Phrenic Nerve Conduction Studies Research Articles

Severe respiratory failure secondary to unilateral phrenic nerve injury: A case report

AbstractPatients with unilateral phrenic nerve paralysis are usually asymptomatic at rest. We present a 77‐year‐old woman with a chest wall osteoarthropathy associated with synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome that developed severe hypercapnic respiratory failure following cryoballoon ablation for the management of atrial fibrillation. Her right phrenic nerve injury (PNI) was confirmed by chest radiography, phrenic nerve conduction studies, and diaphragmatic ultrasonography. We conclude that unilateral PNI during ablation invalidated the diaphragmatic compensation for pre‐existing reduced thoracic expansion, resulted in severe hypoventilation. Clinicians should be careful of the fact even unilateral PNI could cause catastrophic respiratory failure in patients with restricted thoracic expansion.

Diaphragm weakness in late-onset Pompe disease: A complex interplay between lower motor neuron and muscle fibre degeneration

BackgroundLate-onset Pompe disease (LOPD) patients may still need ventilation support at some point of their disease course, despite regular recombinant human alglucosidase alfa treatment. This suggest that other pathophysiological mechanisms than muscle fibre lesion can contribute to the respiratory failure process. We investigate through neurophysiology whether spinal phrenic motor neuron dysfunction could contribute to diaphragm weakness in LOPD patients. Material and methodsA group of symptomatic LOPD patients were prospectively studied in our centre from January 2022 to April 2023. We collected both demographic and clinical data, as well as neurophysiological parameters. Phrenic nerve conduction studies and needle EMG sampling of the diaphragm were perfomed. ResultsEight treated LOPD patients (3 males, 37.5%) were investigated. Three patients (37.5%) with no respiratory involvement had normal phrenic nerve motor responses [median phrenic compound muscle action potential (CMAP) amplitude of 0.49 mV; 1st-3rd interquartile range (IQR), 0.48–0.65]. Those with respiratory failure (under nocturnal non-invasive ventilation) had abnormal phrenic nerve motor responses (median phrenic CMAP amplitude of 0 mV; 1st-3rd IQR, 0–0.15), and were then investigated with EMG. Diaphragm needle EMG revealed both myopathic and neurogenic changes in 3 (60%) and myopathic potentials in 1 patient. In the last one, no motor unit potentials could be recruited. ConclusionsOur study provide new insights regarding respiratory mechanisms in LOPD, suggesting a contribution of spinal phrenic motor neuron dysfunction for diaphragm weakness. If confirmed in further studies, our results recommend the need of new drugs crossing the blood-brain barrier.

Retraction: Utility of phrenic nerve conduction studies for identification of patients with neuromuscular diseases requiring invasive mechanical ventilation.

Retraction: Utility of phrenic nerve conduction studies for identification of patients with neuromuscular diseases requiring invasive mechanical ventilation. S. Narukawa, K. Ishizuka, K. Sugimoto, K. Nomura. Muscle & Nerve 65, 211-216. https://doi.org/10.1002/mus.27449. The above article, published online on 28 October 2021 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the Editor-in-Chief Zachary Simmons, and Wiley Periodicals, Inc. The corresponding author informed the journal that there is an inconsistency between the time for which the clinical research reported in this article received approval and the time period in which the research was performed. The retraction has been agreed due to this violating the journal's requirements for ethical approval of clinical research involving human participants.

Mutational screening of GDAP1 in dysphonia associated with Charcot-Marie-Tooth disease: clinical insights and phenotypic effects

IntroductionMutations in GDAP1 (Ganglioside-induced differentiation-associated protein 1) gene are linked to Charcot-Marie-Tooth disease (CMT), a Heterogenous group of disorders with multiple phenotypes, characterized by peripheral nerve dysfunction that can lead to vocal cord paralysis and diaphragmatic dysfunction. Main bodyAll three affected children of this chosen family have manifested the same clinical symptoms with progressive weakness, mild sensory impairment, and absent tendon reflexes in their early years. Electrodiagnostic analysis displayed an axonal type of neuropathy in affected patients. Sequencing of the GDAP1 gene was requested for all members of the family. Diagnostic assessments included pulmonary and vocal cord function tests, as well as phrenic and peripheral nerve conduction studies. Pathogenicity of GDAP1 variant p.Pro419Leu with axonal CMT2 and autosomal recessive inheritance was confirmed via in silico analysis. Patients with GDAP1 mutations showed dysphonia, speech difficulties, and the characteristic symptoms of CMT. The severity of symptoms correlated with the presence of a type of GDAP1 mutation. Patients with normal vocal cords and pulmonary function exhibited milder symptoms compared to those with GDAP1 mutations. Our study provides clinical insights into the phenotypic effects of GDAP1 mutations in CMT patients. The findings highlight the adverse clinical course and severe disability associated with GDAP1 mutations, including weak limb and laryngeal muscles. ConclusionPatients with GDAP1 mutations and autosomal recessive neuropathy present with dysphonia and require interventions such as surgery, braces, physical therapy, and exercise. Early diagnosis and comprehensive clinical evaluations are crucial for managing CMT patients with GDAP1 mutations.

Prolonged Limb and Respiratory Muscle Weakness Associated with Japanese Encephalitis Virus Infection: A Case Report

Patients diagnosed with Japanese encephalitis (JE) may present with flaccid paralysis. JE has also been reported to be accompanied by anterior horn cell disease or motor axonal polyneuropathy. We report a case of a patient with JE with prolonged limb and respiratory muscle weakness who underwent electrodiagnostic studies, including a phrenic nerve conduction study, 10 months after the onset of paralysis. During that 10-month period, severe weakness of the upper and lower extremities showed no recovery, and the patient required long-term ventilator support through a tracheostomy. Nerve conduction studies and electromyography revealed chronic anterior horn cell disease with abundant denervation potentials involving the craniobulbar, cervical, thoracic, and lumbosacral segments. In addition to the nerves in the upper and lower extremities, the phrenic motor nerves showed abnormalities indicative of diaphragmatic weakness. Therefore, in patients with JE with chronic limb weakness and respiratory difficulty, thorough electrodiagnostic studies should be performed to diagnose the combination of anterior horn cell disease with encephalitis and to evaluate the condition’s severity and prognosis.

Diaphragmatic paralysis associated with IgLON5 autoimmunity (P5-5.022)

<h3>Objective:</h3> To describe a rare presentation of IgLON5 IgG mediated neurological disorder <h3>Background:</h3> IgLON5 autoimmunity was previously described with sleep disorder, rhombencephalopathy, vocal cord paresis, progressive-supranuclear-palsy-like syndrome, and recently motor-neuron-disease (MND)-like syndrome. Although diaphragmatic paralysis has been known as a presenting symptom of degenerative (MND) but has never been reported with IgLON5 autoimmunity. <h3>Design/Methods:</h3> Case report <h3>Results:</h3> A 67-year-old man with obstructive sleep apnea and history of vocal cord paralysis 11 years ago, presented with 2-year history of dream enactment behavior, progressive dyspnea and orthopnea. The symptoms became more noticeable and rapidly progressive in the past 10 months. Initially, he felt shortness of breath during the daytime when he bent over. Within a few months, he had to sleep on the recliner with a minimal tilt back at night. Neurological examination demonstrated moderate right facial weakness, mild weakness of interossei muscles of right hand, and triceps. Deep tendon reflexes were marginally brisk without Babinski sign. Sensory examination was normal. Occasional fasciculation was noted in deltoid region. Right upper extremity electromyography was normal. Diaphragmatic ultrasound showed no diaphragmatic expansion during inspiration. Ultrasound-guided electromyography of diaphragm and phrenic nerve conduction study showed no phrenic nerve response on the right, and markedly reduced amplitude of diaphragmatic compound motor action potential on the left side. Brain MRI and cervical spine was essentially unremarkable. Blood work showed normal vitamin B12, creatinine kinase and monoclonal gammopathy screen. Serological evaluation of neural specific antibodies was remarkable for IgLON5-IgG (titer 1:480). The patient was treated with high-dose methylprednisolone and is scheduled to follow up in autoimmune neurology clinic for outcome assessment. <h3>Conclusions:</h3> IgLON5 autoimmunity should be considered in patients with diaphragmatic paralysis, especially ones with sleep disorder, vocal cord paresis, and episodic respiratory disturbances. <b>Disclosure:</b> Dr. Thakolwiboon has nothing to disclose. Dr. Klein has a non-compensated relationship as a Klein with Neurology Journal that is relevant to AAN interests or activities. The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for UCB. The institution of Dr. Dubey has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Astellas. The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Argenx. Dr. Dubey has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for AGRIMS. Dr. Dubey has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Advances in Neurology . Dr. Dubey has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Moffit Cancer Center . Dr. Dubey has received research support from Department of Defense . Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care.

Woman with dyspnea after skin rash.

Woman with dyspnea after skin rash.

MEASUREMENT OF DIAPHRAGMATIC DYSFUNCTION AND PHRENIC NERVE PALSY IN PATIENTS UNDERGOING THORACIC SURGERY FOR LUNG- OR ESOPHAGEAL CANCER

<h3>Introduction and Objective</h3> Thoracic surgery carries a substantial risk of postoperative pulmonary complications. Recent studies have shown that the risk of postoperative pulmonary complications is significantly higher in patients suffering from postoperative diaphragmatic dysfunction. Diaphragmatic dysfunction may be accompanied by phrenic nerve palsy. However, the extent of phrenic nerve palsy and its association with diaphragmatic dysfunction following thoracic surgery is unknown. Therefore, we aimed to quantify changes in diaphragmatic function and phrenic nerve conductance in patients undergoing thoracic surgery for lung- or esophageal cancer using ultrasonographic measures and phrenic nerve conduction studies. <h3>Design and Methods</h3> This was a prospective observational study including patients scheduled for pulmonary lobectomy or esophageal resection. Examinations were carried out the day prior to surgery and respectively 3 days and 10-14 days after surgery. Endpoints for diaphragmatic function included ultrasonographic measurements of diaphragmatic excursion of the posterior part of the right hemidiaphragm, excursion of the hemidiaphragmatic top point, change in intrathoracic area and diaphragmatic thickening fraction. Ultrasonographic measurements were recorded during a standardized respiration cycle. Endpoints for phrenic nerve conductance included baseline-to-peak amplitude, peak-to-peak amplitude and transmission delay of the diaphragmatic compound muscle action potential (CMAP). Measurements for both diaphragmatic- and phrenic nerve recordings were assessed for both the surgical side and the non-surgical side of the thorax and thus measured over time. <h3>Results</h3> We included 40 patients of which 13 had pulmonary lobectomies and 27 had esophageal resections performed. Significant reductions in diaphragmatic excursion were seen on the surgical side of the thorax for all excursion measures (posterior part of the right hemidiaphragm, p < 0.001; hemidiaphragmatic top point, p < 0.001; change in intrathoracic area, p < 0.001) (Figure 1). Conversely, all ultrasound excursion measures did not change significantly on the non-surgical side. Diaphragmatic thickening fraction did not change significantly on either side. For phrenic nerve measures, significant reductions were seen for both CMAP amplitude measures on the surgical side (baseline-to-peak, p < 0.001; peak-to-peak, p < 0.001) and non-surgical side (baseline-to-peak, p < 0.001; peak-to-peak, p < 0.001). Transmission delay also changed significantly between assessments on both the surgical (p =0.041) and the non-surgical side (p =0.021) (Figure 2). <h3>Conclusion</h3> Thoracic surgery caused a significant unilateral reduction in diaphragmatic excursion on the surgical side of the thorax, whereas the contralateral hemidiaphragm's excursion did not decrease significantly. Diaphragmatic compound muscle action potential amplitude was reduced significantly bilaterally. Therefore, our findings show that a postoperative reduction in diaphragmatic excursion is accompanied by partial phrenic nerve palsy, which may be a contributing factor in the pathogenesis of postoperative pulmonary complications.

Diaphragmatic weakness related to radiotherapy: 2 cases and a review

Post-radiation diaphragmatic weakness have rarely been described. We report two cases of post-radiation diaphragmatic weakness from our center, and review the other published cases, computing clinical, electromyography and magnetic resonance imaging data. Including our two cases, seven cases of post-radiation diaphragmatic weakness have been described. Most occurred after mantle-field radiotherapy for Hodgkin lymphoma (5/7), often in associations with chemotherapy (4/7). Other radiations-induced complications were found (5/7) such as brachial plexopathy, cardiac involvement or hypothyroidy. When studied, phrenic nerve conduction studies revealed different profiles, from clearly abnormal responses to limit amplitudes. Imaging can be a useful diagnostic tool, displaying abnormalities with sharp limits matching the radiation field. Data is limited about long-term evolution. Presentation of post-radiation diaphragmatic weakness seems relatively homogeneous. We propose a diagnosis work-up for post-radiation diaphragmatic weakness, to exclude potentially treatable differential diagnoses.

Value of Diaphragm Electromyography and Phrenic Nerve Conduction Studies in Suspected Diaphragm Paresis (P5-13.005)

Value of Diaphragm Electromyography and Phrenic Nerve Conduction Studies in Suspected Diaphragm Paresis (P5-13.005)

The Amplitude of Diaphragm Compound Muscle Action Potential Correlates With Diaphragmatic Excursion on Ultrasound and Pulmonary Function After Supraclavicular Brachial Plexus Block.

ObjectiveThis prospective, double-blind, randomized study assessed (1) the associations between diaphragm compound muscle action potential (CMAP), hemidiaphragmatic excursion, and pulmonary function after supraclavicular brachial plexus block (SCBPB) and (2) diagnostic efficacy of pulmonary function for hemidiaphragmatic paralysis evidenced by diaphragm CMAP as an assessment of diaphragm strength was evaluated.MethodsEighty-six patients were scheduled for the removal of hardware after healing of a right upper limb fracture distal to the shoulder who were randomly assigned in a 1:1 ratio to two groups: Group A (diaphragmatic excursion), or Group B (pulmonary function). Phrenic nerve conduction studies (PNCSs), M-mode ultrasonography of the diaphragm, and pulmonary function tests (PFTs) were performed before and 30 min after SCBPB. PNCSs were used to determine the latency and amplitude of diaphragm CMAP. Ultrasonography of the diaphragm was performed with patients in a supine position using a low-frequency probe over the subcostal space at the midclavicular line. The diaphragmatic excursion was measured during quiet breathing and deep breathing. Pulmonary function, i.e., forced vital capacity (FVC), predicted value of FVC, and forced expiratory flow in the first second (FEV1), was measured with spirometry. Receiver Operating Characteristic (ROC) curve analysis was used to assess the diagnostic efficacy of pulmonary function for hemidiaphragmatic paralysis evidenced by diaphragm CMAP as an assessment of diaphragm strength.ResultsThere were significant associations between the reduction in amplitude of diaphragm CMAP and reductions in diaphragmatic excursion during quiet breathing (r = 0.70, p < 0.01) and deep breathing (r = 0.63, p < 0.01) when expressed as a percentage of baseline values. There were significant associations between the reduction in amplitude of diaphragm CMAP and reductions in FVC (r = 0.67, p < 0.01), FVC% (r = 0.67, p < 0.01), and FEV1 (r = 0.62, p < 0.01), when expressed as percentage of baseline values. The area under the ROC curve for FVC was 0.86. A decrease of >8.4% in FVC compared to pre-block predicted hemidiaphragmatic paralysis (determined by diaphragm CMAP) with sensitivity and specificity of 79.2 and 100%, respectively.ConclusionsThe relative reduction in diaphragm CMAP amplitude after SCBPB was correlated with relative reductions in diaphragmatic excursion and pulmonary function. FVC has potential as a useful diagnostic indicator of hemidiaphragmatic paralysis, evidenced by diaphragm CMAP, after SCBPB. These data establish diaphragm CMAP as a direct and objective index of diaphragmatic paralysis after SCBPB.

Epidural electrical spinal cord stimulation of the thoracic segments (T2-T5) facilitates respiratory function in patients with complete spinal cord injury

IntroductionPatients with high cervical Spinal Cord Injury (SCI) usually require mechanical ventilation support. Phrenic Nerve Stimulation (PNS) both direct and indirect is the main alternative for these patients to wean off ventilator although PNS has several limitations and phrenic nerve could be also damaged after cervical spinal cord injury. ObjectiveIn this study, we assessed if the spinal cord Epidural Electrical Stimulation (EES) at the segments T2-T5, related to intercostal muscles, can facilitate respiratory function and particularly inspired tidal volume during mechanic ventilation. MethodsTwo patients with a high cervical injury were selected for this study with ethical committee permission and under review board supervision. A phrenic nerve conduction study with diaphragm electromyography (DEMG) was performed before and after trial of EES. ResultsResults demonstrate that EES at T2-T5 substantially increase the inspired volume. The results of this study also demonstrate that EES at spinal segments T2-T5 can bring patients dependent from mechanical ventilation to pressure support (on CPAP), preventing Baro-trauma and other complications related to mechanical ventilation. ConclusionThese findings suggest that tested approach applied alone or in combination with the phrenic nerve stimulation could help to reduce time on mechanical ventilation and related complications.

A New Surface Technique for Phrenic Nerve Conduction Study.

To report a new patient friendly and convenient technique for phrenic nerve conduction with alternative sites of stimulation and recording. Phrenic nerve conduction was performed in forty volunteers and ten patients of peripheral neuropathy. Active recording electrode was placed in tenth intercostal space 2.5 cm away from para-spinal muscles (mid-scapular line), reference electrode in eighth intercostal space just medial to subcostal margin with ground between stimulating and recording electrode. Stimulation was done at the level of crico-thyroid space near or under the posterior margin of sternocleidomastoid muscle. This new method was compared with existing ones. Data was analysed using SPSS 23 version. Correlation between height, weight, body mass index, age, and chest expansion was done using bi-variate correlation. Mean latency and amplitude of the study method were compared with other methods using MANNOVA test. Total of forty subjects were studied. Thirty-seven were male subjects. Mean age was 28.03 ± 9.63 years, height 168.0 ± 9.60 cm and chest expansion 3.53 ± 0.64 cm. Right sided phrenic nerve mean latency was 5.99 ± 0.629 ms and amplitude 1.088 ± 0.178 mV. Left sided phrenic nerve conductions showed mean latency of 6.02 ± 1.82 ms, amplitude of 1.092 ± 0.2912 mV. These standard deviations were smaller than what were observed with other methods suggesting increased consistency of our results. There was no correlation between phrenic nerve conduction with age, height, gender or chest expansion. This study method gave a better as well as consistent morphology, higher amplitude and required lower amount of current strength. It was superior to previously reported methods in consistency of normative data.

Utility of phrenic nerve conduction studies for identification of patients with neuromuscular diseases requiring invasive mechanical ventilation.

Predicting when a patient will require invasive mechanical ventilation (IMV) is a major challenge in routine care for some neuromuscular diseases. In this study, we prospectively investigated whether phrenic nerve conduction studies (PNCS) can predict when IMV will be required in patients with amyotrophic lateral sclerosis (ALS), Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), and myotonic dystrophy (DM). PNCS amplitude (avAMP) and latency (avLAT) were compared between patients who required IMV (IMV group) and those who did not (non-IMV group). PNCS were performed in 62 healthy controls and in patients with four different diseases that may require IMV: ALS (n=56), GBS (n=72), CIDP (n=38), and DM (n=24). The IMV group consisted of 12 patients with ALS, 14 with GBS, 2 with CIDP, and 4 with DM. avAMP was significantly lower in the IMV group with ALS than in the non-IMV group (P< .05), but no significant difference was observed in avLAT. avAMP was significantly lower and avLAT was significantly longer in the IMV group with GBS than in the non-IMV group (both P< .05). Receiver operating characteristic analysis showed that the avAMP cutoff between the IMV and non-IMV groups was 184.3 μV (area under the curve=0.921; sensitivity, 84.6%; specificity, 88.2%) for ALS and GBS. PNCSs may aid in determining whether a patient with ALS or GBS requires IMV.

A prospective evaluation of phrenic nerve injury after lung transplantation: Incidence, risk factors, and analysis of the surgical procedure

Phrenic nerve injury (PNI) is a complication of lung transplantation related to the surgical procedure and associated with increased morbidity. However, the incidence and risk factors, specifically regarding surgical techniques, have not been adequately studied. We conducted a prospective single-center study over 4-years, in recipients of lung transplantation with a normal pretransplant phrenic nerve conduction study (PNCS). Diaphragm ultrasound and PNCS were performed in the first 21 postoperative days and PNI was defined when both tests were abnormal. Patients were followed up until hospital discharge. The association between transplant characteristics and PNI was analyzed by using logistic regression models. Two hundred eleven lung grafts implanted in 127 patients were included in the study. After lung transplantation, PNI was diagnosed in 43.3% of the subjects and 29% of the operated hemithorax. Regression logistic model showed that the variables related to PNI were female gender (p=0.02), bilateral lung transplantation (BLT) (p=0.001), right lung graft (p=0.003), clamshell incision (p=0.01), mediastinal adhesions (p=0.002), longer operative time (p=0.003), intraoperative extracorporeal support (p=0.02), and blood transfusion (p=0.003). Conversely, age >61 years (p=0.008) and higher thoracic diameter (p=0.04) were protective factors. The use of electrocautery, cardiac mechanical retractors, and diaphragmatic traction was not associated with PNI. Morbidity was increased without any difference in mortality. PNI is a frequent complication after lung transplantation, associated with higher morbidity. Mainly risk factors were age, BLT, female gender, and variables related to surgical difficulties. Lung graft in the right hemithorax and mediastinal adhesiolysis were the most relevant technical variables.

P-MN004. Multiple neurophysiologic biomarkers evaluated the pulmonary function of ALS

Introduction . Declining respiratory-muscle function is the primary cause of death in patients with amyotrophic lateral sclerosis (ALS). Spirometry is the most frequently used to predict hypoventilation and survival in ALS, but their cut off value cannot indicate disease prognosis. Multiple neurophysiological evaluations, which performed using diaphragmatic compound motor-action potential (DCMAP) by phrenic nerve conduction study, diaphragm thickness (DDT) by ultrasonography and new measurement system of thoracic excursion are proposed as new variable biomarkers. Methods . A total of 14 ALS patients diagnosed by El Escorial criteria were enrolled (4 females and 10 males, mean age 71.0 years, mean disease duration 29.2 months, mean body mass index ( BMI ) 19.5 kg/m 2 ). We prospectively evaluated the spirometry, arterial partial pressure of oxgen and carbon dioxide (PaO2 and PaCO2), baseline-to-peak amplitude of DCMAP, and the differences in DDT and thoracic excursion between timed maximal inspiration and maximal expiration (UMIN:000042222). We then analyzed the relationships between neurophysiological biomarkers, the respiratory-function test, and the other quantitative evaluations. Results . All patients completed the examinations with the exception of the respiratory-function test of two patients. The test–retest analysis of neurophysiologic biomarkers showed a high level of reliability. Decrease of DCMAP and DDT was detected in patients who reported no subjective dyspnea. DCMAP and DDT were found to correlate strongly with both PaCO2 and forced vital capacity (FVC); in contrast, thoracic excursion was strongly correlated to PaCO2 but not to FVC. Except for one female patient with high BMI (> 25), correlation with thoracic excursion and FVC was observed. Conclusion . Multiple neurophysiologic evaluations are reliable and reflects respiratory function. DCMAP and DDT are useful for the objective evaluations of respiratory function before the awareness of subjective dyspnea in patients with ALS.

PHRENIC NERVE CONDUCTION STUDY IN HEALTHY POPULATION

The phrenic nerve provides the primary motor supply to the diaphragm Phrenic nerve conduction study provides a sensitive indicator of phrenic nerve function when the nerve is affected either by local lesions or by generalized neuropathies. Percutaneous phrenic nerve stimulation is an easy and rapid procedure that achieves successful stimulation of the nerve. It is associated with little or no discomfort. Amplitude, latency, area, and duration are measures used to evaluate phrenic nerve integrity. Only limited data has however been published on normative data of phrenic nerve conduction study. Aim of the work The aim of this study was to determine normative values of phrenic nerve conduction parameters in healthy population.Subjects & Methods • Seventy-three healthy individuals (47 men and 26 women) aged from 18 to 61 years participated in the study. • Motor conduction studies of the phrenic nerve were performed bilaterally both during inspiration and expiration. The phrenic nerve was stimulated at the posterior border of the sternocleidomastoid muscle at the level of the cricoid cartilage. Recording was made from both sternal and costal diaphragm. • Measured parameters were latency, amplitude, area and duration of the diaphragmatic compound muscle action potential )DCMAP( at each recording site. Side-side differences were determined.

Phrenic nerve conduction study to diagnose unilateral diaphragmatic paralysis.

Unilateral diaphragmatic paralysis (UDP) has major clinical and etiological implications and, therefore, is important to diagnose. Lung function tests and invasive transdiaphragmatic pressure (Pdi) measurements are widely used to this end but, contrary to phrenic nerve conduction study (NCS), they require volitional maneuvers and/or may be poorly tolerated by patients. The purpose of this study was to compare the diagnostic accuracy of Pdi and phrenic NCS for UDP. We retrospectively reviewed 28 patients with suspected UDP. The diagnosis established during a multidisciplinary meeting was the reference standard. Phrenic NCS correlated well with Pdi (r = 0.82, P < .005), and the two tests showed good agreement (κ = 0.82, P < .005). Phrenic NCS and Pdi measurements both had 95% sensitivity, 87.5% specificity, 95% positive predictive, and 87.5% negative predictive values. Both tests were highly sensitive and specific. Phrenic NCS measurement is a simple, reproducible, noninvasive method whose results correlate well with Pdi and provide insight into the UDP mechanism. In the most difficult cases, combining lung function tests, respiratory muscle assessments, and phrenic NCS can help to establish the diagnosis.

Diaphragm ultrasound in the diagnosis of respiratory dysfunction in patients with amyotrophic lateral sclerosis.

In this study, we aimed to select the best diaphragm ultrasonography (DUS) parameter as an alternative index for the diagnosis of lung function impairment in amyotrophic lateral sclerosis (ALS). Twenty-nine patients with ALS and 15 healthy subjects were enrolled in the study. DUS, lung function tests, phrenic nerve conduction study and arterial blood gas analysis were performed. Patients with respiratory dysfunction had a significantly lower level of ΔTmax than those without (P=0.039). Significant correlations (P<0.05) were found between forced vital capacity (FVC) and Tdi-ins (r=0.665, P<0.0001) and ΔTmax (r=-0.748, P<0.0001) and Δins-exp (r=0.627, P<0.0001) and ΔTdi (r=0.485, P<0.0001). Receiver Operating Curves analysis demonstrated that ΔTmax (AUC=0.76, P=0.044) had a better overall accuracy for detection of respiratory dysfunction compared with Tdi-ins (AUC=0.27, P=0.067), Δins-exp (AUC=0.312, P=0.139), and ΔTdi (AUC=0.38, P=0.359). ΔTmax is the most valuable DUS index in the diagnosis of diaphragmatic dysfunction. DUS can provide functional and structural information of diaphragm and help to diagnose diaphragmatic dysfunction in ALS.

Spinal cord injury level and Phrenic Nerve Conduction Studies do not predict diaphragm pacing success or failure- all patients should undergo diagnostic laparoscopy

BackgroundDiaphragm Pacing(DP) demonstrates benefits over mechanical ventilation(MV) for spinal cord injured(SCI) patients. The hypothesis of this report is that phrenic nerve conduction study(PNCS) results cannot differentiate success or failure in selection of patients for DP. Direct surgical evaluation of the diaphragm should be performed. MethodsObservational report of prospective databases of patients undergoing laparoscopic evaluation of their diaphragms to assess for ability to stimulate to cause contraction for ventilation. ResultsIn 50 SCI patients who could not be weaned from MV, PNCS results showed latencies in stimulated patients (n = 44) and non-stimulated(n = 6) overlapped (7.8 ± 2.5 ms vs 9.4 ± 2.8 ms) and the null hypothesis cannot be rejected (p-value>0.05). Amplitudes overlapped (0.4 ± 0.2 mV vs 0.2 ± 0.2 mV) and the null hypotheses cannot be rejected (P-value >0.05). In 125 non SCI patients with diaphragm paralysis, there were 78(62.4%) with false negative PNCS. ConclusionPNCS are inadequate pre-operative studies. Direct laparoscopic evaluation should be offered for all SCI patients to receive the benefit of DP.