Cerebrospinal fluid markers and magnetic resonance imaging lesion volume predicting relapse in canine meningoencephalitis of unknown origin

Introduction: Meningoencephalitis of unknown origin (MUO) is a potentially lethal neurological disease in dogs with a high relapse rate. Prognostic factors for relapse based on neurological examination, magnetic resonance imaging (MRI), or cerebrospinal fluid (CSF) examination are inconsistently reported. Methods: This retrospective single center study included 35 dogs with MUO. Brain MRI, CSF findings, clinical signs at diagnosis and during follow-up MRI (routine or relapse-related) were analyzed. Lesion volumes were calculated using the Cavalieri method. Relapse predictors were evaluated for routine follow- up MRI examinations using logistic regression and ROC/AUC. Result: = 0.0288) at routine follow-up examination were predictive of future relapse. ROC analyses identified thresholds of 9.64 mg/dl for CSF albumin (AUC: 0.75; sensitivity 86.7%, specificity 61.1%) and 74.0% for CSF lymphocytes (AUC 0.76; sensitivity 66.7%, specificity 64.3%). Total lesion volume and volume of contrast-enhancing lesions decreased after treatment and increased again at relapse. Increased lesion volume or normal MRI on routine follow-up MRI did not reliably predict future relapse, although increased lesion volume in T1-weighted contrast enhancement and Fluid-attenuated inversion recovery (FLAIR) was observed at or after relapse. Lesion volume, lesion number, and lesion localization in different sequences was associated with neurodisability scale (NDS) and epileptic seizures. Discussion: In this study, CSF albumin and lymphocyte proportion were identified as predictors of future relapse. Routine follow-up MRI was not predictive of future relapse, but useful for detection of an active inflammation.