Neuralgic amyotrophy: An update in evaluation, diagnosis, and treatment approaches

Neuralgic amyotrophy (NA) is an underrecognized peripheral nerve disorder distinguished by severe pain followed by weakness in the distribution of one or more nerves, most commonly in the upper extremity. While classically felt to carry a favorable prognosis, updates in research have demonstrated that patients frequently endure delay in diagnosis and continue to experience long term pain, paresis, and fatigue even years after the diagnosis is made. A transition in therapeutic approach is recommended and described by this review, which emphasizes the necessity to target compensatory abnormal motor control and fatigue by focusing on motor coordination, energy conservation strategies, and behavioral change, rather than strength training which may worsen the symptoms. The development of structural hourglass-like constrictions (HGCs) on imaging can help confirm the suspected clinical diagnosis, and in association with persistent weakness and limited recovery on electrodiagnostic testing may be considered for surgical consultation. Given the complex nature of management, a multidisciplinary approach is described, which can provide an optimal level of care and support for patients with persistent symptoms from NA and allow more unified guidance of rehabilitation and surgical referrals.

Early Surgical Decompression for the Treatment of Hourglass-Like Constriction of the Posterior Interosseus Nerve

Posterior interosseous nerve (PIN) syndrome refers to a rare compressive neuropathy of the PIN resulting in motor dysfunction of the forearm extensor compartment. Often, surgical exploration will reveal extrinsic structures that mechanically compress the nerve. Less frequently, PIN syndrome has been reported with a visible hourglass-like constriction and no identifiable causative adjacent structures. In our report, we describe an adolescent patient with PIN syndrome and associated hourglass-like constriction of the PIN. For diagnosis, we used physical examination, preoperative imaging, nerve studies, and intraoperative findings. To monitor recovery, we performed serial neurological examinations and documented patient-reported functional outcomes. The patient underwent early surgical decompression (< 6 weeks from presentation). Complete resolution of pain was reported 2 weeks after surgery. Complete resolution of wrist extension motor function occurred at 28 weeks after surgery. We demonstrate effective pain relief and complete motor recovery with early surgical release in this adolescent high-level athlete.

[Therapeutic options in patients with neuralgic amyotrophy]

OBJECTIVE

To evaluate the outcomes of patients with neuralgic amyotrophy (NA) depending on the type of treatment received - surgical or glucocorticosteroid administration.

MATERIAL AND METHODS

The outcome of 101 patients with verified NA was analyzed. The mean age of NA patients was 38.21±16.09 years (8 to 76 years), of which 69.3% were males (n=70) and 30.7% were females (n=31). The diagnosis was confirmed by electromyography, cervical spine MRI, and clinical data evaluation: pain according to VAS, duration of pain, timing of diagnosis from the disease onset, and severity of muscle weakness using the MRC scale. Most patients had a classic form (50.5%, n=51), followed by a distal form (39.6%, n=40), and nerve damage above the elbow joint or cranial nerves (9.9%, n=10). Most patients were examined during the phase of pain and muscle weakness (59.4%, n=60) and in the recovery phase (40.6%, n=41). 48.5% (n=49) of patients received steroids. Surgical treatment was performed in 15.8% of cases (n=16). The median follow-up of all patients was 12 months (Q1-Q3 6.00-20.00).

RESULTS

Patients who received GCS recovered better - 67.7% had a complete recovery compared to patients who did not receive pathogenetic therapy. Regardless of the GCS use, the outcome also depended on the NA form and the initial severity of muscle weakness (p<0.001 and p=0.001, respectively). Comparing the outcomes in the groups with and without surgery showed no statistically significant differences. However, in the non-surgery group, a higher percentage of non-recovery was found (71.4%) compared to the group receiving surgical treatment (28.6%). In 97.4% (n=38) of cases of distal NA, ultrasound revealed focal changes in the nerves, which initially indicated a poor prognosis for recovery.

CONCLUSION

Steroid therapy affects muscle strength recovery in patients with NA. The NA form and the initial severity of motor deficit also affect the outcome. Surgical treatment is indicated for patients with distal NA.

Single center experience with hourglass-like constriction neuropathy of suprascapular nerve

INTRODUCTION/AIMS

Hourglass-like constriction (HGC) may occur in several peripheral nerves. However, data on the prognosis of motor weakness in patients with HGC of the suprascapular nerve (SSN) are limited compared with other nerves. Here, we aimed to describe the clinical and imaging features of HGC of the SSN.

METHODS

We retrospectively reviewed patients diagnosed with suprascapular neuropathy using magnetic resonance imaging (MRI) or electrodiagnostic studies over 16 years. After excluding extrinsic causes, patients with HGC of the SSN detected using MRI were included.

RESULTS

Fourteen patients with HGC of the SSN were identified. MRI revealed that all HGCs were located between the origin of the SSN from the upper trunk of the brachial plexus and the suprascapular notch. Seven patients exhibited HGC precisely at the origin of the SSN from the brachial plexus. Four patients showed T2 hyperintensity of the SSN extending to the upper trunk of the brachial plexus or the extraforaminal cervical root. The initial treatments included observation (n = 1), steroid therapy (n = 12), suprascapular notch release (n = 1). Of the 12 patients with a sufficient follow-up period, nine fully recovered from motor weakness of the SSN with non-operative treatments. Six of the nine patients who recovered fully experienced their first clinical improvement more than 6 months after onset.

DISCUSSION

Treatment strategies for HGC differ depending on the affected nerve. For HGC of the SSN, due to the high spontaneous recovery rate observed in our study, conservative management for at least 6 months should be initially considered.

Isolated Radial Nerve Palsy in a Newborn Due to a Congenital Myofibroma: A Rare Case of Peripheral Nerve Injury

Isolated musculoskeletal infantile myofibroma is a rare tumor of pediatric age. The majority of cases are seen in children under two years old, but it can occur at any age as a painless enlarging mass that involves bone, skin, or soft tissue, typically accompanied by compression symptoms. Perineural involvement is extremely rare in myofibromas. Neurological impairment can occur during infancy but isolated nerve palsy, particularly in peripheral nerves within the upper extremity, is very uncommon. Neonatal radial nerve palsy is a rare entity caused by different conditions. Among these, we mention local tumors affecting peripheral nerves, such as myofibroma. There are few cases described in the literature, which mainly concern adult patients. The authors present a case of congenital isolated radial nerve palsy in a newborn with MF of the right elbow, which resulted in impairment of the wrist and finger extension. Following a six-month monitoring period, the patient underwent surgical treatment to restore function to his right wrist and hand. This involved excising the infiltrated radial nerve segment associated with palliative surgery. Despite the benignity of this lesion, severe nerve damage and perineural involvement may require surgical treatment with nerve resection and reconstruction.

Neuralgic Amyotrophy

BACKGROUND

Neuralgic amyotrophy (NA) is a multifactorial, monophasic neuritis that mainly affects the nerves of the shoulder girdle. It is characterized by very severe pain and by weakness that arises some time after the pain. Its reported incidence is high (100 cases per 100 000 persons per year), but our data suggest that many or most cases are diagnosed late or not at all.

METHODS

This review of the epidemiology, pathophysiology, diagnosis, and treatment of NA is based on pertinent publications retrieved by a selective literature search, and on data provided by the scientific institute of AOK, a German statutory health-insurance carrier.

RESULTS

It is currently thought that the combination of a genetic predisposition, an immunological trigger factor, and mechanical stress on the affected nerve segment(s) is pathophysiologically determinative. The prognosis of untreated NA is poor, with 25% of patients remaining unable to work at three years. The main form of treatment is with corticosteroids that are administered as early as possible. If there is evidence of nerve constriction or torsion, surgery may also help. There have only been six controlled cohort studies on the treatment of NA, and no randomized trials. It is not uncommon for the acute phase to develop into a chronic pain syndrome requiring multidimensional treatment.

CONCLUSION

Particularly in view of the high incidence and improved therapeutic options, NA should be included in the differential diagnosis of all patients with suggestive symptoms.

Parsonage-Turner Syndrome and SARS-CoV-2 Infection: A Literature Review With Case Presentation

Neuralgic amyotrophy, also known as Parsonage-Turner syndrome (PTS), is characterized by severe pain and muscle wasting affecting the anterior body, including the head, shoulder, upper limb, and chest wall. Often triggered by an antecedent event, such as infection, PTS encompasses various conditions historically identified as separate entities. In 1948, Parsonage and Turner unified these conditions under the term neuralgic amyotrophy based on shared features of intense pain and muscular atrophy. Recent studies have highlighted PTS as a spectrum disorder with diverse manifestations, including pure sensory neuropathy, extensive neuropathy, spinal accessory nerve involvement, and diaphragmatic palsy. We reviewed 26 documented cases of PTS following SARS-CoV-2 infection, emphasizing the importance of considering PTS in individuals with a history of COVID-19 due to varied clinical presentations. Standardized diagnostic methods and comprehensive evaluations are crucial for accurate diagnosis and management. Future research should focus on consistent evaluation methods and employing a comprehensive differential diagnosis approach.

Neuralgic Amyotrophy and Hourglass Nerve Constriction/Nerve Torsion: Two Sides of the Same Coin? A Clinical Review

Neuralgic amyotrophy, also called Parsonage-Turner syndrome, in its classic presentation is a brachial plexopathy or a multifocal neuropathy, involving mainly motor nerves of the upper limb with a monophasic course. Recently, a new radiological entity was described, the hourglass constriction, which is characterized by a very focal constriction of a nerve, or part of it, usually associated with nerve thickening proximally and distally to the constriction. Another condition, which is similar from a radiological point of view to hourglass constriction, is nerve torsion. The pathophysiology of neuralgic amyotrophy, hourglass constriction and nerve torsion is still poorly understood, and a generic role of inflammation is proposed for all these conditions. It is now widely accepted that nerve imaging is necessary in identifying hourglass constrictions/nerve torsion pre-surgically in patients with an acute mononeuropathy/plexopathy. Ultrasound and MRI are useful tools for diagnosis, and they are consistent with intraoperative findings. The prognosis is generally favorable after surgery, with a high rate of good motor recovery.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Focal inflammatory neuropathies

This chapter focuses on neuropathies that present with focal involvement of nerve roots, plexus, and/or peripheral nerves associated with autoimmune and inflammatory mechanisms that present with focal involvement of nerve roots, plexus and/or peripheral nerves. The clinical presentation, diagnosis, and treatment of focal autoimmune demyelinating neuropathies, focal nonsystemic vasculitic disorders (diabetic and nondiabetic radiculoplexus neuropathies, postsurgical inflammatory neuropathy, and neuralgic amyotrophy), and focal neuropathies associated with sarcoidosis and bacterial and viral infections are reviewed.

[Diagnostics and treatment of hourglass-like nerve constrictions and torsions in neuralgic amyotrophy]

Neuralgic amyotrophy is a disease of the peripheral nervous system characterized by severe neuropathic pain followed by peripheral paralysis. A distinction is made between a hereditary and an idiopathic form, which is assumed to have an autoimmunological origin. Conservative medicinal treatment mainly consists of nonsteroidal anti-inflammatory drugs (NSAID), opioids and glucocorticoids; however, despite treatment, symptoms in the form of pain or paralysis persist in over 50% of cases. Inflammation can lead to strictures and torsions of peripheral nerves, which can be visualized by imaging using nerve sonography or magnetic resonance (MR) neurography and confirmed intraoperatively during surgical exploration. Based on the currently available data, patients with strictures and torsions of peripheral nerves can benefit from neurosurgical treatment.

[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.

Application of a nerve stereoscopic reconstruction technique based on ultrasonic images in the diagnosis of neuralgic amyotrophy

Objective: To propose a nerve stereoscopic reconstruction technique based on ultrasound imaging for site diagnosis, intuitive reflection of disease severity, and classification of neuralgic amyotrophy (NA). Methods: We enrolled 44 patients with NA who underwent high-frequency ultrasonography examination. Multiple sites on the normal side and the affected side were scanned to calculate the ratio of the cross-section area (CSA) of the affected side to the normal side at each location measured, i.e., the cross-section area swelling ratio (CSASR). The CSASR of 44 patients and 30 normal controls was analyzed to determine their threshold value for the diagnosis of NA. Then, ultrasound images of the cross-section were used to reconstruct the stereoscopic model of the nerve on the affected side and the normal side. Using the CSASR values in each measurement location, a CSASR stereoscopic model was developed. Results: The threshold value of CSASR for ultrasound diagnosis of NA was 1.55. The average diseased segments per patient was 2.49 ± 1.97, with an average overall length of 10.03 ± 7.95 cm. Nerve stereoscopic reconstruction could be conducted for swelling, torsion, incomplete constriction, and complete constriction. Conclusion: The ultrasound image reconstruction method proposed in this study can accurately determine the site, range, and type of neuropathies in patients with NA, and simultaneously provide complete and accurate data information and intuitive morphological information.

Spontaneous radial nerve palsy with hourglass-like constriction

Hourglass-like constriction (HLC) is an uncommon spontaneous mononeuropathy that is typically characterised by a sudden onset of pain followed by palsy, affecting branches of the radial (posterior interosseous nerve) and median nerves (anterior interosseous nerve). HLC of the radial nerve (RN) is rare, with only a few reported cases. Here, we report a case of a man who presented with acute wrist and finger drop due to the HLC of the RN. Surgery was recommended 5 months after clinical observation, when the lesion was resected and primarily repaired, resulting in satisfactory recovery. There is still much that remains unknown about HLC, especially for RN. The current understanding points out an inflammatory disease that should be treated conservatively for 3-7 months. The surgical technique depends mostly on the severity and extent of constriction; however, considering only RN constrictions, primary repair by neurorrhaphy or nerve grafts resulted in better functional outcomes.

Nerve Torsion as a Pattern of Parsonage-Turner Syndrome: Literature Review and Two Representative Cases

(1) Background: Parsonage-Turner Syndrome (PTS) is a rare peripheral nerve disease characterized by different degrees of nerve impairment. The recent development of nerve ultrasound has enabled the use of new data in the diagnosis of the disease. The aim of this study is to conduct a literature review about the ultrasound evaluation of PTS and present two clinical cases that are characteristic of the disease. (2) Methods: A review of the literature from the last 10 years on the topic containing data regarding nerve ultrasound was performed. In addition, two cases of patients on whom nerve ultrasound was performed at the first evaluation and at follow-up after the indicated treatment were described. (3) Results: The results of our review show that although it is defined as plexopathy, PTS is most often a form of multifocal neuropathy. We also report the most frequently used ultrasound classification and possible prognostic correlations and report our experience with the description of two paradigmatic clinical cases. (4) Conclusions: Further studies are needed to understand the true prognostic power of each degree of nerve impairment and the possible implications in clinical practice regarding treatment indications.

Hourglass-like constriction of the anterior interosseous nerve in the left forearm: A case report

BACKGROUND

Hourglass-like constriction neuropathy is a rare neurological disorder. The main clinical manifestation is peripheral nerve injury with no apparent cause, and the pathomorphological change is an unexplained narrowing of the diseased nerve. The diagnosis and treatment of the disease are challenging and there is no accepted diagnostic or therapeutic approach.

CASE SUMMARY

This report describes a rare hourglass constriction of the anterior interosseous nerve in the left forearm in a 47-year-old healthy male who was treated surgically and gradually recovered function over a 6-mo follow-up period.

CONCLUSION

Hourglass-like constriction neuropathy is a rare disorder. With the development of medical technology, more examinations are now available for diagnosis. This case aims to highlight the rare manifestations of Hourglass-like constriction neuropathy and provides a reference for enriching the clinical diagnosis and treatment experience.

Parsonage-Turner Syndrome Following SARS-CoV-2 Infection: A Systematic Review

Parsonage-Turner syndrome (PTS) is an inflammatory disorder of the brachial plexus. Hypothesized underlying causes focus on immune-mediated processes, as more than half of patients present some antecedent event or possible predisposing condition, such as infection, vaccination, exercise, or surgery. Recently, PTS was reported following the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We aimed to investigate data on PTS triggered by SARS-CoV-2 infection to provide an extensive perspective on this pathology and to reveal what other, more specific, research questions can be further addressed. In addition, we aimed to highlight research gaps requiring further attention. We systematically reviewed two databases (LitCOVID and the World Health Organization database on COVID-19) to January 2023. We found 26 cases of PTS in patients with previous SARS-CoV-2 infection. The clinical and paraclinical spectrum was heterogeneous, ranging from classical PTS to pure sensory neuropathy, extended neuropathy, spinal accessory nerve involvement, and diaphragmatic palsy. Also, two familial cases were reported. Among them, 93.8% of patients had severe pain, 80.8% were reported to present a motor deficit, and 53.8% of patients presented muscle wasting. Paresthesia was noted in 46.2% of PTS individuals and a sensory loss was reported in 34.6% of patients. The present systematic review highlights the necessity of having a high index of suspicion of PTS in patients with previous SARS-CoV-2 infection, as the clinical manifestations can be variable. Also, there is a need for a standardized approach to investigation and reporting on PTS. Future studies should aim for a comprehensive assessment of patients. Factors including the baseline characteristics of the patients, evolution, and treatments should be consistently assessed across studies. In addition, a thorough differential diagnosis should be employed.

A standardized ultrasound approach in neuralgic amyotrophy

Neuralgic amyotrophy (NA), also referred to as idiopathic brachial plexitis and Parsonage-Turner syndrome, is a peripheral nerve disorder characterized by acute severe shoulder pain followed by progressive upper limb weakness and muscle atrophy. While NA is incompletely understood and often difficult to diagnose, early recognition may prevent unnecessary tests and interventions and, in some situations, allow for prompt treatment, which can potentially minimize adverse long-term sequalae. High-resolution ultrasound (HRUS) has become a valuable tool in the diagnosis and evaluation of NA. Pathologic HRUS findings can be grouped into four categories: nerve swelling, swelling with incomplete constriction, swelling with complete constriction, and fascicular entwinement, which may represent a continuum of pathologic processes. Certain ultrasound findings may help predict the likelihood of spontaneous recovery with conservative management versus the need for surgical intervention. We recommend relying heavily on history and physical examination to determine which nerves are clinically affected and should therefore be assessed by HRUS. The nerves most frequently affected by NA are the suprascapular, long thoracic, median and anterior interosseous nerve (AIN) branch, radial and posterior interosseous nerve (PIN) branch, axillary, spinal accessory, and musculocutaneous. When distal upper limb nerves are affected (AIN, PIN, superficial radial nerve), the lesion is almost always located in their respective fascicles within the parent nerve, proximal to its branching point. The purpose of this review is to describe a reproducible, standardized, ultrasonographic approach for evaluating suspected NA, and to share reliable techniques and clinical considerations when imaging commonly affected nerves.

Autoimmune polyneuropathies

The autoimmune peripheral neuropathies with prominent motor manifestations are a diverse collection of unusual peripheral neuropathies that are appreciated in vast clinical settings. This chapter highlights the most common immune-mediated, motor predominant neuropathies excluding acute, and chronic inflammatory demyelinating polyradiculoneuropathy (AIDP and CIDP, respectively). Other acquired demyelinating neuropathies such as distal CIDP and multifocal motor neuropathy will be covered. Additionally, the radiculoplexus neuropathies, resulting from microvasculitis-induced injury to nerve roots, plexuses, and nerves, including diabetic and nondiabetic lumbosacral radiculoplexus neuropathy and neuralgic amyotrophy (i.e., Parsonage-Turner syndrome), will be included. Finally, the motor predominant peripheral neuropathies encountered in association with rheumatological disease, particularly Sjögren's syndrome and rheumatoid arthritis, are covered. Early recognition of these distinct motor predominant autoimmune neuropathies and initiation of immunomodulatory and immunosuppressant treatment likely result in improved outcomes.

The role of ultrasonography in diagnosis of neuralgic amyotrophy

OBJECTIVE

To investigate the value of high frequency ultrasound in diagnosis of neuralgic amyotrophy.

MATERIALS AND METHODS

From January 2010 to December 2020, the ultrasonographic images of 117 patients with neuralgic amyotrophy diagnosed by the Department of Neurology and hand & foot surgery of Shandong Provincial Hospital Affiliated to Shandong First Medical University were retrospectively analyzed. The ultrasonographic features were summarized.

RESULTS

High frequency ultrasound could clearly show the degree of the affected nerves: No ultrasonic findings were found in 12 cases (10%). The affected nerves were thickening and hypoechogenicity with loss of normal fascicular definition in 28 cases (24%). The affected nerves showed hourglass-like changes, including constriction and torsion in 77 cases (66%). In addition, ultrasound can determine the extent of the lesion, and microvascular imaging can display small blood flow signal within the nerve. There was a significant statistical difference between the diameter of the thickened nerve fascicle and the diameter of the nerve fascicle at the corresponding site of the contralateral normal limb.

CONCLUSIONS

High frequency ultrasound is a valuable imaging method for diagnosis of neuralgic amyotrophy.

Imaging of neuralgic amyotrophy in the acute phase

INTRODUCTION/AIMS

Hourglass-like constrictions (HGCs) occur in neuralgic amyotrophy (NA), but the earliest time at which they can be recognized by imaging is poorly understood. We aimed to determine the prevalence of abnormal imaging findings in the acute phase of NA.

METHODS

Magnetic resonance neurography (MRN) and high-resolution ultrasound (US) examinations were performed at five sites. The investigation included 39 patients with acute NA who underwent imaging within 31 days of symptom onset. Correlation between imaging and electromyography (EMG) findings was measured.

RESULTS

US was performed in 29 patients and MRN in 23; 16 patients underwent US only, 10 MRN only, and 13 had both. US and MRN showed nerve abnormalities within 1 mo from NA onset in 90% of patients. HGCs were found in 74% (29/39) of the patients: 4 within 1 wk, 8 within 2 wk, 5 within 3 wk, and 12 within 4 wk. The earliest HGC on US was found within 12 h, and on MRN within 3 days from symptom onset. MRN demonstrated a denervation edema pattern of affected muscles in 91% of the patients. The shortest time to observe an edema pattern on MRN was 8 days. EMG was performed in 30 patients and revealed fibrillation potentials in affected muscles in 22 (73%). A denervation edema pattern on MRN was significantly associated with the presence of HGCs both on MRN and US, and with fibrillation potentials on EMG.

DISCUSSION

In the early phase of NA, US and MRN are useful diagnostic techniques for demonstrating nerve abnormalities.

Posterior Interosseous Fascicular Constriction Within the Radial Nerve in a Diabetic Patient With Bilateral Neuralgic Amyotrophy: A Case Report

Background: Neuralgic amyotrophy (NA) is an acute, monophasic, painful inflammatory dysimmune focal, or multifocal mononeuropathy. The lesion in NA is not always restricted to the brachial plexus but also involves individual nerves or branches. The prognosis of NA is less favorable than previously assumed, but the reasons for poor recovery remain unknown. Nerve constriction may be one of the causes of poor prognosis in NA.

Case Presentation: Herein, we described a 54-year-old male with a history of type 2 diabetes in whom bilateral neuralgic amyotrophy developed with constriction of the posterior interosseous fascicle within the radial nerve. The patient experienced sudden-onset severe pain in both shoulders followed, 2 days later, by weakness in bilateral shoulders and the left forearm extensors over the subsequent month. The left forearm extensors were more severely affected than both shoulder girdle muscles. He noted a 7-kg weight loss for 1 month before pain onset. After diagnosing diabetic NA based on the clinical symptoms, imaging, and electrophysiological studies, treatment with systemic steroids improved pain and weakness in both shoulder muscles. Weakness in the left forearm extensors persisted after 1 month of steroid treatment. Follow-up ultrasound revealed constriction of the posterior interosseous fascicle within the main trunk of the left radial nerve at the elbow. Surgical exploration at 6 months after onset identified fascicle constriction, for which neurolysis was performed. Weakness in the extensors of the wrist and fingers did not improve during the 16-month follow-up.

Conclusion: A single constriction of the fascicle within a peripheral nerve may often be under-recognized if NA presents with variable degrees of weakness in bilateral upper limbs. Furthermore, fascicular constriction without edema of the parent nerve may be easily missed on the initial ultrasound. A lack of early recognition of nerve constriction and delay in surgical intervention can result in unfavorable outcomes. The physician should consider the possibility of the fascicular constriction when evaluating patients suspected of brachial NA with significant weakness in the distal upper limb compared to the proximal weakness or weakness of the distal upper limb that does not improve over time.

Hourglass-Like Constriction Neuropathy of the Upper Limb Nerve: Diffusion-Weighted Magnetic Resonance Neurography Imaging Findings

OBJECTIVE

The purposes of this study were to determine reliable diffusion-weighted magnetic resonance neurography (DW-MRN) features of hourglass-like constriction of the upper limb nerve and to evaluate the application value of DW-MRN compared with ultrasonography (US).

METHODS

We retrospectively reviewed MRN studies of 13 patients. Qualitative and quantitative image analyses were carried out. The number of constrictions based on DW-MRN and US findings was compared.

RESULTS

Of the 13 cases, there were 7 cases with radial nerve abnormalities, 4 with median nerve abnormalities, and 2 with radial and median nerve abnormalities. Diffusion-weighted MRN showed a single-segmental constriction in 7 of 13 cases and multisegmental constrictions in 6 of 13 cases; the hourglass-like constriction appeared in all cases (13 of 13). Thirty-three nerve constrictions were found in DW-MRN, and 29 nerve constrictions were found in US.

CONCLUSIONS

Diffusion-weighted MRN is a noninvasive and helpful diagnostic for hourglass-like constriction of the upper limb nerve.

Surgical treatment of hourglass-like radial nerve constrictions

INTRODUCTION

Spontaneous radial nerve palsy with the surgical revelation of an hourglass-like constriction is a complicated condition. In general, the surgical strategy is decided in accordance with the results of surgical exploration. This study aimed to investigate the efficacies of various choices of surgical methods in the treatment of hourglass-like radial nerve constrictions.

MATERIAL AND METHODS

Ten patients with spontaneous radial nerve palsy undergoing surgical exploration with the revelation of hourglass-like constrictions between November 2010 and December 2018 were reviewed in our hospital. Preoperative physical, electrophysiological and ultrasound examinations were performed for all patients. Varying levels, degrees and numbers of radial nerve constrictions were shown by surgical exposure. Epineurectomy and interfascicular neurolysis were performed in 4 cases with incomplete constrictions; resection and primary suture repair in 2 radial nerves with neurotmesis; resection and autologous nerve grafting in 4 patients with nerve defect>2cm. Both motor and sensory evaluations were performed at a follow-up visit.

RESULTS

Ten patients underwent different history before the onset of symptom. Nerve ultrasound demonstrated swelling as well as constrictions of the radial nerve. All patients who were followed up presented with good to excellent recovery of motor function. The effectiveness of suture and autograft repair tended to be better than that of simple neurolysis.

CONCLUSION

The etiology of hourglass-like fascicular constrictive neuropathy of radial nerve involve with torsional factors. Nerve ultrasound is an important and useful measurement in diagnosing the pathology of spontaneous radial nerve palsy and in helping determine surgical approach. The surgical intervention is beneficial for the patients who do not recover in 4 weeks after onset of symptoms and for severe hourglass-like constrictions that are confirmed by preoperative ultrasound imaging. We recommend that nerve grafting be a suitable method in confrontation of nerve defect>2cm.

Outcomes of Microneurolysis of Hourglass Constrictions in Chronic Neuralgic Amyotrophy

PURPOSE

Wide variability in the recovery of patients affected by neuralgic amyotrophy (NA) is recognized, with up to 30% experiencing residual motor deficits. Using magnetic resonance imaging and ultrasound (US), we identified hourglass constrictions (HGCs) in all affected nerves of patients with chronic motor paralysis from NA. We hypothesized that chronic NA patients undergoing microsurgical epineurolysis and perineurolysis of constrictions would experience greater recovery compared with patients managed nonsurgically.

METHODS

We treated 24 patients with chronic motor palsy from NA and HGCs identified on magnetic resonance imaging and US either with microsurgical epineurolysis and perineurolysis of HGCs (11 of 24) or nonsurgically (13 of 24). Muscle strength (both groups) and electrodiagnostic testing (EDX) (operative group) was performed before and after surgery. Preoperative EDX confirmed muscle denervation in the distribution of affected nerve(s). All patients met criteria for microneurolysis: 12 months without improvement since onset or failure of clinical and EDX improvement after 6 months documented by 3 successive examinations, each at least 6 weeks apart.

RESULTS

Mean time from onset to surgery was 12.5 ± 4.0 months. Average time to most recent post-onset follow-up occurred at 27.3 months (range, 18-42 months; 15 nerves). Average time to latest follow-up among nonsurgical patients was 33.6 months (range, 18-108 months; 16 nerves). Constrictions involved individual fascicular groups (FCs) of the median nerve and the suprascapular, axillary and radial nerves proper (HGCs). Nine of 11 operative patients experienced clinical recovery compared with 3 of 13 nonsurgical patients. EMG revealed significant motor unit recovery from axonal regeneration in the operative group.

CONCLUSIONS

Microsurgical epineurolysis and perineurolysis of FCs and HGCs was associated with significantly improved clinical and nerve regeneration at an average follow-up of 14.8 months compared with nonsurgical management. We recommend microneurolysis of HGCs and FCs as a treatment option for patients with chronic NA who have failed to improve with nonsurgical treatment.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Pathological Findings of Hourglass-Like Constriction in Spontaneous Posterior Interosseous Nerve Palsy

We report the pathological findings of hourglass-like fascicular constriction (HLFC) under optical and electron microscopy. A 24-year-old man with spontaneous posterior interosseous nerve palsy was treated by interfascicular neurolysis at 29 weeks after onset. One fascicle in the radial nerve presented severe HLFC with torsion at 5 cm proximal to the elbow. Functional recovery was achieved by resection of the enlarged fascicle including HLFC and sural nerve grafting. Proximal to the HLFC, the endoneurium was filled with clusters of regenerating nerve fibers. At the level of the HLFC, a complete loss of myelinated nerve fibers and vascular occlusion of endo- and perineurial vessels were found. Few regenerating nerve fibers were observed. Distal to the HLFC, severe endoneurial edema, a complete loss of myelinated and unmyelinated nerve fibers, and bands of Büngner were noted. These electron microscopic findings demonstrated a detailed pathology of the nerve around the HLFC.

Neuralgic amyotrophy: a paradigm shift in diagnosis and treatment

Neuralgic amyotrophy (NA), also known as Parsonage-Turner syndrome, is characterised by sudden pain attacks, followed by patchy muscle paresis in the upper extremity. Recent reports have shown that incidence is much higher than previously assumed and that the majority of patients never achieve full recovery. Traditionally, the diagnosis was mainly based on clinical observations and treatment options were confined to application of corticosteroids and symptomatic management, without proven positive effects on long-term outcomes. These views, however, have been challenged in the last years. Improved imaging methods in MRI and high-resolution ultrasound have led to the identification of structural peripheral nerve pathologies in NA, most notably hourglass-like constrictions. These pathognomonic findings have paved the way for more accurate diagnosis through high-resolution imaging. Furthermore, surgery has shown to improve clinical outcomes in such cases, indicating the viability of peripheral nerve surgery as a valuable treatment option in NA. In this review, we present an update on the current knowledge on this disease, including pathophysiology and clinical presentation, moving on to diagnostic and treatment paradigms with a focus on recent radiological findings and surgical reports. Finally, we present a surgical treatment algorithm to support clinical decision making, with the aim to encourage translation into day-to-day practice.

Update on classification, epidemiology, clinical phenotype and imaging of the nonsystemic vasculitic neuropathies

PURPOSE OF REVIEW

Single-organ vasculitis of the peripheral nervous system (PNS) is often designated nonsystemic vasculitic neuropathy (NSVN). Several variants or subtypes have been distinguished, including migratory sensory neuropathy, postsurgical inflammatory neuropathy, diabetic radiculoplexus neuropathies, skin-nerve vasculitides, and, arguably, neuralgic amyotrophy. NSVN often presents as nondiabetic lumbosacral radiculoplexus neuropathy (LRPN). This review updates classification, clinical features, epidemiology, and imaging of these disorders.

RECENT FINDINGS

A recent study showed the annual incidence of LRPN in Olmstead County, Minnesota to be 4.16/100 000:2.79/100 000 diabetic and 1.27/100 000 nondiabetic. This study was the first to determine the incidence or prevalence of any vasculitic neuropathy. In NSVN, ultrasonography shows multifocal enlargement of proximal and distal nerves. In neuralgic amyotrophy, MRI and ultrasound reveal multifocal enlargements and focal constrictions in nerves derived from the brachial plexus. Histopathology of these chronic lesions shows inflammation and rare vasculitis. Diffusion tensor imaging of tibial nerves in NSVN revealed decreased fractional anisotropy in one study.

SUMMARY

Single-organ PNS vasculitides are the most common inflammatory neuropathies. Neuralgic amyotrophy might result from PNS vasculitis, but further study is necessary. The usefulness of focal nerve enlargements or constrictions in understanding pathological mechanisms, directing biopsies, and monitoring disease activity in NSVN should be further investigated.

Development of Parsonage-Turner Syndrome After Heat Stroke in Firefighters: A Report of 2 Cases

CASE

Two firefighters developed Parsonage-Turner syndrome (PTS) shortly after sustaining episodes of heat stroke. Patient 1 was a 40-year-old man who presented with shoulder pain and supraspinatus and infraspinatus weakness. Patient 2 was a 35-year-old man who presented with shoulder pain and absent external rotation strength. Both had electrodiagnostic testing and magnetic resonance imaging findings consistent with PTS. Both demonstrated partial but incomplete recovery at 1- and 2.5-year follow-ups, respectively.

CONCLUSIONS

PTS should remain on the differential diagnosis for any patient presenting with sudden onset shoulder pain and neurological deficits after an episode of heat-related illness.

Spontaneous peripheral nerve palsy with hourglass-like fascicular constriction in the upper extremity

OBJECTIVE

Spontaneous paralysis from hourglass-like fascicular constriction of peripheral nerves is rare, its clinical manifestations are not well documented, and its pathogenesis remains unknown. The unclear origin of this disorder and difficulty in diagnosis result in its uncertain management. The authors sought to gain a more thorough understanding of this condition through describing the anatomy, clinical features, etiology, and treatment of hourglass-like constriction.

METHODS

The authors retrospectively reviewed 20 patients (22 nerves) with hourglass-like constriction. The patients' clinical information was reviewed. Preoperative sonographic assessment and electrophysiological examination of involved nerves were performed. Surgical treatments included interfascicular neurolysis and neurorrhaphy. Samples of tissue subjected to resected constriction were sent for pathological analysis. The patients had regular face-to-face follow-up visits.

RESULTS

Acute pain was always the first symptom and was followed by paralysis. Paralysis progression was rapid and serious. Surgical exploration indicated an hourglass-like constricted segment completely unrelated to the compressive structures. Electrophysiological analysis showed severe denervation, and histopathological examination showed inflammatory cell infiltration, demyelination, and reduction of nerve fibers.

CONCLUSIONS

Hourglass-like fascicular constrictive neuropathy has an integrative effect from multiple different mechanisms. Surgical intervention is beneficial for selected patients who do not recover in a timely fashion and have hourglass-like lesions confirmed by preoperative ultrasound imaging. The authors recommend that early surgical intervention of the nerve be offered to patients who do not show any signs of recovery 3 months after onset. Both interfascicular neurolysis and neurorrhaphy are effective treatment methods. Mild to moderate constriction can usually be treated successfully by interfascicular neurolysis alone, whereas more advanced lesions with loss of fascicle continuity (severe constriction) may be best treated with resection and direct neurorrhaphy.

Spontaneous Radial Nerve Palsy due to an Unrecognized Myofibroma: A Case Report

CASE

A 33-year-old woman presented with a six-month history of spontaneous radial nerve palsy and no identified lesion on imaging. She underwent operative exploration where an hourglass deformity was seen and resected. Pathology returned as a rare tumor, a myofibroma. The patient regained full radial nerve function.

CONCLUSIONS

A trial of observation is often indicated in the cases of isolated nerve palsy where anatomic lesions have been eliminated. This case highlights that imaging studies can miss a tumor involving nerve and that painless, spontaneous nerve palsy may be a time where early surgical intervention offers a better chance of recovery.

Bilateral idiopathic neuralgic amyotrophy involving selective branches of peripheral nerves with a stepwise progression: A case report

RATIONALE

This is a report about a rare case of idiopathic neuralgic amyotrophy (INA) involving selective peripheral nerve branches of bilateral upper extremities, which exhibited a stepwise progression.

PATIENT CONCERN

A 66-year-old woman presented with paresis of selective branches of bilateral median nerves, followed by paresis of bilateral posterior interosseous nerve (PIN) 8 weeks later.

DIAGNOSES

We diagnosed it as INA involving the selective motor branches of bilateral median nerves and bilateral PINs. Forearm magnetic resonance imaging combined with electrodiagnostic testing helped accurately identify the affected regions, and ultrasonography demonstrated a severe constriction of the left PIN.

INTERVENTIONS

Intravenous methylprednisolone partially relieved the pain and paralysis. Surgical neurolysis of the constricted left PIN was done for persistent paralysis.

OUTCOMES

The muscle power of the bilateral median nerve territories was recovered to nearly normal, but the muscle power of the left PIN territories remained at grade 1.

LESSONS

This case indicates that INA can manifest as a multiple mononeuropathy involving individual fascicular levels of peripheral nerve branches with focal constriction, and electrodiagnostic study combined with forearm MRI and ultrasonography can help in identifying affected lesion and predicting the prognosis.

Isolated spontaneous posterior interosseous nerve palsy: a review of aetiology and management

Isolated posterior interosseous nerve palsy is an uncommon condition and its management is controversial. Existing literature is sparse and a treatment algorithm based on existing best evidence is absent. A comprehensive review was undertaken to elucidate the causes of spontaneous posterior interosseous nerve palsy and suggest a management strategy based on the current evidence. Posterior interosseous nerve palsy can be broadly categorized as compressive and non-compressive, and the existing evidence supports surgical intervention for compressive palsy. For posterior interosseous nerve pathology with no compressive lesion on imaging, conservative management should be tried first. Surgery is therefore reserved for compressive lesions and for failure of conservative management. The commonly performed operative procedures include decompression and neurolysis, neurorrhaphy and nerve grafting, and tendon transfers with or without nerve grafting performed as a salvage procedure. The prognosis is poorer in patients aged > 50 years, those with a delay to surgery, and those who have had long-standing compression with severe fascicular thinning.

Ultrasonography in neuralgic amyotrophy: Sensitivity, spectrum of findings, and clinical correlations

INTRODUCTION

The aim of this study was to assess the value of ultrasonography in neuralgic amyotrophy.

METHODS

Fifty-three patients with 70 affected nerves were examined with high-resolution ultrasound.

RESULTS

The most commonly affected nerve was the anterior interosseous (23%). Ultrasonographic abnormalities in the affected nerves, rather than in the brachial plexus, were observed, with an overall sensitivity of 74%. Findings included the swelling of the nerve/fascicle with or without incomplete/complete constriction and rotational phenomena (nerve torsion and fascicular entwinement). A significant difference was found among the categories of ultrasonographic findings with respect to clinical outcome (P = 0.01). In nerves with complete constriction and rotational phenomena, reinnervation was absent or negligible, indicating surgery was warranted.

DISCUSSION

Ultrasonography may be used as a diagnostic aid in neuralgic amyotrophy, which was hitherto a clinical and electrophysiological diagnosis, and may also help in identifying potential surgical candidates. Muscle Nerve 56: 1054-1062, 2017.

Hourglass-Like Constriction of the Brachial Plexus in the Posterior Cord: A Case Report

BACKGROUND AND IMPORTANCE

Hourglass-like constrictions are fascicular conditions confirmed definitively by interfascicular neurolysis. Certain peripheral nerves have vulnerable areas such as around the elbow in the posterior interosseous nerve. We report the first hourglass-like constriction in the brachial plexus supplying the radial innervated forearm musculature. Preoperative magnetic resonance imaging (MRI) findings of the brachial plexus were consistent with neuralgic amyotrophy (NA).

CLINICAL PRESENTATION

A 9-yr-old boy experienced worsening left arm pain and difficulty in elevating the shoulder. Sequentially, severe palsy emerged when extending the wrist, thumb, and fingers. Based on the clinical picture, we diagnosed him with NA. The oblique coronal T2-weighted short-tau inversion recovery images showed mildly diffuse enlargement and hyperintensity of the brachial plexus. He showed few signs of improvement and interfascicular neurolysis was performed 11 mo after the onset. One of the fascicles in the posterior cord had developed an hourglass-like constriction. Electrical stimulation confirmed that the fascicle supplied forearm muscles. His wrist and finger extension had almost recovered at the 12-mo postoperative visit.

CONCLUSION

Hourglass-like constrictions can occur in the brachial plexus. Although surgical approaches for the constrictions are still controversial, several reports demonstrated their effectiveness. Meanwhile, concerning NA treatment, evidence on the surgical intervention is lacking. Brachial plexus MRI might help in discerning the lesion and planning treatment options including surgical interventions. Hourglass-like constrictions are a possible etiology for certain NA patients with residual symptoms or paresis.