The role of functional MRI in diagnosing chronic disorders of consciousness

Purpose: The accurate diagnosis of chronic disorders of consciousness (DOC), and its differential diagnosis, is essential for clinical, rehabilitative care and decision-making (additionally for research reasons). In clinical routine, neurobehavioral tests, which rely on the patients' intellectual and motor ability to communicate, are the most widely used diagnostic tools, since their advantage over clinical assessment has been validated. However, with the emergence of modern neuroimaging methods, especially functional MRI, objective physiological markers for assessing the state of consciousness are available in specialized clinics. They are, however not fully integrated in clinical routine, because their benefit has yet to be determined. Material and methods: In this study, 15 patients in vegetative state and 5 patients in minimally conscious state, according to the Coma Recovery Scale Revised, were examined with somatosensory, auditory and event related paradigms in fMRI. The findings were compared to the neurobehavioral diagnosis and it was analyzed, if the additional information from fMRI confirmed or questioned the diagnosis. Results: At least 3 of the 15 patients in vegetative state showed fMRI activation in event related paradigms, suggesting the patients being in minimally conscious state (MCS) or even better. Conclusion: Uncertainty in diagnosis still exists even with well established diagnostic assessment scales, as the Coma Recovery Scale Revised. As long as internationally accepted guidelines for assessing patients with chronic DOC do not exist, every single diagnostic modality available in each clinical setting should be performed, to minimize diagnostic error and to find ways, in terms of perceptive channels, to approach the patients. FMRI has the potential to bring diagnostics in chronic DOC forward to the next level.