In pontine lesions with tetraplegia and cranial-nerve disturbances--including trismus--and with speech disability paralytic akinesia and loss of reactivity may be misinterpreted as coma. "Pseudocoma" of this kind may be associated with normal consciousness or relatively mild psychological disorders. This explains the discrepancy between a normal EEG (only minor abnormalities) and presumed unconsciousness. The term "locked-in" expresses the patient's inability to communicate. In typical cases there may be only vertical eye movements and blinking. Using remaining innervation facilities, those examining and treating the patient must try to communicate with him. The locked-in state may be mistaken for coma particularly if there had been a preceding episode of unconsciousness. Moreover, the "locked-in" syndrome often passes into a state of unconsciousness or coma. The degree of communication can markedly differ from hour to hour. Most of the cases of this syndrome are caused by basilar artery thrombosis.