The Spinal Cord

Abstract

The spinal canal has until recently been a ‘blind spot’ in computed tomography. Initial attempts at visualisation of the spine and spinal cord with the body scanner (Isherwood et al., 1977; Stephens et al.,1976) showed that, whilst vertebral bodies could be clearly demonstrated, structures within the spinal canal could only be poorly and inconsistently visualised, especially in the dorsal and lumbar regions. Four factors are responsible for this. First, movement artefacts often obscure the detail within the spinal canal, especially in the thoracic spine adjacent to the heart. Minimisation of all types of patient movement is therefore important but difficult with the longer scanning times of the early body scanners. Secondly, the width of the cerebrospinal fluid space around the spinal cord is critical for its visualisation. The spinal cord is only seen as a distinct structure by virtue of the low-attenuation cerebrospinal fluid surrounding it. With normal-resolution scanners, the cord will not be identified if the cerebrospinal space is less than about 2 mm.