Survival in dogs with meningoencephalomyelitis of unknown etiology with and without lesions detected by magnetic resonance imaging

Abstract

Background: The prognosis of individual dogs with meningoencephalomyelitis of unknown etiology (MUE) remains difficult to predict. MUE cases with no lesions detected by magnetic resonance imaging (MRI) occur, but it is unknown whether this finding is associated with prognosis.

Hypothesis: MUE cases without detectable lesions on MRI have a better outcome than cases with detectable lesions.

Animals: Study included 73 client-owned dogs with MUE presenting to Purdue University Veterinary Hospital from 2010 to 2020.

Methods: Retrospective study. Dogs with a clinical diagnosis of MUE were identified by medical record search. MRI reports were reviewed for presence or absence of lesions consistent with MUE. Clinical findings at presentation, treatment, disease-specific survival, and outcomes including rates of remission and relapse were compared between cases with normal MRI or abnormal MRI.

Results: Overall, 54 dogs (74%) were classified as abnormal MRI, and 19 dogs (26%) were classified as normal MRI cases. Death caused by MUE occurred in 1/19 (5%) normal MRI dogs and 18/54 (33%) abnormal MRI dogs (P = .016). Median survival was >107 months in both groups, but survival was significantly longer in the normal MRI group (P = .019). On multivariate analysis, abnormal MRI was significantly related to death (hazard ratio, 7.71; 95% confidence interval 1.03-58.00, P = .0470), whereas significant relationships with death were not identified for either the use of secondary immunosuppressive medications or cerebrospinal fluid nucleated cell count.

Conclusions: MUE dogs with no detectable lesions on MRI have reduced disease-related death compared with dogs with abnormal MRI. The presence or absence of MRI lesions in MUE dogs is prognostically relevant.

Keywords: GME; brain; canine; encephalitis; meningitis; necrotizing encephalitis.

FIGURE 1

Case selection for inclusion in the current study. Flow chart demonstrating criteria for inclusion of 73 dogs in the study. CRTS, corticosteroid‐responsive tremor syndrome; CSF, cerebrospinal fluid; EME, eosinophilic meningoencephalitis; MRI, magnetic resonance imaging; SRMA, steroid responsive meningitis‐arteritis; TNCC, total nucleated cell count.

FIGURE 2

Disease‐specific survival. Kaplan‐Meier analysis of 73 dogs with meningoencephalitis of unknown etiology, comparing cases with normal magnetic resonance imaging (MRI) (n = 19) and abnormal MRI (n = 54). Each vertical tick mark represents a censored dog that was either lost to follow‐up or deceased because of causes unrelated to meningoencephalomyelitis of unknown etiology. Median survival because of disease was not reached in either group. Survival time because of disease differed by group (P = .02, log rank test).

FIGURE 3

Survival in dogs with and without magnetic resonance imaging (MRI) features of mass effect. Survival in 73 dogs with meningoencephalitis of unknown etiology, with 0, 1, or 2 features of mass effect on MRI. Features of mass effect evaluated were midline shift, loss of sulci, and transforaminal herniation. There were only 2 dogs with 2 features of mass effect. Survival was not significantly different between groups (P = .12, log rank test). Mass = 2, 2 features of mass effect present. Mass = 1, 1 features of mass effect present. Mass = 0, no features of mass effect present.