13例婴儿型脊髓性肌萎缩症临床及电生理分析

Clinical features and electrophysiology analysis of 13 cases of infantile spinal muscular atrophy

目的探讨婴儿型脊髓性肌萎缩症的临床、电生理特点及基因诊断的临床意义。方法分析13例婴儿型脊髓性肌萎缩症患儿的临床资料。检测患儿血清肌酸磷酸激酶;进行正中神经、尺神经、胫神经和腓神经运动传导检查,分析参数包括远端潜伏期、运动传导速度和复合肌肉动作电位波幅;进行至少4块肢体肌肉的肌电图检查,观察插入电位、自发电位和运动单位电位;采用聚合酶链反应-限制性片段长度多态性分析(PCR-RFLP)检测SMN1基因7号外显子纯合缺失。结果婴儿型脊髓性肌萎缩症的主要临床特征为出生后进行性加重的四肢弛缓性瘫痪。所有患儿的复合肌肉动作电位波幅显著下降,伴有远端潜伏期和运动传导速度轻度改变。肌电图显示神经源性损伤。基因检查显示13例患儿SMN1基因第7号外显子全部纯合缺失。结论婴儿型脊髓性肌萎缩症有较典型的临床及电生理特征,肌电图检查是重要的诊断方法,产前基因检查可避免该类患儿的出生。

Objective To investigate the clinical and electrophysiology features of infantile spinal muscular atrophy, and explore the clinical significance of genetic diagnosis. Methods The clinical data of 13 infants suffering from infantile spinal muscular atrophy were analysed. The serum creatine phosphokinase was examined, and nerve conduction velocity was tested in median nerve, ulnar nerve, tibial nerve and peroneal nerve. The parameters such as distal motor latency, motor nerve conduction velocity and amplitude of compound motor active potential were analysed. Electromyography was performed in no less than four muscles, and the insertion potential, spontaneous potential and motor unit action potential were observed. Deletion of exon 7 in SMN1 gene was detected by polymerase chain reaction-restriction fragment length polymorphism （ PCR-RFLP）. Results All these infants were characterized by progressive flaccid paralysis in limbs. In all cases, amplitude of muscle response was significantly decreased, with prolonged distal latency and slowed conduction velocity. Electromyography demonstrated motoneuron degeneration. Deletion of exon 7 in SMN1 gene was detected in all 13 infants. Conclusion There are unique clinical and electrophysiology features for infantile spinal muscular atrophy, and electromyography may play an important role in the diagnosis. Prenatal genetic diagnosis may help to avoid the birth of this kind of infants.