Microsurgical relations of the roots of the brachial plexus. Practical applications

Safety and Efficacy of Posterior Upper Rib Excision and Decompression Technique for Surgical Treatment of Neurogenic Thoracic Outlet Syndrome

BACKGROUND

There are several approaches used for surgical treatment of neurogenic thoracic outlet syndrome (n-TOS). The posterior upper rib excision and decompression technique is a novel technique that was developed and used by the author for the past 8 years. The purpose of this paper is to report clinical outcomes of patients treated with this approach.

METHODS

All patients with n-TOS operated by single surgeon from 2015 to 2023 were retrospectively analyzed. Demographic, clinical, radiologic, surgical, and postoperative data were collected and reported with emphasis on efficacy and complications. The surgical success was evaluated subjectively as excellent, good, fair, poor, and bad. Radiologic data were analyzed to assess the extent of accessory/first rib removal.

RESULTS

Eighty procedures were performed in 61 patients with a mean follow-up of 1153 (87-3048) days. The majority (60.7%) of patients were women, with 39.3% being men. In 11 cases (18%) causative factor was bone abnormality. Two patients were previously operated at another centers (3.3%). Total mean subjective improvement rate was 91.5%. More than half (55) of the patients reported "excellent" (>75%) and 6 "good" improvements (50%-75%); no fair, poor, and worse outcomes were reported. Patients reporting "good" outcome had statistically significant shorter follow-ups than the "excellent" group (P < 0.001). Complications included pleural opening, Horner syndrome, and apical hematoma, none of which were permanent.

CONCLUSIONS

The posterior upper rib excision and decompression approach provides excellent clinical outcomes in patients with n-TOS. It allows better intraoperative visualization and removal of the first rib and full decompression of the neurovascular bundle.

C5 Palsy After Cervical Spine Decompression: Topographic Correlation With C6 Chassaignac Tubercle?: A Fresh-Cadaveric Study of the Cervical Spine and Rediscussion of Etiological Hypotheses

STUDY DESIGN

Cadaveric study on fresh unprocessed, nonpreserved, undyed specimens, which has not previously been reported.

OBJECTIVE

Our aim was to explore the possible topographic correlation of the C5 nerve root with regards to its course and regional relation to C6 Chassaignac tubercle.

SUMMARY OF BACKGROUND DATA

C5 palsy is reported amongst the most frequent postoperative complications of cervical spinal procedures. We hypothesized that etiologic mechanisms proposed thus far in the current literature, although with some plausible explanation, still cannot explain why the C5 nerve root and not any other level suffer a postoperative palsy.

METHODS

Six fresh cadavers had extensive layer by layer dissection performed by two surgeons (one of whom has experience as an anatomy demonstrator and dissector). Roots of brachial plexus were exposed in relation to cervical transverse processes. Photographs were taken at each stage of the exposure.

RESULTS

We observed a close relation of the path of the C5 nerve root with the C6 tubercle bilaterally. Moreover, we noted a steeper descent of C5 in comparison with the other adjacent roots.

CONCLUSION

Steeper angle of the C5 nerve root and close proximity to C6 Chassaignac tubercle may play a role in predisposing it to neuropraxia. Detailed anatomical photographs on fresh unprocessed cadaveric specimens are novel. Peculiar anatomical features and recent experimental evidence discussed do highlight a postganglionic extraforaminal etiology corresponding well to the demographic meta-analysis data on clinical features of postoperative C5 palsy. Exploring an alternative unified "neurophysiologic stress and critical tipping point" etiological model that encompasses current theories and correlates known metanalyses observations, we believe further studies would be prudent to ascertain/refute these findings.

LEVEL OF EVIDENCE

3.

Foraminal Ligaments Tether Upper Cervical Nerve Roots: A Potential Cause of Postoperative C5 Palsy

Background  Nerve root tethering upon dorsal spinal cord (SC) migration has been proposed as a potential mechanism for postoperative C5 palsy (C5P). To our knowledge, this is the first study to investigate this relationship by anatomically comparing C5–C6 nerve root translation before and after root untethering by cutting the cervical foraminal ligaments (FL).

Objective  The aim of this study is to determine if C5 root untethering through FL cutting results in increased root translation.

Methods  Six cadaveric dissections were performed. Nerve roots were exposed via C4–C6 corpectomies and supraclavicular brachial plexus exposure. Pins were inserted into the C5–C6 roots and adjacent foraminal tubercle. Translation was measured as the distance between pins after the SC was dorsally displaced 5 mm before and after FL cutting. Clinical feasibility of FL release was examined by comparing root translation between standard and extended (complete foraminal decompression) foraminotomies. Translation of root levels before and after FL cutting was compared by two-way repeated measures analysis of variance. Statistical significance was set at 0.05.

Results  Significantly more nerve root translation was observed if the FL was cut versus not-cut, p  = 0.001; no difference was seen between levels, p  = 0.33. Performing an extended cervical foraminotomy was technically feasible allowing complete FL release and root untethering, whereas a standard foraminotomy did not.

Conclusion  FL tether upper cervical nerve roots in their foramina; cutting these ligaments untethers the root and increases translation suggesting they could be harmful in the context of C5P. Further investigation is required examining the value of root untethering in the context of C5P.

Diagnostic Function of 3-Tesla Magnetic Resonance Imaging for the Assessment of Brachial Plexus Injury

Background:

This study aimed to evaluate the diagnostic function of 3-Tesla (T) magnetic resonance imaging (MRI) during the assessment of brachial plexus injury (BPI), in comparison with intraoperative findings.

Methods:

A retrospective study was performed on 60 patients (47 men and 13 women), who had clinical manifestations of BPI, underwent 3T MRI of the brachial plexus, and were surgically treated at the Viet Duc and Vinmec Times City hospitals, in Hanoi, Vietnam, from March 2016 to December 2019. Preganglionic and postganglionic lesion features were identified on MRI. The diagnostic function of MRI features for the determination of BPI was evaluated and correlated with intraoperative findings.

Results:

The root avulsion and pseudomeningocele preganglionic injuries were observed in 57% and 43% of MRIs, respectively, and were commonly observed at the C7 and C8 roots. Nerve disruption and never edema were observed in 47.56% and 33.53% of MRIs, respectively, and were commonly observed at the C5 and C6 roots. The sensitivity, specificity, accuracy, positive prognostic value, and negative prognostic value of 3T MRI were 64.12%, 92.90%, 80.33%, 87.50%, and 76.96%, respectively, for the diagnosis of total avulsion, and 68.52%, 83.33%, 80.67%, 47.44%, and 92.34%, respectively, for the diagnosis of nerve disruption.

Conclusion:

MRI offers valuable details regarding the location, morphology, and severity of both preganglionic and postganglionic injuries during the preoperative diagnosis of BPI. However, this modality played a moderate diagnostic role. Therefore, 3T MRI should be used as a supplemental evaluation, coupled with clinical tests and electromyography, to determine the most appropriate treatment strategies for BPI patients.

Surgical reconstructions for adult brachial plexus injuries. Part I: Treatments for combined C5 and C6 injuries, with or without C7 injuries

Brachial plexus injuries will cause a significantly decreased quality of life. Patients with upper arm type brachial plexus injuries, which means C5 and C6 roots injury, will lose their shoulder elevation/abduction/external rotation, and elbow flexion function. Additional elbow, wrist, and hand extension function deficit will occur in patients with C7 root injury. With the advances of reconstructive procedures, the upper arm brachial plexus injuries can be successfully restored through nerve repair, nerve grafting, nerve transfer, muscle / tendon transfer and free functioning muscle transfer. In this review article, we summarized the various reconstructive procedures to restore the function of shoulder and elbow. Nowadays, the upper arm type BPI can be treat with satisfied outcomes (80-90% successful rate).

Factors Associated With C5 Palsy Following Cervical Spine Surgery: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

C5 palsy (C5P) is a not uncommon and disabling postoperative complication with a reported incidence varying between 0% and 30%. Among others, one explanation for its occurrence includes foraminal nerve root tethering. Although different risk factors have been reported, controversy about its causation and prevention persists. Inconsistent study findings contribute to the persistent ambiguity leading to an assumption of a multifactorial nature of the underlying C5P pathophysiology. Here, we report the results of a systematic review on C5P with narrow inclusion criteria in the hope of elucidating risk factors for C5P due to a common pathophysiological mechanism.

METHODS

Electronic databases from inception to March 9, 2019 and references of articles were searched. Narrow inclusion criteria were applied to identify studies investigating demographic, clinical, surgical, and radiographic factors associated with postoperative C5P.

RESULTS

Sixteen studies were included after initial screening of 122 studies. Eighty-four risk factors were analyzed; 27 in ≥2 studies and 57 in single studies. The pooled prevalence of C5P was 6.0% (range: 4.2%-24.1%) with no consistent evidence that C5P was associated with demographic, clinical, or specific surgical factors. Of the radiographic factors assessed, specifically decreased foraminal diameter and preoperative cord rotation were identified as risk factors for C5P.

CONCLUSION

Although risk factors for C5P have been reported, ambiguity remains due to potentially multifactorial pathophysiology and study heterogeneity. We found foraminal diameter and cord rotation to be associated with postoperative C5P occurrence in our meta-analysis. These findings support the notion that factors contributing to, and acting synergistically with foraminal stenosis increase the risk of postoperative C5P.

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.

Microanatomy of the brachial plexus roots and its clinical significance

PURPOSE

To provide the anatomical basis of brachial plexus roots for the diagnosis and treatment of brachial plexus root avulsion injury.

METHODS

The morphological features of brachial plexus roots were observed and measured on 15 cervicothoracic spine of adult cadavers. The relationship of brachial plexus nerve roots and the surrounding tissues also were observed, as well as the blood supply of anterior and posterior roots of the brachial plexus.

RESULTS

Origination of the nerve roots in the dorsal-ventral direction from the midline was fine-tuned at each level along the spinal cord. The minimum distance of the origin of the nerve root to midline was 2.2 mm at C ₅, while the maximum was 3.1 mm at T ₁. Inversely, the distance between the origin of the posterior root and the midline of the spinal cord gradually decreased, the maximum being 4.2 mm at C ₅ and minimum 2.7 mm at T ₁. Meanwhile, there was complicated fibrous connection among posterior roots of the brachial plexus. The C _5-6 nerve roots interlaced with tendons of the scalenus anterior and scalenus medius and fused with the transverse-radicular ligaments in the intervertebral foramina. However, these ligaments were not seen in C _7-8, and T ₁. The blood supply of the anterior and posterior roots of the brachial plexus was from the segmental branches of the vertebral artery, deep cervical artery and ascending cervical artery, with a mean outer diameter of 0.61 mm.

CONCLUSIONS

The systematic and comprehensive anatomic data of the brachial plexus roots provides the anatomical basis to diagnose and treat the brachial plexus root avulsion injury.

The morphology and clinical significance of the extraforaminal ligaments at the cervical level

STUDY DESIGN

A dissection-based study of 6 embalmed cadavers.

OBJECTIVE

To identify and describe the extraforaminal ligaments (EFLs) in relation to the area of the cervical intervertebral foramina and to evaluate their clinical significance.

SUMMARY OF BACKGROUND DATA

EFLs between the lumbar spinal nerves and the tissues surrounding the intervertebral foramens have been well established. However, research work has been undertaken to describe the local anatomy of the extraforaminal part of the cervical spine; detailed anatomic studies of the EFLs of cervical nerves have not been performed.

METHODS

One hundred ninety-six cervical intervertebral foramina from 6 adult embalmed cadavers were studied, and the existence and type of the EFLs were identified. The morphology, quantity, origin, insertion, and the spatial orientation of the EFLs in the cervical region were observed, and the length, width, or diameter and thickness of the ligaments were measured with a vernier caliper.

RESULTS

The EFLs could be found from the second cervical to the first thoracic spinal nerve. These ligaments could be divided into 2 types: radiating ligaments, which connected the nerve root sleeves that radiated to the transverse processes, the wall of the intervertebral foramina, and even the adjacent nerve root through the small transverse foramen; transforaminal ligaments, which originated from the anteroinferior margin of cranial transverse process and inserts in the superior margin of the anterior tubercle of caudal transverse process crossing the spinal nerve ventrally.

CONCLUSION

Between the cervical spinal nerves and nearby structures, there are 2 types of the EFLs. The radiating ligaments may serve as a protective mechanism against traction and play an important role in the positioning of the nerves in the intervertebral foramen. However, in all probability, the transforaminal ligaments may be the underlying cause of the cervical radiculopathy.

A new cervical nerve root avulsion model using a posterior extra-vertebral approach in rats

BACKGROUND

The nerve root avulsion injury causes decrease of motor neurons in the spinal ventral horn. To investigate the motoneuron death after avulsion injury in rats, the intradural root avulsion procedure is usually used, although it is technically demanding and associated with a risk of unexpected spinal cord damage. We have developed a new cervical nerve root avulsion procedure in rats and investigated the validity of our procedure.

METHODS

Our procedure is using a posterior approach and pulling the C6 nerve root outside the vertebral foramen without intradural procedures. The lateral third of the lateral mass is needed to be resected before pulling the nerve root. The accomplishment of our procedure is judged by confirmation of the bifurcated stump of the avulsed nerve root and the leakage of the spinal fluid from vertebral foramen. At first, four Sprague-Dawley (SD) rats were used for the examination of C6 motor neuron distribution in the normal spinal cord. Then, 40 SD rats were divided into following four groups and the survival rate of motor neuron was examined. (A) an intradural avulsion group, (B) an intradural rhizotomy group, (C) our extravertebral avulsion group, and (D) an extravertebral rupture group. Another 26 SD rats were used for the examination of histomorphorogic changes in the spinal cord after our extra-vertebral avulsion procedure.

RESULTS

At 28 days after injury, the percentage of surviving motor neurons in groups A (39.0 ± 2.1%) and C (47.5 ± 7.1%) were significantly lower than those in groups B (77.1 ± 12.3%) and D (98.9 ± 9.9%). Compared with other groups, our procedure was easier and associated with less unexpected spinal cord damage. Although the length of the distal stump of the extravertebrally avulsed ventral rootlets was varied between 1.5 and 3.2 mm, this difference did not affect motoneuron death. The extravertebral avulsion injury showed intraspinal bleeding along the motoneuron axons, glial reaction and macrophage infiltration in the lesioned side of the ventral horn.

CONCLUSIONS

Our extravertebral avulsion procedure is simple and reproducible. It would become a useful tool for the study of cervical nerve root avulsion injury.

Extraforaminal ligaments of the cervical spinal nerves in humans

BACKGROUND CONTEXT

During the last 120 years, several mechanisms to protect the spinal nerve against traction have been described. All the described structures were located inside the spinal canal proximal to the intervertebral foramen. Ligaments with a comparable function just outside the intervertebral foramen are mentioned ephemerally. No studies are available about ligamentous attachments of cervical spinal nerves to adjacent vertebrae.

PURPOSE

To identify and describe ligamentous structures at each cervical level that attaches spinal nerves to structures in the extraforaminal region.

STUDY DESIGN/SETTING

An anatomical study of the extraforaminal attachments of the cervical spinal nerves was performed using human spinal columns.

METHODS

Five embalmed human cervical spines (C1-C8) were dissected. The extraforaminal region was dissected bilaterally to describe and measure anatomical structures and their relationships with the cervical spinal nerves. Histology was done on the ligamentous connections of nerves to the adjacent vertebral structures.

RESULTS

The cervical spinal nerves are attached to the transverse process of the vertebrae. The connecting ligaments consist mainly of collagenous fibers.

CONCLUSIONS

At the cervical level, direct ligamentous connections exist between extraforaminal cervical spinal nerves and nearby structures. They may serve as a protective mechanism against traction. In addition, these ligaments play an important role in the positioning of the nerves in the intervertebral foramen.

Undeveloped semiconic posterosuperior ligament and susceptibility to avulsion of the C-7 spinal nerve in Erb palsy

OBJECT

In Erb palsy, the C-7 spinal nerve has been found to be more subject to avulsion than the C-5 and C-6 spinal nerves. This study investigated the morphological and biomechanical characteristics of the semiconic posterosuperior ligaments (SPLs) at the C-5, C-6, and C-7 spinal nerves in neonates.

METHODS

Twenty-four brachial plexuses from 12 fresh neonate cadavers were used in this study. In 12 brachial plexuses from 6 cadavers, the following studies were performed with respect to the SPLs at the C-5, C-6, and C-7 spinal nerves: gross observation of morphological and histological characteristics; measurement of length, thickness, and width; and a semiquantitative analysis of collagen. In the other 6 cadavers, biomechanical tension testing was performed bilaterally on the C5-7 SPLs to assess the tensile strength of the ligaments.

RESULTS

The C5-7 spinal nerves are fixed to the transverse process through the SPL, a structure not observed at the C-8 and T-1 spinal nerves. Except for the width of the SPL insertion on the spinal nerve, which was found to increase gradually from C-5 to C-7, there was no statistically significant difference in the dimensions of the C-5, C-6, and C-7 SPLs. The sectional area percentage of collagen was 51% ± 10% in SPLs for C-5, 51% ± 11% for C-6, and 41% ± 10% for C-7; and this percentage was significantly lower in SPLs for C-7 than for C-5 or C-6 (1-way ANOVA, F = 4.3, p = 0.02; Tukey honestly significant difference test, p = 0.04 and 0.04, respectively). Sharpey fibers were observed at the transverse process origin of the SPL at C-5 and C-6 but not at C-7. Biomechanical tension testing showed that the mean failure load was 6.6 ± 0.9 N for the C-5 SPL, 6.4 ± 1.0 N for the C-6 SPL, and 5.4 ± 0.9 N for the C-7 SPL, and the failure load was significantly lower in SPLs at C-7 than in those at C-5 or C-6 (1-way ANOVA, F = 5.1, p = 0.01; Tukey honestly significant difference, p = 0.01 and 0.048, respectively). Nine of 12 C-7 SPLs failed at their origin from the transverse process, while only 4 of 12 C-5 SPLs and 3 of 12 C-6 SPLs failed at the origin site.

CONCLUSIONS

These findings suggest that the lower density of collagen and absence of Sharpey fibers decrease the biomechanical properties of the C-7 SPL, and this may account for the higher frequency of avulsion of the C-7 spinal nerve (in comparison with the C-5 or C-6 nerve) in Erb palsy.

Nerve transfers for brachial plexus reconstruction

Brachial plexus injuries result in devastating loss of function for patients and present incredible challenges for peripheral nerve surgeons. Recently, nerve transfers have produced superior results compared with traditional interposition nerve grafts for brachial plexus reconstruction. The authors present a review of current surgical options for treatment of partial and complete adult brachial plexus injuries using nerve transfers.

Functional assessment of C-5 ventral rootlets by intraoperative electrical stimulation of the supraclavicular segment of the long thoracic nerve during brachial plexus surgery

Object

Anatomical and functional assessment of the intradural segment of the spinal nerves is imperative in brachial plexus surgery, as the repair of postganglionic elements in the setting of a confirmed nerve root avulsion is of no benefit. None of the current techniques to detect these avulsions can provide full information that ensures the functional status of the preganglionic segment of the roots. The objective of this study was to evaluate intraoperative electrical stimulation of the supraclavicular segment of the long thoracic nerve (LTN) as a method to differentiate C-5 nerve root extraforaminal rupture from its intradural avulsion.

Methods

The author performed a prospective analysis of data obtained in 14 patients presenting with the loss of C-5 nerve root function secondary to traumatic brachial plexus injury. The patients were divided into 2 groups: 8 patients in whom the intradural segment of C-5 nerve root was preserved (5 cases of closed traction injuries in whom the computed tomography [CT] myelograms confirmed the integrity of C-5 root and 3 cases of open sharp injuries) and a control group of 6 patients in whom CT myelography demonstrated avulsion of the root.

Results

The results of the intraoperative electrical stimulation of the LTN and the surgical outcome of each patient were recorded. The LTN electrical stimulation elicited serratus anterior muscle contraction in cases in which C-5 root was not avulsed, and there were no responses in patients whose radiological evaluation had demonstrated nerve root avulsion. In those patients in whom LTN stimulation proved to be positive, the C-5 root was used as a graftable stump to the suprascapular nerve and/or to the posterior division of the superior trunk. In these cases, favorable results were observed regarding arm abduction in all cases—Medical Research Council Grades M3 (37%) and M4 (62%). In the control group, the C-5 root was not used as a donor stump and a multiple nerve transfer technique was adopted as the preferred surgical option.

Conclusions

Intraoperative electrical stimulation of the supraclavicular segment of the LTN is a useful complementary method to test the functional status of the C-5 ventral rootlets. If the test is positive (that is, a response is present) it is indicative of extraforaminal rupture of the root, and if negative, it is suggestive of its avulsion.

Use of clinical signs and computed tomography myelography findings in detecting and excluding nerve root avulsion in complete brachial plexus palsy

Object

The purpose of this study was to investigate the usefulness of preoperative evaluation based on clinical testing and computed tomography (CT) myelography in differentiating root rupture (that is, graftable root) from root avulsion in total brachial plexus palsy.

Methods

Thirty-two patients with total brachial plexus palsy were clinically tested for the presence of phrenic nerve palsy, supraclavicular Tinel sign, shoulder protraction, Bernard–Horner syndrome, and hand pain. The patients underwent CT myelography and then underwent surgery. The combination of a positive Tinel sign and a positive shoulder protraction test accurately predicted the presence of a graftable root in 93.7% of the cases. A 96.8% rate of accuracy was attained if the results of the CT myelography were considered together with the clinical signs. The presence of Bernard–Horner syndrome and hand pain accurately indicated avulsion of the lower roots in 93.7% of the patients. Computed tomography myelography accurately predicted the condition of the lower roots in 100% of the cases. Total avulsion injury was observed in five cases (16%). The lower roots were avulsed in 94% of the cases. The C-5 and C-6 roots were grafted 40 times, and a suitable root stump for grafting lay in a retroscalenic position in 18 (45%) of the 40 cases.

Conclusions

Preoperative assessment based on clinical examination and CT myelography allowed correct surgical planning in more than 90% of the cases.

The prevalence of spinal trauma associated with brachial plexus injuries

Severe closed traction lesions to the adult brachial plexus are caused by high energy transfer injuries, in which injuries to other systems are common. Of the 149 patients urgently operated on for lesions of the brachial plexus between 1 June 1997 and 1999, 18 (12%) suffered significant injury to the spinal column. Accurate diagnosis of the spinal injury was made in 13 cases of these before transfer to our unit.The injury to the spine was not necessarily a contraindication to urgent exploration of the brachial plexus.

Anatomy of the cervical spine: implications for the upper limb tension test

A detailed investigation of the anatomy of the lower cervical nerves and associated structures was undertaken, as these structures would most likely be affected by any stresses generated in the nerves of the brachial plexus during the upper limb tension test (ULTT). The investigation used dissection of three adult human spines and histological sections of three cervical spines. The results support the hypothesis that the lower cervical nerves have a specialised anatomical arrangement which may protect them from forces generated in the upper limb and cervical spine by the ULTT. The fifth, sixth and seventh cervical nerves are securely attached to many structures as they emerge from the spinal cord to form the brachial plexus. Furthermore, the posterior longitudinal ligament anchors the nerve roots to the vertebral bodies and intervertebral discs. The results suggest that innervated structures other than neuromeningeal tissue may also need to be considered when evaluating a patient's positive ULTT response.