stimuli and mental tasks. It allows researchers and clinicians to study the changes in injured neuronal circuits. However, fMRI relies on the metabolic changes that occur in response to neural activity and the images obtained by fMRI are not a direct measure of neural activity. Therefore, caution should be placed on interpretation of the accuracies of the spatial maps generated by fMRI (Ugurbil et al., 2003). The National Institutes of Health has recommended that fMRI techniques be developed to assess the degree of loss and recovery of sensation in rodents with contusion injuries to their spinal cords (Hofstetter et al., 2003; NINDS, 2004).

Radiologists use CT scans as a standard procedure to clarify areas of clinical concern (Youmans, 1996; AANS/CNS, 2002). Although MRI is better suited for analyzing the soft tissue of the spinal cord, the strength of using CT scans is in investigating the bone structure and detecting fractures of the vertebrae (Figure 3-2). Helical CT scans offer advantages over traditional radiology X-rays due to their speed in accruing the images and increased accuracy (4.5 minutes and 98.5 percent, respectively, for helical CT compared with 25 minutes and 43 percent, respectively, for X-rays). Therefore, in conjunction with MRI, CT scans provide useful tools for emergency clinicians (Nunez et al., 1994).

FIGURE 3-2 MRI (A) and CT (B) of an injured spinal cord. Imaging of a spinal cord contusion injury by MRI and CT helps to reveal different aspects of the injury. The MRI image on the left reveals the soft spinal cord and bone, whereas the CT scan image on the right clearly delineates bone structures.

SOURCE: Reprinted with permission, from AANS, 1999. Copyright 1999 from AANS.