Relationship of Cervical Spinal Cord Diameter to Vertebral Dimensions: A Radiographic Study of Normal Dogs

Abstract

Cervical spinal cord abnormalities are often unapparent on myelographic studies, because no normal values for cervical spinal cord diameter are currently available. The purpose of this study was to establish, myelographically, the normal sagittal diameter of the cervical spinal cord in large and small breed dogs and its relationship to the sagittal diameter of the vertebral canal and sagittal height/length of the corresponding vertebral bodies. Forty-one adult dogs underwent cervical radiography and myelography. Spinal cord and vertebral canal sagittal diameter, vertebral body height at C2 to 5, body length at C3 to 5, and dorsal spine length of C2 were measured on lateral views. Ratios of spinal cord:vertebral canal diameter, spinal cord:body height, and spinal cord:body length/spine were calculated, and a normal range was determined for small and large breed dogs. The spinal cord:vertebral canal ratios showed that small breeds have a higher cervical cord-to-canal ratio than large breeds. The mean values and ranges of 14 ratios are reported. The ratios of spinal cord:body length at C2 to 4 in small breeds and spinal cord:body height at C3 to 5 in large breeds were found to be the most accurate for assessing spinal cord sagittal diameter. These normal ranges would allow quantitative and objective evaluation of the cervical spinal cord by myelography and early identification of dogs with altered spinal cord diameter, which could be further evaluated by means of alternative imaging techniques.

Computed tomographic evaluation of cervical vertebral canal and spinal cord morphometry in normal dogs

“…In human medicine, the normal range of cross-sectional diameter and spinal cord area has been established, and correlation between alterations of the spinal cord area and clinical signs has been assessed with CT myelography in the cervical vertebra [20,22]. In dogs, the normal range of the cervical spinal cord to vertebral canal area ratio was proposed using radiographic myelography in small and large animals [6]. The vertebral canal and body ratio as well as morphologic features of the cervical vertebra have been investigated in studies of Doberman pinschers focused on cervical spondylomeylopathy [1,3].…”

“…Variations of the vertebral and spinal cord structures according to body size have been reported in the literature [6,12,17]. In small dogs, the subarachnoid space is relatively narrow and conforms closely to bones forming the vertebral canal in the thoracolumbar region.…”

“…However, accurate delineation of the spinal cord, subarachnoid space, and spinal canal in the cervical region is important for suspected cases of cervical intervertebral disk disease, spinal tumors, or syringohydromyelia because characteristic changes of the diameter or area ratio between spinal cord and vertebral canal can provide useful information for differentiating these cervical diseases. The ratio of the diameter of spinal cord to that of vertebral canal in the cervical vertebra has been previously evaluated using radiographic myelography [6]. In the present study, we measured the normal range of spinal cord dimensions including height, width, and area, and the ratio of spinal cord to vertebral canal area in canines using CT myelography.…”

“…Previous studies have evaluated the ratios of the diameter or area between spinal cord and vertebral canal in specific vertebral regions in dogs according to body size [5-6,9,12]. Data from these studies supported the conclusion that evaluation of the spinal cord, subarachnoid space, epidural space, and vertebral canal should performed based on the variety of breed-specific characteristics because there are significant differences in the component proportion ratio of subarachnoid space, spinal cord, and vertebral canal.…”

Morphologic and morphometric magnetic resonance imaging features of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy

“…Morphometric investigations increase our understanding of spinal diseases by comparing anatomic measurements obtained from clinically normal and affected populations. Postmortem and radiographic morphometric investigations [18][19][20][21][22] of the canine cervical vertebral column have been recently conducted. A few quantitative studies 23-25,b of the lumbosacral, cervical, and thoracic portions of the vertebral column of dogs have been performed by use of CT images, but to our knowledge, no morphometric or morphologic investigation of the canine vertebral column has been conducted via MR imaging.…”