Cervical canal stenosis

Last revised by Dr Bahman Rasuli on 24 Jul 2020

Cervical canal stenosis can be acquired (e.g. trauma, discs, and ossification of the posterior longitudinal ligament) or congenital. It refers to the narrowing of the spinal canal, nerve root canals, or intervertebral foramina of the cervical spine.

Radiographic features

  • normal AP diameter is ~17 mm
  • relative stenosis 10-13 mm
  • absolute stenosis <10 mm

The width of the canal is not, however, constant and progressively decreases as one moves down the cervical spine.

  • C1: 23 mm
  • C2: 20 mm
  • C3-C6: 17 mm
  • C7: 15 mm
Canal-to-body ratio of Torg and Pavlov

The standard method of evaluating cervical canal stenosis was historically the sagittal diameter in millimeters, using various cut-offs 1. In two articles published in 1986 and 1987 1,2 American orthopedic surgeon Joseph Torg (fl. 2018) and American radiologist Helene Pavlov (fl. 2018) et al. introduced the ratio method in order to reduce inter- and intraobserver error caused by variance in magnification and landmarking.

This method uses the ratio of the diameter of the cervical canal to the width of the cervical body, with a ratio of <0.8 on the lateral view taken as an indication of cervical stenosis 1.

This ratio is variously referred to as the Torg ratio 3, the Pavlov ratio 3,4, the Torg-Pavlov ratio 5, or the canal-to-body ratio 3.

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Cases and figures

  • Case 1: congenital canal stenosis
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  • Case 2: due to OPLL
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  • Case 3
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  • Case 4: from C5/6 disc extrusion
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  • Case 5: on CT myelogram
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