New MRI Predictors of Brain Herniation Risk in Epileptic Dogs Identified

Peritumoral MRI Findings and Brain Herniations in Epileptic Dogs With Prosencephalic Brain Tumors: A Multicentre Retrospective Study

Marco Tabbì, D. Fugazzotto, C. Caterino, S. Minniti, V. Toneatti, G. Barillaro, S. Minato, C. Giannetto, G. Fatone, F. Macrì

Background

Brain tumors in dogs account for 2–4.5% of post-mortem findings, with most primary tumors classified as meningiomas, gliomas, or choroid plexus tumors . These neoplasms can cause intracranial hypertension and brain herniation, which may worsen neurological signs, including epilepsy. Magnetic resonance imaging (MRI) is essential for evaluating peritumoral changes, yet data specifically linking MRI abnormalities to brain herniation in epileptic dogs remain limited. This study aimed to describe peritumoral MRI findings and characterize the types and frequency of brain herniations in epileptic dogs with prosencephalic tumors.

Methods

The study was a multicentre retrospective analysis, conducted using medical records from routine diagnostic procedures with no experimental interventions performed . Data collected included MRI examinations of epileptic dogs diagnosed with prosencephalic brain tumors. MRI findings were reviewed for peritumoral changes and types of herniation, and patient clinical histories were evaluated to classify tumor types and correlate imaging abnormalities with herniation features.

Results

MRI evaluation of 80 epileptic dogs with prosencephalic brain tumors revealed several peritumoral imaging abnormalities strongly associated with brain herniation. Peritumoral edema was common (85% of cases), and lateral ventricular compression occurred in 77.5% of dogs. Midline shift, a key indicator of intracranial mass effect and a major contributor to herniation, was present in 87.5% of cases. Multiple forms of herniation were identified, most frequently subfalcine herniation (77.5%) and caudal transtentorial herniation (31–41.25%), followed by displacement of the quadrigeminal lamina (57%) and foramen magnum herniation (26.25%). Larger tumor volumes were positively correlated with the presence of peritumoral edema, ventricular compression, and laminar displacement, indicating that these mass effect–related features predispose dogs to herniation. Importantly, the study found that tumors anatomically distant from the midbrain could still cause quadrigeminal lamina displacement, highlighting that herniation patterns can occur independently of strict tumor proximity. Collectively, the MRI characteristics most strongly associated with brain herniation were peritumoral edema, midline shift, ventricular compression, and mass effect–related structural displacements.

Limitations

This study relied on retrospective clinical records and MRI studies obtained during routine care, which may have introduced variability in imaging protocols and diagnostic completeness. As a retrospective design, the study could not control for MRI timing relative to clinical deterioration. The authors note that cases were collected across multiple centers, which may have contributed to heterogeneity in imaging interpretation and diagnostic documentation. Additionally, tumor diagnoses were based primarily on imaging, with histopathology not available for every case.

Conclusions

This multicentre study provides a detailed description of peritumoral MRI findings and identifies patterns of brain herniation in epileptic dogs with prosencephalic brain tumors. The results underscore the importance of recognizing MRI features that may signal elevated herniation risk. Enhanced understanding of these imaging markers can support earlier clinical intervention, improve prognostication, and help guide therapeutic decision-making, particularly in dogs presenting with epilepsy secondary to intracranial neoplasia.

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