前臂肌群急性高压电击伤的MRI研究

MRI study of acute high voltage electric injury in forearm muscle

目的 分析前臂肌群急性高压电击伤的MRI表现 ,并探讨其临床意义。方法 9例 17只急性高压电击伤的前臂均于 72h内行术前MRI检查 ,并作病理对照。 7例 14只前臂并行增强扫描。结果 9例 17只前臂均于MRI检查后立即行筋膜切开扩创术。单纯扩创者 6例 11只前臂 ,MRI表现主要为前群肌肉的损伤 ,范围较小 ,呈等T1、长T2 信号 ;后群肌肉损伤较分散 ,无一定规律 ,损伤程度较轻 ,病灶近端增强后和T2 WI均示边界锐利 ,呈刀尖样改变 ;其中 4例 8只做了增强扫描 ,见显著异常强化 (Ⅰ型信号 ) ,术中电灼刺激相应肌肉有收缩 ,但较正常减弱 ,病理见不同程度坏死 ;在增强4例 8只前臂中 ,有 1个移行区者 6只 ,有 2个移行区者 2只 ,各移行区边界均较清楚。扩创后截肢者3例 6只前臂 ,MRI表现为弥漫性前后群肌的损伤 ,呈混合信号 ,前臂近端以Ⅰ型信号为主 ,远端大片呈等T1、长T2 或短T2 信号 ,且无明显异常强化 (Ⅱ、Ⅲ型信号 ) ,术中电灼刺激相应肌肉 ,未见明确收缩 ,病理提示几乎完全坏死。所有截肢前臂均有 2个移行区 ,边界不清 ,第 2移行区均呈花边状强化。结论 前臂肌群急性高压电击伤MRI表现为 3种信号模式 ,与病理有明确对应关系 。

Objective To investigate the features of MR imaging of acute high voltage electric injury in forearm muscle. Methods Nine patients (17 forearms, 8 males and 1 female, 15～36 years of age) with clinically and pathological proved acute high voltage electric injury were studied on MRI retrospectively. MRI studies were obtained within 72 hours on Siemens 1 0 T MR scanner. 2 forearms were examined with body coil, and 15 with head coil. The severe area was placed as near as possible to the isocenter in the magnet and was used as the center of the MR imaging acquisition. Spin echo T 1 weighted images, spin echo and fast spin echo T 2 weighted images were acquired in all patients. 14 out of 17 were performed with Ⅳ administration of Gd DTPA. Results All 17 forearms had fascistomy after MRI. 11 had only debridement. The lesions were mainly observed in the flexor digitorum supericialis or profunduds muscle appearing as isointense on T 1 weighted images, hyperintense on T 2 weighted images, and strongly enhanced after Ⅳ administration of Gd DTPA in 8. The proximal aspect of the lesion appeared as sharp knife in 11. There was a weaker twitch response to electrocauterization in the injury muscle than in healthy muscle. It was variably necrotic in histopathology. Two transitional zones accompanied with the suffered forearm in 2, and one transitional zone in 6. Both of them had well defined margin. 6 forearms had amputation after debriding. There was Ⅰ,Ⅱ,and Ⅲ mixture signal all over the forearms. The proximal lesions showed type Ⅰ changes. Distal to the zone of forearm showed type Ⅱ and Ⅲ pattern appearing as isointense on T 1 weighted images, hyperintense and hypointense on T 2 weighted images. It was hardly enhanced after Ⅳ administration of Gd DTPA. There was no twitch response to electrocauterization in the injury muscle. It was almost completely necrotic in histopathology. ALL amputated forearms had two transitional zones and ill defined margin. The second transitional zone was enhanced something like flower border. Conclusion MR imaging of acute high voltage electric injury in forearm appeared as three kinds of signal mode, which was closely related with histopathology. MRI was useful in dealing with clinic problem and in judging the prognosis.