Introduction

It is appropriate to say that the imaging modality of choice for the majority of spinal conditions is magnetic resonance (MR). However there will be many reasons why CT might still be used, not least for those patients who cannot tolerate the narrow ‘tunnel’ of most current designs of MR scanners, those who are just too large to fit into the MR scanner, or those who have implanted metal which means that MR scanning is contraindicated.

CT is essential when the requirement is for bone imaging of fractures in spinal trauma and for visualisation of foraminal stenosis, particularly in the cervical region.

There are situations where MR has failed to produce a definitive diagnosis or the MR findings do not correlate with the clinical observations and examination. This problem is particularly common in the cervical region and is resolved by the combination of cervical myelography plus CT and 3D reformatting to assess cervical root exit foramina.

In the writer's neurosurgical unit it is becoming the practice in spinal surgery to use some type of preoperative spinal marking under CT control to indicate accurately the correct level of interest and to thus minimise the surgery involved.

The lumbar spine

The two commonest reasons for imaging the lumbar spine are:

• Lumbar disc disease, most commonly at L5/S1 and L4/L5;

• Spinal stenosis, i.e. narrowing of either or both the spinal canal and lateral recesses.