Cervical Spinal Meningeal Enhancement on Magnetic Resonance Imaging in Healthy Dogs: Characteristics of Enhancement Patterns and the Effect of Acquisition Time

Meningeal enhancement on magnetic resonance imaging (MRI) is commonly associated with pathological conditions, including inflammation, neoplasia, or ischemia. However, short and thin segments of contrast enhancement are considered normal in the brain meninges, but studies on spinal meningeal enhancement in dogs are limited. This prospective, exploratory study aimed to determine the presence and characteristics of cervical spinal meningeal enhancement in healthy dogs as well as the impact of acquisition time on enhancement. Cervical spinal MRI was performed from the dens of the axis to the C4-5 intervertebral disc (IVD) in 12 healthy beagles. T2-weighted, T1-weighted, contrast-enhanced T1-weighted (T1CE), immediate fat-saturated T1CE (T1CE_FS), and 15-min delayed T1CE_FS images were acquired. Enhancement patterns were categorized by their distribution, location (dorsal, lateral, or ventral aspect of the meninges), and shape (long segments, short segments, or spots). The enhancement percentage (E%) was calculated to quantitatively evaluate the enhancement. All dogs showed contrast enhancement at the IVD level, not the vertebral body. On immediate imaging, the enhanced regions predominantly appeared as short segments, most commonly at the C2-3, primarily in the dorsal aspect of the meninges. No significant differences were found between the two acquisitions except for the decrease in the E% in C3-4 after a 15-min delay. These results suggest that cervical spinal meningeal enhancement is a normal finding in healthy dogs, primarily appearing as short segments in the dorsal aspect of the meninges at the C2-3 level, with minimal changes between immediate and delayed imaging.