Respiratory weakness in neuralgic amyotrophy: report of two cases with phrenic nerve involvement

An isolated affection of the phrenic nerve is a rare feature in patients with neuralgic amyotrophy. We report 1 case each of bilateral and unilateral phrenic neuropathy. The first patient presented a sudden onset of severe respiratory failure without pain. The second patient developed intense pain in the neck and in the right shoulder followed by dyspnea on mild effort and orthopnea. Chest X-rays showed elevation of the diaphragm. Needle electromyography revealed denervation restricted to the diaphragm. The phrenic nerve conduction was within the normal range. The diagnosis of neuralgic amyotrophy may be particularly difficult when the palsy of the phrenic nerve appears without brachial plexus involvement or the typical shoulder pain of acute onset. In our patients, electrophysiological evaluation combined with radiographic studies, ventilatory parameters and biochemical analyses were helpful in establishing the diagnosis. Received: 18 March 2000 / Accepted in revised form: 26 May 2000     

肌萎缩侧索硬化患者膈神经传导的电生理分析

目的 通过分析肌萎缩侧索硬化(Amyotrophic Lateral Sclerosis,ALS)患者膈神经传导检测,并结合其它神经电生理资料,为该病提供更深入的认识,进一步指导临床诊疗。方法 研究范围为武汉大学人民医院2014年1月-2021年12月就诊的ALS患者共88例,收集患者的一般资料、主要症状及体征、肌萎缩侧索硬化改良量表(ALSFRS-R)评分、运动神经传导检测中的复合肌肉动作电位(CMAP)波幅和远端运动潜伏期(DML)等指标。结果(1)运动神经传导检测中CMAP波幅降低192条(43.6%),膈神经波幅异常率为35.2%; 远端潜伏期延长116条(26.4%),膈神经DML异常率为77.3%;(2)膈神经DML在性别方面存在明显差异(P<0.01);(3)ALSFRS-R评分与膈神经、尺神经、正中神经、腓总神经、胫神经的CMAP波幅呈正相关(r=0.393,P<0.01; r=0.375,P<0.01; r=0.413,P<0.01; r=0.251,P<0.05; r=0.442,P<0.01);(4)膈神经DML及CMAP波幅在起病部位方面存在明显差异(P<0.05; P<0.05);(5)膈神经DML在判断病情中度和轻度之间的最佳界点为9.095 ms,敏感性为85.7%,特异性为80.2%。结论 ALS患者的运动神经传导可表现异常,CMAP波幅下降占比较大,但膈神经中潜伏期延长比CMAP波幅降低更多见。膈神经传导检测存在一定程度的性别差异。行运动神经传导检测时多条神经CMAP波幅变化可反映ALS患者病情严重程度。膈神经潜伏期变化可更敏感地反映ALS的病情严重程度,以期指导临床诊断与治疗。     

Supraorbital nerve conduction study in normal subjects

There is currently no examination technique that allows direct measurement of supraorbital nerve conduction velocity and amplitude. Therefore, in this study we describe a novel nerve conduction technique that allows measurement of the supraorbital sensory nerve action potential (SNAP) distal to the supraorbital foramen. Supraorbital SNAPs were recorded bilaterally from 17 healthy volunteers using an antidromic technique. The SNAPs were consistently recordable over the site 6 cm lateral to the midline point that was marked 10 cm above the nasion. Measured parameters included peak latency (mean 2.3 ms, SD 0.3), amplitude (mean 14.6 μV; SD 10.5), and velocity (mean 51.3 m/s, SD 6.8). The mean percentage of interside difference in amplitude was 25.6% (SD 17.3). Cut-off values (97th percentile) were 2.7 ms (peak latency), 3.3 μV (amplitude), 41.9 m/s (conduction velocity), and 54.9% (interside difference in amplitude). Supraorbital SNAPs can be recorded in all normal subjects and used as a quantitative measure of the functioning large fibers in the nerve.     

臂丛神经损伤的膈神经传导测定结果分析

目的 评估膈神经传导功能测定方法的临床应用价值. 方法 对292例臂丛神经损伤患者进行膈神经诱发电位的检测,根据积水潭医院肌电图室建立的正常值将其分为传导功能正常组与传导功能异常组,比较2组膈神经诱发电位的潜伏期和波幅. 结果 传导功能正常组膈神经诱发电位的潜伏期较异常组明显降低,波幅较异常组明显增加,差异有统计学意义(P＜0.05). 结论 膈神经运动传导功能测定方法简便、易行.安全可靠,是一种临床了解膈神经功能的可靠方法.     

正常膈神经功能的电生理学研究

运用表面电极刺激并记录，建立正常膈神经功能的电生理参数。方法利用ＥｓａｏｔｅＰｈａｓｉｓ肌电仪测定４０例正常人膈神经功能。刺激部位：利用表面电极在胸锁乳突肌后缘，平环状软骨水平刺激。记录部位：腋前线水平，在第７、８肋间分别放置记录电极（负极和正极）。记录诱发电位的潜伏期、波幅和时程。运用Ｅｐｉｉｎｆｏ软件进行统计分析。结果４０名正常人膈神经电刺激后膈肌均可记录到双相诱发电位，潜伏期：７．３±０．９ｍｓ（左侧），７．７±０．８ｍｓ（右侧）；诱发电位波幅：３９６．６±１５１．３μＶ（左侧），３９０．１±１８７．８μＶ（右侧）；诱发电位时程：２１．５±５．０ｍｓ（左侧），２４．０±１０．７ｍｓ（右侧），诱发电位波幅左侧与右侧比值：１．１±０．４。潜伏期相关分析：ｒ＝０．７７，Ｐ值＜０．０５，回归方程：Ｙ＝０．７１Ｘ＋２．５３（右侧为Ｙ值，左侧为Ｘ值），潜伏期与年龄、身高和体重无显著相关，诱发电位波幅相关分析：ｒ＝０．６５，Ｐ值＜０．０５，回归方程：Ｙ＝０．８０Ｘ＋７１．５９（右侧为Ｙ值，左侧为Ｘ值）。结论运用表面电极刺激并记录能准确判断膈神经功能     

健康成人感觉神经传导相关影响因素及正常值范围研究

目的 研究影响健康成人感觉神经传导的相关因素,并建立正常值范围.方法 对213例正常成人的正中神经腕-示指、尺神经腕-小指和腓肠神经的感觉神经传导进行测定,分析其感觉传导各参数,结果 按照不同年龄、性别、身高和体质量,分别进行统计学分析.结果 体质量、身高对感觉神经传导各参数影响不大;年龄是最主要的影响因素,主要影响正中神经感觉传导各参数、尺神经和腓肠神经感觉传导波幅,而这种影响在40岁前后最明显;性别仅对某些感觉神经传导参数有影响.结论 年龄和性别是影响感觉神经传导的主要因素,正常参考值的建立应参考年龄和性别.     

Analysis of reflex activity in cardiac sympathetic nerve induced by myelinated phrenic nerve afferents

Electrical stimulation of the phrenic nerve afferents evoked excitatory responses in the right inferior cardiac sympathetic nerve in chloralose-anaesthetized cats. The reflex was recorded in intact and spinal cats. The latency and threshold of the volley recorded from the phrenic nerve as well as of the cord dorsum potentials evoked by electrical stimulation of the phrenic nerve indicated that group III afferents were responsible for this reflex. The phrenicocardiac sympathetic reflex recorded in intact cats was followed by a silent period. The maximum amplitude of the reflex discharges was 800 microV, the latency was 83 ms and the central transmission time 53 ms. Duration of the silent period lasted up to 0.83 s. In spinal cats the reflex was recorded 5.5-8 h after spinalization. The maximum amplitude of the spinal reflex discharges ranged from 22 to 91 microV and the latency from 36 to 66 ms.     

Misinterpretation of sural nerve conduction studies due to anatomical variation

Objective

Anatomical variation of the sural nerve has been documented in numerous cadaver studies. The sural nerve conduction parameters can potentially be influenced by the sural nerve type A formation formed by the union of the medial sural cutaneous nerve (MSCN) and the peroneal communicating branch (PCB) and the type C formation with the sural nerve formed solely by the PCB.

Methods

In 17 out of 240 prospectively examined subjects referred for polyneuropathy a suspicion of an anatomical variation of the sural nerve was raised due to decreased amplitude or substantial side-to-side variation (>50%) of the sensory nerve action potential (SNAP) in disproportion to the clinical findings. To verify the variation the sural nerve was examined further with surface electrodes and near-nerve technique, including extra lateral and distal needle placements.

Results

In all 17 subjects an anatomical variation affecting the sural SNAP was confirmed as a normal sural SNAP could be obtained by changing the electrode placement. The most frequent variation, seen in 15 subjects, was a type A formation with union of the MSCN and the PCB distally at low calf, while a type C formation was seen in 2 subjects.

Conclusions

In case of a decreased sural SNAP amplitude or substantial side-to-side variation in disproportion to the neurologic evaluation, an anatomical variation instead of pathology could be suspected and a different electrode placement be considered.

Significance

Neurophysiologists should be aware of different types of formations of the sural nerve which may cause misinterpretations of nerve conduction studies, especially when needle electrodes are used.     

Visualization of the diaphragm muscle with ultrasound improves diagnostic accuracy of phrenic nerve conduction studies

Introduction: Evaluation of phrenic neuropathy (PN) with phrenic nerve conduction studies (PNCS) is associated with false negatives. Visualization of diaphragmatic muscle twitch with diaphragm ultrasound (DUS) when performing PNCS may help to solve this problem. Methods: We performed bilateral, simultaneous DUS–PNCS in 10 healthy adults and 12 patients with PN. The amplitude of the diaphragm compound muscle action potential (CMAP) (on PNCS) and twitch (on DUS) was calculated. Results: Control subjects had <38% side‐to‐side asymmetry in twitch amplitude (on DUS) and 53% asymmetry in phrenic CMAP (on PCNS). In the 12 patients with PN, 12 phrenic neuropathies were detected. Three of these patients had either significant side‐to‐side asymmetry or absolute reduction in diaphragm movement that was not detected with PNCS. There were no cases in which the PNCS showed an abnormality but the DUS did not. Conclusions: The addition of DUS to PNCS enhances diagnostic accuracy in PN. Muscle Nerve 49 : 669–675, 2014     

Whole plantar nerve conduction study with disposable strip electrodes

Introduction: A new method to evaluate whole plantar nerve conduction with disposable strip electrodes (DSEs) is described. Methods: Whole plantar compound nerve action potentials (CNAPs) were recorded at the ankle. DSEs were attached to the sole for simultaneous stimulation of medial and lateral plantar nerves. We also conducted medial plantar nerve conduction studies using an established method and compared the findings. Results: Whole plantar CNAPs were recorded bilaterally from 32 healthy volunteers. Mean baseline to peak amplitude for CNAPs was 26.9 ± 11.8 μV, and mean maximum conduction velocity was 65.8 ± 8.3 m/s. The mean amplitude of CNAPs obtained by our method was 58.2% higher than that of CNAPs obtained by the Saeed method (26.9 μV vs. 17.0 μV; P < 0.0001). Conclusions: The higher mean amplitude of whole plantar CNAPs obtained by our method suggests that it enables CNAPs to be obtained easily, even in elderly people. Muscle Nerve 53: 209–213, 2016     

Prognosis of phrenic nerve injury following thoracic interventions: four new cases and a review

Introduction

Phrenic nerve lesion is a known complication of thoracic surgical intervention, but it is rarely described following thymectomy and lung surgery.

Objective

To review the literature on thoracic intervention and phrenic nerve lesion and to describe four new cases, in which regular neurophysiological studies were performed.

Methods

We reviewed the literature concerning phrenic nerve lesion after cardiac, lung and thymus surgical interventions. We described four cases of phrenic nerve lesion, three associated with thymectomy and one in lung surgery.

Results

The review shows that cryogenic or thermal injuries during cardiac surgeries are associated with good prognosis. The information on the outcome of phrenic nerve lesion in thymectomy or lung surgery is insufficient. Our cases and this review suggest that phrenic lesion in the last two interventions are associated with a poor recovery.

Conclusion

Our data suggests that the prognosis of phrenic nerve lesion following thoracic intervention depends on the nature of the damage. Probably, in thymectomy and lung surgery, nerve stretch or laceration are involved, consequently the outcome is poorer in comparison with cardiac surgery, where cold lesion is more frequent. Neurophysiological tests give a direct, quantified and reliable assessment of nerve regeneration.     

Somatosensory evoked potentials,sensory nerve potentials and sensory nerve conduction in hereditary motor and sensory neuropathy type I

Summary Thirty-nine patients from six families with hereditary motor and sensory neuropathy type I and control subjects were included in this study. A neurological deficit score (NDS) was derived from a neurological examination and compared with neurophysiological test findings. Further, sensory nerve conduction velocities (SNCV) were compared with the motor nerve conduction velocities (MNCV). Five patients whom peaks of N11/N13 complex and N20 of the median nerve sensory evoked potential (SEP) could be recorded showed normal interpeak latency. The interpeak separation P14 N20 measured in six patients was normal. These findings point to the normal function of the central conductive pathways. Erb and cervical potentials of the median nerve SEP could be recorded in 10% and 12% of the patients, respectively. In contrast, about half of the patients showed a scalp N20, while in most of them no SNCV could be measured. In six patients far-field potential P14 of the median nerve SEP was the first detectable potential. Therefore, we argue in view of the anatomical structure of the thalamus, that the first generator for synchronizing and amplification of impulses is probably located in the thalamus. A third of the patients had a cortical sural nerve SEP, while no sural nerve potentials could be recorded. No association was found between the SEP findings and the NDS. There was an inverse correlation between median SNCV and the NDS, but no relationship between the former and sensory deficit alone. In 40% of the patients median SNCV and in 13% sural SNCV could be recorded and considered to be severely decreased. In contrast, the majority of the patients had mild to moderate sensory deficit. Furthermore, patients with measurable SNCVs had higher MNCVs and lower NDS than patients without measurable SNCVs.     

Phrenic nerve conduction studies.

To refine the technique of phrenic nerve conduction, we first studied electrode positioning and sources of chest wall artifact. Diaphragmatic compound motor action potentials (DCMAPs) were mapped at close intervals over 4 hemithoraces of two subjects, finding optimum recording sites which were then used to quantitate artifacts due to EKG, chest wall EMG, and configurational thoracic changes of respiration. Based on these findings, 20 normal subjects were studied, showing ease of application and good side-to-side agreement for DCMAP latencies; but, in contrast to prior reports, right-to-left correlation for amplitude and waveform was poor, making the unaffected side an unreliable standard in unilateral partial phrenic nerve lesions.     

Prognostic value of phrenic nerve conduction study in amyotrophic lateral sclerosis: Systematic review and meta-analysis

ObjectivesTo assess the prognostic value of phrenic nerve conduction (PNC) in amyotrophic lateral sclerosis (ALS).MethodsWe conducted a systematic review to identify studies reporting on PNC, and mortality and/or forced vital capacity (FVC) in patients with ALS. We searched Medline, EMBASE, and Web of Science. Two independent authors selected studies and extracted data. Risk of bias was assessed using the QUIPS tool. Hazard-ratios and correlation coefficients were pooled using a random effects generic inverse-variance model. Evidence quality was evaluated with GRADE.ResultsIn the pooled analysis, patients with CMAP-amplitude equal or below 0.4 mV are 2.021 more likely to die over the studied period (95%CI 1.161–3.522; I² = 55.9%; 338 participants). CMAP-amplitude showed a moderate positive correlation with FVC (r = 0.400, 95%CI = 0.226–0.550; I² = 69.77%; 381 participants). However, there was a weak negative correlation between CMAP-latency and FVC (r = −0.235; 95%CI = −0.447 to −0.024; I² = 15.92%; 112 participants).ConclusionsThere is moderate-quality evidence that CMAP-amplitude of the PNC is correlated with FVC. Results favour a predictive value for mortality, but the risk of bias is high.SignificancePNC is a simple test that should be considered to assess respiratory function in ALS, especially in patients with bulbar involvement or cognitive impairment.     

Determinants of nerve conduction recovery after nerve injuries: Compression duration and nerve fiber types

Introduction: The aims of this study were to determine the influences of: (1) timing of nerve decompression; and (2) nerve fiber types on the patterns of nerve conduction studies (NCS) after nerve injury. Methods: Nerve conduction studies (NCS) were performed on 3 models of nerve injury: (1) crush injury due to transient nerve compression (crush group); (2) chronic constriction injury (CCI), or permanent compression (CCI group); and (3) CCI with removal of ligatures, or delayed nerve decompression (De‐CCI group). Results: There were distinct patterns of NCS recovery. The crush and De‐CCI groups achieved similar motor nerve recovery, better than that of the CCI group. In contrast, recovery of sensory nerves was limited in the CCI and De‐CCI groups and was lower than in the crush group. Conclusions: Immediate relief of compression resulted in the best recovery of motor and sensory nerve conduction. In contrast, delayed decompression restored only motor nerve conduction. Muscle Nerve 52 : 107–112, 2015