C7 Spinal Nerve Research Articles

Quantifying the Impact of C7 Spinal Nerve Harvest on Spontaneous, Patient-Initiated Movement of the Donor Upper Extremity.

Transfer of a healthy C7 spinal nerve is a tool for upper extremity reanimation in patients with severe brachial plexus injury (BPI). Its use remains controversial owing to concern for neurological injury to the donor arm. Utilizing wearable motion-sensor technology, we aimed to quantify donor arm morbidity after C7 spinal nerve harvest in patients with pan-BPI, reporting both the time and magnitude of donor arm movement in a real-world setting compared to healthy controls. Seventeen patients who underwent contralateral C7 (CC7) transfer for traumatic pan-BPI at least 2 years prior were compared to 14 healthy controls. Each participant wore an accelerometer on both arms for 7 consecutive days. The vector time (VT), or time of movement measured in hours/day, and the vector magnitude (VM), or magnitude of arm movement measured as a single vector magnitude per second, were collected and compared between groups. The correlation between VT and VM and time from C7 spinal nerve harvest was also calculated. At mean 7.7 years after C7 spinal nerve harvest, there was no difference between donor and control arms for VT (5.76±1.55] vs 5.45±1.22 hours, P = 0.56) or VM (2242236±753853 vs 1919223±579723 activity counts, P = 0.20), regardless of donor arm dominance. The C7 harvest cohort used the injured arm 53% of the time and with 27% of the power of the donor arm. There was no significant difference in time or magnitude of arm movement between donor arms and the arms of healthy controls.

Lateral atlanto-axial joint access using the C2 pedicle.

Neck pain and headaches can arise from the lateral atlanto-axial (LAA) joint. This pain can be diagnosed with intra-articular injections of local anesthetic. A widely used technique for access to the lateral atlanto-axial joint uses a posterior approach, but this approach can be hazardous because of the proximity of the vertebral artery, the dural sac, and the C2 spinal nerve and dorsal root ganglion. The objective was to describe and test a new technique for accessing the LAA joint that avoids structures that lie behind the joint. The new technique was described and tested for tolerance in 10 patients with unilateral suboccipital pain and tenderness over the LAA joint, along with evidence of LAA joint arthropathy on SPECT CT. The technique requires inserting a needle along a trajectory tangential to the dorsal surface of the C2 lamina. It involves obtaining a declined view of the C2 lamina and C2 pedicle. In all cases, the C2 pedicle was easily identified and allowed the needle to pass asymptomatically underneath the neurovascular structures behind the joint. The tactile response of the lamina of C2 provided important feedback regarding needle depth caudal to the LAA joint.

Strategies and safety simulations for ultrasonic cervical spinal cord neuromodulation

Objective. Focused ultrasound spinal cord neuromodulation has been demonstrated in small animals. However, most of the tested neuromodulatory exposures are similar in intensity and exposure duration to the reported small animal threshold for possible spinal cord damage. All efforts must be made to minimize the risk and assure the safety of potential human studies, while maximizing potential treatment efficacy. This requires an understanding of ultrasound propagation and heat deposition within the human spine. Approach. Combined acoustic and thermal modelling was used to assess the pressure and heat distributions produced by a 500 kHz source focused to the C5/C6 level via two approaches (a) the posterior acoustic window between vertebral posterior arches, and (b) the lateral intervertebral foramen from which the C6 spinal nerve exits. Pulse trains of fifty 0.1 s pulses (pulse repetition frequency: 0.33 Hz, free-field spatial peak pulse-averaged intensity: 10 W cm−2) were simulated for four subjects and for ±10 mm translational and ±10∘ rotational source positioning errors. Main results. Target pressures ranged between 20%–70% of free-field spatial peak pressures with the posterior approach, and 20%–100% with the lateral approach. When the posterior source was optimally positioned, peak spine heating values were below 1 ∘C, but source mispositioning resulted in bone heating up to 4 ∘C. Heating with the lateral approach did not exceed 2 ∘C within the mispositioning range. There were substantial inter-subject differences in target pressures and peak heating values. Target pressure varied three to four-fold between subjects, depending on approach, while peak heating varied approximately two-fold between subjects. This results in a nearly ten-fold range between subjects in the target pressure achieved per degree of maximum heating. Significance. This study highlights the utility of trans-spine ultrasound simulation software and need for precise source-anatomy positioning to assure the subject-specific safety and efficacy of focused ultrasound spinal cord therapies.

Origin and distribution of the brachial plexus in red-necked wallaby (Notamacropus rufogriseus, Marsupialia: Macropodidae).

Notamacropus rufogriseus (red-necked wallaby) are in the family Macropodidae, which is the second largest family of marsupials after the family Didelphidae. This study was conducted with the aim of providing a detailed description of the origin and distribution of the brachial plexus in N. rufogriseus. Two-year-old male and 3-year-old female red-necked wallabies were used for the study. The brachial plexus was formed by ventral rami of C4, C5, C6, C7, C8, and T1 spinal nerves. It is composed of three trunks that give rise to 12 principal nerves. The cranial trunk is formed by the combination of the rami C4-C7; the middle trunk is formed by the combination of the rami C6 and C7; and the caudal trunk is formed by the combination of the rami C8 and T1. Differences between left and right side of the plexus brachialis were not observed. C6 ventral spinal rami contribute the most to brachial plexus nerve formation, while C4 contributes the least. The formation and distribution of the plexus in N. rufogriseus exhibited more resemblance to the patterns observed in marsupial animals rather than placental mammals. Marsupial mammals demonstrate the involvement of C4 in the development of the brachial plexus. The formation and branching of the brachial plexus sequentially adapt in accordance with changes in their thoracic limb activities and innervation points. Anatomical data from brachial plexus studies optimizes thoracic limb clinical and surgical treatments. This work can provide baseline data for future marsupial brachial plexus studies and fill gaps in the scarce literature.

Features of the spatial orientation of the thoracodorsal nerve bundles

BACKGROUND: Studying the spatial arrangement of nerve bundles makes it possible to better understand the characteristics of the occurrence and mechanisms of injuries to peripheral nerves, to develop and perform new reconstructive operations.
 AIM: To identify the features of the route, spatial orientation and relationships of the thoracodorsal nerve bundles along its entire length.
 MATERIAL AND METHODS: Intrastem dissection of 121 thoracodorsal nerves was performed in the corpses of men and women aged 40–97 years. The obtained indicators of the length (mm) and angles of deviation (degrees) of the thoracodorsal nerve bundles at different levels of their entire path were checked for normality of distribution using the Shapiro–Wilk test. When describing the studied indicators, the median (Me) and quartile intervals (Q1, Q3) were determined, and the significance of intergroup differences was determined using the Mann–Whitney U test.
 RESULTS: Along the entire path, the bundles of the thoracodorsal nerve change their spatial position 6 times and their relationship with each other 1 time. The closer the bundles are to the spinal cord and spine, the more changes (85.7%); the further to the periphery, the fewer (14.3%). The bundles of the thoracodorsal nerve are located twice in the horizontal plane, and in the proximal half of the C7 spinal nerve they are twisted relative to each other by 180° [170°; 190°], change places: the sensory ones move from the posterior position to the anterior one, and the motor one — from the anterior to the posterior one. The bundles of the thoracodorsal nerve deviate downward 4 times in the frontal plane at a total angle of 105° [95°; 115°], and in the sagittal plane they change their position 2 times and move from an oblique-anterior (15° [5°; 25°]) to an oblique-posterior (20° [10°; 30°]) position.
 CONCLUSION: The route of passage of the thoracodorsal nerve bundles along the entire path from the spinal cord to the latissimus dorsi muscle consists of eight levels of different lengths, 6 times they change their spatial orientation and 1 time their relationship with each other.

Head tilt as a clinical sign of cervical spinal or paraspinal disease in dogs: 15 cases (2000-2021).

To characterise head tilt as a rare clinical sign of cervical spinal or paraspinal disease in dogs. Retrospective single-centre case-series study of dogs with head tilt and cervical spinal or paraspinal disease in the absence of intracranial abnormalities. Descriptive statistics were used. Fifteen dogs met the inclusion criteria of this study. Median age at onset was 6 years (range 2.5 to 12 years). Onset of neurological signs was mainly chronic (9/15, 60%). Most common presenting complaints included head tilt (9/15, 60%) and cervical hyperaesthesia (8/15, 53%). Most common neurological findings included head tilt (15/15, 100%), generalised proprioceptive ataxia and tetraparesis (6/15, 40%) and cervical hyperaesthesia (8/15, 53%). Diagnoses included post-operative complication of C2 spinal nerve root mass removal (2/15, 13%), C3-C4 intervertebral disc extrusion (2/15, 13%), cervical paraspinal myositis (2/15, 13%) and one of each: C2 vertebral malformation, C2 spinal nerve root mass, C1-C2 meningioma, C2 vertebral fracture, C4-C5 intervertebral disc extrusion, C4 vertebral body mass, C5-C7 osseous-associated cervical spondylomyelopathy, and concurrent C5-C6 and C6-C7 intervertebral disc protrusions. Two dogs were euthanased shortly after diagnosis and two of 15 were dogs lost to follow-up. No post-mortem examination was performed for these cases. For the 11 of 15 remaining dogs, head tilt resolved in eight of 15 (53%) dogs after treatment of the underlying condition and in three of 15 (20%) dogs, it remained static. Head tilt can be a rare clinical sign of cervical spinal or paraspinal disease in dogs.

Anatomical variations and coding of the intra-trunk pathways in the thoracodorsal nerve

Aim. To study anatomical variations of the intra–trunk pathways in the thoracodorsal nerve bundles and to develop a system for their coding.Materials and methods. After fixation in a 2% solution of acetic acid using the MBS-10 stereomicroscope, we performed macro- and microscopic intra-trunk dissection of thoracodorsal nerve bundles in 121 specimens obtained from 105 corpses of males and females who died at the age of 40–97 years. Using the obtained findings, we compiled a database in the MS Excel 12.0 software and determined the number of anatomical variations in absolute and relative (% from 121 specimens) units.Results. The study revealed that the thoracodorsal nerve is a mixed nerve, which consists of 1 motor and 1– 3 sensory bundles that variously pass through the spinal nerves, trunks, and the axillary nerve with the formation of 20 intra-trunk pathways. In 77% of cases, sensory bundles arising from the thoracodorsal nerve pass through the posterior bundle, the posterior division, the middle trunk, and the C7 spinal nerve or the inferior trunk and the C8 spinal nerve. In 22% of cases, the thoracodorsal nerve has one or, rarely, two duplicate sensory pathways besides the main one. In 93% of cases, the motor bundle to the thoracodorsal nerve passes through the C7 spinal nerve and the middle trunk, the posterior division, and the posterior bundle. Coding the anatomical variations of the intra-trunk pathways in the direction of sensory bundle «posterior bundle → posterior division → trunk → spinal nerve; motor bundle ← posterior bundle ← posterior division ← trunk ← spinal nerve allows to briefly yet clearly and fully display the morphological diversity of the nerve anatomy.Conclusion. The identified anatomical variations of the intra-trunk pathways can be useful in the diagnosis of injuries and diseases. They expand indications for the use of spinal nerves, trunks of the brachial plexus, and the thoracodorsal nerve in reconstructive surgery.

Clinical Predictors of C5 Spinal Nerve Viability in Pan-Brachial Plexus Injuries.

In pan-brachial plexus injury, distinguishing between preganglionic and postganglionic injuries is crucial to reconstructive planning. This study aimed to identify preoperative factors that would accurately predict a reconstructible C5 spinal nerve. Patients with pan-brachial plexus injury from a single institution between 2001 and 2018 were reviewed. Patient demographics, clinical examination, diagnostic imaging, and electrodiagnostic results were recorded. C5 viability was determined based on supraclavicular exploration and intraoperative electrophysiologic testing. Univariate analysis identified significant factors for regression analysis. A multivariable parsimonious model was created using stepwise high-performance logistic regression. A total of 311 patients (mean age, 29.9 years; 46 women and 265 men; mean Injury Severity Score, 17.2) were included. A total of 134 patients (43%) had a viable C5 nerve, and 50 patients (12%) had a viable C6 nerve. Intact C5 spinal nerve on computed tomographic (CT) myelogram (OR, 5.4), positive Tinel test (OR, 2.6), muscle strength greater than or equal to 4 (according to the modified British Medical Research Council scale) for the rhomboid (OR, 1.3) or greater than or equal to 4 for the serratus anterior (OR, 1.4), and rhomboid needle electromyography (OR, 1.8) were predictive of having a viable C5 spinal nerve. The multivariable parsimonious stepwise model (area under the curve, 0.77) included four factors: positive Tinel test, intact C5 spinal nerve on CT myelogram, hemidiaphragmatic elevation, and midcervical paraspinal fibrillations. In this cohort of pan-brachial plexus patients with major polytrauma, there was a 43% incidence of viable C5 spinal nerve. A positive Tinel test (OR, 2.1) and intact C5 spinal nerve on CT myelogram (OR, 4.9) predicted a viable C5 nerve. In contrast, hemidiaphragmatic elevation (OR, 3.1) and midcervical paraspinal fibrillations (OR, 2.92) predicted root avulsion. Risk, III.

Morphometric analysis of dry atlas vertebrae in a northeastern Thai population and possible correlation with sex

The uppermost segment of the cervical vertebra or atlas (C1) is a critically important anatomical structure, housing the medulla oblongata and containing the grooves for the C1 spinal nerve and the vertebral vessels. Variations of the C1 vertebra can affect upper spine stability, and morphometric parameters have been reported to differ by population. However, there are few data regarding these parameters in Thais. The use of this bone to predict sex and age has never been reported. This study aimed to examine C1 morphometry and determine its ability to predict sex. Twelve diameter parameters were taken from the C1 vertebrae of identified skeletons (n = 104, males [n, 54], females [n, 50]). Correlation analysis was also performed for sex and age, which were predicted using machine learning algorithms. The results showed that 8 of the 12 measured parameters were significantly longer in the male atlas (p < 0.05), while the remaining 4 (distance between both medial-most edges of the transverse foramen, transverse dimension of the superior articular surface, frontal plane passing through the canal's midpoint, and anteroposterior dimension of the inferior articular surface) did not differ significantly by sex. There was no statistically significant difference in these parameters on the lateral side. The decision stump classifier was trained on C1 parameters, and the resulting model could predict sex with 82.6% accuracy (root mean square error = 0.38). Assertation of the morphometric parameters of the atlas is important for preoperative assessment, especially for the treatment of atlas dislocation. Our findings also highlighted the potential use of atlas measurements for sex prediction.

Kimmerle anomaly as a cause of extravasal compression of the vertebral artery

Kimmerle anomaly, also known as ponticulus posticus, is a commonly known variant of the atlas anatomy. It occurs as a result of complete or incomplete ossification of the posterior atlanto-occipital membrane over the groove of the vertebral artery, which leads to the formation of an arcuate foramina containing the vertebral artery and the posterior branch of the C1 spinal nerve. This anatomical variation is associated with symptoms of vertebrobasilar insufficiency, various types of headache, visual impairment, photopsia, syncope, drowsiness, reduced work capacity, unsteady gait, sleep disturbance, panic attacks.Objective of the article is to highlight the attention of physicians on the widespread and not well understood Kimmerle anomaly, which is the cause of ischemic disorders in the vertebrobasilar circulation due to extravasal compression of the vertebral arteries.In the case of signs of impaired blood flow in the vertebrobasilar circulation, an X-ray of the cervical spine has to be done. In case of Kimmerle anomaly, ultrasound of neck vessels and transcranial doppler with functional tests should be performed. In the case of significant influence of disorder on the vertebrobasilar circulation, computed tomography with angiography is mandatory. If the patient's large vertebral artery is compressed, indications for surgical decompression of the vertebral artery at the level of the atlas is indicated. In cases of mild symptoms of cerebral vertebrobasilar circulation, symptomatic medication, wearing a Chance collar, physical therapy, and regimen restrictions are prescribed.

Patients having surgery for ulnar nerve compression at the elbow rarely have affection of the spinal nerve root at C8-Th1 levels.

Cervical pathology may contribute to residual problems after surgery for ulnar nerve compression. We aimed to evaluate the presence of pathological conditions in spinal cord and cervical spinal nerve roots in patients surgically treated for ulnar nerve compression at elbow. In a cohort of patients, surgically treated for ulnar nerve compression at elbow, magnetic resonance images (MRI; performed 3 years pre/postoperatively) were evaluated by a neuroradiologist blinded to patient characteristics and outcome of surgery. Cervical conditions were assessed and related to patient characteristics, preoperative McGowan grade, and outcome. Among 62 patients (45 unilaterally and 17 bilaterally), only one had spinal nerve root affection of nerve roots contributing to the ulnar nerve (C8-Th1). About half of the patients, mainly those at higher age, had alterations affecting C3-C7 spinal nerve roots at both surgically treated and contralateral, non-surgically treated, sides. Only few other changes were observed at cervical levels. A high McGowan grading was related to a high frequency of spinal nerve root affection. Smokers were more frequently observed among those with spinal nerve root affection at C3-C7 levels at surgically treated side. Residual problems, expressed as patient dissatisfaction and DASH score ≥40, were common. Spinal nerve roots, contributing to the ulnar nerve, are rarely affected in surgically treated patients with ulnar nerve compression at elbow even though pathology is often observed at other cervical levels. Pathology is often detected at other cervical spinal nerve root levels at surgically treated and contralateral sides, particularly among older patients, smokers, and in conjunction with worse preoperative McGowan grade. No relation between cervical pathology and outcome of ulnar nerve surgery is seen.

Dural arteriovenous fistula of the craniocervical junction along the first cervical nerve: A single-center experience and review of the literature

BackgroundDural arteriovenous fistulas (DAVFs) of the craniocervical junction (CCJ) are relative rare lesions. Most studies of DAVFs of the CCJ included the fistulas at the foramen magnum, first cervical (C1), and second cervical (C2) level. DAVFs of the CCJ along C1 spinal nerve are rare vascular lesions with distinctive features. Our aim is to review cases of DAVFs of the CCJ along C1 spinal nerve at our institution. MethodsFrom June 2008 and December 2021. We reviewed a consecutive series of intracranial and spinal DAVFs at our institution and collected all patients harboring DAVFs of the CCJ along C1 spinal nerve. Medical charts were retrospectively reviewed regarding patient demographic data (i.e., gender and age), presenting symptoms and signs, treatment methods, and neurological outcome and complications after treatment. All image studies, including cranial computed tomography (CT) scan, cervical magnetic resonance imaging, CT angiography, and digital subtraction angiography (DSA) with rotational CT angiography were analyzed by experienced neuroradiologists. The authors also review of the literature of DAVFs of the C1 spinal nerve. ResultsThe authors identified 7 patients, including 5 men (71.4 %) and 2 women (28.6 %) with median age 54 years, range 48–72 years. Subarachnoid hemorrhage (SAH) occurred in 5 (71.4 %) patients, and progressive myelopathy in 2 (28.6 %). All fistulas except one received blood supply from the radiculomeningeal branch of the VA at C1 level. Venous aneurysms, being the source of bleeding, were detected in all fistulas with SAH. All patients except one were treated by surgical management. One fistula was treated by balloon-assisted Onyx embolization. Most patients had good neurological outcome following surgery. Complete obliteration of all fistulas treated by surgery was confirmed by follow-up DSA obtained 1 week after surgery. Two patients developed temporary pain and spasm of the trapezius muscle after the surgery. One patient resulted in poor neurological outcome and died due to sepsis and acute upper gastrointestinal bleeding one month after failed embolization. For patients with SAH, only one patient required ventriculoperitoneal shunt. ConclusionsDAVFs of the CCJ along the first spinal nerve are rare and a unique subtype of DAVFs at the CCJ. These fistulas account for 1.74 % of all intracranial and spinal DAVFs in the present study. SAH is the major manifestation of DAVFs at C1 spinal nerve that may be overlooked on routine initial DSA. Rotational CT angiography is useful for clarification of the angioarchitecture of these fistulas, including small feeding artery and venous varix. Surgical treatment by interruption of the intradural draining vein should be the treatment of choice for C1 spinal nerve DAVF

Shoulder Internal Rotation Contracture Formation in Surgically Managed C5, C6 Brachial Plexus Birth Injuries: Neurotmetic Lesions Fare Worse Than Avulsions.

A typical feature in infants with severe C5-C6 brachial plexus birth injury (BPBI) requiring nerve repair is the formation of shoulder internal rotation contracture (IRC). The underlying pathophysiological mechanism is unknown, and the sequelae can be difficult to treat. The severity of the IRC differs among children. C5-C6 lesions are heterogeneous at the root level. Our null hypothesis was that the type of root-level lesion (axonotmesis or neurotmesis versus avulsion) was not associated with the extent of IRC formation over time in children with upper-trunk BPBI. We performed a retrospective analysis of all patients with upper-trunk BPBI who underwent primary surgery of the C5 and/or C6 spinal nerves between 1990 and 2020 and had follow-up of at least 2 years. The primary outcome was passive shoulder external rotation (ER) in adduction at 1, 3, 5, 7, and 15 years of age. The secondary outcome was whether additional shoulder surgery was performed. The relationship between the nature of the C5-C6 lesion and IRC formation was analyzed using linear mixed models. The Kaplan-Meier method was used to estimate the cumulative risk of secondary shoulder procedures. In total, 322 patients were analyzed; mean follow-up was 7.2 ± 4.6 years. The C5-C6 root lesion type was significantly related to the passive range of ER (overall test in linear mixed model, p = 0.007). Children with avulsion of C5 and C6 (n = 21) had, on average, 18° (95% confidence interval [CI], 6.3° to 30°) less IRC formation than those with neurotmesis of C5 and C6 (n = 175) and 17° (2.9° to 31°) less than those with neurotmesis of C5 and avulsion of C6 (n = 34). IRC formation did not differ between the neurotmesis C5-C6 and neurotmesis C5-avulsion C6 groups. Secondary shoulder procedures were performed in 77 patients (10-year risk, 28% [95%CI, 23% to 34%]). Shoulder IRC formation in infants with BPBI with surgically treated C5-C6 lesions occurs to a lesser degree if the C5 root is avulsed than when C5 is neurotmetic. This finding provides insight into the possible causative pathoanatomy and may ultimately lead to strategies to mitigate IRC. Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Motor nerve transfers for restoration of upper arm function in adult brachial plexus injuries

Introduction. Nerve transfers are the only surgical option in reconstruction of directly irreparable injuries of the brachial plexus. In the recent years there has been a trend toward the increased use of nerve transfers with introduction of many new methods and novel indications. Patients with total brachial plexus palsy generally have a poor outcome because of a very limited number of donor nerves. On the contrary, patients with partial injuries involving the C5, C6 and sometimes C7 spinal nerves have a remarquable outcome in a large majority of cases. In both situations , restoration of elbow flexion and shoulder functions are the main priorities. It should be emphasized, that in the cases with upper brachial plexus palsy this could be a complete functional recovery. The intention of this review article is a detailed survey on basics of nerve transfers with the comments concerning their advantages, problems and controversies. Analysis is documented with reported outcomes in the literature dealing with the most common methods of nerve transfer.Methods. PubMed/Medline databases were searched for English language basic articles concernig nerve transfers and series of adult patients who had nerve transfers for functional restoration of the upper arm nerves, performed within one year after injury and with minimum follow-up of one year. Finally, we selected 70 articles . Furthermore, literature search for outcome analysis was limited to the articles published after 1990 that included 45 systematic reviews and meta-analyses of the most common nerve transfers ( intercostal, spinal accessory, fascicular and collateral branches of the brachial plexus ). Analysis of clinical outcomes was based on Medical Research Council (MRC) grading system for muscle strenght, and grades M3 or more were considered as useful functional recovery.Results. Generally, intraplexal nerve transfers resulted with higher rate and better quality of recovery, comparing to the extraspinal transfers. Grades M3 or more were obtained in 72% of the intercostal and 73% of the spinal accessory nerve transfers for restoration of elbow flexion, and in 56% vs. 98% of transfers for restoration of shoulder function. Among intraplexal nerve transfers , elbow flexion was restored in 84% to 91% of the medial pectoral, 100% of the thoracodorsal and 94% to 100% of the single or double fascicular nerve transfers. Shoulder function was restored in 81,8% of the medial pectoral, 86% to 93% of the thoracodorsal and 100% of the triceps branch nerve transfers. Dual nerve transfers, meanning simultaneous reinnervation of the suprascapular and axillary nerves, resulted with 100% rate of recovery.Conclusion. Double fascicular transfer for restoration of elbow flexion and dual nerve transfer for restoration of shoulder function resulted with significantly better results than the other transfers, especially regarding the quality of recovery, meanning representation of grades M4 and M5 among recoveries. Medial pectoral and thoracodorsal nerve transfers proved as a good alternative for restoration of both functions.

C6 and not C5 nerve fibers more commonly contribute most to deltoid muscle innervation: anatomical study with application to better diagnosing cervical nerve injuries.

Most anatomical textbooks list both the C5 and C6 spinal nerves as contributing to the deltoid muscle's innervation via the axillary nerve. To our knowledge, no previous study has detailed the exact spinal nerve components of the axillary nerve terminating in the deltoid via cadaveric dissection. Twenty formalin-fixed cadavers (40 sides) underwent dissection of the brachial plexus. The fascicles making up the axillary nerve branch that specifically terminated in the deltoid muscle were traced proximally. The axillary nerve branch to the deltoid muscle was most commonly (70%) made up of three spinal nerve segments and less commonly (30%) by two spinal nerve segments. For all axillary nerve branches to the deltoid muscle, C4 spinal nerves contributed 0-5%, C5 spinal nerves contributed 1-80%, C6 spinal nerve contributed 15-99%, C7 spinal nerves contributed 0-30%, and C8 and T1 spinal nerves were not found to contribute any fibers to any deltoid muscle branches. The nerve to the deltoid muscle was contributed to equally by C5 and C6 nerve fibers on 10% of sides. On 16% of sides, C5 contributed the most nerve fibers to this muscle. On 35% of sides, C6 contributed the majority fibers found in the axillary nerve branches to the deltoid. Based on our anatomical study, C6 is more often than not the main level of innervation. C5 was never the sole component of the axillary nerve branches to the deltoid muscle. Such anatomical data will now need to be reconciled with clinical studies.

A significant association between C5 nerve sheath tumors and new postoperative weakness.

The objective of this study was to determine if patients with nerve sheath tumors affecting the C5 spinal nerve are at greater risk for postoperative weakness than those with similar tumors affecting other spinal nerves contributing to the brachial plexus. A retrospective chart review (1998-2020)identified patients with pathologically confirmed schwannomas or neurofibromas from the C5 to T1 nerves. Patients with plexiform nerve sheath tumors, tumors involving more than 1 nerve, and malignant peripheral nerve sheath tumors were excluded. Collected variables included basic demographics, tumor dimensions, its location relative to the dura, involved nerve level, surgical approach, extent of resection, presenting symptoms, postoperative neurological deficits, and recurrence rate. Forty-six patients (23 men, 23 women) were identified for inclusion in the study with an average age of 47 ± 17 years, BMI of 28 ± 5 kg/m2, and follow-up of 32 ± 45 months. Thirty-nine patients (85%) had schwannomas and 7 (15%) had neurofibromas. Tumors involved the C5 (n = 12), C6 (n = 11), C7 (n = 14), C8 (n = 6), and T1 (n = 3) nerves. Multivariable logistic regression analysis with an area under the curve of 0.85 demonstrated C5 tumor level as an independent predictor of new postoperative weakness (odds ratio 7.4, p = 0.028). Of those patients with new postoperative weakness, 75% improved and 50% experienced complete resolution of their motor deficits. Patients with C5 nerve sheath tumor resections are at higher odds of new postoperative weakness. This may be due to the predominant single innervation of shoulder muscle targets in contrast to other upper extremity muscles that receive input from 2 or more spinal nerves. These findings are important for clinical decision-making and preoperative patient counseling.

Processing of trigeminocervical nociceptive afferent input by neuronal circuity in the upper cervical lamina I.

Afferents from the C2 spinal nerve (SN) and trigeminal nerve (TN) innervate neighboring cranial territories, and their convergence on the upper cervical dorsal horn neurons represents neural substrate of pain referral in primary headache disorders. Unfortunately, little is known about trigeminocervical input to the major spinal nociceptive projection area lamina I. Here, we used ex vivo brainstem-cervical cord preparation for the visually guided whole-cell recording from the upper cervical lamina I neurons. We show that 50% of them receive convergent monosynaptic input from both nerves, whereas 35% and 11% of neurons receive specific supply from the C2 SN and TN, respectively. Altogether, 10 distinct patterns of synaptic input from the C2 SN and TN to lamina I neurons could be identified. Although stimulation of both nerves evoked excitatory/inhibitory responses, more numerous pure inhibitory inputs arose from the TN. We show that cervical and trigeminal nociceptors converge on to lamina I projection and inhibitory neurons. Thus, trigeminocervical input in lamina I is processed in both nerve-specific and convergent circuitries. Afferent convergence on to inhibitory interneurons serves as a feedforward mechanism balancing excitatory drive to projection neurons. Disruption of this balance may cause pain in primary headache syndromes.

Long head function preserving modification of Somsak’s nerve transfer for the reanimation of shoulder abduction in the adult upper partial brachial plexus injuries: a cadaver and clinical study

We modified the conventional Somsak procedure to preserve the innervation to the long head of triceps, which is an indispensable component of inferior and posterior shoulder stability. The latter is also an extensor and external rotator of the shoulder. Our modification is also based on the finding that normal force of the reinnervated muscle could be achieved with just one-third of the axonal population. Shoulder abduction and external rotation are second priority in adult brachial plexus injury (ABPI) treatment. The aim of this study is to evaluate the functional outcomes of our modification of Somsak’s procedure A preliminary cadaver study was conducted by us to study the anatomy of the donor nerve (the nerve to the long head of triceps-NLHOT) and feasibility for function preserving nerve transfer to the anterior branch of the axillary nerve. We followed this with a retrospective study (2007 to 2017) in which the documents of 46 closed adult upper partial brachial plexus injuries (AUPBPI) patients who had undergone only the modified Somsak’s procedure for the shoulder animation were assessed. All patients had levels 1, 2, and 3 preganglionic or wide gap postganglionic injuries involving the C5 and C6 spinal nerves. The patients also had a simultaneous target neurotization procedure for elbow flexion. The cadaver study highlighted the vasa nervorum and branching patterns of the axillary nerve and NLHOT. The cadaver study also established the ways and means of harvesting the vascularized size-matched branch of NLHOT facilitating target neurotization to the anterior branch of the axillary nerve. On evaluation with the institution objective assessment score, 42 patients (91.3%) had grade 4 scores and four patients (8.7%) had grade 3 scores (p < 0.05). At the end of the follow-up period, patients were assessed with the institutional subjective assessment score, which showed that 43 patients (93.5%) had grade “A” and three patients (6.5%) had grade “B” scores (p < 0.05). Preserving the innervation of the long head of triceps bestows good shoulder stability. A diligent intraneural dissection along the nerve to the long head of triceps fetches a branch of adequate size and length and possibly with a sufficient number of regenerating axons, facilitating a tensionless coaptation of vascularized nerve ends and resulting in useful functional outcomes. Thus the modified Somsak’s procedure can be a useful addendum in the shoulder animation of AUPBPI patients. Level of evidence: Level III, therapeutic study

Predicting Healthy C5 Spinal Nerve Stumps Eligible for Grafting with MRI, Tinel Test, and Rhomboid Electromyography: A Retrospective Study of 295 Consecutive Brachial Plexus Surgeries.

Background MRI, Tinel test, and rhomboid electromyography (EMG) can be used to predict whether C5 spinal nerve stumps are healthy and eligible for grafting in acute adult brachial plexus injuries, but their comparative diagnostic efficacies have not been evaluated. Purpose To compare diagnostic performances of MRI, Tinel test, and rhomboid EMG in predicting healthy C5 spinal nerve stumps that are eligible for grafting. Materials and Methods This retrospective study included consecutive adult patients with acute brachial plexus injury who underwent microreconstructions between January 2008 and December 2018. Healthy C5 spinal nerve stumps eligible for grafting with preceding normal intradural nerve rootlets were diagnosed by an experienced neuroradiologist using an avulsion severity score system based on fast imaging employing steady-state acquisition or FIESTA neurography, which separates intradural nerve rootlets into normal, partial mild, severe, and complete avulsions. Tinel test and rhomboid EMG results were assessed by an experienced nerve surgeon and neurologist, respectively. The accuracy, sensitivity, and specificity of the three tests were compared using microdissection as the reference standard. P < .05 was considered to indicate a significant difference. Results A total of 251 patients (mean age, 31 years ± 13 [standard deviation]; 217 men) with brachial plexus injuries who had -undergone MRI (n = 251), Tinel test (n = 235), rhomboid EMG (n = 181) and MRI, Tinel test, and EMG (n = 172) were -included. Accuracy, sensitivity, and specificity, respectively, in predicting healthy C5 spinal nerve stumps eligible for grafting were 93% (233 of 251), 84% (58 of 69), and 96% (175 of 182) for MRI; 59% (139 of 235), 56% (37 of 66), and 60% (102 of 169) for Tinel test; and 39% (71 of 181), 85% (43 of 50), and 21% (28 of 131) for rhomboid EMG. MRI (area under the receiver operating characteristic curve [AUC], 0.90; P < .001) -outperformed MRI and Tinel test (AUC, 0.74), Tinel test (AUC, 0.59), and rhomboid EMG (AUC, 0.53). Conclusion MRI performed best in the prediction of healthy graftable C5 spinal nerve stumps in acute adult brachial plexus injuries. © RSNA, 2021 Online supplemental material is available for this article.

A quantitative analysis of the dimensions and content of the vertebral triangle.

The vertebral triangle (VT) located in the root of the neck most commonly contains the vertebral artery (VA), cervical sympathetic chain and certain roots of the brachial plexus. Although other structures have been reported, few studies have reported on the overall content of this space. Based on the current literature, there is a general paucity of anatomical information pertaining to the dimensional anatomy of the VT and specifically the structures related to it. Therefore, this study aimed to quantitatively analyze the size, position, content, and anatomical structures in relation to the vertebral triangle in a South African sample. Forty-three VTs were dissected on bodies donated to science. Measurements taken include the dimensions of the triangle, as well as distances between prominent structures and landmarks of the VT. Observations were made on the presence/absence of the varying neurovascular structures within the VT. Mean height was 30.1 ± 1.51mm (R) and 32.9 ± 1.78mm (L). Mean width was 18.3 ± 0.74mm (R) and 19.3 ± 0.98mm (L). The C8 spinal nerve was found on average approximately halfway [16.4 ± 0.74mm (R) and 15.9 ± 0.95mm (L)] in the VT. The VA was present in the VT in 100% of the sample and the C7 spinal nerve and inferior sympathetic ganglia were present in more than 80% of the sample. Understanding the VT and the content is of the utmost importance and of great interest to neurosurgeons, to avoid these important neurovascular structures and prevent iatrogenic complications during surgery.