What MRI Really Tells Us About Canine Neosporosis—and What Actually Improves Survival

A systematic review of clinical and diagnostic findings, treatment, and outcomes in canine neosporosis cases evaluated by magnetic resonance imaging

Neringa Alisauskaite

Background

Canine neosporosis, caused by Neospora caninum, is an uncommon but serious protozoal disease affecting the central and peripheral nervous systems of dogs. Although magnetic resonance imaging (MRI) is increasingly used in the diagnostic evaluation of canine neurological disease, its role in neosporosis has not been systematically characterised. Prior knowledge is largely derived from case reports and small case series, leaving uncertainty regarding typical MRI features, diagnostic correlations, and prognostic indicators. This study aimed to systematically review published cases of MRI-evaluated canine neosporosis and to identify clinical, diagnostic, imaging, treatment, and outcome variables associated with survival.

Methods

A systematic literature review was conducted using PubMed and Google Scholar. Included cases required confirmed N. caninum infection by serology, PCR, or histopathology and MRI of the brain and/or spinal cord performed at diagnosis. Data extracted included signalment, clinical signs, neurological localisation, MRI findings, cerebrospinal fluid (CSF) analysis, serology, CSF PCR results, treatment protocols, and outcomes. Descriptive statistics were used to summarise findings, and statistical analyses assessed associations between laboratory variables, imaging features, treatment duration, corticosteroid use, and survival.

Results

Eighty-two cases from 11 publications met inclusion criteria. Dogs were predominantly young-to-middle-aged adults, with multifocal CNS involvement being the most common neurological localisation. MRI abnormalities were detected in nearly all brain studies and in most spinal studies, with multifocal intra-axial lesions and frequent cerebellar involvement. Cerebellar atrophy and a T2-weighted/FLAIR hyperintense cerebellar rim were common but not universal findings. Contrast enhancement of CNS lesions was variable and was consistently present in affected muscles when muscle involvement was reported. CSF abnormalities were present in the majority of cases, most commonly pleocytosis, and higher CSF total nucleated cell counts were significantly associated with positive CSF PCR results. No associations were found between survival and serology titres, CSF PCR status, CSF cell counts, serum creatine kinase levels, or MRI contrast enhancement. Treatment duration showed a strong positive correlation with survival, whereas corticosteroid use was not significantly associated with outcome. Death or euthanasia due to neosporosis occurred in approximately one-third of cases, while sustained remission was uncommon and relapses were frequent.

Limitations

The study was limited by its retrospective design and reliance on heterogeneous published case reports and series. MRI protocols, diagnostic testing, treatment regimens, and follow-up durations varied widely, and incomplete reporting limited some analyses. Selection bias toward more severe or atypical cases is likely, as only MRI-investigated and definitively diagnosed cases were included.

Conclusions

Canine neosporosis most commonly presents as a multifocal CNS disease in young-to-middle-aged dogs, with diverse MRI features and frequent cerebellar and muscular involvement. While MRI and CSF analysis are valuable diagnostic tools, most laboratory and imaging variables lacked prognostic significance. The only consistent predictor of improved survival was longer duration of antimicrobial treatment. Prognosis remains guarded, with relapses common, but early recognition and prolonged antimicrobial therapy appear critical for improving outcomes.

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