Evaluation of L7-S1 nerve root pathology with Magnetic Resonance Imaging in dogs with degenerative lumbosacral stenosis assessment of the diagnostic value of the water excitation technique (WET)

Master’s Dissertation in Veterinary Medicine

Degenerative lumbosacral stenosis (DLSS) is a multifactorial degenerative disorder characterized by an acquired narrowing of the vertebral canal, intervertebral foramina, or both due to degenerative changes of the lumbosacral area. Stenosis of the L7-S1 intervertebral foramen and compression of the sciatic nerve are relevant components of lumbosacral disease that causes lower back pain and neurologic deficits. Magnetic resonance imaging is a sensitive and non-invasive diagnostic tool for lesion localization and characterization in DLSS, providing great diagnostic value in determining presence of foraminal stenosis and compressive radiculopathy. A correct and efficient diagnosis of nerve injury is extremely important as the earlier the diagnosis is made, the earlier a treatment plan can be applied and the higher are the chances of functional recovery. The water excitation technique (WET) is a fat suppression imaging sequence that increases conspicuity between normal and pathological tissue by eliminating the hyperintense signal of fat that usually encircles nervous structures. In the particular case of evaluating the lumbosacral region, this sequence is used on the dorsal plane with the aim of improving visualization of the spinal nerve roots. Including these types of sequences in the imaging studies can help to identify lesions that would otherwise not be clearly visible in conventional sagittal and transverse T1, T2-weighted imaging. A retrospective study analysis of 31 dogs was conducted to explore the hypothesis that WET would increase the diagnostic accuracy of sciatic nerve root pathology due to lumbosacral foraminal stenosis. Therefore, an agreement study was performed between the diagnosis obtained from T1 and T2-weighted imaging and the diagnosis obtained from the water excitation method. The study supported the hypothesis that WET increases the diagnostic accuracy of sciatic nerve root pathology and helps to decide for a conservative or surgical treatment route by adding valuable information to the conventional T1, T2-weighted imaging.