Dyspnea as the predominant manifestation of bilateral phrenic neuropathy

Perioperative Diaphragm Dysfunction

Diaphragm Dysfunction (DD) is a respiratory disorder with multiple causes. Although both unilateral and bilateral DD could ultimately lead to respiratory failure, the former is more common. Increasing research has recently delved into perioperative diaphragm protection. It has been established that DD promotes atelectasis development by affecting lung and chest wall mechanics. Diaphragm function must be specifically assessed for clinicians to optimally select an anesthetic approach, prepare for adequate monitoring, and implement the perioperative plan. Recent technological advancements, including dynamic MRI, ultrasound, and esophageal manometry, have critically aided disease diagnosis and management. In this context, it is noteworthy that therapeutic approaches for DD vary depending on its etiology and include various interventions, either noninvasive or invasive, aimed at promoting diaphragm recruitment. This review aims to unravel alternative anesthetic and operative strategies that minimize postoperative dysfunction by elucidating the identification of patients at a higher risk of DD and procedures that could cause postoperative DD, facilitating the recognition and avoidance of anesthetic and surgical interventions likely to impair diaphragmatic function.

[Neuralgic amyotrophy: a common cause of unilateral and bilateral diaphragmatic pareses]

There are several causes for unilateral or bilateral diaphragmatic paresis. The most common cause is an (intraoperative) injury to the phrenic nerve.However, in up to 20% of cases, no explanation can be found despite extensive workup. Neuralgic amyotrophy (NA, also known as Parsonage-Turner syndrome) is a common underdiagnosed multifocal autoimmune-inflammatory disease that predominantly affects proximal nerve segments of the upper extremities. Classic symptoms include acute onset of severe pain in the shoulder girdle with delayed onset of paresis of the shoulder and arm muscles. In at least 7% of cases, the phrenic nerve is also affected. Based on the annual incidence of NA of 1:1000, the entity as a cause of diaphragmatic dysfunction is probably not as uncommon as previously thought. However, clinical experience shows that this diagnosis is often not considered, and diaphragmatic paresis gets wrongly classified as idiopathic.This is particularly disastrous because in the early stage of NA, medical therapy with corticosteroids is mostly not considered and the possibility that surgical repair of the diaphragm may be performed prematurely, given that the condition may resolve spontaneously many months after symptom onset.The aim of the present article is to raise awareness of the entity of NA as a cause of diaphragmatic paresis and to establish a standardized approach to diagnosis and treatment.

Conservative rehabilitation therapy for respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor: A case series study

RATIONALE

Cases of respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor have rarely been studied in detail. Diaphragmatic dysfunction in such cases can lead to potentially fatal respiratory and circulatory disturbances. Therefore, timely diagnosis and intervention are important. Conservative rehabilitation therapy is the first choice for respiratory dysfunction due to diaphragmatic dysfunction.

PATIENT CONCERNS, DIAGNOSES AND INTERVENTIONS

We present 3 patients with respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor. The diagnostic methods and therapeutic procedures for diaphragmatic dysfunction for each patient are described in detail. This study highlights the role of ventilator support combined with physical therapy in the treatment of respiratory dysfunction in such cases. The diagnosis of diaphragmatic dysfunction as well as the risk assessment of phrenic nerve involvement are also discussed. The modalities of ventilator support, including modes and parameters, are listed.

OUTCOMES AND LESSONS

This study provides experiences of diagnosis and treatment of respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor. Timely diagnosis of diaphragmatic dysfunction primarily relies on clinical manifestations and radiography. Conservative rehabilitation therapy can improve or restore diaphragmatic function in majority of patients, and avert or delay the need for surgical intervention. Preoperative assessment of the risk of phrenic nerve involvement is important in such cases.

Isolated diaphragm weakness and the diagnostic value of phrenic nerve stimulation

Acute onset, atraumatic, bilateral diaphragm paralysis due to isolated bilateral phrenic neuropathy is uncommon. Respiratory physicians should be alert to this disorder because it is associated with considerable morbidity and diagnosis is often delayed. These case reports highlight important aspects of the presentation, investigations and management of this disorder.

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

Objective

This 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.

Methods

Eighty-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.

Results

There 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.

Conclusions

The 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.

Diaphragm dysfunction: A comprehensive review from diagnosis to management

Although the diaphragm represents a critical component of the respiratory pump, the clinical presentations of diaphragm dysfunction are often non-specific and can be mistaken for other more common causes of dyspnoea. While acute bilateral diaphragm dysfunction typically presents dramatically, progressive diaphragm dysfunction associated with neuromuscular disorders and unilateral hemidiaphragm dysfunction may be identified incidentally or by recognising subtle associated symptoms. Diaphragm dysfunction should be considered in individuals with unexplained dyspnoea, restrictive respiratory function tests or abnormal diaphragm position on plain chest imaging. A higher index of suspicion should occur for individuals with profound orthopnoea, those who have undergone procedures in proximity to the phrenic nerve(s) or those with co-morbid conditions that are associated with diaphragm dysfunction, particularly neuromuscular disorders. A systematic approach to the evaluation of diaphragm function using non-invasive diagnostic techniques such as respiratory function testing and diaphragm imaging can often confirm a diagnosis. Neurophysiological assessment may confirm diaphragm dysfunction and assist in identifying an underlying cause. Identifying those with or at risk of respiratory failure can allow institution of respiratory support, while specific cases may also benefit from surgical plication or phrenic nerve pacing techniques. This article is protected by copyright. All rights reserved.

Minimally Invasive Plication of the Diaphragm: A Single-Center Prospective Study

OBJECTIVE

Plication of the diaphragm is a life-changing procedure for patients affected by diaphragm paralysis. Traditionally, this procedure is performed through a thoracotomy. Access to the diaphragm via this incision is poor and the indications for surgery are limited to patients who can actually sustain such an invasive approach and associated morbidities. A minimally invasive approach was developed to improve the surgical management of diaphragm paralysis.

METHODS

Patients underwent minimally invasive diaphragm plication either by video-assisted or robotic surgery through a 3-port technique with CO₂ insufflation. Patients were followed at the routine 6-week clinic and also by telephone consultation 6 to 12 months postoperatively. Data were collected on postoperative complications, postoperative pain or numbness, symptomatic improvement, and change to quality of life following surgery.

RESULTS

Forty-eight patients underwent 49 minimally invasive diaphragm plication. Median postoperative length of hospital stay was 4 days (range: 2 to 34 days) and there were no cases of mortality. Mean reduction in Medical Research Council dyspnea score per patient was 2.2 points (mode: 3 points). Twenty-eight patients (77.8%) reported a significant symptomatic improvement enabling improvements in quality of life, and 97.2% (n = 35) were satisfied with the surgical outcome.

CONCLUSIONS

Minimally invasive diaphragm plication is a safe procedure associated with prompt postoperative recovery. It is effective at reducing debilitating dyspnea and improving quality of life.

Determinants and functional impacts of diaphragmatic involvement in patients with inclusion body myositis

BACKGROUND

We evaluated the functional consequences of diaphragm involvement in patients with inclusion body myositis (IBM).

METHODS

Ultrasound diaphragm thickening fraction (TFdi), lung function and dyspnea levels were compared between IBM patients and matched controls. Patients with IBM were grouped into "low" and "high" diaphragm activity based on TFdi values (with cutoff value being the lowest observed TFdi in the control group), and clinical characteristics were compared between groups.

RESULTS

20 IBM patients were included. TFdi was significantly lower in patients and correlated with time since symptom onset (rho = 0.74, P < .001). Patients had significantly lower forced vital capacity and higher dyspnea scores than controls. IBM patients with "low" diaphragm activity (n = 9) had lower 6-min walking distance, higher resting and exertional dyspnea and a larger positional decrease in vital capacity (all P ≤ .03) than patients with 'high' activity. Timed Up and Go time and St. George's Respiratory Questionnaire were not different between groups.

CONCLUSIONS

Diaphragm involvement in IBM is related to disease duration and has detrimental effects on lung function, dyspnea and exercise capacity. Further studies are required to investigate its potential as a therapeutic target.

Assessing the impact of posture on diaphragm morphology and function using an open upright MRI system-A pilot study

PURPOSE

The diaphragm is the most important muscle of respiration. Disorders of the diaphragm can have a deleterious impact on respiratory function. We aimed to evaluate the use of an open-configuration upright low-field MRI system to assess diaphragm morphology and function in patients with bilateral diaphragm weakness (BDW) and chronic obstructive pulmonary disease (COPD) with hyperinflation.

METHOD

The study was approved by the National Research Ethics Committee, and written consent was obtained. We recruited 20 healthy adult volunteers, six subjects with BDW, and five subjects with COPD with hyperinflation. We measured their vital capacity in the upright and supine position, after which they were scanned on the 0.5 T MRI system during 10-s breath-holds at end-expiration and end-inspiration in both positions. We developed and applied image analysis methods to measure the volume under the dome, maximum excursion of hemidiaphragms, and anterior-posterior and left-right extension of the diaphragm.

RESULTS

All participants were able to complete the scanning protocol. The patients found scanning in the upright position more comfortable than the supine position. All differences in the supine inspiratory-expiratory parameters, excluding left-right extension, were significantly smaller in the BDW and COPD groups compared with healthy volunteers. No significant correlation was found between the postural change in diaphragm morphology and vital capacity in either group.

CONCLUSION

Our combined upright-supine MR imaging approach facilitates the assessment of the impact of posture on diaphragm morphology and function in patients with BDW and those with COPD with hyperinflation.

A rare case of chemotherapy induced phrenic neuropathy

Background

While chemotherapeutic agents result in an improvement in both disease-free and overall survival in cancer patients, treatment can result in short and long-term complications. One well-known complication is neuropathy which can result from a number of chemotherapeutic agents. However, chemotherapy-induced phrenic neuropathy is an exceedingly rare phenomenon with few cases reported in the literature.

Case

A 34-year-old male with metastatic testicular cancer presented with progressive dyspnea on exertion after initiation of chemotherapy with bleomycin, cisplatin, and etoposide. Multiple diagnostic studies were performed including pulmonary function testing, chest computed tomography, fluoroscopic sniff evaluation, in addition to phrenic nerve electromyography. Based on results of these tests, the diagnosis of chemotherapy-induced phrenic neuropathy was made.

Conclusion

Chemotherapy-induced phrenic neuropathy, although rare, should be considered as a cause of dyspnea in cancer patients following initiation of chemotherapy.

Brief Communication: Immune Checkpoint Inhibitor-induced Diaphragmatic Dysfunction: A Case Series

Diaphragmatic dysfunction is a rare cause of dyspnea that can lead to hypercapnic respiratory failure. A variety of causes of diaphragmatic dysfunction have been identified, including myopathies and neuropathies, the latter of which can be further subdivided into infectious, idiopathic, demyelinating, malignant, and iatrogenic etiologies. Now, in the era of immune checkpoint inhibitors (ICIs), case reports of immune-mediated phrenic nerve palsies have been described. This diagnosis can be challenging to make, as dyspnea is a common presenting complaint and immune-mediated palsy of the phrenic nerve is a rarely described complication of ICI therapy. At Mayo Clinic, 3 patients with diaphragmatic dysfunction in the setting of ICI therapy were successfully treated without mortality. This case series describes the presentation, diagnoses, and management of these patients and their clinical outcomes.

Disorders of the Diaphragm

Pathologic processes that involve the central nervous system, phrenic nerve, neuromuscular junction, and skeletal muscle can impair diaphragm function. When these processes are of sufficient severity to cause diaphragm dysfunction, respiratory failure may be a consequence. This article reviews basic diaphragm anatomy and physiology and then discusses diagnostic and therapeutic approaches to disorders that result in unilateral or bilateral diaphragm dysfunction. This discussion provides a context in which disorders of the diaphragm and their implications on respiratory function can be better appreciated.

Diaphragmatic Palsy

The diaphragm is the primary muscle of respiration, and its weakness can lead to respiratory failure. Diaphragmatic palsy can be caused by various causes. Injury to the phrenic nerve during thoracic surgeries is the most common cause for diaphragmatic palsy. Depending on the cause, the symptoms of diaphragmatic palsies vary from completely asymptomatic to disabling dyspnea requiring mechanical ventilation. On pulmonary function tests, there will be a decrease in the maximum respiratory muscle power. Spirometry shows reduced lung functions and a significant drop of lung function in supine position is typical of diaphragmatic palsy. Diaphragmatic movements with respiration can be directly visualized by fluoroscopic examination. Currently, this test is being replaced by bedside thoracic ultrasound examination, looking at the diaphragmic excursion with deep breathing or sniffing. This test is found to be equally efficient, and without risks of ionizing radiation of fluoroscope. Treatment of diaphragmatic palsy depends on the cause. Surgical approach of repair of diaphragm or nonsurgical approach of noninvasive ventilation has been tried with good success. Overall prognosis of diaphragmatic palsy is good, except when it is related to neuromuscular degeneration conditions.

An unusual cause of orthopnoea-hashimoto's thyroiditis presenting as bilateral diaphragmatic palsy

We report a case of 36 yr old male without any comorbidities, who presented with a history of gradually progressive dyspnoea and orthopnoea for 6 months. Physical examination revealed bradycardia, paradoxical respiration suggestive of bilateral diaphragmatic palsy. Fluoroscopy demonstrated the presence of bilateral diaphragmatic paralysis. Etiological work up showed evidence of autoimmune hypothyroidism due to hashimoto's thyroiditis. Other possibilities were ruled out with appropriate tests. He was started on thyroxine and showed symptomatic improvement.

Ultrasound in the Assessment of Respiration

Electromyographers are often asked to evaluate patients presenting with dyspnea or respiratory failure, to rule out an underlying neuromuscular cause for those symptoms. Available tools for diagnosing such patients include pulmonary function tests, transdiaphragmatic pressure testing, various imaging modalities, phrenic nerve conduction studies, and diaphragm electromyography. Phrenic nerve conduction studies and diaphragm electromyography are technically challenging and can be limited by both false positive and false negative results. Integration of diagnostic ultrasound can enhance the accuracy and safety of diaphragm electromyography, and improve sensitivity and specificity of phrenic nerve conduction studies. In addition, brightness-mode ultrasound imaging of the diaphragm allows for measurement of muscle thickness and contractility, and is a very sensitive and specific diagnostic test in this setting. This article will review the electromyographer's approach to patients presenting with respiratory symptoms, with a focus on neuromuscular ultrasound.

Diaphragm Dysfunction: Diagnostic Approaches and Management Strategies

The diaphragm is the main inspiratory muscle, and its dysfunction can lead to significant adverse clinical consequences. The aim of this review is to provide clinicians with an overview of the main causes of uni- and bi-lateral diaphragm dysfunction, explore the clinical and physiological consequences of the disease on lung function, exercise physiology and sleep and review the available diagnostic tools used in the evaluation of diaphragm function. A particular emphasis is placed on the clinical significance of diaphragm weakness in the intensive care unit setting and the use of ultrasound to evaluate diaphragmatic action.

Idiopathic bilateral diaphragmatic dysfunction as a cause of dyspnea

Diaphragmatic paralysis is an unusual and often underrecognized cause of dyspnea. We present a case of bilateral diaphragmatic paralysis with no identifiable etiology. Our patient is a 73-year-old female with a history of smoking who presented with dyspnea and orthopnea. She was treated for obstructive lung disease with no improvement in dyspnea despite adequate therapy. She had pulmonary function tests (PFTs) that revealed marked decrease in vital capacity and was unable to perform lung volume maneuvers supine due to marked dyspnea. The maximal inspiratory pressure was 37 in the upright position and decreased to 27 in the supine position. She was given a presumptive diagnosis of idiopathic bilateral diaphragmatic dysfunction. Given the history, physical exam, and PFT findings, we felt that the patient did not need further invasive testing. The patient was treated with noninvasive mechanical ventilation due to hypercapnia and her symptoms improved.

The Effectiveness of Sonography in the Detection of Diaphragmatic Paralysis

Unilateral or bilateral paralysis of the diaphragm is an acquired dysfunction caused by injury or trauma to the phrenic nerve. Patients will often experience symptoms of respiratory distress, and severe cases can be life-threatening. Though not widely used, sonography, specifically M-mode imaging, has proven to be convenient and effective in the detection of this condition. A case is presented describing the sonographic techniques used to evaluate this entity.

Severe Acute Orthopnea: Ipilimumab-Induced Bilateral Phrenic Nerve Neuropathy

Ipilimumab is a monoclonal antibody used in the treatment of unresectable or metastatic melanoma. Several immune-related adverse events including potential fatal events have been reported following its use. We report a case of a 66-year-old man who presented with severe acute exertional dyspnea and orthopnea following administration of ipilimumab for metastatic melanoma. Although various peripheral neuropathy syndromes associated with ipilimumab have been reported, bilateral phrenic nerve paralysis has not been previously reported. This case also highlights the clinical features of bilateral phrenic nerve neuropathy. Pulmonologists have to be aware of these unusual immune-related respiratory adverse events in patients being treated with monoclonal antibodies.

Nosology of idiopathic phrenic neuropathies

Phrenic neuropathies (PN) are an important cause of dyspnoea, orthopnoea and hypercapnic respiratory failure. However, there is no agreement on the nosology of this disorder. The aim of this cohort study was to analyze the author's and published PN patients and compare them with other immune-mediated focal neuropathies to determine the most appropriate nomenclature and classification of the disorder. All patients with PN referred to the author from March 2004 to March 2013 were included. In addition, to identify previously published patients with PN, a PubMed search was done. The demographic and clinical characteristics of both series were then compared with the published series of neuralgic amyotrophy (NA) patients. Of 19 PN patients from the author's series, 11 % fulfilled the criteria for definite and 58 % for probable NA; while in 58 previous patients, the values were 16 and 48 %, respectively. PN and NA both have a male preponderance and a frequent history of preceding events, but PN occur in an older population and more often in diabetics, are less commonly associated with pain, and have a less complete recovery. Although demonstrating some similarities with NA, the high proportion of isolated (particularly bilateral) PN point to a probable immune-mediated attack against some phrenic nerve-specific antigen with occasional spill-over to neighboring nerves. As a consequence, idiopathic PN seems to be more appropriately regarded as a distinct entity within the spectrum of immune-mediated focal neuropathies rather than as a variant of NA.

[Diseases of the diaphragm]

The diaphragm is the main muscle involved in ventilation and is supplied exclusively by the phrenic nerves. Congenital defects of the diaphragm muscle or phrenic nerve injury cause diaphragmatic paralysis-eventration. Prognosis and treatment depend on whether involvement is unilateral or bilateral and on the patient's previous clinical status. In addition, the diaphragm is an anatomical barrier between the thoracic and abdominal cavities and is traversed by the esophagus and important vascular and nerve structures. Abnormal dilation of the natural orifices of the diaphragm or loss of its continuity can cause abdominal structures to pass into the chest cavity, an occurrence known as diaphragmatic hernias. According to their etiology, hernias are divided into congenital, acquired and traumatic. Clinical manifestations, prognosis and treatment depend mainly on hernia size and age at diagnosis. Like any muscle, the diaphragm can develop benign or malignant primary tumors. However, diaphragm involvement due to tumors arising in adjacent organs is much more common. The prognosis is good in benign primary tumors and poor in both primary and secondary malignant tumors. This article reviews the main anatomical and physiological characteristics of the diaphragm, routes of surgical access and the most frequent diseases affecting this structure.

Pulmonary issues in patients with chronic neuromuscular disease

Patients with chronic neuromuscular diseases such as spinal cord injury, amyotrophic lateral sclerosis, and muscular dystrophies experience respiratory complications that are cared for by the respiratory practitioner. An organized anatomical approach for evaluation and treatment is helpful to provide appropriate clinical care. Effective noninvasive strategies for management of hypoventilation, sleep-disordered breathing, and cough insufficiency are available for these patients.

Brachial plexopathy

Brachial plexus injury can occur as a result of trauma, inflammation or malignancies, and associated complications. The current topic is concerned with various forms of brachial plexopathy, its clinical features, pathophysiology, imaging findings, and management. Idiopathic brachial neuritis (IBN), often preceded with antecedent events such as infection, commonly present with abruptonset painful asymmetric upper limb weakness with associated wasting around the shoulder girdle and arm muscles. Idiopathic hypertrophic brachial neuritis, a rare condition, is usually painless to begin with, unlike IBN. Hereditary neuralgic amyotrophy is an autosomal-dominant disorder characterized by repeated episodes of paralysis and sensory disturbances in an affected limb, which is preceded by severe pain. While the frequency of the episodes tends to decrease with age, affected individuals suffer from residual deficits. Neurogenic thoracic outlet syndrome affects the lower trunk of the brachial plexus. It is diagnosed on the basis of electrophysiology and is amenable to surgical intervention. Cancer-related brachial plexopathy may occur secondary to metastatic infiltration or radiation therapy. Traumatic brachial plexus injury is commonly encountered in neurology, orthopedic, and plastic surgery set-ups. Trauma may be a direct blow or traction or stretch injury. The prognosis depends on the extent and site of injury as well as the surgical expertise.

Unilateral phrenic nerve lesion in Lyme neuroborreliosis

Background

Among a variety of more common differential diagnoses, the aetiology of acute respiratory failure includes Lyme neuroborreliosis.

Case presentation

We report an 87-years old huntsman with unilateral phrenic nerve palsy as a consequence of Lyme neuroborreliosis.

Conclusion

Although Lyme neuroborreliosis is a rare cause of diaphragmatic weakness, it should be considered in the differential workup because of its potentially treatable nature.

Lung disease at high altitude

Large numbers of people travel to high altitudes, entering an environment of hypobaric hypoxia. Exposure to low oxygen tension leads to a series of important physiologic responses that allow individuals to tolerate these hypoxic conditions. However, in some cases hypoxia triggers maladaptive responses that lead to various forms of acute and chronic high altitude illness, such as high-altitude pulmonary edema or chronic mountain sickness. Because the respiratory system plays a critical role in these adaptive and maladaptive responses, patients with underlying lung disease may be at increased risk for complications in this environment and warrant careful evaluation before any planned sojourn to higher altitudes. In this review, we describe respiratory disorders that occur with both acute and chronic exposures to high altitudes. These disorders may occur in any individual who ascends to high altitude, regardless of his/her baseline pulmonary status. We then consider the safety of high-altitude travel in patients with various forms of underlying lung disease. The available data regarding how these patients fare in hypoxic conditions are reviewed, and recommendations are provided for management prior to and during the planned sojourn.

Clinical and pathophysiological concepts of neuralgic amyotrophy

Neuralgic amyotrophy--also known as Parsonage-Turner syndrome or brachial plexus neuritis--is a distinct and painful peripheral neuropathy that causes episodes of multifocal paresis and sensory loss in a brachial plexus distribution with concomitant involvement of other PNS structures (such as the lumbosacral plexus or phrenic nerve) in a large number of patients. The phenotype can be limited or extensive and the amount of disability experienced also varies between patients, but many are left with residual disabilities that affect their ability to work and their everyday life. Both idiopathic and hereditary forms exist. The latter form is genetically heterogeneous, but in 55% of affected families, neuralgic amyotrophy is associated with a point mutation or duplication in the SEPT9 gene on chromosome 17q25. The disease is thought to result from an underlying genetic predisposition, a susceptibility to mechanical injury of the brachial plexus (possibly representing disturbance of the epineurial blood-nerve barrier), and an immune or autoimmune trigger for the attacks. The precise pathophysiological mechanisms are still unclear; treatment is empirical, and preventive measures are not yet available. This Review provides an overview of the current clinical and pathophysiological concepts and research topics in neuralgic amyotrophy.

An unusual case of neuralgic amyotrophy presenting with bilateral phrenic nerve and vocal cord paresis

Background

Neuralgic amyotrophy (brachial plexus neuropathy, brachial plexus neuritis, or Parsonage-Turner syndrome) is an uncommon inflammatory condition typically characterized by acute and severe shoulder pain followed by paresis with muscle weakness and atrophy of the upper limb or shoulder girdle. We report an unusual clinical manifestation of neuralgic amyotrophy, namely bilateral phrenic nerve palsy with concomitant laryngeal paresis.

Case Report

A 55-year-old male presented with orthopnea and aphonia after an episode of bilateral shoulder pain preceded by an upper respiratory tract infection. Spirometry, chest X-ray and videolaryngoscopy revealed bilateral and simultaneous paresis of the diaphragm and the vocal cords. Clinical examination at admission and at the 2-month follow-up did not show upper limb weakness or atrophy, except for a mild atrophy of the right supraspinatus muscle. An electromyography of the upper limb muscles and nerve conduction studies did not reveal signs of denervation. Analysis of the cerebrospinal fluid and an MRI of the neuraxis were unremarkable. After treatment with prednisolone, vocal cord function markedly improved within 8 weeks, whereas paresis of the diaphragm persisted.

Conclusion

Shoulder pain followed by diaphragmatic paralysis with dyspnea and hoarseness may be a manifestation of neuralgic amyotrophy even if upper limb or shoulder girdle palsies are absent.

A4V superoxide dismutase mutation in apparently sporadic ALS resembling neuralgic amyotrophy

We report a case of apparently sporadic amyotrophic lateral sclerosis (ALS) in a young pregnant woman presenting subacutely with severe left shoulder pain followed by progressive weakness and wasting of the left arm, mimicking neuralgic amyotrophy. She was later found electrophysiologically to have widespread denervation involving more than just the arm and an alanine for valine substitution in codon 4 (A4V) in the gene for Cu/Zn superoxide dismutase 1 (SOD1). Her case illustrates that pain on initial presentation, though uncommon, does not exclude a diagnosis of ALS.

[A bilateral diaphragmatic paralysis due to Parsonage and Turner syndrome--its evolution over eight years]

The diaphragmatic paralysis is a rare disease whose causes and evolving forms are numerous. We report the development to eight years of paralysis diaphragmatic bilateral attributed to a Parsonage-Turner syndrome: the lack of recovery is proved by respiratory functional follow-up. The therapeutic possibilities, limited, are discussed.

Monitoring recovery from diaphragm paralysis with ultrasound

BACKGROUND

Diaphragmatic paralysis is an uncommon, yet underdiagnosed cause of dyspnea. Data regarding the time course and potential for recovery has come from a few small case series. The methods that have been traditionally employed to diagnose diaphragmatic weakness or paralysis are either invasive or limited in sensitivity and specificity. A new technique utilizing two-dimensional, B-mode ultrasound (US) measurements of diaphragm muscle thickening during inspiration (Deltatdi%) has been validated in the diagnosis of diaphragm paralysis (DP). The purpose of this study was to assess whether serial US evaluation might be utilized to monitor the potential recovery of diaphragm function.

METHODS

Twenty-one consecutive patients with clinically suspected DP were referred to the pulmonary physiology laboratory. Sixteen patients were found to have DP by US (unilateral, 10 patients; bilateral, 6 patients). Subjects were followed up for up to 60 months. On initial and subsequent visits, Deltatdi% was measured by US. Additional measurements included upright and supine vital capacity (VC), maximal inspiratory pressure (Pimax), and maximal expiratory pressure.

RESULTS

Eleven of 16 patients functionally recovered from DP. The mean (+/- SD) recovery time was 14.9 +/- 6.1 months. No diaphragm thickening was noted in those patients who did not recover. Positive correlations were found between improvement in Deltatdi% and interval changes in VC, Pimax, and end-expiratory measurements of diaphragm thickness.

CONCLUSIONS

US may be used to assess for potential functional recovery from diaphragm weakness or DP. As in previous series, recovery occurs in a substantial number of individuals, but recovery time may be prolonged.

Respiratory failure in infants due to spinal muscular atrophy with respiratory distress type 1

BACKGROUND

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disease of unknown prevalence characterized by degeneration of anterior horn alpha-motoneurons and manifesting in the first 6months of life as life-threatening irreversible diaphragmatic paralysis associated with progressive symmetrical muscular weakness (distal lower limbs mainly involved), muscle atrophy, and peripheral sensory neuropathy.

SETTING

Pediatric intensive care unit of tertiary care hospital.

PATIENTS

We present two new cases of SMARD1 and report two new mutations in the gene IGHMBP2 which encodes immunoglobulin mu-binding protein 2 on chromosome 11q13.

CONCLUSIONS

SMARD1 is a poor-prognosis disease that should be considered when acute respiratory insufficiency, of suspected neuromuscular or unclear cause, develops during the first 6months of life. Diaphragmatic paralysis, manifesting as dyspnea and paradoxical respiration, is the most prominent presenting sign and diaphragmatic motility should be investigated early by fluoroscopy or ultrasound. Electromyography and nerve conduction studies revealing peripheral motor and sensory neuropathy then suggest the diagnosis which should be confirmed by genetic analysis.