Event-related potentials in patients with total locked-in state due to fulminant Guillain-Barre syndrome

A series of electrophysiological investigations were performed over a 6-mon th period in two patients affected by fulminant Guillain-Barre polyradiculo neuropathy, who developed an ascending paralysis leading, within 72 h, to f laccid quadriplegia, internal and external ophthalmoplegia, absence of all brainstem reflexes and no respiratory effort: the clinical state resembled brain death. Brain CTs were normal and spinal fluid examination revealed al buminocytological dissociation. All motor nerves tested were unexcitable, w hereas sensory responses were markedly abnormal but present. Sequential EEG recordings revealed normal, partially reactive alpha rhythm in both patien ts. In one patient, normal auditory event-related potentials (ERPs: peak N1 , P2, N2, P3, evoked in an 'odd-ball' paradigm) and CNV-like potentials cou ld be recorded not earlier than the 20th day into the illness. In earlier r ecordings, N1 and P2 peaks as well as mismatch negativity (MMN) were presen t over the frontal and central scalp electrodes. This patient has now parti ally recovered motor functions and no cognitive defects are present, but he has little recollection of the events occurring in the first 2 weeks spent in the ICU, when he was completely paralyzed. The other patient generated normal N1 and P2 ERP peaks, but no N2, P3 and MMN were detected in a series of recordings. He died without having ever regained appropriate behavioral responses. The ERP abnormalities observed raise the matter of the origin o f cognitive dysfunction in patients with severe and prolonged de-efferentat ion/de-afferentation. ERPs allow monitoring the level of alertness and atte ntion and appear more specific than EEG in identifying a state of awareness in patients in which communication is severely impaired as a consequence o f neurological disorders. (C) 2000 Elsevier Science B.V. All rights reserve d.