The evaluation of the level of consciousness in patients with disorders of consciousness (DOC) is primarily based on behavioural assessments. Patients with unresponsive wakefulness syndrome (UWS) do not show any sign of awareness of their environment, while minimally conscious state (MCS) patients show reproducible but fluctuating signs of awareness. Some patients, although with remaining cognitive abilities, are not able to exhibit overt voluntary responses at the bedside and may be misdiagnosed as UWS. Several studies investigated functional neuroimaging and neurophysiology as an additional tool to evaluate the level of consciousness and to detect covert command following in DOC. Most of these studies are based on auditory stimulation, neglecting patients suffering from decreased or absent hearing abilities. In the present study, we aim to assess the response to a P3-based paradigm in 40 patients with DOC and 12 healthy participants using auditory (AEP) and vibrotactile (VTP) stimulation. To this end, an EEG-based brain-computer interface was used at DOC patient’s bedside. We compared the significance of the P3 performance (i.e., the interpretation of significance of the evoked P3 response) as obtained by ‘direct processing’ (i.e., theoretical-based significance threshold) and ‘offline processing’ (i.e., permutation-based single subject level threshold). We evaluated whether the P3 performances were dependent on clinical variables such as diagnosis (UWS and MCS), aetiology and time since injury. Last we tested the dependency of AEP and VTP performances at the single subject level. Direct processing tends to overestimate P3 performance. We did not find any difference in the presence of a P3 performance according to the level of consciousness (UWS vs. MCS) or the aetiology (traumatic vs. non-traumatic brain injury). The performance achieved at the AEP paradigm was independent from what was achieved at the VTP paradigm, indicating that some patients performed better on the AEP task while others performed better on the VTP task. Our results support the importance of using multimodal approaches in the assessment of DOC patients in order to optimise the evaluation of patient’s abilities.

中文翻译：

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听觉和体感 P3 可作为意识障碍患者评估的补充

意识障碍（DOC）患者意识水平的评估主要基于行为评估。无反应觉醒综合征（UWS）患者没有表现出任何对周围环境有意识的迹象，而最低意识状态（MCS）患者则表现出可重复但波动的意识迹象。有些患者虽然尚有认知能力，但无法在床边表现出明显的自愿反应，可能会被误诊为 UWS。几项研究调查了功能性神经影像学和神经生理学作为评估意识水平和检测 DOC 中秘密命令跟踪的附加工具。大多数这些研究都是基于听觉刺激，忽略了听力下降或丧失的患者。在本研究中，我们的目标是使用听觉 (AEP) 和振动触觉 (VTP) 刺激来评估 40 名 DOC 患者和 12 名健康参与者对基于 P3 范例的反应。为此，DOC 患者的床边使用了基于脑电图的脑机接口。我们比较了通过“直接处理”（即基于理论的显着性阈值）和“离线处理”（即基于排列的单个受试者）获得的 P3 表现的显着性（即诱发 P3 反应显着性的解释）电平阈值）。我们评估了 P3 表现是否依赖于诊断（UWS 和 MCS）、病因学和受伤后时间等临床变量。最后我们在单个主题级别测试了 AEP 和 VTP 性能的依赖性。直接处理往往会高估 P3 性能。根据意识水平（UWS 与 MCS）或病因（创伤性与非创伤性脑损伤），我们没有发现 P3 表现存在任何差异。在 AEP 范式中实现的表现与在 VTP 范式中实现的表现无关，这表明一些患者在 AEP 任务中表现更好，而另一些患者在 VTP 任务中表现更好。我们的结果支持在 DOC 患者评估中使用多模式方法的重要性，以优化患者能力的评估。