Prognosis in meningoencephalitis of unknown origin in dogs: Risk factors associated with survival, clinical relapse, and long-term disability

Rita Gonçalves, Steven De Decker, Gemma Walmsley, Thomas W. Maddox

Background

This study addresses the prognosis in dogs diagnosed with Meningoencephalitis of Unknown Origin (MUO), a group of non-infectious inflammatory diseases affecting the central nervous system. Despite existing studies on individual risk factors for survival in MUO, comprehensive prognostication remains challenging. The research aims to identify clinical prognostic variables related to survival, clinical relapse, and long-term disability in dogs with MUO.

Methods

A retrospective review was conducted on medical records from 447 dogs presented to two UK referral hospitals diagnosed with MUO. The study utilized multivariable logistic regression to identify risk factors for survival and Cox proportional hazards analysis for risk factors related to clinical relapse.

Results

Survival and Clinical Presentation: 82% (366/447) of dogs survived to discharge, and 63.5% (284/447) were alive at 6 months. Among the survivors, 36% (103/284) displayed persistent neurological deficits. Negative associations with survival to 6 months included breed (specifically pugs), epileptic seizures, paresis, and higher neurodisability scale (NDS) scores at presentation.

Clinical Relapse: During the follow-up (median time of 11 months), 50.6% (160/316) of dogs experienced relapse, with a median time to relapse of 7 months. Factors associated with relapse included incomplete resolution of clinical signs within 6 months post-diagnosis, higher NDS scores, and longer duration of clinical signs before diagnosis.

Limitations

• Retrospective Nature: The study's retrospective design may limit the accuracy of recorded clinical features, potentially affecting the identification of associations between certain clinical features and outcomes.

• Standardization of Treatment: The lack of standardized treatment protocols across cases could have influenced individual survival times and the likelihood of relapse, reflecting the complex and varied clinical practice rather than controlled study conditions.

• Diagnosis Confirmation: The absence of histopathologic examination in most cases introduces the possibility of misdiagnosis, affecting the study's findings regarding specific MUO subtypes.

• Assessment of Clinical Relapse: Clinical relapse was primarily identified based on the recurrence of symptoms, without consistent confirmatory diagnostic testing across all cases, potentially leading to misclassification of relapse events.

• Treatment Variability: The wide range of treatments and dosing regimens used reflects the lack of consensus on the optimal management strategy for MUO, making it challenging to draw firm conclusions about the efficacy of specific treatments.

Conclusions

The study identifies significant risk factors associated with survival, incomplete recovery, and clinical relapse in dogs diagnosed with MUO. Understanding these risk factors can enhance monitoring, treatment strategies, and communication with pet owners regarding the prognosis of this debilitating disease. The study highlights the critical role of the NDS as a tool for assessing and predicting outcomes in dogs with MUO.

Clinical Importance

The findings underscore the importance of early and aggressive treatment strategies for dogs with MUO, especially those presenting with higher risk factors for adverse outcomes. Clinicians can use this information to tailor management plans and set realistic expectations for owners, potentially improving the quality of life for affected dogs.

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