Auditory ERPs in unresponsive patients
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1
Hospices Civils de Lyon, Neurological Hospital, France
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2
INSERM U821 (Brain Dynamics and Cognition), France
Passive auditory stimulation paradigms make it possible to assess brain function in severely disabled unresponsive patients. It is widely accepted now that the presence of an MMN response to duration deviant tones may be of good prognostic value for coma outcome in comatose patients recorded a few days after coma onset. In a recent study, we showed that a novelty P3 (nP3) could be obtained in response to the subject’s own name (SON) in 21/50 comatose patients (Glasgow Coma Scale <8) patients). In 12 patients a parietal component (P3b ?) was clearly present in the late part of P3. Eleven patients had a novelty P3 but no MMN. We also applied this auditory stimulation paradigm in 27 patients in a permanent vegetative or minimally conscious state (i.e. in patients opening their eyes, but still unresponsive several months after coma onset). In most patients the unresponsive state followed a coma due to brain anoxia (cardiac arrest) or traumatic brain injury. MMN was present in only 5/27 and the nP3 component to the SON in 7/27 patients. Their presence or absence was significantly less present in anoxia than in traumatic brain injury and not related to the time from the coma onset. While MMN highlights automatic sensory memory comparison, nP3 discloses attention orienting and higher level processes. In comatose patients, we found that, compared to MMN, the nP3 improves the sensitivity of awakening prognosis. Among permanent vegetative states, clinical evaluation tries to distinguish between vegetative and minimally conscious patients, the latter showing some reproducible, albeit inconstant, evidence of awareness of themselves and/or environment. Surprisingly, nP3s were obtained in response to the patient’s own name in either behavioral category, with no significant difference. In both studies a few patients, either comatose or in a vegetative state, showed a parietal component following the nP3, raising the question of the some highly cognitive function at work. In other words we infer that such patients could be able to put certain awareness marker processes to work. Both studies show that unconsciously perceived stimuli were processed and activated brain areas similarly to consciously perceived auditory stimuli.
Conference:
MMN 09
Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009.
Presentation Type:
Oral Presentation
Topic:
Review Talk
Citation:
Fischer
C and
Morlet
D
(2009). Auditory ERPs in unresponsive patients.
Conference Abstract:
MMN 09
Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications.
doi: 10.3389/conf.neuro.09.2009.05.027
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Received:
20 Mar 2009;
Published Online:
20 Mar 2009.
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Correspondence:
Catherine Fischer, Hospices Civils de Lyon, Neurological Hospital, Lyon, France, catherine.fischer@chu-lyon.fr