Calabrò Rocco Salvatore, Pignolo Loris, Müller-Eising Claudia, Naro Antonino
IRCCS Centro Neurolesi Bonino Pulejo, 98123 Messina, Italy.
Istituto Sant'Anna, 88900 Crotone, Italy.
Brain Sci. 2021 May 20;11(5):665. doi: 10.3390/brainsci11050665.
Pain perception in individuals with prolonged disorders of consciousness (PDOC) is still a matter of debate. Advanced neuroimaging studies suggest some cortical activations even in patients with unresponsive wakefulness syndrome (UWS) compared to those with a minimally conscious state (MCS). Therefore, pain perception has to be considered even in individuals with UWS. However, advanced neuroimaging assessment can be challenging to conduct, and its findings are sometimes difficult to be interpreted. Conversely, multichannel electroencephalography (EEG) and laser-evoked potentials (LEPs) can be carried out quickly and are more adaptable to the clinical needs. In this scoping review, we dealt with the neurophysiological basis underpinning pain in PDOC, pointing out how pain perception assessment in these individuals might help in reducing the misdiagnosis rate. The available literature data suggest that patients with UWS show a more severe functional connectivity breakdown among the pain-related brain areas compared to individuals in MCS, pointing out that pain perception increases with the level of consciousness. However, there are noteworthy exceptions, because some UWS patients show pain-related cortical activations that partially overlap those observed in MCS individuals. This suggests that some patients with UWS may have residual brain functional connectivity supporting the somatosensory, affective, and cognitive aspects of pain processing (i.e., a conscious experience of the unpleasantness of pain), rather than only being able to show autonomic responses to potentially harmful stimuli. Therefore, the significance of the neurophysiological approach to pain perception in PDOC seems to be clear, and despite some methodological caveats (including intensity of stimulation, multimodal paradigms, and active vs. passive stimulation protocols), remain to be solved. To summarize, an accurate clinical and neurophysiological assessment should always be performed for a better understanding of pain perception neurophysiological underpinnings, a more precise differential diagnosis at the level of individual cases as well as group comparisons, and patient-tailored management.
意识长期障碍（PDOC）患者的疼痛感知仍是一个有争议的问题。先进的神经影像学研究表明，即使是无反应觉醒综合征（UWS）患者，与最低意识状态（MCS）患者相比，也存在一些皮层激活。因此，即使是UWS患者也必须考虑疼痛感知。然而，先进的神经影像学评估实施起来可能具有挑战性，其结果有时也难以解释。相反，多通道脑电图（EEG）和激光诱发电位（LEP）可以快速进行，并且更适应临床需求。在本综述中，我们探讨了PDOC中疼痛的神经生理学基础，指出对这些个体的疼痛感知评估如何有助于降低误诊率。现有文献数据表明，与MCS个体相比，UWS患者在疼痛相关脑区之间的功能连接中断更为严重，这表明疼痛感知随着意识水平的提高而增加。然而，也有值得注意的例外情况，因为一些UWS患者表现出与疼痛相关的皮层激活，部分与MCS个体中观察到的激活重叠。这表明一些UWS患者可能具有残余的脑功能连接，支持疼痛处理的躯体感觉、情感和认知方面（即对疼痛不愉快的有意识体验），而不仅仅是能够对潜在有害刺激表现出自主反应。因此，神经生理学方法对PDOC中疼痛感知的意义似乎很明确，尽管一些方法学上的警告（包括刺激强度、多模态范式以及主动与被动刺激方案）仍有待解决。总之，为了更好地理解疼痛感知的神经生理学基础、在个体病例水平以及组间比较中进行更精确的鉴别诊断以及进行针对患者的管理，应始终进行准确的临床和神经生理学评估。
