Cervical epidural block could cause spinal cord injury if the epidural needle is over-inserted and punctures the spinal cord. Investigators retrospectively evaluated the imaging data of 100 patients (50 men and 50 women) who underwent both cervical computed tomography (CT) and cervical magnetic resonance imaging (MRI) at our hospital. Investigators measured the diameters of the spinal canal and spinal cord from the 3rd cervical vertebra to the 1st thoracic vertebra (T1) at each level by using the patients' cervical CT and MR images. The spinal cord and spinal canal diameters were measured in the transverse plane of cervical MR and CT images, respectively.

The spinal canal diameter, i.e., the epidural transverse diameter, was measured as the distance between the innermost border of the left and right pedicles at each upper pedicular level from C3 to T1 on transverse CT images by using a picture archiving and communication system (PACS; INFINITT PACS G3, INFINITT Healthcare, Korea) The spinal cord diameter was measured between the left and right outermost distances of the cord at each upper pedicular level, which were almost the same locations used for measuring the spinal canal diameter, from C3 to T1 on transverse MR images by using the PACS.

Inclusion Criteria:

• 100 patients (50 men and 50 women aged 20 to 70 years old) who visited our hospital and underwent both cervical CT and MRI simultaneously

Exclusion Criteria:

• patients who had a history of cervical spine surgery or cervical cord edema, whose CT or MR images did not include all the cervical vertebrae from C3 to T1,
• patients who had at least one missing medical detail such as diagnosis, age, height, or weight.

patients who visited Daegu catholic university hospital