Hourglass-like constrictions on MRI are common in electromyography-confirmed cases of neuralgic amyotrophy (Parsonage-Turner syndrome): A tertiary referral center experience.

INTRODUCTION/AIMS: Hourglass-like constrictions (HGCs) of involved nerves in neuralgic amyotrophy (NA) (Parsonage-Turner syndrome) have been increasingly recognized with magnetic resonance neurography (MRN). This study sought to determine the sensitivity of HGCs, detected by MRN, among electromyography (EMG)-confirmed NA cases. METHODS: This study retrospectively reviewed records of patients with the clinical diagnosis of NA, and with EMG confirmation, who underwent 3-Tesla MRN within 90 days of EMG at a single tertiary referral center between 2011 and 2021. "Severe NA" positive cases were defined by a clinical diagnosis and specific EMG criteria: fibrillation potentials or positive sharp waves, along with motor unit recruitment (MUR) grades of "discrete" or "none." On MRN, one or more HGCs, defined as focally decreased nerve caliber or diffusely beaded appearance, was considered "imaging-positive." Post hoc inter-rater reliability for HGCs was measured by comparing the original MRN report against subsequent blinded interpretation by a second radiologist. RESULTS: A total of 123 NA patients with 3-Tesla MRN performed within 90 days of EMG were identified. HGCs were observed in 90.2% of all NA patients. In "severe NA" cases, based on the above EMG criteria, HGC detection resulted in a sensitivity of 91.9%. Nerve-by-nerve analysis (183 nerve-muscle pairs, nerves assessed by MRN, muscles assessed by EMG) showed a sensitivity of 91.0%. The second radiologist largely agreed with the original HGC evaluation, (94.3% by subjects, 91.8% by nerves), with no significant difference between evaluations (subjects: χ2 = 2.27, P = .132, nerves: χ2 = 0.98, P = .323). DISCUSSION: MRN detection of HGCs is common in NA.

Quantitative T2 -mapping magnetic resonance imaging for assessment of muscle motor unit recruitment patterns.

INTRODUCTION: In this study, we aimed to determine whether muscle transverse relaxation time (T2 ) magnetic resonance (MR) mapping results correlate with motor unit loss, as defined by motor unit recruitment patterns on electromyography (EMG). METHODS: EMG and 3-Tesla MRI exams were acquired no more than 31 days apart in subjects referred for peripheral nerve MRI. Two musculoskeletal radiologists qualitatively graded T2 -weighted, fat-suppressed sequences for severity of muscle edema-like patterns and manually placed regions of interest within muscles to obtain T2 values from T2 -mapping sequences. Concordance was calculated between qualitative and quantitative MR grades and EMG recruitment categories (none, discrete, decreased) as well as interobserver agreement for both MR grades. RESULTS: Thirty-four muscles (21 abnormal, 13 control) were assessed in 13 subjects (5 females and 8 males; mean age, 46 years) with 14 EMG-MRI pairs. T2 -relaxation times were significantly (P < .001) increased in all EMG recruitment categories compared with control muscles. T2 differences were not significant between EMG grades of motor unit recruitment (P = .151-.702). T2 and EMG score concordance was acceptable (Harrell's concordance index [c index]: rater A, 0.71; 95% confidence interval [CI], 0.51-0.87; rater B, 0.77; 95% CI, 0.57-0.91). Qualitative MRI and EMG score concordance was poor to acceptable (c index: rater A, 0.60; 95% CI, 0.50-0.79; rater B, 0.72; 95% CI, 0.55-0.89). T2 values had moderate-to-substantial ability to distinguish between absent vs incomplete (ie, decreased or discrete) motor unit recruitment (c index: rater A, 0.78; 95% CI, 0.50-1.00; rater B, 0.86; 95% CI, 0.57-1.00). DISCUSSION: Quantitative T2 MR muscle mapping is a promising tool for noninvasive evaluation of the degree of motor unit recruitment loss.

Surgical Treatment of Iatrogenic Nerve Injury Following Arthroscopic Capsulolabral Repair.

PURPOSE: Case reports of nerve injuries following arthroscopic capsulolabral repair emphasize the proximity of major nerves to the glenoid. This study describes preoperative localization using nerve-sensitive magnetic resonance imaging in a small cohort of patients with iatrogenic nerve injuries following arthroscopic capsulolabral repair and the outcomes of nerve repair in these patients. METHODS: Cases of iatrogenic nerve injury following arthroscopic capsulolabral repair referred to 2 surgeons from January 2017 to December 2019 were identified. Clinical charts, electrodiagnostic testing, magnetic resonance imaging studies, and operative reports were reviewed. RESULTS: Four cases of iatrogenic nerve injury were identified. The time to presentation to our institution ranged from 2 weeks to 8 years. The axillary nerves in 3 cases were tethered by a suture at the inferior glenoid, whereas 1 case had a suture tied around the radial and median nerves inferior to the glenohumeral joint capsule. One case underwent excision and nerve transfer, 1 underwent excision and nerve repair, and 2 underwent suture removal and neurolysis. Open and arthroscopic approaches, including a recently described approach to the axillary nerve in the "blind zone," were used. Three cases demonstrated good recovery of all affected motor and sensory functions after surgery. At the 10-month follow-up, 1 case had persistent weakness, but there was evidence of axonal regeneration on electrodiagnostic testing. CONCLUSIONS: Arthroscopic capsulolabral repair places regional nerves, particularly the axillary nerve, at risk owing to their proximity to the joint capsule and inferior glenoid. Patients with neuropathic pain in the distribution of affected nerves with corresponding sensorimotor loss following arthroscopic capsulolabral surgery should undergo focused magnetic resonance imaging with nerve-sensitive sequences and electrodiagnostic testing to localize the injury. The use of multiple surgical windows to the axillary nerve in the "blind zone" enables full visualization for neurolysis, suture removal, and nerve repair or transfer. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

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.

Fascicular constrictions above elbow typify anterior interosseous nerve syndrome.

INTRODUCTION: In this study we tested the hypothesis that fascicular constrictions (FCs) of the median nerve proximal to the elbow joint characterize anterior interosseous nerve syndrome (AINS). METHODS: Magnetic resonance neurography (MRN) and ultrasound (US) examinations were evaluated in 45 patients with clinically suspected AINS. All 22 patients at site 1 underwent MRN and 8 underwent US; all 23 patients at site 2 underwent US. RESULTS: Median nerve FCs were identified in all MRN cases; FCs and/or fascicular enlargements were identified in 88% of US cases. Most FCs were in the mediannerve posterior/posteromedial region and were proximal to the elbow joint line (mean distance: MRN, 5.4 cm; US, 7.5 cm), with the exception of a single FC (located 1 cm distal). No extrinsic compression of median or anterior interosseous nerves was identified in the arm or forearm. DISCUSSION: AINS is a noncompressive neuropathy characterized by median nerve FCs in the arm.

Ultrasound imaging of brachial plexus trauma in gunshot injury.

INTRODUCTION: Brachial plexus trauma related to gunshot (GS) injury requires early examination and characterization to ensure appropriate treatment. Magnetic resonance imaging (MRI) may be contraindicated when there are metal fragments in a patient's body. Ultrasound (US) may present an alternative to imaging GS-related brachial plexus injury. METHODS: Three patients with GS-related brachial plexus injury who underwent US imaging evaluation at our institution were identified. A retrospective review of the patients' medical records was performed. RESULTS: US characterization of nerve abnormalities after GS injury to the brachial plexus was in agreement with electrodiagnostic and intraoperative findings. DISCUSSION: Information from the US reports was useful in preparation for brachial plexus reconstruction surgery. As such, US has unique utility when MRI cannot be performed. US imaging can provide useful characterization of the brachial plexus after GS injury when performed by an experienced operator. Muscle Nerve 59:707-711, 2019.

Electrodiagnostic evidence of suprascapular nerve recovery after decompression.

INTRODUCTION: The purpose of this study was to determine whether surgical arthroscopic decompression or ultrasound-guided aspiration of a paralabral cyst would result in suprascapular nerve recovery from axonal regeneration based on electrodiagnostic testing. METHODS: Nine patients with preoperative electromyography (EMG) evidence of suprascapular neuropathy due to paralabral cysts at the suprascapular or spinoglenoid notch were prospectively studied. Eight patients underwent arthroscopic surgical decompression, and 1 patient underwent ultrasound-guided aspiration. Postoperative EMG was performed in all patients to evaluate nerve regeneration. RESULTS: Three (33%) patients had cysts at the suprascapular notch, whereas 6 (67%) patients had cysts at the spinoglenoid notch. All patients showed complete electrophysiological recovery after decompression. DISCUSSION: Decompression of paralabral cysts at the suprascapular or spinoglenoid notch resulted in postoperative EMG evidence of nerve recovery. Long-term studies with a greater number of patients are required to elucidate time to recovery. Muscle Nerve 59:247-249, 2019.

A Comparison Between Two Collagen Nerve Conduits and Nerve Autograft: A Rat Model of Motor Nerve Regeneration.

PURPOSE: To compare recovery in a rat model of sciatic nerve injury using a novel polyglycolic acid (PGA) conduit, which contains collagen fibers within the tube, as compared with both a hollow collagen conduit and nerve autograft. We hypothesize that a conduit with a scaffold will provide improved nerve regeneration over hollow conduits and demonstrate no significant differences when compared with autograft. METHODS: A total of 72 Sprague-Dawley rats were randomized into 3 experimental groups, in which a unilateral 10-mm sciatic defect was repaired using either nerve autograft, a hollow collagen conduit, or a PGA collagen-filled conduit. Outcomes were measured at 12 and 16 weeks after surgery, and included bilateral tibialis anterior muscle weight, voltage and force maximal contractility, assessment of ankle contracture, and nerve histology. RESULTS: In all groups, outcomes improved between 12 and 16 weeks. On average, the autograft group outperformed both conduit groups, and the hollow conduit demonstrated improved outcomes when compared with the PGA collagen-filled conduit. Differences in contractile force, however, were significant only at 12 weeks (autograft > hollow collagen conduit > PGA collagen-filled conduit). At 16 weeks, contractile force demonstrated no significant difference but corroborated the same absolute results (autograft > hollow collagen conduit > PGA collagen-filled conduit). CONCLUSIONS: Nerve repair using autograft provided superior motor nerve recovery over the 2 conduits for a 10-mm nerve gap in a murine acute transection injury model. The hollow collagen conduit demonstrated superior results when compared with the PGA collagen-filled conduit. CLINICAL RELEVANCE: The use of a hollow collagen conduit provides superior motor nerve recovery as compared with a PGA collagen-filled conduit.

MRI of Foot Drop: How We Do It.

Various pathologic conditions extending from the lumbar and pelvic regions to the lower leg may manifest as foot drop, or weakness of ankle dorsiflexion. Potential causes of foot drop include L5 radiculopathy, lumbosacral plexopathy, sciatic neuropathy, and peroneal neuropathy. Although the first-line test in lesion localization is most commonly electrodiagnostic testing, MR neurography has emerged as a useful tool to verify lesion site, to accurately characterize the cause of the neuropathy, and to guide patient treatment. MR neurography, when tailored and focused, can help overcome potential pitfalls in clinical and electrodiagnostic evaluation and is commonly performed in the authors' practice. MR neurography studies are protocoled in advance after careful review of clinical notes and electrodiagnostic findings and often after discussion with the referring clinician. Radiologists who interpret MR neurography studies should have a sound understanding not only of peripheral nerve anatomy and common pathologic conditions, but also of the clinical and electrodiagnostic evaluation performed in patients with foot drop. In this way, the radiologist can actively guide the referring clinician in ordering the most appropriate imaging examination, efficiently reaching the correct diagnosis, and deciding appropriate treatment.

Brachial plexitis or neuritis? MRI features of lesion distribution in Parsonage-Turner syndrome.

INTRODUCTION: This study seeks to characterize lesion distribution in Parsonage-Turner Syndrome (PTS) using high-resolution MRI. METHODS: MRIs of 27 patients with clinically confirmed PTS were reviewed. Two radiologists independently evaluated the brachial plexus proper, side and terminal plexus branches, and more distal, upper extremity nerves. RESULTS: All patients had at least 1 clinically involved nerve. MRI revealed that the plexus appeared normal in 24 of 27 patients; in 3 other patients, signal hyperintensity was seen immediately proximal to the take-off of abnormal side or terminal branch nerves. Focal intrinsic constrictions were detected in 32 of 38 nerves. MRI interobserver agreement was high (Cohen's κ = 0.839). DISCUSSION: MRI findings, corroborated by electrodiagnostic testing, localized abnormalities to plexus branches and peripheral nerves, suggesting that PTS is characterized by 1 or more mononeuropathies rather than changes involving a portion of or the complete plexus proper. These results may improve diagnosis, prognostication, and management. Muscle Nerve 58: 359-366, 2018.

The electrodiagnostic natural history of parsonage-turner syndrome.

INTRODUCTION: Recovery from Parsonage-Turner syndrome (PTS) is generally favorable, although recovery times have been shown to vary, in part because there are no universally accepted outcome measures. In this study, we describe the electrodiagnostic natural history of this condition based on objective electrodiagnostic testing, and propose that complete electrodiagnostic recovery can be seen as early as 1 year. METHODS: Twenty-six subjects with 29 affected nerves confirmed as PTS were followed every 3 months for electrodiagnostic testing, or until full reinnervation was confirmed. RESULTS: Twenty-three cases (79.3%) demonstrated electrodiagnostic evidence of initial recovery at a mean of 5.8 months. Nine cases (31%) showed complete electrodiagnostic recovery at a mean of 1 year. When excluding cases with <1 year of follow-up, 52.9% achieved complete electrodiagnostic recovery. CONCLUSIONS: In contrast to previous reports, full electrodiagnostic recovery of PTS was demonstrated at a mean of 1 year in > 50% of patients with longer term follow-up. Muscle Nerve 56: 737-743, 2017.

MRI bullseye sign: An indicator of peripheral nerve constriction in parsonage-turner syndrome.

INTRODUCTION: The role of MRI in identifying hourglass constrictions (HGCs) of nerves in Parsonage-Turner syndrome (PTS) is largely unknown. METHODS: Six patients with PTS and absent or minimal recovery underwent MRI. Surgical exploration was performed at identified pathologic sites. RESULTS: The time between symptom onset and surgery was 12.4 ± 6.9 months; the time between MRI and surgery was 1.3 ± 0.6 months. Involved nerves included suprascapular, axillary, radial, and median nerve anterior interosseous and pronator teres fascicles. Twenty-three constriction sites in 10 nerves were identified on MRI. A "bullseye sign" of the nerve, identified immediately proximal to 21 of 23 sites, manifested as peripheral signal hyperintensity and central hypointensity orthogonal to the long axis of the nerve. All constrictions were confirmed operatively. CONCLUSIONS: In PTS, a bullseye sign on MRI can accurately localize HGCs, a previously unreported finding. Causes of HGCs and the bullseye sign are unknown. Muscle Nerve 56: 99-106, 2017.

Pins and Needles From Fingers to Toes: High-Resolution MRI of Peripheral Sensory Mononeuropathies.

OBJECTIVE: The purpose of this article is to review advanced MRI techniques and describe the MRI findings of pure sensory mononeuropathy with relevant clinical and anatomic correlation. CONCLUSION: Peripheral sensory mononeuropathy can be challenging to evaluate with MRI because of the small caliber of pure sensory nerves and the lack of changes in secondary muscular denervation. Advances in MRI afford the necessary signal-intensity contrast and resolution for adequate evaluation of many of these small peripheral nerves.

Rhabdomyolysis resulting in concurrent Horner's syndrome and brachial plexopathy: a case report.

This case report describes a 29-year-old male who presented with immediate onset of Horner's syndrome and ipsilateral brachial plexopathy after sleeping with his arm dangling outside a car window for 8 h. Outside workup and imaging revealed rhabdomyolysis of the left neck musculature. Subsequent electrodiagnostic testing and high-resolution brachial plexus magnetic resonance imaging at the authors' institution attributed the Horner's syndrome and concurrent brachial plexopathy to rhabdomyolysis of the longus colli and scalene musculature, which had compressed-and consequently scar tethered-the cervical sympathetic trunk and brachial plexus. This case of co-existent Horner's syndrome and brachial plexopathy demonstrates the role of high-resolution brachial plexus MRI in diagnosing plexopathy and the importance of being familiar with plexus and paravertebral muscle anatomy.

Magnetic resonance imaging patterns of mononeuropathic denervation in muscles with dual innervation.

Magnetic resonance imaging (MRI) of mononeuropathy in muscles with dual innervation depicts geographic denervation corresponding to the affected nerve. Knowledge of the normal distribution of a muscle's neural supply is clinically relevant as partial muscle denervation represents a potential imaging pitfall that can be confused with other pathology, such as muscle strain. This article reviews the normal innervation pattern of extremity muscles with dual supply, providing illustrative examples of mononeuropathy affecting such muscles.

Shoulder and Elbow Recovery at 2 and 11 Years Following Brachial Plexus Reconstruction.

PURPOSE: To report short-term and long-term outcomes on a single patient cohort observed longitudinally after nerve reconstruction for adult brachial plexus injury. METHODS: Eleven male patients who underwent plexus reconstruction by the same surgeon at 2 institutions presented for clinical examination 7.5 or more years after surgery (average, 11.4 years; range, 7.5-22 years). Average age at the time of operation was 35 years (range, 17-73 years). Mean delay until surgery was 5 months (range, 2-11 months). Two patients had C5 paralysis, 2 had C5-C6 paralysis, 2 had C5-C7 paralysis, and 5 had complete 5-level injuries. Outcome parameters included active range of motion (ROM) in degrees, a modified British Medical Research Council (mBMRC) scale for muscle strength, and electromyographic motor unit configuration and recruitment pattern. Differences in ROM and mBMRC between 2-year and long-term follow-up were assessed with paired-sample t tests using an alpha value of .05. RESULTS: Average shoulder abduction and mBMRC at final follow-up were both significantly improved compared with the 2-year follow-up results (P < .05). Average elbow flexion and mBMRC increased significantly between 2 years and final follow-up (P < .05). Electromyographic results for 6 patients at final follow-up showed improved motor unit configuration in 10 of 15 muscles and improved recruitment in 3 of 15 muscles compared with 2-year electromyographic results. CONCLUSIONS: Patients continued to gain ROM and strength in the shoulder and elbow well after 2 to 3 years after surgery, contrary to previous reports. Although the precise mechanism is unknown, we speculate that a number of factors may be involved, including terminal collateral sprouting, maturation of motor units, improvements in motor unit recruitment, additional muscle fiber hypertrophy, or an as-yet undescribed mechanism. We recommend that patients be encouraged to continue strengthening exercises well after the initial recovery period and that more comparative long-term data be collected to expand on these observations.

Long-nerve grafts and nerve transfers demonstrate comparable outcomes for axillary nerve injuries.

PURPOSE: To compare the functional and EMG outcomes of long-nerve grafts to nerve transfers for complete axillary nerve palsy. METHODS: Over a 10-year period at a single institution, 14 patients with axillary nerve palsy were treated with long-nerve grafts and 24 patients were treated with triceps-to-axillary nerve transfers by the same surgeon (S.W.W.). Data were collected prospectively at regular intervals, beginning before surgery and continuing up to 11 years after surgery. Prior to intervention, all patients demonstrated EMG evidence of complete denervation of the deltoid. Deltoid recovery (Medical Research Council [MRC] grade), shoulder abduction (°), improvement in shoulder abduction (°), and EMG evidence of deltoid reinnervation were compared between cohorts. RESULTS: There were no significant differences between the long-nerve graft cohort and the nerve transfer cohort with respect to postoperative range of motion, deltoid recovery, improvement in shoulder abduction, or EMG evidence of deltoid reinnervation. CONCLUSIONS: These data demonstrate that outcomes of long-nerve grafts for axillary nerve palsy are comparable with those of modern nerve transfers and question a widely held belief that long-nerve grafts do poorly. When healthy donor roots or trunks are available, long-nerve grafts should not be overlooked as an effective intervention for the treatment of axillary nerve injuries in adults with brachial plexus injuries. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.

Preoperative donor nerve electromyography as a predictor of nerve transfer outcomes.

PURPOSE: We hypothesized that health of the donor nerve and corresponding muscle, as assessed by electromyography (EMG), could predict the outcome of nerve transfer surgery. METHODS: A retrospective review was performed to investigate outcomes of nerve transfers for elbow flexion and shoulder abduction. Motor strength was graded preoperatively and after a minimum 1-year follow-up. Preoperative EMG results were classified as functionally normal or affected based on motor unit recruitment pattern and correlated with follow-up motor strength and range of motion. RESULTS: Forty nerve transfers were identified: 27 were performed for elbow flexion and 13 for shoulder abduction. Overall, the 29 transfers in the normal EMG cohort showed significantly greater postoperative improvement in motor strength (Medical Research Council grade 0.2-4.1) than the 11 transfers in the affected EMG cohort (grade 0.0-3.0). In the shoulder cohort, normal donor nerves resulted in greater strength (grade 4.0 vs. 2.4) and active motion (83° vs. 25°) compared with affected donor nerves. Double fascicular transfers with 2 normal donor nerves demonstrated improved strength compared with double nerve transfers when 1 donor nerve was affected (grade 4.5 vs. 3.2). CONCLUSIONS: Our findings demonstrate that a simple EMG classification that describes the quality of donor nerves can predict outcome as measured by postoperative motor strength and range of motion. Preoperative EMG evaluation should be considered a valuable supplementary component of the donor nerve selection process when planning brachial plexus reconstruction. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic II.