Fornander Lotta, Brismar Tom, Hansson Thomas, Wikström Heidi
a Department of Clinical Neuroscience , Karolinska Institutet , Stockholm , Sweden.
b Department of Orthopaedics , Vrinnevi Hospital , Norrköping , Sweden.
Somatosens Mot Res. 2016 Sep-Dec;33(3-4):178-185. doi: 10.1080/08990220.2016.1230094. Epub 2016 Sep 20.
We have previously shown age- and time-dependent effects on brain activity in the primary somatosensory cortex (SI), in a functional magnetic resonance imaging (fMRI) study of patients with median nerve injury. Whereas fMRI measures the hemodynamic changes in response to increased neural activity, magnetoencephalography (MEG) offers a more concise way of examining the evoked response, with superior temporal resolution. We therefore wanted to combine these imaging techniques to gain additional knowledge of the plasticity processes in response to median nerve injury. Nine patients with median nerve trauma at the wrist were examined with MEG. The N1 and P1 responses at stimulation of the injured median nerve at the wrist were lower in amplitude compared to the healthy side (p < .04). Ulnar nerve stimulation of the injured hand resulted in larger N1 amplitude (p < .04). The amplitude and latency of the response did not correlate with the sensory discrimination ability. There was no correlation between N1 amplitude and size of cortical activation in fMRI. There was no significant difference in N1 latency between the injured and healthy median nerve. N1 latency correlated positively with age in both the median and ulnar nerve, and in both the injured and the healthy hand (p < .02 or p < .001). It is concluded that conduction failure in the injured segment of the median nerve decreases the amplitude of the MEG response. Disinhibition of neighboring cortical areas may explain the increased MEG response amplitude to ulnar nerve stimulation. This can be interpreted as a sign of brain plasticity.
在一项针对正中神经损伤患者的功能磁共振成像（fMRI）研究中，我们之前已经表明了年龄和时间对初级体感皮层（SI）脑活动的影响。fMRI测量的是对神经活动增加做出反应的血流动力学变化，而脑磁图（MEG）提供了一种更简洁的方法来检测诱发反应，具有更高的时间分辨率。因此，我们希望结合这些成像技术，以获得关于正中神经损伤后可塑性过程的更多知识。对9名手腕部正中神经创伤患者进行了MEG检查。与健康侧相比，刺激受伤手腕部正中神经时的N1和P1反应幅度较低（p < 0.04）。刺激受伤手部的尺神经会导致更大的N1幅度（p < 0.04）。反应的幅度和潜伏期与感觉辨别能力无关。fMRI中N1幅度与皮层激活大小之间没有相关性。受伤和健康正中神经的N1潜伏期没有显著差异。N1潜伏期在正中神经和尺神经中，以及受伤和健康手部中均与年龄呈正相关（p < 0.02或p < 0.001）。结论是正中神经损伤段的传导失败会降低MEG反应的幅度。邻近皮层区域的去抑制可能解释了对尺神经刺激的MEG反应幅度增加。这可以被解释为脑可塑性的一个标志。
