Why don’t they have lesions on MRI?

Perhaps we’re catching these cases early in the course of disease. This would stand to reason why they might have a lower death rate than those with more progressive disease at the time of diagnosis. Another option is that this is a different form of inflammatory brain disease. MUE is a “catch all” for inflammatory brain disease that isn’t infectious, or a specific form such as SRMA or EME. It likely includes all of the previously diagnosed cases of GME and NME.
Take away: If you have a dog with spinal pain, seizures, vestibular signs or multifocal CNS signs remember MUE! This disease can cause all of those signs, and a collection of other signs, in dogs. Early detection may = improved outcomes. So, if your patient is showing neurologic signs, please reach out to get a consult ASAP and to proceed with additional testing when able. We might just save their life!

Thanks for reading! I hope you are scratching out the very best that summer has to offer. I look forward to working with you soon!

Reference: Survival in dogs with meningoencephalomyelitis of unknown etiology with and without lesions detected by magnetic resonance imaging. Ostrager A, Bently, TR, Lewis MJ, Moore GE.