Instrumental methods in the diagnostics of locked-in syndrome

The locked-in syndrome (LiS) is typically characterized by a paralysis of almost all body muscles combined with intact cognitive functions. In practice, there are often additional brain damages besides the one directly causing LiS. These damages can lead to cognitive impairment, which substantially complicates the diagnosis of LiS. At the level of behavior, therefore, the disease can be confused with akinetic mutism, vegetative state (syn. unresponsive wakefulness state) and some other conditions. Using instrumental methods in addition to behavioral diagnostics helps to avoid diagnostic errors and to improve prognosis of rehabilitation of such patients. These methods, which include measurements of brain electric or magnetic fields, electrical potential of muscles, blood flow and oxygen consumption in the brain, are reviewed in this paper.