急性脑梗死患者初级体感皮质中枢脑磁图特征的研究

目的　研究急性脑梗死患者初级体感皮质中枢脑磁图 (MEG)的变化特征。方法　对 17例急性脑梗死患者于发病后 3～ 4周进行体感诱发磁场 (SEF)检测 ;同时检测 18名健康志愿者 (作为正常对照 )。电刺激部位为腕部正中神经处 ,电流脉冲宽度 0 3ms,刺激间隔 0 5s。将SEF发生源位置通过影像融合技术标注于超薄磁共振 (MRI)上。SEF波峰由等价电流偶极子 (ECD)评估。结果　所有受检者SEF的最基本波形为M2 0 ,其ECD位于两侧初级体感皮质“手区”附近。患者组多个SEF参数均存在异常 ,即 :(1)健康对照组两侧M2 0ECD空间位置差值为 (8± 4 )mm ;患者组为 (11± 3)mm ,患者组不对称性增大 (P <0 0 1) ;(2 )健康对照组M2 0潜伏期为 (2 0 7± 1 1)ms;患者组健侧半球潜伏期为 (2 1 8± 1 2 )ms,患侧半球潜伏期为 (2 3 6± 1 9)ms ,与正常相比均明显延迟 (P <0 0 1) ;(3)患者组患侧ECD强度为 (17± 10 )nAm ,健侧ECD强度为 (2 6± 10 )nAm ,患侧ECD强度减小 (P <0 0 1)。结论　MEG可灵敏地检测出急性脑梗死患者体感皮质中枢功能损伤 ,并能够客观地评价该病体感皮层中枢的功能状态。

The clinical study of somatosensory evoked magnetic fields in patients with acute cerebral infarction by magnetoencephalography

OBJECTIVE: To investigate the characteristics of somatosensory evoked magnetic fields (SEF) in patients with acute cerebral infarction by magnetoencephalgraphy (MEG). METHODS: SEFs were recorded from 17 patients with acute cerebral infarction and 18 healthy volunteers using 306-channel whole-head MEG. The electric stimuli were presented with interstimulus intervals of 0.5 s. The peaks of SEF were estimated by equivalent current dipole (ECD), which were superimposed on MRI. RESULTS: M20 was the most elemental components of SEF in all subjects, originating from the area close to the "hand area" of the primary somatosensory cortex. There appeared several abnormal SEF parameters in the patient group: (1) the value of interhemispheric difference of the M20 positions was (8 +/- 4) mm in the normal group and (11 +/- 3) mm in the patient group (P < 0.01); (2) the peak latency of M20 responses in the healthy group was (20.7 +/- 1.1) ms, significantly shorter than those in both the unaffected hemisphere and affected hemisphere in the patient group, (21.8 +/- 1.2) ms and (23.6 +/- 1.9) ms, (both P < 0.01); (3) the strength of ECD in the affected hemisphere was (17 +/- 10) nAm, significantly smaller than that in the unaffected hemisphere, (26 +/- 10) nAm (P < 0.01). CONCLUSION: Latent cortical impairment may be evaluated by MEG with higher spatial and temporal resolution. MEG provides objective and sensitive indexes to evaluate the function of somatosensory cortex in patients with acute cerebral infarction.