Variability in electrodiagnostic findings associated with neurogenic thoracic outlet syndrome

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.

Sports-related peripheral nerve injuries of the upper limb

Peripheral nerve injuries in athletes affect the upper limb more commonly than the lower limb. Common mechanisms include compression, traction, laceration, and ischemia. Specific sports can have unique mechanisms of injury and are more likely to be associated with certain neuropathies. Familiarity with these sport-specific variables and recognition of the common presentations of upper limb neuropathic syndromes are important in assessing an athlete with a suspected peripheral nerve injury. Evaluation may require imaging modalities and/or electrodiagnostic testing to confirm a nerve injury. In some cases, diagnostic injections may be needed to differentiate neuropathic versus musculoskeletal etiology. Early and accurate diagnosis is essential for treatment/management and increases the likelihood of a safe return-to-sport and avoidance of long-term functional consequences. Most nerve injuries can be treated conservatively, however, severe or persistent cases may require surgical intervention. This monograph reviews key diagnostic, management, and preventative strategies for sports-related peripheral nerve injuries involving the upper limb.

Botulinum toxin injections for the treatment of neurogenic thoracic outlet syndrome: A systematic review

Botulinum toxin (BTX) injections into the musculature surrounding the brachial plexus have been examined as a potential treatment for neurogenic thoracic outlet syndrome (nTOS). This systematic review identified 15 publications, of which one was a randomized controlled trial. BTX injections performed with ultrasound or electromyographic guidance, and with the inclusion of the pectoralis minor muscle, in addition to the anterior and/or middle scalenes, tended to provide greater symptom improvement and may predict response to first rib resection. Importantly, most studies were of low quality; thus, the results should be interpreted with caution. Further high-quality studies are needed to confirm these findings.

Upper-limb neurovascular compression, pectoralis minor and quadrilateral space syndromes: A narrative review of current literature

Pectoralis minor syndrome (PMS) and quadrilateral space syndrome (QSS) are uncommon neurovascular compression disorders affecting the upper extremity. PMS involves compression under the pectoralis minor muscle, and QSS results from compression in the quadrilateral space-both are classically observed in overhead-motion athletes. Diagnosing PMS and QSS may be challenging due to variable presentations and similarities with other, more common, upper-limb pathologies. Although there is no gold standard diagnostic, local analgesic muscle-block response in a patient with the appropriate clinical context is often all that is required for an accurate diagnosis after excluding more common etiologies. Treatment ranges from conservative physical therapy to decompressive surgery, which is reserved for refractory cases or severe, acute vascular presentations. Decompression generally yields favorable outcomes, with most patients experiencing significant relief and restored baseline function. In conclusion, PMS and QSS, although rare, can cause debilitating upper-extremity symptoms; accurate diagnosis and appropriate treatment offer excellent outcomes, alleviating pain and disability.

Surgical approaches for thoracic outlet decompression in the treatment of thoracic outlet syndrome

Thoracic outlet syndrome (TOS) is a controversial and uncommon syndrome. Three different diagnoses can be made based on the compressed structure: arterial TOS, venous TOS, and neurogenic TOS. Diagnosing TOS, especially neurogenic TOS, remains difficult since a single diagnostic tool does not exist. Although this resulted in a lot of confusion, standardization of care and outcome improved daily care practice measures in the last decade. Current treatment algorithms consist of both conservative and surgical treatment approaches, which should be chosen depending on the type of TOS and extend of the complaints. Surgical treatment of TOS is performed via thoracic outlet decompression (TOD). TOD surgery includes complete resection of the first rib (cartilage to cartilage), transection of the scalene muscles and complete neurolysis/venolysis or arteriolysis. Four different approaches can be chosen for TOD surgery: the transaxillary (TA), supraclavicular (SC), paraclavicular (PC), and infraclavicular (IC) approach. The TA, SC, and PC approach can be used for every form of TOS. However, the PC approach is mostly used for treating venous TOS. The IC approach has no role in treating neurogenic or arterial TOS and is only used for venous TOS. Every approach has its own benefits and limitations and literature does not agree on what approach is best. Therefore, the used surgical approach for TOD should be based on the surgeon's preference and experience. The aim of this review is to present an overview of the diagnostic pathway and provide an in-depth description of the surgical approach in each form of TOS.

Thoracic outlet syndrome in females: A systematic review

Thoracic outlet syndrome (TOS) is a rare anatomic condition caused by compression of neurovascular structures as they traverse the thoracic outlet. Depending on the primary structure affected by this spatial narrowing, patients present with one of three types of TOS-venous TOS, arterial TOS, or neurogenic TOS. Compression of the subclavian vein, subclavian artery, or brachial plexus leads to a constellation of symptoms, including venous thrombosis, with associated discomfort and swelling; upper extremity ischemia; and chronic pain due to brachial plexopathy. Standard textbooks have reported a predominance of females patients in the TOS population, with females comprising 70%. However, there have been few comparative studies of sex differences in presentation, treatment, and outcomes for the various types of TOS.

Diagnosis of thoracic outlet syndrome with the lower trunk compression of brachial plexus by high-frequency ultrasonography

BACKGROUND

Thoracic outlet syndrome (TOS) with the lower trunk compression of brachial plexus (BP) is difficult to diagnosis. This study aimed to summarize the features of thoracic outlet syndrome (TOS) with the lower trunk compression of brachial plexus observed on high-frequency ultrasonography (HFUS).

METHODS

The ultrasound data of 27 patients who had TOS with the lower trunk compression of brachial plexus were collected and eventually confirmed by surgery. The imaging data were compared, and the pathogenesis of TOS was analyzed on the basis of surgical data.

RESULTS

TOS occurred predominantly in females (70.4%). Most cases had unilateral involvement (92.6%), mainly on the right side (66.7%). The HFUS features of TOS can be summarized as follows: (1) Lower trunk compression. HFUS revealed focal thinning that reflected compression at the level of the lower trunk; furthermore, the distal part of the nerve was thickened for edema (Affected side: 0.49 ± 0.12 cm vs. Healthy side: 0.38 ± 0.06, P = 0.009), and the cross-sectional area of brachial plexus cords was markedly greater on the injured side than on the healthy side (0.95 ± 0.08 cm² vs. 0.65 ± 0.11 cm², P = 0.004). (2) Hyperechoic fibromuscular bands behind the compressed nerve (mostly the scalenus minimus muscle). (3) Abnormal bony structures: cervical ribs or elongated transverse processes of the 7th cervical vertebra (C7). Surgical results showed that the etiological factors contributing to TOS were (1) muscle hypertrophy and/or fibrosis (100%) and (2) cervical ribs/elongated C7 transverse processes (20.7%).

CONCLUSION

TOS with the lower trunk compression of brachial plexus can be diagnosed accurately and reliably by high-frequency ultrasound.

Rapid Functional Recovery After Thoracic Outlet Decompression in a Series of Adolescent Athletes With Chronic Atraumatic Shoulder-Girdle Pain, Scapular Winging/Dyskinesis, and Normal Electrodiagnostic Studies

BACKGROUND

Spontaneous shoulder-girdle pain and scapular winging/dyskinesis can be caused by several neuromuscular disorders identifiable by electrodiagnostic studies (EDX). We describe a group of adolescent athletes with this clinical presentation but normal EDX, followed by later development of neurogenic thoracic outlet syndrome (NTOS).

METHODS

We identified patients referred for evaluation of NTOS that had a history of chronic atraumatic shoulder-girdle pain, scapular winging/dyskinesis, and normal EDX. Each was refractory to conservative management and underwent supraclavicular decompression and brachial plexus neurolysis for NTOS. Functional disability was quantified by Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) scores.

RESULTS

There were 5 female patients with a mean age at symptom onset of 14.2 ± 0.4 years, including spontaneous severe pain in the shoulder, scapula, and arm, along with prominent scapular winging/dyskinesis, and normal EDX. Symptoms had persisted for 18.9 ± 4.0 months prior to referral, with pronounced upper extremity disability (mean QuickDASH, 54.6 ± 6.9). By 3 months after surgical treatment for NTOS, all 5 patients experienced near-complete symptom resolution, including scapular winging/dyskinesis, with markedly improved function (mean QuickDASH, 2.2 ± 1.3) and a return to normal activity.

CONCLUSIONS

A subset of patients with chronic atraumatic shoulder-girdle pain, scapular winging/dyskinesis, and normal EDX may develop dynamic brachial plexus compression characteristic of NTOS, exhibiting an ischemic "Sunderland-zero" nerve conduction block for which surgical decompression can result in rapid and substantial clinical improvement. The presence of surgically treatable NTOS should be considered for selected patients with long-standing scapular winging/dyskinesis who fail conservative management.

General Overview and Diagnostic (Imaging) Techniques for Neurogenic Thoracic Outlet Syndrome

Thoracic outlet syndrome is an uncommon and controversial syndrome. Three different diagnoses can be made based on the compressed structure, arterial TOS, venous TOS, and neurogenic TOS, though combinations do exist as well. Diagnosing NTOS is difficult since no specific objective diagnostic modalities exist. This has resulted in a lot of controversy in recent decades. NTOS remains a clinical diagnosis and is mostly diagnosed based on the exclusion of an extensive list of differential diagnoses. To guide the diagnosis and treatment of TOS, a group of experts published the reporting standards for TOS in 2016. However, a consensus was not reached regarding a blueprint for a daily care pathway in this document. Therefore, we constructed a care pathway based on the reporting standards for both the diagnosis and treatment of NTOS patients. This care pathway includes a multidisciplinary approach in which different diagnostic tests and additional imaging techniques are combined to diagnose NTOS or guide patients in their treatment for differential diagnoses. The aim of the present work is to discuss and explain the diagnostic part of this care pathway.

Relationships between the Clinical Test Results and Neurophysiological Findings in Patients with Thoracic Outlet Syndrome

A thoracic outlet syndrome (TOS) is the type of brachial plexus disorder most difficult to objectively assess using a clinical examination and differential diagnosis. Its symptoms can be frequently misdiagnosed, especially among others with cervical disc-root conflicts, plexopathies, and peripheral neuropathies. In this study, we aim to identify the correlations between positive Doppler ultrasonography results indicating pathological changes in the subclavian flow velocity, clinical tests, and chosen clinical neurophysiology recordings as proposed alternative or supplementary diagnostic tools for evaluating TOS patients. Sixty TOS patients with positive Doppler ultrasonography and Roos test results and sixty healthy people as a control group were bilaterally examined, and the results were compared. Pain intensity was assessed using a visual analogue scale (VAS). Sensory perceptions within C4–C8 dermatomes were assessed with Von Frey filament (FvF) tests. The activity of motor units in the proximal and distal muscles of the upper extremities was evaluated using surface electromyography (sEMG) during maximal contractions before and after a provocative raised hands test (RHT). An electroneurography (ENG) was used to evaluate the transmission of nerve impulses peripherally. Motor evoked potential (MEP) recordings, induced by the over-vertebral magnetic stimulation of the C5–C7 neuromeres, were used to examine motor transmissions from the cervical motor centres to the upper extremities muscles. The results revealed a relationship between positive Doppler test scores and pathological changes in the subclavian flow velocity through the results of the following diagnostic tools: a VAS score of 1.9 was detected on average, superficial sensory perception abnormalities were found in the innervation areas of the ulnar nerves detected by FvF tests, a decrease in the amplitudes of sEMG recordings was seen in distal rather than proximal muscles (especially following the RHT), a decrease in the motor and sensory peripheral transmissions of nerve impulses in the median, ulnar and cutaneous anterobrachial median nerves was seen, as well as MEP amplitudes recorded from the abductor pollicis brevis muscle. The provocative RHT combined with sEMG and MEP recordings can be considered accurate and objective clinical neurophysiology tools that could supplement the commonly used clinical tests. Such an approach may result in a more precise neurogenic TOS diagnostic algorithm.

Use of Electroneuromyography in the Diagnosis of Neurogenic Thoracic Outlet Syndrome: A Systematic Review and Meta-Analysis

Neurogenic thoracic outlet syndrome (NTOS) is a disabling condition. Its diagnosis remains challenging and is mainly guided by examination. Yet, electrophysiological evaluations are the gold standard for diagnosis of entrapment syndromes. We aimed to assess the interest of electrophysiological evaluation to diagnose NTOS. A systematic literature research was performed using PubMed, ScienceDirect, Embase, Cochrane and Google Scholar databases to collect studies reporting results of electrophysiological assessment of patients with NTOS. Then, a meta-analysis was conducted. Nine studies were eligible and concerned two hundred and thirteen patients. Results were heterogenous among studies and the quality of evidence was very low to moderate. Data could not evaluate sensitivity or specificity of electrophysiological evaluations for NTOS. The meta-analysis found significantly decreased amplitudes of medial antebrachial cutaneous nerve SNAP (sensory nerve action potential), ulnar SNAP, median CMAP (compound motor action potential) and ulnar CMAP. Needle examination found abnormalities for the abductor pollicis brevis, first dorsal interosseous and adductor digiti minimi. Unlike most upper-limb entrapment syndromes, nerve conduction assessment only provided clues in favour of NTOS. Decreased amplitude for ulnar SNAP, medial antebrachial cutaneous SNAP, median CMAP and ulnar CMAP should be assessed, as well as needle examination. Larger studies are needed to evaluate the sensitivity and specificity of electrophysiology in NTOS diagnosis.