Dynamic MRI Reveals Hidden Lumbosacral Compression in Dogs

Dynamic Magnetic Resonance Imaging of the Lumbosacral Spine in Neutral and Extended Positions in Dogs with Suspected Lumbosacral Disease

Maria Baldo Clemot, Susan M. Schaub, Rachel D. Pollard, Julia P. Sumner

Background

Degenerative lumbosacral stenosis (DLSS) is a common cause of caudal lumbar pain and neurologic deficits in dogs, especially large breeds. Traditional MRI in neutral spine positioning may not reveal dynamic compressive changes that occur during motion. In human medicine, positional MRI has improved diagnostic sensitivity for similar conditions. This study aimed to compare MRI findings in neutral and extended lumbosacral positions in dogs with suspected DLSS to assess whether dynamic imaging improves lesion detection.

Methods

A prospective study included 21 client-owned dogs with clinical signs of DLSS. Each dog underwent dynamic MRI under general anesthesia using a 1.5T system. Imaging was performed in both neutral and extended positions. Parameters evaluated included intervertebral disc protrusion, ligamentum flavum hypertrophy, spinal canal diameter, foraminal dimensions, and displacement of soft tissues. Images were interpreted by board-certified radiologists blinded to clinical data. Changes between positions were statistically analyzed to determine the frequency and severity of dynamic compressive changes.

Results

Extension MRI revealed additional or worsened compressive changes in 81% of dogs compared to neutral positioning. Key findings included increased intervertebral disc protrusion, reduced spinal canal diameter, and exacerbated foraminal stenosis in extension. In 38% of cases, neural compression was only evident in extension, not in neutral. Dynamic imaging also showed increased displacement of the ligamentum flavum. These findings correlated with clinical signs in most cases, suggesting added diagnostic value.

Limitations

The study’s small sample size limits generalizability. No control group of healthy dogs was included, and all patients were under general anesthesia, which may influence soft tissue and joint positioning. Clinical correlation was based on subjective assessment rather than quantitative functional outcomes. Long-term follow-up was not performed to assess impact on surgical or treatment decisions.

Conclusions

Dynamic MRI using spinal extension can reveal occult lumbosacral compressive lesions not apparent in neutral imaging. This technique enhances the diagnostic accuracy for DLSS and may guide more effective treatment planning. The findings support broader clinical use of positional MRI in veterinary neurology, particularly for dogs with ambiguous or non-localizing imaging in neutral spine position.

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