Computed tomography and magnetic resonance imaging of the vertebral column and spinal cord in cats

Objective: In human medicine, advanced imaging modalities such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are widely utilized in the diagnosis of numerous diseases, especially when conventional radiography proves insufficient. While reference values and pathological evaluations of the vertebral column and spinal cord are extensively documented in human medicine, the use of these imaging modalities in veterinary medicine, particularly in Turkey, has remained limited since their introduction in the late 1990s. Most veterinary studies and reference texts predominantly focus on dogs, with considerably fewer investigations addressing cat subjects. However, in clinical practice, a significant number of cat cases involving vertebral and spinal cord lesions—often resulting from trauma such as falls or vehicular accidents—are frequently encountered. The present study aimed to delineate the detailed CT and MRI anatomy of the vertebral column and spinal cord in domestic cats. Materials and Methods: The study was conducted on 10 adult mixed-breed cats, aged between 1 and 5 years and weighing an average of 4.22±0.96 kg, which were presented to the clinic for unrelated clinical complaints and exhibited no signs of vertebral or spinal cord pathology. Non-contrast sagittal and transverse CT images were obtained and analyzed to identify anatomical structures, perform dimensional measurements, and compute various morphometric indices. The vertebral column was segmented into cervical, thoracic, and lumbar regions. At each vertebral level, multiple measurements were recorded, including vertebral body length, intervertebral disc height and width, vertebral canal height and width, spinal cord height and width, vertebral body height and width, pedicle width and length, transverse pedicle angle, and foraminal dimensions. Additional indices, such as vertebral body roundness and spinal cord-to-canal roundness indices, were calculated. MRI scans were evaluated for spinal canal and spinal cord dimensions, nucleus pulposus height and width, and the spinal cord-to-canal ratio at each disc level. Results: In our CT study, the highest CVU value in sagittal sections along the columna vertebralis was recorded at the C2 vertebra in the cervical region (20,45 mm), while the lowest value was measured at the T3 level (8,06 mm). The IVAY reached its lowest value at the T3–T4 interval (3,65 mm) and the highest at the L6–L7 interval (6,25 mm) along the entire vertebral column. IVAG values showed a relatively homogeneous distribution throughout the columna vertebralis. In transverse CT images, CVY reached its minimum at the C4 level (3,53 mm) and maximum at the L7 level (5,91 mm). The lowest CVG value was observed at the T2 level (5,71 mm), while the highest was recorded at the L7 level (10,39 mm). The CVY/CVG ratio (roundness index) was highest at C2 (1.12) and lowest at L6 (0.43). A marked decrease in the roundness index was observed at T3–T5 levels, with the lowest value detected at T5. In the lumbar region, the lowest roundness index was also identified at L6 (0.43). At C1 and C2 vertebral levels, a significant difference was observed between the height and width values of both the medulla spinalis and the canalis vertebralis. While these parameters reached their highest values at the C1 level, they were at their lowest throughout the thoracic region. The roundness index of both the medulla spinalis and canalis vertebralis demonstrated a prominent increase at the C2 level. In terms of area ratio, the MS/Cv ratio was generally higher in the cervical region, reaching its peak at the C5–C6 level with a value of 24.82%. This ratio showed the lowest value along the vertebral column at the Th13–L1 transition, with a value of 6.66%. Following the transition to the lumbar region, a renewed increasing trend in the MS/Cv ratio was observed, rising to approximately 15% at the L5–L6 level. At C6–C7, both indices declined to approximately 0.8, indicating a more cylindrical morphology. The close values of these indices in the thoracic region suggest a proportionate, cylindrical structure. In the lumbar region, both indices gradually decreased, indicating a transition to a more rectangular form. Across the entire columna vertebralis, PU reached its lowest value at T10 (4,19 mm) and its highest at L5 (7,33 mm). TPG was lowest at T4 (1,17 mm) and highest at L7 (2,36 mm). The highest TPA value was measured at C6 (42.81°), while the lowest was recorded at L3 (21.54°). Regarding the transverse and sagittal diameters of the foramen transversum, the highest transverse width was measured at C5 (1,12 mm), and the lowest at C4 (0,98 mm). The sagittal diameter ranged from 1,03 mm at C4 to 1,20 mm at C6, which corresponds with the relatively larger passage of the a. vertebralis at this level. In our MRI study, sagittal MR images revealed that SCvY values were consistently higher than SMsY values across all regions. Both parameters were higher in the cervical region compared to the thoracic and lumbar regions. The MS/Cv ratio was significantly elevated between C2 and C6, showed a marked decline in the thoracic region, and increased again toward the lumbar region. SNpY was lowest at the T1–T2 interval (2,35 mm) and highest at the L2–L3 interval (3,67 mm). SNpG showed its minimum value at T1–T2 (1,32 mm) and maximum at L7–S1 (2,31 mm). In transverse MR images, TCvY reached its maximum at the C5–C6 interval (9,75 mm) and its minimum at the L6–L7 interval (6,85 mm). TCvG was highest at the C1–C2 interval (12,78 mm) and lowest at the T6–T7 level (7,63 mm). TMsY and TMsG values were found to be highest in the cervical region. The highest TMsY and TMsG values were recorded at C5–C6 (4,33 mm and 6,68 mm, respectively). Both values were lowest in the thoracic region, with TMsY measured at 1,76 mm (T12–T13) and TMsG at 2,18 mm (T10–T11). TNpY reached its minimum at T7–T8 (3,29 mm) and its maximum at L7–S1 (9,70 mm). TNpG was lowest at C3–C4 (2,25 mm) and highest at L5–L6 (3,41 mm). Conclusion: This thesis yielded significant anatomical insights into the vertebral column and spinal cord of cats through the use of CT and MRI. Some findings represent the first documented measurements in cats, thus offering significant contributions to the existing veterinary anatomical literature. The data provided here in are expected to serve as an essential reference for veterinary clinicians specializing in cat medicine and will guide further investigations in the field.