Comparison of CT myelography performed in the prone and supine positions in the detection of cervical spinal stenosis

AIM: To quantify the change in the cross-sectional area of the cervical spi nal cord and subarachnoid space (SAS) in the supine neutral vs prone extens ion positions in patients with myelopathy undergoing cervical CT myelograph y, MATERIAL AND METHODS: Axial CT myelgrams of 21 myelopathic patients were pe rformed in both the supine neutral and prone extension positions. The SAS a nd cord cross-sectional areas were then measured at the disk spaces and mid -pedicle levels from C2 to T1 in both the supine and prone positions using a public domain NIH Image program, version 156b18, Mean area measurements i n both positions were then compared for each level examined. RESULTS: Mean SAS cross-sectional area in the prone position was notably re duced compared with the supine position at C4-C5 [128.8 mm(2) vs 168.1 mm(2 ) (P <.05)], and C5-C6 [98.8 mm(2) vs 143.2 mm(2) (P<.05)] disk levels. The mean cord cross-sectional area failed to change significantly with positio ning. CONCLUSIONS: Prone myelography may demonstrate a greater degree of cervical spine stenosis compared with CT myelography performed in the supine positi on in myelopathic patients. Imaging with the patient prone with neck extend ed in both myelography and CTM may improve precision in the results of meas urements of the stenotic spinal canal when comparing these two methods. Ble ase Graham III, C. et al. (2001). Clinical Radiology 56, 35-39. (C) 2001 Th e Royal College of Radiologists.