Objective: To analyze and compare the characteristics and causes of F wave changes in patients with Charcot-Marie-Tooth1A (CMT1A) and chronic inflammatory demyelinating polyneuropathy (CIDP).
Methods: Thirty patients with CMT1A and 30 patients with CIDP were enrolled in Peking University Third Hospital from January 2012 to December 2018. Their clinical data, electrophysiological data(nerve conduction velocity, F wave and H reflex) and neurological function scores were recorded. Some patients underwent magnetic resonance imaging of brachial plexus and lumbar plexus, and the results were analyzed and compared.
Results: The average motor conduction velocity (MCV) of median nerve was (21.10±10.60) m/s in CMT1A and (31.52±12.46) m/s in CIDP. There was a significant difference between the two groups (t=-6.75, P < 0.001). About 43.3% (13/30) of the patients with CMT1A did not elicit F wave in ulnar nerve, which was significantly higher than that of the patients with CIDP (4/30, 13.3%), χ2=6.65, P=0.010. Among the patients who could elicit F wave, the latency of F wave in CMT1A group was (52.40±17.56) ms and that in CIDP group was (42.20±12.73) ms. There was a significant difference between the two groups (t=2.96, P=0.006). The occurrence rate of F wave in CMT1A group was 34.6%±39%, and that in CIDP group was 70.7%±15.2%. There was a significant difference between the two groups (t=-5.13, P < 0.001). The MCV of median nerve in a patient with anti neurofascin 155 (NF155) was 23.22 m/s, the latency of F wave was 62.9-70.7 ms, and the occurrence rate was 85%-95%. The proportion of brachial plexus and lumbar plexus thickening in CMT1A was 83.3% (5/6) and 85.7% (6/7), respectively. The proportion of brachial plexus and lumbar plexus thickening in the CIDP patients was only 25.0% (1/4, 2/8). The nerve roots of brachial plexus and lumbar plexus were significantly thickened in a patient with anti NF155 antibody.
Conclusion: The prolonged latency of F wave in patients with CMT1A reflects the homogenous changes in both proximal and distal peripheral nerves, which can be used as a method to differentiate the CIDP patients characterized by focal demyelinating pathology. Moreover, attention should be paid to differentiate it from the peripheral neuropathy caused by anti NF155 CIDP. Although F wave is often used as an indicator of proximal nerve injury, motor neuron excitability, anterior horn cells, and motor nerve myelin sheath lesions can affect its latency and occurrence rate. F wave abnormalities need to be comprehensively analyzed in combination with the etiology, other electrophysiological results, and MRI imaging.
目的: 分析比较腓骨肌萎缩症1A型(Charcot-Marie-Tooth1A，CMT1A)患者和慢性炎性脱髓鞘性多发性神经病(chronic inflammatory demyelinating polyneuropathy, CIDP)患者F波改变的特点和原因。
方法: 收集自2012年1月到2018年12月在北京大学第三医院诊治的CMT1A和CIDP患者各30例，记录临床资料、电生理指标(神经传导速度和F波、H反射)、神经功能等级评分等，部分患者行臂丛和腰丛的磁共振影像检查，分析比较结果。
结果: CMT1A患者的正中神经平均运动传导速度为(21.10±10.60) m/s, CIDP患者为(31.52±12.46)m/s, 二者差异有统计学意义(t=-6.75, P < 0.001)，CMT1A患者中约43.3%(13/30)未引出尺神经F波，明显高于CIDP未引出F波的患者比例(4/30，13.3%)，χ2=6.65，P=0.010。在可引出F波的患者中，CMT1A组患者的F波潜伏期为(52.40±17.56) ms，CIDP组为(42.20± 12.73) ms, 二者差异有统计学意义(t=2.96, P=0.006)，F波的出现率CMT1A组是34.6%±39%，CIDP组是70.7%±15.2%，二者差异有统计学意义(t=－5.13, P < 0.001)。神经束蛋白155(neurofascin 155, NF155)患者的正中神经传导速度为23.22 m/s, F波潜伏期为62.9~70.7 ms，出现率为85%~95%。CMT1A型臂丛和腰丛神经增粗的比例分别为83.3%(5/6)和85.7%(6/7)，CIDP患者臂丛和腰丛神经增粗的比例仅为25.0%(1/4，2/8)。NF155抗体阳性患者可见臂丛和腰丛MRI神经根明显增粗。
结论: CMT1A患者F波延长反应了近端和远端周围神经的均一性改变，可以作为与局灶性脱髓鞘受损为主的CIDP患者的鉴别方法，但同时需要注意与神经结蛋白病NF155引起的周围神经损害相鉴别。F波虽然经常作为反应近端神经受累的指标，但是运动神经元兴奋性、前角细胞和运动神经髓鞘病变均可以影响它的潜伏期和出现率，F波异常需要结合患者的病因和其他电生理指标及影像学等检查手段综合分析。
Keywords: Charcot-Marie-Tooth; Chronic inflammatory demyelinating polyneuropathy; Electromyography.