DISORDERS OF CONSCIOUSNESS AND FUNCTIONAL LOCKED-IN SYNDROME
In the last decade, patients clinically diagnosed in the vegetative state who are able to perform mental imagery tasks [1-2] have been still considered to be in the vegetative state with preserved islands of consciousness, not as having functional locked-in syndrome [3-7]. Indeed, patients with residual cognitive functions, who are able to perform complex mental imagery tasks or show intentional communication ability by means of functional neuroimaging techniques, should be diagnosed with functional locked-in syndrome [3] and not vegetative state with hidden consciousness [6;8].
In this paper, Chennu et al., by applying graph theory with high-density electroencephalographic investigation of a series of patients with disorders of consciousness (DoC), found that the metric of alpha network efficiency also correlated with the degree of behavioral awareness. In particular, some patients in behaviourally unresponsive vegetative states, who demonstrated evidence of covert awareness with functional neuroimaging, had alpha networks that were preserved and similar to those of the controls. These findings parallel the alpha rhythm commonly found in patients with locked-in syndrome and supports the hypothesis that behaviourally unresponsive patients who follow commands based on functional neuroimaging or neurophysiological tests are not, in fact, in a vegetative/unresponsive wakefulness syndrome, but instead in a total locked-in or functional locked-in syndrome [7].
In conclusion, the recovery of functional communication, either behaviourally or by means of advanced diagnostic techniques (neurophysiological and/or neuroimaging) should coincide with the diagnosis of the emergence from DoC.
REFERENCES
1.Owen, A. M., Coleman, M. R., Boly, M., et al.. (2006). Detecting awareness in the vegetative state. Science, 313(5792), 1402-1402.
2.Monti MM, Laureys S, Owen AM. The vegetative state. BMJ. 2010;341:3765.
3.Bruno, M. A., Vanhaudenhuyse, A., Thibaut, A., et al. (2011). From unresponsive wakefulness to minimally conscious PLUS and functional locked-in syndromes: recent advances in our understanding of disorders of consciousness. Journal of neurology, 258(7), 1373-1384.
4.Formisano, R., Pistoia, F., & Sarà, M. (2011a). Disorders of consciousness: A taxonomy to be changed? Brain injury, 25(6), 638-639.
5.Formisano, R., D'Ippolito, M., Risetti, M., et al. (2011b). Vegetative state, minimally conscious state, akinetic mutism and Parkinsonism as a continuum of recovery from disorders of consciousness: an exploratory and preliminary study. Functional neurology, 26(1), 15.
6.Formisano, R., D’Ippolito, M., & Catani, S. (2013). Functional locked-in syndrome as recovery phase of vegetative state. Brain injury, 27(11), 1332-1332.
7.Formisano and Zasler, comment in PLOS Computational Biology, 2015.
8.Laureys, S., Celesia, G. G., Cohadon, F., et al. (2010). Unresponsive wakefulness syndrome: a new name for the vegetative state or apallic syndrome. BMC medicine, 8(1), 68.