Diagnostic value and surgical implications of the magnetic resonance imaging in the management of adult patients with brachial plexus pathologies

An optimized 1.5 Tesla MRI protocol of the brachial plexus

PURPOSE

Creating an effective MRI protocol for examining the brachial plexus poses significant challenges, and despite the abundance of protocols in the literature, there is a lack of reference standards for basic sequences and essential parameters needed for replication. The aim of this study is to establish a reproducible 1.5 T brachial plexus imaging protocol, including patient positioning, coil selection, imaging planes, and essential sequence parameters.

METHODS

We systematically investigated MRI sequences, testing each parameter through in vivo experiments, examining their effects on signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), visual quality scores, and acquisition time. Sequences were refined based on optimal quality and timing scores. The final protocol was tested on scanners from two other vendors for reliability.

RESULTS

The final protocol included a combination of 2D turbo-spin-echo and 3D SPACE T1, SPACE STIR, and VIBE DIXON sequences. Recommendations for imaging planes, phase encoding, field of view, TR, TE, resolution, number of slices, slice thickness, fat and blood suppression, and acceleration strategies are provided. The protocol was successfully translated to other vendor's scanners with comparable quality.

CONCLUSION

We present an optimized protocol detailing the essential parameters for reproducibility. Our comprehensive list of experiments describes the impact of each parameter on image quality and scan time, addressing common artifacts and potential solutions. This protocol can benefit both young radiologists new to the field and experienced professionals seeking to refine their existing protocols.

Diagnostic accuracy of imaging studies for diagnosing root avulsions in post-traumatic upper brachial plexus traction injuries in adults

BACKGROUND

There is no consensus about which type of imaging study, computed tomography myelography (CTM) or magnetic resonance imaging (MRI), provides better information concerning root avulsion in adult brachial plexus injuries.

METHODS

Patients with upper brachial plexus traumatic injuries underwent both CTM and MRI and surgical exploration. The imaging studies were analyzed by two independent radiologists and the data were compared with the intraoperative findings. The statistical analysis was based on dichotomous classification of the nerve roots (normal or altered). The interobserver agreement was assessed using Cohen's Kappa. The accuracy of CTM and MRI in comparison with the intraoperative findings was evaluated using the same methodology.

RESULTS

Fifty-two adult patients were included. CTM tended to yield slightly higher percentages of alterations than MRI The interobserver agreement was better on CTM than on MRI for all nerve roots: C5, 0.9960 (strong) vs. 0.145 (poor); C6, 0.970 (strong) vs. 0.788 (substantial); C7, 0.969 (strong) vs. 0.848 (strong). The accuracy regarding the intraoperative findings was also higher on CTM (moderate, kappa 0.40-0.59) than on MRI (minimal, kappa 0.20-0.39) for all nerve roots. Accordingly, the overall percentage concordance (both normal or both altered) was superior in the CTM evaluation (approx. 70-75% vs. 60-65%). CTM was superior for both sensitivity and specificity at all nerve roots.

CONCLUSION

CTM had greater interobserver agreement and higher diagnostic accuracy than MRI in adult patients with root avulsions due to brachial plexus injury.

Diagnostic accuracy of MRI for traumatic adult brachial plexus injury: A comparison study with surgical findings

We studied the diagnostic accuracy of MRI in 35 adult patients with traumatic brachial plexus injury in comparison with intra operative findings. The overall sensitivity to detect root avulsions was 39% and specificity was 75%. MRI was more useful in the diagnosis of lower root avulsions. At trunk and division level injuries, the sensitivity was 87% but specificity was only 26%. It was not able to differentiate the type and extent of post-ganglionic injuries. The accuracy of pseudomeningocele as avulsion on surgical finding was 96% (27/28). Pseudomeningocele correlates well with root avulsions. Its presence warrants early referral and surgical exploration.

MR Imaging of Brachial Plexus and Limb-Girdle Muscles in Patients with Amyotrophic Lateral Sclerosis

PURPOSE

To assess brachial plexus magnetic resonance (MR) imaging features and limb-girdle muscle abnormalities as signs of muscle denervation in patients with amyotrophic lateral sclerosis (ALS).

MATERIALS AND METHODS

This study was approved by the local ethical committees on human studies, and written informed consent was obtained from all subjects before enrollment. By using an optimized protocol of brachial plexus MR imaging, brachial plexus and limb-girdle muscle abnormalities were evaluated in 23 patients with ALS and clinical and neurophysiologically active involvement of the upper limbs and were compared with MR images in 12 age-matched healthy individuals. Nerve root and limb-girdle muscle abnormalities were visually evaluated by two experienced observers. A region of interest-based analysis was performed to measure nerve root volume and T2 signal intensity. Measures obtained at visual inspection were analyzed by using the Wald χ(2) test. Mean T2 signal intensity and volume values of the regions of interest were compared between groups by using a hierarchical linear model, accounting for the repeated measurement design.

RESULTS

The level of interrater agreement was very strong (κ = 0.77-1). T2 hyperintensity and volume alterations of C5, C6, and C7 nerve roots were observed in patients with ALS (P < .001 to .03). Increased T2 signal intensity of nerve roots was associated with faster disease progression (upper-limb Medical Research Council scale progression rate, r = 0.40; 95% confidence interval: 0.001, 0.73). Limb-girdle muscle alterations (ie, T2 signal intensity alteration, edema, atrophy) and fat infiltration also were found, in particular, in the supraspinatus muscle, showing more frequent T2 signal intensity alterations and edema (P = .01) relative to the subscapularis and infraspinatus muscles.

CONCLUSION

Increased T2 signal intensity and volume of brachial nerve roots do not exclude a diagnosis of ALS and suggest involvement of the peripheral nervous system in the ALS pathogenetic cascade. MR imaging of the peripheral nervous system and the limb-girdle muscle may be useful for monitoring the evolution of ALS and distinguishing patients with ALS from those with inflammatory neuropathy, respectively.

Accuracy of MRI in diagnosing peripheral nerve disease: a systematic review of the literature

OBJECTIVE

MRI is increasingly being used to evaluate extracranial peripheral nerve disease in clinical practice. The objective of this study was to systematically review the accuracy of MRI in distinguishing normal from abnormal extracranial peripheral nerves.

CONCLUSION

There is significant heterogeneity between studies investigating the accuracy of MRI. Studies have shown that nerve T2-weighted or STIR hyperintensity, nerve enlargement, and nerve flattening are associated with peripheral nerve disease.

Topographic pattern of the brachial plexus at the axillary fossa through real-time ultrasonography in Koreans

Background

The ability to explore the anatomy has improved our appreciation of the brachial anatomy and the quality of regional anesthesia. Using real-time ultrasonography, we investigated the cross-sectional anatomy of the brachial plexus and of vessels at the axillary fossa in Koreans.

Methods

One hundred and thirty-one patients scheduled to undergo surgery in the region below the elbow were enrolled after giving their informed written consent. Using the 5-12 MHz linear probe of an ultrasound system, we examined cross-sectional images of the brachial plexus in the supine position with the arm abducted by 90°, the shoulder externally rotated, and the forearm flexed by 90° at the axillary fossa. The results of the nerve positions were expressed on a 12-section pie chart and the numbers of arteries and veins were reported.

Results

Applying gentle pressure to prevent vein collapse, the positions of the nerves changed easily and showed a clockwise order around the axillary artery (AA). The most frequent positions were observed in the 10-11 section (79.2%) for the median, 1-2 section (79.3%) for the ulnar, 3-5 section (78.4%) for the radial, and 8-9 section (86.9%) for the musculocutaneous nerve. We also noted anatomical variations consisting of double arteries (9.2%) and multiple axillary veins (87%).

Conclusions

Using real-time ultrasonography, we found that the anatomical pattern of the major nerves in Koreans was about 80% of the frequent position of individual nerves, 90.8% of the single AA, and 87% of multiple veins around the AA.

Management of intrathoracic benign schwannomas of the brachial plexus

Primary tumours of the brachial plexus are rare entities. They usually present as extrathoracic masses located in the supraclavicular region. This report describes two cases of benign schwannomas arising from the brachial plexus with an intrathoracic growth. In the first case the tumour was completely intrathoracic and it was hardly removed through a standard posterolateral thoracotomy. In the second case the tumour presented as a cervicomediastinal lesion and it was resected through a one-stage combined supraclavicular incision followed by left video-assisted thoracoscopic surgery. A brachial plexus tumour should be suspected not only in patients with a supraclavicular or cervicomediastinal mass but also in those with intrathoracic apical lesions. A preoperative magnetic resonance imaging study of brachial plexus should be performed in such cases in order to plan the correct surgical approach.

Pictorial essay: Role of magnetic resonance imaging in evaluation of brachial plexus pathologies

Brachial plexopathies, traumatic and nontraumatic, often present with vague symptoms. Clinical examination and electrophysiological studies are useful but may not localize the lesion accurately. Magnetic resonance imaging (MRI) with its multiplanar imaging capability and soft tissue contrast resolution plays an important role in evaluation of the abnormal brachial plexus.

Ultrasound anatomy of the brachial plexus nerves in the neurovascular bundle at the axilla in patients undergoing upper-extremity block anesthesia

PURPOSE

Familiarity with the localization of the nerves in the neurovascular bundle that constitutes the axillary segment of the brachial plexus (BP) is important when applying ultrasound (US)-guided block anesthesia. Therefore in this study we aimed to delineate the anatomy of the median, radial, and ulnar nerves of the BP at the axilla with US and electrical stimulation.

MATERIALS AND METHODS

The study included 60 patients who were scheduled to undergo upper-arm surgery with axillary block anesthesia. Prior to anesthesia, ulnar, radial, and median nerves were localized with US using a 12-h quadrant identification system that placed the axillary artery (AA) in the middle. The nerves were then functionally tested using a neurostimulator.

RESULTS

The radial nerve was mainly located in the 4-6 o'clock arc (posterior and posteromedial to AA) in 50 (83 %) of patients. Ulnar nerve was mainly at the 12-3 o'clock arc (anteromedial to AA) in 51 (85 %) of patients. Ulnar nerve showed a second peak at 9-10 o'clock quadrant (anterolateral to AA) in 11 % (7) of patients. Median nerve location was most common in the 12 and 9 o'clock arc (anterior and anterolateral to AA) in 53 (88 %) of the patients.

CONCLUSIONS

Ultrasound is a useful tool for depicting BP anatomy in the axillary fossa prior to block anesthesia. Median, ulnar, and radial nerves form a highly consistent triangular pattern around the axillary artery that is easily recognizable with US.

Diagnostic performance of ultrasound in patients with suspected brachial plexus lesions in adults: a multicenter retrospective study with MRI, surgical findings and clinical follow-up as reference standard

PURPOSE

To evaluate brachial plexus ultrasound (US) performance in a large multicenter study.

MATERIALS AND METHODS

The research was approved by the Institutional Review Boards, and all patients gave written informed consent. A multicenter retrospective trial including three centers was performed between March, 2006 and April, 2011. A total of 204 patients who received a brachial plexus ultrasound requested by the referring physician were enrolled: magnetic resonance imaging, surgical findings and clinical follow-up of at least 12 months were used as the reference standard. Sensitivity, specificity with 95 % confidence intervals (CIs), positive predictive value (PPV), pre-test-probability (the prevalence), negative predictive value (NPV), pre- and post- test odds (OR), likelihood ratio for positive results (LH+), likelihood ratio for negative results (LH-), accuracy and post-test probability (post-P) were reported on a per-patient basis.

RESULTS

The overall sensitivity and specificity with 95 % CIs were: 0.76 (0.75-0.97); 0.96 (0.77-0.89). Overall PPV, pre-test probability, NPV, pre-OR, post-OR, LH+, LH-, Accuracy and post-P were: 0.93/0.43/0.84/0.75/0.75/13.4/17.6/0.25/0.88/0.93, respectively.

CONCLUSIONS

The specificity of brachial plexus US in patients suspected of having a brachial plexus lesion is very high.

Obstetric brachial plexus lesions: CT myelography

PURPOSE

To evaluate the value of computed tomographic (CT) myelography in the detection of root damage and differentiation of root avulsions from neurotmesis in a large cohort of patients with an obstetric brachial plexus lesion (OBPL).

MATERIALS AND METHODS

Institutional review board approval was obtained. Informed consent was waived by the medical ethics committee. One hundred eighteen patients with OBPL born in the cephalic position and six patients born in the breech position were selected for surgery by two neurosurgeons in a multidisciplinary team. Functional loss of the C5 through T1 innervated muscles was noted. All patients underwent preoperative CT myelography at an average age of 19 weeks. CT myelographic examination results were reviewed by two radiologists, who were blinded to the clinical findings, for the presence of root avulsions and pseudocysts. Interobserver agreement was assessed by calculating κ values.

RESULTS

CT myelographic results showed root avulsions in at least one level in 66 (56%) of 118 patients born in the cephalic position and in six (100%) of six patients born in the breech position. Levels C7 and C8 showed the most root avulsions, even if not expected from clinical examination results. A large number of root avulsions showed pseudocysts (73 [68%] of 107 levels in patients born in the cephalic position and 11 [73%] of 15 levels in patients born in the breech position).

CONCLUSION

CT myelographic results showed root avulsions in more than half of patients with OBPL. Root avulsions were even detected at levels that were not expected at clinical examination. Because root avulsions require specific reconstructive techniques, CT myelography is recommended for every preoperative patient with OBPL.

Assessment of topographic brachial plexus nerves variations at the axilla using ultrasonography

BACKGROUND

The aim of this study was to describe topographic variations in the arrangement of the four main brachial plexus nerves at the junction of the axilla and the upper part of the arm.

METHODS

In 153 patients undergoing upper arm surgery using axillary block, we studied nerve arrangements with a three-step approach, combining: (A) cross-sectional ultrasound imaging using a 12 MHz linear ultrasound probe; (B) distal shift of the ultrasound scanhead from the axilla to the elbow joint following the paths of individual nerves; and (C) identifying the distal motor response to electrical nerve stimulation of each nerve. These results were then converted into a 12-section pie chart with the axillary artery (AA) as the axis.

RESULTS

The order of the nerves around the AA was median, ulnar, radial, and musculocutaneous in all cases. The most frequent arrangement was observed in 65% of the patients. Five less frequent variations were observed in 4-20% of the patients, with four other variations seen in <2% of the patients. In 78% of the cases, the four nerves were seen separately using static ultrasound imaging. The musculocutaneous nerve was close to the artery in 18% of the patients.

CONCLUSIONS

Topographic variations of the four main nerves at the axilla were found to be numerous, the most frequent arrangement being seen in less than two-thirds of the patients. Four separate nerves were seen on static ultrasound imaging at this sectional level of the axilla in only 78% of the cases.

[Simplified exploration of brachial plexopathies by reduction to well-known mononeuropathies and radiculopathies]

The anatomic complexity of the brachial plexus makes its electrophysiological exploration difficult. Electrodiagnosis nevertheless plays a crucial role in assessing brachial plexopathies, particularly in the perspective of post-traumatic surgical reconstructions. The evaluation aims to locate as precisely as possible injuries within the plexus, as well as to determine their severity and capacity for recovery. This requires various sensory nerve conduction studies and needle EMG recordings of "marker" muscles. Plexopathies differ from radiculopathies by altered sensory nerve responses and unaltered functional innervation of paracervical muscles. We propose to simplify the exploration of brachial plexopathies by following some practical rules derived from a reanalysis of the brachial plexus anatomic sketch. Two main simplification rules can be deduced from an analysis of the anatomic sketch. First it would be judicious to associate the plexopathies involving a single element of the brachial plexus with distinct etiological and symptomatic patterns according to the altered element, as one does for peripheral nerve and root pathologies. The second proposal relies on the observation that each supraclavicular "truncal" element (upper, middle, or lower) of the brachial plexus results from reunion of cervical root nerves and behaves like a "super-root" for the upper limb, while each infraclavicular "cord" element (posterior, lateral, or medial) is the sum of two or more peripheral nerves and behaves like a "super-nerve". Accordingly, the motor and sensory abnormalities associated with the lesion of a single plexus branch may occupy a clinical and electrophysiological territory that recovers those of its constituants. Except the unaltered paracervical muscles, it is useful to reduce the topographical semiology of truncal lesions to well-known cervical radiculopathies (upper trunk neuropathy to C5 and C6 associated radiculopathies, middle trunk neuropathy to C7 radiculopathy, lower trunk neuropathy to C8 and T1 associated radiculopathies); and that of cord lesions to well-known mononeuropathies of the upper limb (for example, a posterior cord neuropathy may be considered as a full radial mononeuropathy associated with an axillary one). This method of simplification allows to demystify the brachial plexopathies and to facilitate their comprehension and exploration.