Neuromodulation Center and Center for Clinical Research Learning, Spaulding Rehabilitation Hospital and Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Universidad San Ignacio de Loyola, Vicerrectorado de Investigación, Unidad de Investigación para la Generación y Síntesis de Evidencias en Salud, Lima, Peru.
Neuromodulation Center and Center for Clinical Research Learning, Spaulding Rehabilitation Hospital and Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
Clin Neurophysiol. 2020 Oct;131(10):2375-2382. doi: 10.1016/j.clinph.2020.06.024. Epub 2020 Jul 15.
The role of motor cortex reorganization in the development and maintenance of phantom limb pain (PLP) is still unclear. This study aims to evaluate neurophysiological and structural motor cortex asymmetry in patients with PLP and its relationship with pain intensity.
Cross-sectional analysis of an ongoing randomized-controlled trial. We evaluated the motor cortex asymmetry through two techniques: i) changes in cortical excitability indexed by transcranial magnetic stimulation (motor evoked potential, paired-pulse paradigms and cortical mapping), and ii) voxel-wise grey matter asymmetry analysis by brain magnetic resonance imaging.
We included 62 unilateral traumatic lower limb amputees with a mean PLP of 5.9 (SD = 1.79). We found, in the affected hemisphere, an anterior shift of the hand area center of gravity (23 mm, 95% CI 6 to 38, p = 0.005) and a disorganized and widespread representation. Regarding voxel-wise grey matter asymmetry analysis, data from 21 participants show a loss of grey matter volume in the motor area of the affected hemisphere. This asymmetry seems negatively associated with time since amputation. For TMS data, only the ICF ratio is negatively correlated with PLP intensity (r = -0.25, p = 0.04).
There is an asymmetrical reorganization of the motor cortex in patients with PLP, characterized by a disorganized, widespread, and shifted hand cortical representation and a loss in grey matter volume in the affected hemisphere. This reorganization seems to reduce across time since amputation. However, it is not associated with pain intensity.
These findings are significant to understand the role of the motor cortex reorganization in patients with PLP, showing that the pain intensity may be related with other neurophysiological factors, not just cortical reorganization.
运动皮层重组在幻肢痛（PLP）的发展和维持中的作用尚不清楚。本研究旨在评估 PLP 患者运动皮层的神经生理和结构不对称性及其与疼痛强度的关系。
正在进行的随机对照试验的横断面分析。我们通过两种技术评估运动皮层的不对称性：i）通过经颅磁刺激（运动诱发电位、成对脉冲范式和皮层映射）评估皮层兴奋性变化，ii）通过脑磁共振成像进行灰质不对称性分析。
我们纳入了 62 名单侧创伤性下肢截肢患者，平均 PLP 为 5.9（SD=1.79）。我们发现，在受影响的半球中，手区重心向前移位（23mm，95%置信区间 6 至 38，p=0.005），并且代表区广泛且紊乱。关于灰质不对称性分析，来自 21 名参与者的数据显示，受影响半球运动区的灰质体积减少。这种不对称性似乎与截肢后时间呈负相关。对于 TMS 数据，只有 ICF 比值与 PLP 强度呈负相关（r=-0.25，p=0.04）。
PLP 患者的运动皮层存在不对称重组，表现为手皮层代表区紊乱、广泛且移位，以及受影响半球灰质体积减少。这种重组似乎随着截肢后时间的推移而减少。然而，它与疼痛强度无关。
这些发现对于理解运动皮层重组在 PLP 患者中的作用具有重要意义，表明疼痛强度可能与其他神经生理因素有关，而不仅仅是皮层重组。
