Idiopathic phrenic neuropathies: A case series and review of the literature

Paradoxical thinning of the diaphragm on ultrasound is a risk factor for requiring non-invasive ventilation in patients with neuromuscular diaphragmatic dysfunction

INTRODUCTION/AIMS

Point-of-care ultrasound of the diaphragm is highly sensitive and specific in the detection of neuromuscular diaphragmatic dysfunction. In some patients with neuromuscular diaphragmatic dysfunction, paradoxical thinning of the diaphragm during inspiration is observed on ultrasound; however, its frequency, electrodiagnostic associations, and prognostic significance remain uncertain.

METHODS

Medical records of patients presenting to two electrodiagnostic laboratories (Mayo Clinic, Rochester, Minnesota and University of Alberta, Edmonton, Alberta) from January 1, 2022 to December 31, 2022, for evaluation of suspected neuromuscular respiratory failure, were reviewed.

RESULTS

214 patients were referred and 19 patients excluded due to incomplete information. Of 195 patients (384 hemidiaphragms), 104 had phrenic neuropathy, 12 had myopathy, and 79 had no evidence of neuromuscular disease affecting the diaphragm. Paradoxical thinning occurred in 31 (27%) patients with neuromuscular diaphragmatic dysfunction and was unilateral in 30, the majority (83%) having normal contralateral ultrasound. Phrenic nerve conduction studies and diaphragm electromyography results did not distinguish patients with paradoxical thinning versus without. Most patients (71%) with paradoxical thinning required non-invasive ventilation (NIV), including 16 with unilateral paradoxical thinning. Paradoxical thinning and BMI ≥30 kg/m2 were risk factors for requiring NIV in multivariable logistic regression analysis, with odds ratios of 2.887 (95% CI:1.166, 7.151) and 2.561 (95% CI: 1.186, 5.532), respectively.

DISCUSSION

Paradoxical thinning of the diaphragm occurs in patients with prominent neuromuscular diaphragmatic dysfunction, most commonly from phrenic neuropathy, and is a significant risk factor for requiring NIV. Unilateral paradoxical thinning is sufficient for needing NIV. BMI ≥30 kg/m2 additionally increases risk of requiring NIV in patients with neuromuscular diaphragmatic dysfunction.

[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.

Diaphragmatic Dysfunction due to Neuralgic Amyotrophy After SARS-CoV-2 Vaccination: A Case Report

Neuralgic amyotrophy is an idiopathic neuropathy characterized by acute-onset pain, typically in the upper extremity or shoulder, followed by weakness of the associated muscles. Phrenic nerve involvement is rare. We report a 63-year-old man who presented with dyspnea and right shoulder pain after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. His chest radiograph showed an elevated right hemidiaphragm that was absent before vaccination. A pulmonary function test showed a restrictive pattern with a significant reduction (40%) in forced vital capacity in the supine position. Diaphragm ultrasonography revealed a reduction in both diaphragmatic excursion and a thickening fraction of the right hemidiaphragm. Electrophysiological studies suggested a right upper brachial plexopathy. Considering the temporal relationship between the vaccination and absence of other causes, SARS-CoV-2 vaccination was thought to be the reason for neuralgic amyotrophy with diaphragmatic dysfunction. As there was no evidence of hypoventilation or sleep disturbance that may require noninvasive ventilation, the patient was followed with conservative treatment with analgesics. During 8 months of follow-up, his shoulder pain was relieved significantly but dyspnea improved only slightly. Neuralgic amyotrophy is an under-diagnosed etiology of diaphragmatic dysfunction and should be considered in patients with dyspnea and shoulder pain.

Practical approach to respiratory emergencies in neurological diseases

Many neurological diseases may cause acute respiratory failure (ARF) due to involvement of bulbar respiratory center, spinal cord, motoneurons, peripheral nerves, neuromuscular junction, or skeletal muscles. In this context, respiratory emergencies are often a challenge at home, in a neurology ward, or even in an intensive care unit, influencing morbidity and mortality. More commonly, patients develop primarily ventilatory impairment causing hypercapnia. Moreover, inadequate bulbar and expiratory muscle function may cause retained secretions, frequently complicated by pneumonia, atelectasis, and, ultimately, hypoxemic ARF. On the basis of the clinical onset, two main categories of ARF can be identified: (i) acute exacerbation of chronic respiratory failure, which is common in slowly progressive neurological diseases, such as movement disorders and most neuromuscular diseases, and (ii) sudden-onset respiratory failure which may develop in rapidly progressive neurological disorders including stroke, convulsive status epilepticus, traumatic brain injury, spinal cord injury, phrenic neuropathy, myasthenia gravis, and Guillain-Barré syndrome. A tailored assistance may include manual and mechanical cough assistance, noninvasive ventilation, endotracheal intubation, invasive mechanical ventilation, or tracheotomy. This review provides practical recommendations for prevention, recognition, management, and treatment of respiratory emergencies in neurological diseases, mostly in teenagers and adults, according to type and severity of baseline disease.

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.

Diaphragm paralysis: a case report

INTRODUCTION

Bilateral paralysis of the diaphragm may be an idiopathic clinical condition or associated with several diseases such as trauma, surgery, viral infections, neurologic disorders. The diaphragm is the main respiratory muscle. It is a cupoliform muscle-tendon structure, innervated bilaterally by phrenic nerve, which originates from C3-C5 nerve roots. Diaphragmatic paralysis is a clinical disorder that generates hypoventilation and basal pulmonary atelectasis, predisposing to hypercapnic respiratory failure. The clinic manifestations mimic cardio-respiratory pathologies, therefore often misdiagnosticated.

CASE PRESENTATION

A 55-year-old man with a previous C6-7 traumatic fracture, referred multiple accesses to the emergency room for acute nocturnal dyspnoea, treated with antibiotic therapy, diuretic therapy and long-term oxygen therapy, without beneficial effects. He referred to our pulmonary clinic for evaluation of persistent and worsening orthopnoea due to unknown cause for about 2 years. Clinical examination, respiratory functional tests and diaphragm ultrasound revealed a strong suspicion of diaphragmatic deficit, confirmed by electromyography.

CONCLUSIONS

The patient accesses to the emergency room numerous times and the clinical frame have been always oriented towards a cardio-respiratory origin. From the onset of the symptom to the respiratory evaluation, about 2.5 years have passed. The manifestation of clear orthopnoea has addressed the functional respiratory study towards a more thorough diaphragmatic evaluation assessed by ultrasound.

Bilateral phrenic neuropathy responsive to intravenous immunoglobulin treatment

The aetiology of phrenic neuropathy is often unknown, but immune mechanisms may play a role. In a typical case of bilateral phrenic neuropathy with paradoxical breathing (video), an inflammatory pathogenesis was suggested by prolonged distal latency of phrenic nerve compound muscle action potentials in nerve conduction studies and a clear-cut albumin-cytologic dissociation. This encouraged us to treat the patient with a standard dose of intravenous immunoglobulin. After obtaining a strong improvement at spirometry, we repeated the second cycle of intravenous immunoglobulin and observed normalization of symptoms within few weeks and no relapse after 3 years. This case suggests that lumbar puncture should be performed in the acute phase of phrenic neuropathies to detect potential responders to immunomodulatory treatment.

Phrenic neuropathy and diaphragm dysfunction in neuralgic amyotrophy

OBJECTIVE

To describe the clinical phenotype and recovery of diaphragm dysfunction caused by neuralgic amyotrophy in a large cohort of patients, to improve accurate awareness of this entity, and to encourage adoption of a standardized approach for diagnosis and treatment.

METHODS

This observational cohort study recruited adult patients with neuralgic amyotrophy and symptoms of idiopathic phrenic neuropathy from the database of the Dutch expert center for neuralgic amyotrophy and the Dutch centers for home mechanical ventilation. Demographic and clinical information on diagnosis, symptoms, and recovery was obtained from chart review. We attempted to contact all patients for a follow-up interview.

RESULTS

Phrenic neuropathy occurs in 7.6% of patients with neuralgic amyotrophy. Unilateral diaphragmatic dysfunction and bilateral diaphragmatic dysfunction are frequently symptomatic, causing exertional dyspnea, orthopnea, disturbed sleep, and excessive fatigue. Diagnostic practices varied widely and were often not optimally targeted. The majority of patients experienced at least moderate recovery within 2 years.

CONCLUSION

We recommend screening every patient with neuralgic amyotrophy for diaphragm dysfunction by asking about orthopnea and by performing upright and supine vital capacity screening and diaphragm ultrasound in cases of suspected phrenic neuropathy to optimize diagnosis and care.

Respiratory failure because of neuromuscular disease

PURPOSE OF REVIEW

Understanding the mechanisms and abnormalities of respiratory function in neuromuscular disease is critical to supporting the patient and maintaining ventilation in the face of acute or chronic progressive impairment.

RECENT FINDINGS

Retrospective clinical studies reviewing the care of patients with Guillain-Barré syndrome and myasthenia have shown a disturbingly high mortality following step-down from intensive care. This implies high dependency and rehabilitation management is failing despite evidence that delayed improvement can occur with long-term care. A variety of mechanisms of phrenic nerve impairment have been recognized with newer investigation techniques, including EMG and ultrasound. Specific treatment for progressive neuromuscular and muscle disease has been increasingly possible particularly for the treatment of myasthenia, metabolic myopathies, and Duchenne muscular dystrophy. For those conditions without specific treatment, it has been increasingly possible to support ventilation in the domiciliary setting with newer techniques of noninvasive ventilation and better airway clearance. There remained several areas of vigorous debates, including the role for tracheostomy care and the place of respiratory muscle training and phrenic nerve/diaphragm pacing.

SUMMARY

Recent studies and systematic reviews have defined criteria for anticipating, recognizing, and managing ventilatory failure because of acute neuromuscular disease. The care of patients requiring long-term noninvasive ventilatory support for chronic disorders has also evolved. This has resulted in significantly improved survival for patients requiring domiciliary ventilatory support.

Orthopnea and pulmonary hypertension. Treat the underlying disease

We report the case of a patient with longstanding dyspnea upon reclining, who presented with severe right heart failure due to chronic alveolar hypoventilation. Bilateral diaphragmatic paresis was discovered. She recovered from her right ventricular failure with non-invasive mechanical ventilatory support.