Diagnosis of the phenomenon of cognitive-motor dissociation in patients with chronic consciousness disorders

Locked-in syndrome in basilar artery thrombosis is a classic example of dissociation between preserved consciousness and complete deefferentation as total myoplegia with preserved vertical eye movement. Something similar is observed in post-comatose patients, described under the name “functional locked-in syndrome”, and is also a clinical reflection of the phenomenon of cognitive-motor dissociation (CMD). Diagnosis of this condition in a patient with chronic consciousness disorders indicates that there may be a cognitive imprint, which gives a chance for the maximum realization of the rehabilitation potential of latent consciousness as an exit to the clinical level of small consciousness or creation of a brain-interface. In any case, this patient should be given an extended rehabilitation program.

Objective: to search for the optimal set of clinical and instrumental diagnostic methods, allowing the identification of CMD in patients with chronic consciousness disorder.

Patients and methods. The 2016–2018 prospective single-center study enrolled patients with unresponsive wakefulness syndrome (UWS) who had received a treatment cycle at the Clinical Brain Institute (Yekaterinburg). The study included 39 patients (22 men, 17 women) aged 19 to 71 years who had sustained various cerebral injuries (traumatic, hypoxic, and acute vascular disease-associated) in different periods (from 32 to 2431 days) before being included in the study. All the patients underwent 5-fold clinical assessments according to the Coma Recovery ScaleRevised (CRS-R) and navigated transcranial magnetic stimulation (nTMS) in order to determine the time course of changes in the activity of the cortical motor centers at the time of presentation of verbal paradigms. Registration of the changes was assessed as the presence of a cognitive imprint and served as a criterion for diagnosing CMD as a positive predictor for the outcome of UWS. The outcome of the state was analyzed using the Glasgow Outcome Scale (GOS) at 180 days.

Results and discussion. Positive changes (GOS >3) were noted in 10 (66%) patients with established CMD; the patients who had not diagnosed as having the cognitive potential showed a further increase in the level of cognition in 3 (12.5%) cases. Whether the identified sign could be used in the comprehensive prediction of chronic consciousness disorder was discussed.

Conclusion. The use of TMS in diagnosing the phenomenon of CMD optimizes the routing of patients, for whom intensive rehabilitation can contribute to more favorable long-term outcomes. 

1. Giacino JT, Katz DI, Schiff ND, et al. Practice Guideline Update Recommendations Summary: Disorders of Consciousness – Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology; the American Congress of Rehabilitation Medicine; and the National Institute on Disability, Independent Living, and Rehabilitation Research. Arch Phys Med Rehabil. 2018;99(9): 1699-709. doi: 10.1016/j.apmr.2018.07.001

2. Hirschberg R, Giacino JT. The vegetative and minimally conscious states: diagnosis, prognosis and treatment. Neurol Clin. 2011;29:773-86. doi: 10.1016/j.ncl.2011.07.009

3. Curley WH, Forgacs PB, Voss HU, et al. Characterization of electroencephalopgraphic signals revealing covert cognition in the injured brain. Brain. 2018;141(5):1404-21. doi: 10.1093/brain/awy070

4. Boly M, Laureys S. Functional 'unlocking': bedside detection of covert awareness after severe brain damage. Brain. 2018;141(5): 1236-8. doi: 10.1093/brain/awy080

5. Wannez S, Heine L, Thonnard M, et al. Coma Science Group Collaborators. The repetition of behavioral assessments in diagnosis of disorders of consciousness. Ann Neurol. 2017;81:883-9. doi: 10.1002/ana.24962

6. Gosseries O, Di H, Laureys S, Boly M. Measuring consciousness in severely damaged brains. Ann Rev Neurosci. 2014;37:457-78. doi: 10.1146/annurev-neuro-062012-170339

7. Monti MM, Vanhaudenhuyse A, Coleman MR, et al. Willful modulation of brain activity in disorders of consciousness. N Engl J Med. 2010;362: 579-89. doi: 10.1056/nejmoa0905370

8. Cruse D, Chennu S, Chatelle C, et al. Bedside detection of awareness in the vegetative state: a cohort study. Lancet. 2011;378:2088-94. doi: 10.1016/s0140-6736(11)61224-5

9. Schnakers C, Perrin F, Schabus M, et al. Voluntary brain processing in disorders of consciousness. Neurology. 2008;71:1614-20. doi: 10.1212/01.wnl.0000334754.15330.69

10. Belkin AA, Pozdnyakov DG. VS/MCS differential diagnostic using navigated brain stimulating method. Registration № 2596049 since 21.04.2015. Moscow: Rospatent; 2015. Available from: http://www.findpatent.ru/patent/259/2596049.html (In Russ.).

11. Lescovetz VV, Lescovetz EA, Souslov SA, Feratov DM. Cognitive level diagnosis in patients with chronic disorfers of consciousness by functional MRI and navigated brain stimulation. Intensivnaya Terapiya. 2011;(3):40-6 (In Russ.).

12. Boly M, Coleman MR, Davis MH, et al. When thoughts become action: an fMRI paradigm to study volitional brain activity in noncommunicative brain injured patients. Neuroimage. 2007;36:979-92. doi: 10.1016/j.neuroimage.2007.02.047

13. Iazeva EG, Legostaeva LA, Zimin AA, et al. A Russian validation study of the Coma Recovery Scale-Revised (CRS-R). Brain Injury. 2019;33(2):218-25. doi: 10.1101/276881

14. Belkin A, Lescovets V, Lescovets E, et al. A72 Navigated Brain Stimulation in Diagnosis of Minimally Conscious State. Eur J Anaesthesiol. 2012;29:22-3. doi: 10.1097/01.eja.0000412518.25201.32

15. Wright J. Glasgow Outcome Scale: Extended. In: Kreutzer J, DeLuca J, Caplan B, eds. Encyclopedia of Clinical Neuropsychology. Cham: Springer; 2017. doi: 10.1007/978-3-319-56782-2