EVENT-RELATED POTENTIALS RECORDED IN PATIENTS WITH LOCKED-IN SYNDROME

Objective-To determine the possibility of recording ''cognitive'' even t related potentials (ERPs) in locked-in patients and therefore to det ermine whether ERPs can have a role in differential diagnosis of coma. Methods-ERPs to classic auditory or visual ''odd ball paradigms'' wer e recorded three to four days, seven to eight days, and 30 to 60 days after admission to the intensive care unit, in four patients affected by basilar artery thrombembolism resulting in locked-in syndrome. Two patients (one 32 year old man, one 31 year old woman) could move the e yes laterally and vertically spontaneously and on command. One patient (a 39 year old man) had a ''one and half syndrome'', one patient (a 4 0 year old woman) could only elevate the left eyelid and eye. Results were compared with data from 30 age matched controls. In the last reco rding session a letter recognition paradigm was applied, in which ERPs were produced by the identification of letters forming a word. Result s were compared with five age matched controls. Brainstem lesions exte nding to the pontomesencephalic junction were found on MRI and CT. Res ults-ERPs to the oddball paradigms were recorded in three patients in the first recording session, in all patients in the second recording s ession. Latency, amplitude, and topographic distribution of ERP compon ents were inside normal limits. With the letter recognition paradigm t he patients could emit a P3 component to correspond with target letter s, with the same margin of error as controls. Conclusion-It is possibl e to record ERPs in patients with locked-in syndrome shortly after the acute ischaemic lesion, and therefore to assess objectively cognitive activities. Furthermore the letter recognition paradigm could be impl emented to facilitate Linguistic communication with patients with lock ed-in syndrome.