A standardized ultrasound approach in neuralgic amyotrophy

Less Common Mononeuropathies

Uncommon mononeuropathies are challenging to diagnose as they can mimic joint pathology, radiculopathies, or plexopathies. They are less easily diagnosed due to unfamiliarity with their clinical presentation, knowledge of anatomy, and less commonly used diagnostic studies. A careful history, physical examination, and electrodiagnostic evaluation can help identify these neuropathies in a timely manner to administer the best treatment for resolution of symptoms. Recent advances in ultrasound and magnetic resonance techniques are used to confirm clinical suspicion of peripheral neuropathy by clearly depicting the anatomy and pathology as well as describing findings that mimic mononeuropathy. It is important for neurology, orthopedic, rheumatology, emergency, and primary care physicians to be familiar with less common mononeuropathies.

The Role of Neuromuscular Ultrasound in the Diagnosis of Peripheral Neuropathy

The classification of peripheral neuropathies has traditionally been based on etiology, electrodiagnostic findings, or histopathologic features. With the advent of modern imaging, they now can also be characterized based on their varied distribution of imaging findings. We describe the major morphologic patterns of these changes, which include homogeneous enlargement; homogeneous thinning; focal, multifocal, and segmental enlargement; and focal thinning and beading (multifocal thinning). Representative disorders in each of these categories are discussed, along with examples of the more complex imaging manifestations of neuralgic amyotrophy, nerve transection, and hereditary amyloidosis. An appreciation of the diverse morphologic manifestations of neuropathy can help neuromuscular clinicians conduct appropriate imaging studies with ultrasound and, when needed, order suitable investigations with magnetic resonance neurography.

Determining the degree of proximal nerve fascicle rotation in healthy controls using ultrahigh-frequency neuromuscular ultrasound: A pilot study

INTRODUCTION/AIMS

Ultrahigh-frequency ultrasound (UHFUS) allows improved visualization and higher resolution images of nerve fascicles than standard high-frequency ultrasound. Dynamic UHFUS may detect the presence of fascicular entwinement, the recently described sonographic phenomenon of pathologic fascicular rotation seen in neuralgic amyotrophy. This pilot study aims to establish normative reference values and degrees of fascicular rotation for the proximal portions of commonly involved upper limb nerves in healthy controls using UHFUS.

METHODS

Twenty healthy participants underwent sonographic examination of the median, musculocutaneous, and radial nerves on both upper limbs using UHFUS with a 48 MHz linear transducer. A single rater assessed the degree of fascicular rotation in each peripheral nerve.

RESULTS

Fascicular rotation appears to occur in the proximal portion of each of these nerves. The mean degree of fascicular rotation for each of the measured nerves was median 94.5°, musculocutaneous 97.9°, and radial 50.9°. The maximum observed fascicular rotation in each nerve was 180°. Age, sex, height, weight, body mass index, and race did not predict degree of fascicular rotation (all p > .103). A single-factor ANOVA test showed the degree of fascicular rotation differed in median, musculocutaneous, and radial nerves (F = 4.748, p = .011).

DISCUSSION

UHFUS allows quantification of fascicular rotation in healthy controls in the median, musculocutaneous, and radial nerves, and provides normative data. The data from this pilot study may serve as control data for future comparative studies in conditions where fascicular rotation occurs, such as neuralgic amyotrophy.

Early aggressive constriction resection for hourglass-like constriction of peripheral nerve in the upper extremity: a retrospective study

OBJECTIVES

The hourglass like constriction (HGC) of peripheral nerves is a characteristic pathological manifestation of Neuralgic Amyotrophy. Once identified, early surgical intervention is essential. However, the method of surgery is controversial, particularly regarding whether HGC needs to be excised. This study aims to explore the efficacy of early aggressive resection of HGC in the upper limb nerves.

MATERIALS AND METHODS

This retrospective study focuses on 13 nerves of spontaneous upper limb paralysis treated at our hospital from June 2019 to July 2023, in which HGC was identified during surgery. During surgery, epineurectomy and interfascicular neurolysis were performed on the constricted areas. Post-neurolysis, constriction excision was carried out if any of the following conditions were met: (1) A single constriction with constriction ≥75%. (2) Constriction combined with torsion. (3) The presence of ≥2 constrictions. Regular face-to-face follow-ups were conducted postoperatively.

RESULTS

Four cases with a single constriction of less than 75% underwent epineurotomy and interfascicular neurolysis; eight underwent constriction excision, of which four cases with a single constriction and associated torsion had direct end-to-end suturing after excision, and four had more than two constrictions treated with autologous sural nerve grafts. Postoperative follow-ups showed good recovery in all but one case, which had unique pathological features and had underwent only epineurectomy, showing moderate recovery.

CONCLUSIONS

For early surgical treatment of HGCs in peripheral nerves of the upper limbs, if severe constriction, constriction combined with torsion, or the presence of more than two constrictions are identified during surgery, aggressive constriction resection may be a better option.

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.

Ultrasound accuracy for brachial plexus pathology

AIM

To determine (a) the accuracy of ultrasound in detecting brachial plexus pathology and (b) outline the advantages and limitations of ultrasound compared to MRI for imaging the brachial plexus.

MATERIAL AND METHODS

cases with clinically suspected brachial plexus pathology were evaluated first by ultrasound, followed by MRI. Patients with prior brachial plexus imaging were excluded. The final diagnosis was based on a combination of ultrasound, MRI, clinical follow-up, and surgical findings. The accuracy of the ultrasound was assessed by comparing the ultrasound and the final diagnoses. The mean clinical follow-up time following ultrasound was 1.8 ± 1.4 years.

RESULTS

Ninety-two (64%) of the 143 cases had normal brachial plexus ultrasound and MRI examinations. Fifty-one (36%) of 143 cases had brachial plexus pathology on MRI, comprising post-radiation fibrosis (n=25, 49%), nerve sheath tumor (n=11, 21%), traumatic injury (n=7, 14%), inflammatory polyneuropathy (n=4, 8%), malignant infiltration (n=2, 4%), desmoid fibromatosis (n=1,2%), and neuralgic amyotrophy (n=1, 2%). Overall diagnostic accuracy of ultrasound for brachial plexus pathology was 98% (140/143), with three discordant cases (neuralgic amyotrophy n=1, inflammatory neuropathy n=1, postradiation fibrosis n=1) regarded as normal on ultrasound assessment. Sensitivity, specificity, and positive and negative predictive value of ultrasound for identifying brachial plexus pathology were 94%, 100%, 100%, and 97%, respectively.

CONCLUSION

Ultrasound identifies brachial plexus pathology with high accuracy and specificity, showing comparable diagnostic efficacy to MRI. Ultrasound can serve as an effective first-line imaging investigation for suspected brachial plexus pathology.

Neuromuscular Ultrasound in Polyneuropathies

Neuromuscular ultrasound is a painless, radiation-free, high-resolution imaging technique for assessing the peripheral nervous system. It can accurately depict changes in the nerves and muscles of individuals with neuromuscular conditions, and it is therefore a robust diagnostic tool for the assessment of individuals with polyneuropathies. This review will outline the typical ultrasonographic changes found in a wide variety of polyneuropathies. In general, demyelinating conditions result in greater nerve enlargement than axonal conditions, and acquired conditions result in more patchy nerve enlargement compared to diffuse nerve enlargement in hereditary conditions. This review is data-driven, but more nuanced anecdotal findings are also described. The overall goal of this paper is to provide clinicians with an accessible review of the ultrasonographic approaches and findings in a wide variety of polyneuropathies.

Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non-surgeons

Electrodiagnostic evaluation is often requested for persons with peripheral nerve injuries and plays an important role in their diagnosis, prognosis, and management. Peripheral nerve injuries are common and can have devastating effects on patients' physical, psychological, and socioeconomic well-being; alongside surgeons, electrodiagnostic medicine specialists serve a central function in ensuring patients receive optimal treatment for these injuries. Surgical intervention-nerve grafting, nerve transfers, and tendon transfers-often plays a critical role in the management of these injuries and the restoration of patients' function. Increasingly, nerve transfers are becoming the standard of care for some types of peripheral nerve injury due to two significant advantages: first, they shorten the time to reinnervation of denervated muscles; and second, they confer greater specificity in directing motor and sensory axons toward their respective targets. As the indications for, and use of, nerve transfers expand, so too does the role of the electrodiagnostic medicine specialist in establishing or confirming the diagnosis, determining the injury's prognosis, recommending treatment, aiding in surgical planning, and supporting rehabilitation. Having a working knowledge of nerve and/or tendon transfer options allows the electrodiagnostic medicine specialist to not only arrive at the diagnosis and prognosticate, but also to clarify which nerves and/or muscles might be suitable donors, such as confirming whether the branch to supinator could be a nerve transfer donor to restore distal posterior interosseous nerve function. Moreover, post-operative testing can determine if nerve transfer reinnervation is occurring and progress patients' rehabilitation and/or direct surgeons to consider tendon transfers.

Electrodiagnostic studies and new diagnostic modalities for evaluation of peripheral nerve disorders

Electrodiagnostic studies (EDx) are frequently performed in the diagnostic evaluation of peripheral nerve disorders. There is increasing interest in the use of newer, alternative diagnostic modalities, in particular imaging, either to complement or replace established EDx protocols. However, the evidence to support this approach has not been expansively reviewed. In this paper, diagnostic performance data from studies of EDx and other diagnostic modalities in common peripheral nerve disorders have been analyzed and described, with a focus on radiculopathy, plexopathy, compressive neuropathies, and the important neuropathy subtypes of Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), vasculitic neuropathy and diabetic neuropathy. Overall EDx retains its place as a primary diagnostic modality in the evaluated peripheral nerve disorders. Magnetic resonance imaging and ultrasound have developed important complementary diagnostic roles in compressive and traumatic neuropathies and atypical CIDP, but their value is more limited in other neuropathy subtypes. Identification of hourglass constriction in nerves of patients with neuralgic amyotrophy may have therapeutic implications. Investigation of radiculopathy is confounded by poor correlation between clinical features and imaging findings and the lack of a diagnostic gold standard. There is a need to enhance the literature on the utility of these newer diagnostic modalities.

A case report of neuralgic amyotrophy

Neuralgic muscular atrophy is not uncommon in clinical practice. Due to the different branches of brachial plexus involved in the lesion, the clinical symptoms are different, and there is a lack of clear imaging diagnostic criteria, so the diagnosis of this disease brings great challenges to clinicians. We have certain experience in the diagnosis and treatment of this disease, and hereby select a representative case of neuralgic muscular atrophy to share its diagnosis and treatment process, focusing on analyzing the characteristic symptoms of this disease, valuable imaging data and targeted treatment, so as to enable clinicians to better understand this disease.

Neuralgic amyotrophy with multiple hourglass-like constrictions of anterior interosseous nerve: a case report

Hourglass-like constrictions (HLCs) of peripheral nerves in the upper extremity were a rare form of neuralgic amyotrophy, often characterized by the sudden onset of pain in the shoulder or arm, followed by muscle weakness and amyotrophy, with limited sensory involvement. We present a case of multiple HLCs of the anterior interosseous nerve (AIN) in a 22-year-old female with left upper arm pain, finger numbness, and limited activity for 1 month. Physical examination showed weakness of the left index flexor digitorum profundus and flexor pollicis longus, with mild hypoesthesia in the first three fingers and the radial half of the ring finger. Electromyography suggested a median nerve (mainly AIN) lesion. Ultrasonographic imaging of the median nerve shows AIN bundle swelling and multiple HLCs at left upper arm. Despite conservative treatment, which included 15 days of steroid pulse therapy, Etoricoxib, and oral mecobalamin, the patient still complained of extreme pain at night without relief of any symptoms. Operation was recommended for this patient with thorough concerns of surgical advantages and disadvantages. During surgery, a total of 7 HLCs were found in her median nerve along and above the elbow joint. Only Interfascicular neurolysis was performed because the nerve constrictions were still in the early stage. The pain was almost relieved the next day. One month after surgery, she could bend her thumb and index fingers, although they were still weak. 4 months after the surgery, she was able to bend affected fingers, with muscle strength M3 level. At the same time, her fingers had fewer numbness symptoms. There was still controversy regarding treatment strategy; however, early diagnosis and surgical treatment for nerve HLCs might be a better choice to promote nerve recovery.

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.

Increased 18 F-FDG uptake in denervated muscles in a case of Parsonage-Turner syndrome

BACKGROUND

Parsonage-Turner Syndrome (PTS) is a rare brachial plexopathy characterized by the sudden onset of pain in the shoulder girdle followed by upper limb weakness. PTS is frequently under-recognized or misdiagnosed as other more common neurological disorders presenting in a similar fashion, such as cervical radiculopathy which may require surgical intervention. Accurate diagnosis and prompt management implicate a good prognosis. Although electrophysiological studies are considered the most important for evaluating peripheral nerve injuries, it usually takes time, up to 3 weeks after the initial insult of the nerve for electromyogram (EMG) and nerve conduction studies (NCS) to display abnormalities. In the cases of PTS, especially when initial EMG/NCS and magnetic resonance neurography (MRN) results are inconclusive, ¹⁸ F-FDG positron emission tomography and computed tomography (¹⁸ F-FDG PET-CT) may be useful in helping the early detection of muscle denervation.

CASE PRESENTATION

A 60-year-old right-handed Taiwanese woman presented with sudden onset of intense and sharp left shoulder girdle pain without radiating to the arm, followed by muscle weakness of her left arm in abduction and elevation 3 days after the onset of pain. A detailed neurological examination and EMG and NCS suggested the clinical diagnosis of left brachial plexopathy. MRN imaging revealed no significant abnormality. ¹⁸ F-FDG PET-CT showed increased uptake in denervated muscles (supraspinatus, deltoid, and biceps muscles). Treatment with oral prednisolone and physiotherapy significantly improved pain and muscle weakness.

CONCLUSIONS

We present increased ¹⁸ F-FDG uptake in denervated muscles detected by ¹⁸ F-FDG PET-CT. ¹⁸ F-FDG PET-CT may serve as an adjunct examination to evaluate PTS, which has been suggested previously but rarely reported.

Clinical Spectrum of Postsurgical Parsonage-Turner Syndrome: A Perspective From an Electrodiagnostic Laboratory

BACKGROUND

Parsonage-Turner syndrome (PTS) is an underdiagnosed disorder characterized by the acute onset of severe pain in the shoulder/scapula/arm followed by muscle weakness/numbness in the distribution of nerves derived from the brachial plexus (BP). Surgical procedures are one of several antecedent events of PTS. This study describes the clinical spectrum of postsurgical Parsonage-Turner syndrome (PSPTS) in a large cohort of patients.

MATERIALS AND METHODS

Charts of patients diagnosed with PTS during a 16-year (2006-2022) retrospective review were analyzed to identify cases of PSPTS. The clinical criteria for PSPTS included the new onset of severe pain two days to four weeks after a surgical procedure followed by weakness of muscles innervated by one or more nerves arising from the BP. EDX criteria consist of denervation localized to branches of the BP. PSPTS cases were subdivided into two categories: definite PSPTS (surgery at a remote site) and probable PSPTS (surgery of the ipsilateral upper extremity or the cervical spine).

RESULTS

Of 202 patients (204 episodes) diagnosed with PTS, 111 (54%) were idiopathic and 61 (30%) were PSPTS. Of the 61 PSPTS episodes, 26 were definite and 35 were probable PSPTS. The anterior interosseous nerve (AIN) was most affected, followed by the posterior interosseous (PIN), and suprascapular nerve.

CONCLUSION

In this series, surgery was the most commonly recognized antecedent event for PTS, and the AIN and PIN were the most frequent nerves affected. Surgeons should consider PTS in patients who develop postoperative severe shoulder pain and weakness of muscles innervated by the BP.