A Perspective on Electrical Stimulation and Sympathetic Regeneration in Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are common and devastating. The current standard of care relies on the slow and inefficient process of nerve regeneration after surgical intervention. Electrical stimulation (ES) has been shown to both experimentally and clinically result in improved regeneration and functional recovery after PNI for motor and sensory neurons; however, its effects on sympathetic regeneration have never been studied. Sympathetic neurons are responsible for a myriad of homeostatic processes that include, but are not limited to, blood pressure, immune response, sweating, and the structural integrity of the neuromuscular junction. Almost one quarter of the axons in the sciatic nerve are from sympathetic neurons, and their importance in bodily homeostasis and the pathogenesis of neuropathic pain should not be underestimated. Therefore, as ES continues to make its way into patient care, it is not only important to understand its impact on all neuron subtypes, but also to ensure that potential adverse effects are minimized. This piece gives an overview of the effects of ES in animals models and in humans while offering a perspective on the potential effects of ES on sympathetic axon regeneration.

Surgical Interventions Targeting the Nucleus Caudalis for Craniofacial Pain: A Systematic and Historical Review

INTRODUCTION

Craniofacial pain is a prevalent group of conditions, and when refractory to conventional treatments, it poses a significant burden. The last decade has seen a renewed interest in the multimodal management of pain. Interventions targeting the nucleus caudalis (NC) of the trigeminocervical complex have been available as a treatment option since the 1930s, yet evidence for efficacy remains limited.

MATERIALS AND METHODS

We present a systematic review of the literature providing a historical perspective on interventions targeting the NC leading up to the present. We examine the various intervention techniques, clinical indications, and procedural efficacy. A novel outcome-reporting scheme was devised to enable comparison among studies owing to historically variable reporting methods.

RESULTS

A review of the literature revealed 33 retrospective studies published over the last 80 years, reporting on 827 patients. The most common technique was the open NC dorsal root entry zone nucleotomy/tractotomy; however, there has been an emergence of novel approaches such as endoscopic and spinal cord stimulation in the last ten years. Regardless of intervention technique or preoperative diagnosis, 87% of patients showed improvement with treatment.

CONCLUSIONS

The literature surrounding NC intervention techniques is reviewed. Recent advancements and the wide range of craniofacial pain syndromes for which these interventions show potential efficacy are discussed. New and less invasive techniques continue to emerge as putative therapeutic options. However, prospective studies are lacking. Furthermore, the evidence supporting even well-established techniques remains of poor quality. Future work should be prospective, use standard outcome reporting, and address efficacy comparisons between intervention type and preoperative diagnosis.

Tumor microenvironment in a minipig model of spinal cord glioma

BACKGROUND

Spinal cord glioma (SCG) is considered an orphan disease that lacks effective treatment options with margins that are surgically inaccessible and an overall paucity of literature on the topic. The tumor microenvironment is a critical factor to consider in treatment and modeling design, especially with respect to the unresectable tumor edge. Recently, our group developed a high-grade spinal cord glioma (SCG) model in Göttingen minipigs.

METHODS

Immunofluorescence and ELISA were performed to explore the microenvironmental features and inflammation cytokines in this minipig SCG model. Protein carbonyl assay and GSH/GSSG assay were analyzed in the core and edge lesions in the minipig SCG model. The primary core and edge cells proliferation rate were shown in vitro, and the xenograft model in vivo.

RESULTS

We identified an elevated Ki-67 proliferative index, vascular and pericyte markers, CD31 and desmin in the tumor edge as compared to the tumor core. In addition, we found that the tumor edge demonstrated increased pro-inflammatory and gliomagenic cytokines including TNF-α, IL-1β, and IL-6. Furthermore, the mediation of oxidative stress is upregulated in the tumor edge. Hypoxic markers had statistically significant increased staining in the tumor core, but were notably still present in the tumor edge. The edge cells cultures derived from SCG biopsy also demonstrated an increased proliferative rate compared to core cell cultures in a xenotransplantation model.

CONCLUSIONS

Our study demonstrates heterogeneity in microenvironmental features in our minipig model of high-grade SCG, with a phenotype at the edge showing increased oxidative stress, proliferation, inflammatory cytokines, neovascularization, and decreased but present staining for hypoxic markers. These findings support the utility of this model as a means for investigating therapeutic approaches targeting the more aggressive and surgically unresectable tumor border.

Spinal cord and brain concentrations of riluzole after oral and intrathecal administration: A potential new treatment route for amyotrophic lateral sclerosis

Riluzole is the only treatment known to improve survival in patients with Amyotrophic Lateral Sclerosis (ALS). However, oral riluzole efficacy is modest at best, further it is known to have large inter-individual variability of serum concentration and clearance, is formulated as an oral drug in a patient population plagued with dysphagia, and has known systemic side-effects like asthenia (limiting patient compliance) and elevated liver enzymes. In this context, we postulated that continuous intrathecal (IT) infusion of low doses of riluzole could provide consistent elevations of the drug spinal cord (SC) concentrations at or above those achieved with oral dosing, without increasing the risk for adverse events associated with systemic drug exposure or off-target side effects in the brain. We developed a formulation of riluzole for IT delivery and conducted our studies in purpose-bred hound dogs. Our non-GLP studies revealed that IT infusion alone was able to increase SC concentrations above those provided by oral administration, without increasing plasma concentrations. We then conducted two GLP studies that combined IT infusion with oral administration at human equivalent dose, to evaluate SC and brain concentrations of riluzole along with assessments of safety and tolerability. In the 6-week study, the highest IT dose (0.2 mg/hr) was well tolerated by the animals and increased SC concentrations above those achieved with oral riluzole alone, without increasing brain concentrations. In the 6-month study, the highest dose tested (0.4 mg/hr) was not tolerated and yielded SC significantly above those achieved in all previous studies. Our data show the feasibility and safety profile of continuous IT riluzole delivery to the spinal cord, without concurrent elevated liver enzymes, and minimal brain concentrations creating another potential therapeutic route of delivery to be used in isolation or in combination with other therapeutics."

Current and emerging targeted therapies for spinal muscular atrophy

INTRODUCTION

Spinal muscular atrophy (SMA) is a progressive neurodegenerative disorder caused by insufficiency or total absence of the survival motor neuron protein due to a mutation in the SMN1 gene. The copy number of its paralog, SMN2, influences disease onset and phenotype severity. Current therapeutic approaches include viral and non-viral modalities affecting gene expression. Regulatory-approved drugs Spinraza (Nusinersen), Zolgensma (Onasemnogene abeparvovec), and Evrysdi (Risdiplam) are still being investigated during clinical trials and show benefits in the long-term for symptomatic and pre-symptomatic patients. However, some ongoing interventions require repeated drug administration.

AREAS COVERED

In this review, the authors describe the existing therapy based on point of application, focusing on recent clinical trials of antisense oligonucleotides, viral gene therapy, and splice modulators and thepotential routes for correcting the mutation to provide therapeutic levels of SMN protein.

EXPERT OPINION

In the opinion of the authors, multiple treatment options for patients with SMA shifted the treatment paradigm from palliative supportive care to improvedmotor function, increased survival, and greater quality of life for such patients. They further believe that the future in SMA treatment development lies incombining existing treatment options, targeting aspects of the disease refractory to these treatments, and using gene editing technologies.

Complication rate of overlapping versus nonoverlapping functional and stereotactic surgery: a retrospective cohort study

OBJECTIVE

Overlapping surgery, in which one attending surgeon manages two overlapping operating rooms (ORs) and is present for all the critical portions of each procedure, is an important policy that improves healthcare access for patients and case volumes for surgeons and surgical trainees. Despite several studies demonstrating the safety and efficacy of overlapping neurosurgical operations, the practice of overlapping surgery remains controversial. To date, there are no studies that have investigated long-term complication rates of overlapping functional and stereotactic neurosurgical procedures. The primary objective of this study was to investigate the 1-year complication rates and OR times for nonoverlapping versus overlapping functional procedures. The secondary objective was to gain insight into what types of complications are the most prevalent and test for differences between groups.

METHODS

Seven hundred eighty-three functional neurosurgical cases were divided into two cohorts, nonoverlapping (n = 342) and overlapping (n = 441). The American Society of Anesthesiologists (ASA) scale score was used to compare the preoperative risk for both cohorts. A complication was defined as any surgically related reason that required readmission, reoperation, or an unplanned emergency department or clinic visit that required intervention. Complications were subdivided into infectious and noninfectious. Chi-square tests, independent-samples t-tests, and uni- and multivariable logistic regressions were used to determine significance.

RESULTS

There were no significant differences in mean ASA scale score (2.7 ± 0.6 for both groups, p = 0.997) or overall complication rates (8.8% nonoverlapping vs 9.8% overlapping, p = 0.641) between the two cohorts. Infections accounted for the highest percentage of complications in both cohorts (46.6% vs 41.8%, p = 0.686). There were no statistically significant differences between mean in-room OR time (187.5 ± 141.7 minutes vs 197.1 ± 153.0 minutes, p = 0.373) or mean open-to-close time (112.2 ± 107.9 minutes vs 121.0 ± 123.1 minutes, p = 0.300) between nonoverlapping and overlapping cases.

CONCLUSIONS

There was no increased risk of 1-year complications or increased OR time for overlapping functional and stereotactic neurosurgical procedures compared with nonoverlapping procedures.

Patients with Cognitive Impairment in Parkinson's Disease Benefit from Deep Brain Stimulation: A Case-Control Study

Background

Deep brain stimulation (DBS) for Parkinson's disease (PD) is generally contraindicated in persons with dementia but it is frequently performed in people with mild cognitive impairment or normal cognition, and current clinical guidelines are primarily based on these cohorts.

Objectives

To determine if moderately cognitive impaired individuals including those with mild dementia could meaningfully benefit from DBS in terms of motor and non-motor outcomes.

Methods

In this retrospective case-control study, we identified a cohort of 40 patients with PD who exhibited moderate (two or more standard deviations below normative scores) cognitive impairment (CI) during presurgical workup and compared their 1-year clinical outcomes to a cohort of 40 matched patients with normal cognition (NC). The surgery targeted subthalamus, pallidus or motor thalamus, in a unilateral, bilateral or staged approach.

Results

At preoperative baseline, the CI cohort had higher Unified Parkinson's Disease Rating Scale (UPDRS) subscores, but similar levodopa responsiveness compared to the NC cohort. The NC and CI cohorts demonstrated comparable degrees of postoperative improvement in the OFF-medication motor scores, motor fluctuations, and medication reduction. There was no difference in adverse event rates between the two cohorts. Outcomes in the CI cohort did not depend on the target, surgical staging, or impaired cognitive domain.

Conclusions

Moderately cognitively impaired patients with PD can experience meaningful motor benefit and medication reduction with DBS.

MODL-28. DEVELOPING A STRATEGY FOR MODELING HIGH-GRADE GLIOMA IN GӦTTINGEN MINIPIGS

BACKGROUND

The current literature does not describe a reproducible large animal model of intracranial high-grade glioma (HGG). Prior work has demonstrated the feasibility of inducing HGG de-novo in rodents by targeting specific oncogenic pathways. Here we report our approach to the production of supratentorial HGG in a series of minipigs through lentiviral gene transfer and subsequent initial characterization of a porcine glioma cell line.

METHODS

Four minipigs received injections into the subcortical white matter using a combination of lentiviral vectors expressing platelet-derived growth factor beta (PDGF-B), HRAS, and shRNA-p53. Animals underwent behavioral monitoring through porcine neurobehavioral scoring (PNS) and veterinary monitoring. Magnetic resonance imaging (MRI) was conducted at endpoint prior to necropsy. Post-mortem tissue biopsies underwent tissue culture and neuropathologic evaluation with hematoxylin and eosin (H&E) staining, immunohistochemistry, and immunofluorescent staining. Data are presented using appropriate statistical tests where relevant and descriptive statistics.

RESULTS

Two pigs received 50ul injections and reached endpoint by the end of post-operative week 1 and 2. Two pigs received 25 ul injections and were asymptomatic until a pre-determined endpoint of 4 weeks. MRI scans at endpoint demonstrated contrast enhancing, mass forming lesions at the site of injection with evidence of hemorrhage and perilesional edema, consistent with high-grade glioma. On H&E staining high-grade glioma growth was identified in 100% of animals. We observed immunopositivity for tumor markers GFAP, OLIG2, NG2, SOX2, and PDGFRA, as well as redox markers, and microenvironmental features consistent with high-grade glioma. Porcine glioma cell cultures were found to have significantly greater proliferative rate compared to control, and demonstrated GFAP, OLIG2, PDGFRA, and CD68 immunopositivity.

CONCLUSIONS

Lentiviral gene transfer represents a feasible strategy for glioma modeling in the Gӧttingen minipig. With our described methodology, we present a realistic strategy for reproducible modeling of intracranial glioma as a platform for preclinical neurosurgical development programs.

Abstract 1609: Oxidative stress triggers tumor edge progression of tumor microenvironment in the minipig spinal cord glioma model

Oxidative stress is exerted by reactive oxygen species (ROS) that accumulate due to an imbalance between ROS generation and elimination, which impacts cellular metabolism and consequently tumorigenesis in the tumor microenvironment. Recently, our group has developed a spinal cord glioma (SCG) model in Göttingen minipigs. However, the mechanism of how SCGs balance redox and thereby modulate cellular proliferation is unclear. Here, we demonstrated that the NRF2/NQO1 signaling, known to mediate oxidative stress, is upregulated in unresectable SCG cells infiltrating at the leading edge compared with the core cells. Moreover, pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6, were significantly elevated in the edge SCG cells. Immunohistochemistry demonstrated positive staining for a higher Ki-67 proliferative index, GFAP, SOX2 and Olig2 in the edge cells compared to the core cells. The oxidative metabolic heterogeneity of immune and stromal cell subtypes among tumor samples was also explored. Hence, our study demonstrated the tumor microenvironment and involvement of the NRF2/NQO1 pathway for redox homeostasis in our minipig SCG model, which can be used to explore targets of the pre-clinical treatment investigations in SCG.

Citation Format: Kecheng Lei, Muhibullah S. Tora, Stewart G. Neill, Purva P. Nagarajan, Thais Federici, Peter Canoll, Nicholas M. Boulis. Oxidative stress triggers tumor edge progression of tumor microenvironment in the minipig spinal cord glioma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1609.

Lentiviral-Induced Spinal Cord Gliomas in Rat Model

Intramedullary spinal cord tumors are a rare and understudied cancer with poor treatment options and prognosis. Our prior study used a combination of PDGF-B, HRAS, and p53 knockdown to induce the development of high-grade glioma in the spinal cords of minipigs. In this study, we evaluate the ability of each vector alone and combinations of vectors to produce high-grade spinal cord gliomas. Eight groups of rats (n = 8/group) underwent thoracolumbar laminectomy and injection of lentiviral vector in the lateral white matter of the spinal cord. Each group received a different combination of lentiviral vectors expressing PDGF-B, a constitutively active HRAS mutant, or shRNA targeting p53, or a control vector. All animals were monitored once per week for clinical deficits for 98 days. Tissues were harvested and analyzed using hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining. Rats injected with PDGF-B+HRAS+sh-p53 (triple cocktail) exhibited statistically significant declines in all behavioral measures (Basso Beattie Bresnahan scoring, Tarlov scoring, weight, and survival rate) over time when compared to the control. Histologically, all groups except the control and those injected with sh-p53 displayed the development of tumors at the injection site, although there were differences in the rate of tumor growth and the histopathological features of the lesions between groups. Examination of immunohistochemistry revealed rats receiving triple cocktail displayed the largest and most significant increase in the Ki67 proliferation index and GFAP positivity than any other group. PDGF-B+HRAS also displayed a significant increase in the Ki67 proliferation index. Rats receiving PDGF-B alone and PDGF-B+ sh-p53 displayed more a significant increase in SOX2-positive staining than in any other group. We found that different vector combinations produced differing high-grade glioma models in rodents. The combination of all three vectors produced a model of high-grade glioma more efficiently and aggressively with respect to behavioral, physiological, and histological characteristics than the rest of the vector combinations. Thus, the present rat model of spinal cord glioma may potentially be used to evaluate therapeutic strategies in the future.

Percutaneous trigeminal tractotomy for trigeminal neuralgia: Postoperative MRI findings

BACKGROUND AND PURPOSE

Percutaneous trigeminal tractotomy is an ablative procedure that can be used to treat trigeminal neuralgia in patients who have failed prior pharmacologic and surgical treatments. Using perioperative computed tomography (CT) guidance, ablation of the descending spinal trigeminal nucleus and trigeminal tract can be performed precisely to mitigate damage to surrounding structures. These patients are subsequently followed with postoperative imaging and clinical visits to assess long-term pain relief.

METHODS

In this report, we present a series of four patients with trigeminal neuralgia who were had refractory disease after prior medical and surgical interventions. These patients underwent CT-guided percutaneous trigeminal tractotomy for pain relief. The patients underwent postoperative MRI and were followed for up to 6 months for long-term clinical outcomes.

RESULTS

For intraoperative CT, we find that preprocedure lumbar contrast injection enables better visualization of the cord during placement of the ablation probe. On postoperative imaging, we find that all four patients have hyperintense lesions on T2-weighted MRI that correspond with the location of the trigeminal nucleus and tract. Three patients had short-term pain relief, one of which continued to have long-term relief.

CONCLUSION

Intraoperative CT and postoperative MRI serve as useful modalities for confirming localization, evaluating complications, and can be used as a metric for quality control.

Complication Rates in Early Versus Late Cranioplasty-A 14-Year Single-Center Case Series

BACKGROUND

Cranioplasty (CP) following decompressive craniectomy (DC) is a common neurosurgical procedure for cranial cosmesis and protection. There is uncertainty regarding the complication rates and potential benefits related to the timing of CP.

OBJECTIVE

To investigate the impact of the timing of CP on complication rates for different etiologies of DC.

METHODS

A retrospective chart review was performed of all CP cases between 2004 and 2018 for traumatic and nontraumatic indications of DC. Demographics, clinical characteristics, and complications were collected. Early and late CP were defined as replacement of the bone flap at ≤90 and >90 d following DC, respectively.

RESULTS

A total of 278 patients were included, receiving 81 early and 197 late CPs. When analyzing all patients, early CP was associated with a statistically significant higher odds of any complication (odds ratio [OR]: 3.25, P < .001), reoperation (OR: 2.57, P = .019), hydrocephalus (OR: 6.03, P = .003), and symptomatic extra-axial collections (OR: 9.22, P = .003). Subgroup analysis demonstrated statistically significant higher odds of these complications only for the CP trauma subgroup, but not the nontrauma subgroup. The odds of complications postCP demonstrated a statistically significant decrease of 4.4% for each week after DC (Unit Odds Ratio [U-OR]: 0.956, P = .0363).

CONCLUSION

In our retrospective series, early CP was associated with higher odds of postoperative complications compared to late CP in the trauma subgroup. Greater care should be taken in preoperative planning and increased vigilance postoperatively for complications with this potentially more vulnerable subpopulation. Future prospective controlled trials are needed to elucidate optimal timing for CP.

Chemogenetics: Beyond Lesions and Electrodes

The field of chemogenetics has rapidly expanded over the last decade, and engineered receptors are currently utilized in the lab to better understand molecular interactions in the nervous system. We propose that chemogenetic receptors can be used for far more than investigational purposes. The potential benefit of adding chemogenetic neuromodulation to the current neurosurgical toolkit is substantial. There are several conditions currently treated surgically, electrically, and pharmacologically in clinic, and this review highlights how chemogenetic neuromodulation could improve patient outcomes over current neurosurgical techniques. We aim to emphasize the need to take these techniques from bench to bedside.

A Stereotactic Device for Intraparenchymal Spinal Cord Injections: Latest Developments for Practical Clinical Use

This manuscript introduces the latest generation of a patient-mounted platform designed for segmental injections of therapeutics direct into the spinal cord parenchyma. It emphasizes its importance and it presents the rationale for developing this delivery methodology. It compares the newest with the previous generations, detailing how the modifications can streamline transportation, assembly, sterilization, and utilization of the platform by different surgeons. Finally, the illustrations depict the main alterations, as well as a cadaveric assessment of the device prototype in the cervical and thoracolumbar regions.

Percutaneous Trigeminal Stimulation for Intractable Facial Pain: A Case Series

BACKGROUND

Facial pain syndromes can be refractory to medical management and often need neurosurgical interventions. Neuromodulation techniques, including percutaneous trigeminal ganglion (TG) stimulation, are reversible and have emerged as alternative treatment options for intractable facial pain.

OBJECTIVE

To report the complication rates and analgesic effects associated with TG stimulation and identify potential predictors for these outcomes.

METHODS

A retrospective chart review of 59 patients with refractory facial pain who underwent TG stimulation was conducted. Outcomes following trial period and permanent stimulation were analyzed. Patients with >50% pain relief during trial stimulation received permanent implantation of the stimulation system.

RESULTS

Successful trial stimulation was endorsed by 71.2% of patients. During the trial period, 1 TG lead erosion was identified. History of trauma (facial/head trauma and oral surgery) was the only predictor of a failed trial compared to pain of idiopathic etiology (odds ratio: 0.15; 95% CI: 0.03-0.66). Following permanent implantation, approximately 29.6% and 26.5% of patients were diagnosed with lead erosion and infection of the hardware, respectively. TG lead migrations occurred in 11.7% of the patients. The numeric rating scale score showed a statistically significant reduction of 2.49 (95% CI: 1.37-3.61; P = .0001) at an average of 10.8 mo following permanent implantation.

CONCLUSION

TG stimulation is a feasible neuromodulatory approach for the treatment of intractable facial pain. Facial/head trauma and oral surgery may predict a nonsuccessful trial stimulation. Future development of specifically designed electrodes for stimulation of the TG, and solutions to reduce lead contamination are needed to mitigate the relatively high complication rate.

Programming Parameters and Techniques in Trigeminal Ganglion Stimulation for Intractable Facial Pain

OBJECTIVES

Atypical facial pain syndromes are challenging disorders to manage and often incur limited benefit with surgery for classical trigeminal neuralgia presentations, such as microvascular decompression or ablative procedures. Neurostimulation of the trigeminal ganglion and peripheral nerves can be effective at treating atypical presentations of trigeminal facial pain affecting the V1-3 dermatomes, and the surgical techniques are well described. The stimulation parameters, however, have thus far received limited description; we therefore sought to describe programming strategies.

MATERIALS AND METHODS

We performed a retrospective chart review, examining patients that underwent trigeminal ganglion stimulation (TGS) and nerve branch stimulation for atypical facial pain and trigeminal neuropathic pain, and describe the programming strategies in detail.

RESULTS

We describe the use of high-frequency stimulation (1000 Hz), with alteration in pulse width (60-220 msec) and amplitude (0.5-3 V) to achieve effective treatment of refractory trigeminal facial pain. These parameters differ from existing published parameters for trigeminal nerve branch stimulation. We also describe the programming of specific contacts on each lead to target specific aspects of the individual patients' facial pain.

CONCLUSIONS

The use of effective programming strategies is critical to the success of neurostimulation surgical treatments; however, the critical details in programming strategies typically receive limited description. We report on the use of several successful programming strategies for TGS, to assist pain providers in successfully applying these surgical techniques in these difficult to manage atypical facial pain syndromes.

Minimally Invasive Injection to the Phrenic Nerve in a Porcine Hemidiaphragmatic Paralysis Model: A Pilot Study

BACKGROUND

Neurodegenerative diseases and spinal cord injury can affect respiratory function often through motor neuron loss innervating the diaphragm. To reinnervate this muscle, new motor neurons could be transplanted into the phrenic nerve (PN), allowing them to extend axons to the diaphragm. These neurons could then be driven by an optogenetics approach to regulate breathing. This type of approach has already been demonstrated in the peripheral nerves of mice. However, there is no established thoracoscopic approach to PN injection. Also, there is currently a lack of preclinical large animal models of diaphragmatic dysfunction in order to evaluate the efficacy of potential treatments.

OBJECTIVE

To evaluate the feasibility of thoracoscopic drug delivery into the PN and to assess the viability of hemidiaphragmatic paralysis in a porcine model.

METHODS

Two Landrace farm pigs underwent a novel procedure for thoracoscopic PN injections, including 1 nonsurvival and 1 survival surgery. Nonsurvival surgery involved bilateral PN injections and ligation. Survival surgery included a right PN injection and transection proximal to the injection site to induce hemidiaphragmatic paralysis.

RESULTS

PN injections were successfully performed in both procedures. The animal that underwent survival surgery recovered postoperatively with an established right hemidiaphragmatic paralysis. Over the 5-d postoperative period, the animal displayed stable vital signs and oxygenation saturation on room air with voluntary breathing.

CONCLUSION

Thoracoscopic targeting of the porcine PN is a feasible approach to administer therapeutic agents. A swine model of hemidiaphragmatic paralysis induced by unilateral PN ligation or transection may be potentially used to study diaphragmatic reinnervation following delivery of therapeutics.

Controlling the Release of Neurotrophin-3 and Chondroitinase ABC Enhances the Efficacy of Nerve Guidance Conduits

Nerve guidance conduits (NGCs) have the potential to replace autografts in repairing peripheral nerve injuries, but their efficacy still needs to be improved. The efficacy of NGCs is augmented by neurotrophic factors that promote axon growth and by enzymes capable of degrading molecules that inhibit axon growth. In the current study, two types of NGCs loaded with factors (both neurotrophin-3 and chondroitinase ABC) are constructed and their abilities to repair an 8 mm gap in the rat sciatic nerve are examined. The factors are encapsulated in microparticles made of a phase-change material (PCM) or collagen and then sandwiched between two layers of electrospun fibers. The use of PCM allows to achieve pulsed release of the factors upon irradiation with a near-infrared laser. The use of collagen enables slow, continuous release via diffusion. The efficacy is evaluated by measuring compound muscle action potentials (CMAP) in the gastrocnemius muscle and analyzing the nerve histology. Continuous release of the factors from collagen results in enhanced CMAP amplitude and increased axon counts in the distal nerve relative to the plain conduit. In contrast, pulsed release of the same factors from PCM shows a markedly adverse impact on the efficacy, possibly by inhibiting axon growth.

Chimeric Peptide Species Contribute to Divergent Dipeptide Repeat Pathology in c9ALS/FTD and SCA36

GGGGCC hexanucleotide repeat expansions (HREs) in C9orf72 cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and lead to the production of aggregating dipeptide repeat proteins (DPRs) via repeat associated non-AUG (RAN) translation. Here, we show the similar intronic GGCCTG HREs that causes spinocerebellar ataxia type 36 (SCA36) is also translated into DPRs, including poly(GP) and poly(PR). We demonstrate that poly(GP) is more abundant in SCA36 compared to c9ALS/FTD patient tissue due to canonical AUG-mediated translation from intron-retained GGCCTG repeat RNAs. However, the frequency of the antisense RAN translation product poly(PR) is comparable between c9ALS/FTD and SCA36 patient samples. Interestingly, in SCA36 patient tissue, poly(GP) exists as a soluble species, and no TDP-43 pathology is present. We show that aggregate-prone chimeric DPR (cDPR) species underlie the divergent DPR pathology between c9ALS/FTD and SCA36. These findings reveal key differences in translation, solubility, and protein aggregation of DPRs between c9ALS/FTD and SCA36.

Peripheral trigeminal branch stimulation for refractory facial pain: A single-center experience

OBJECTIVE

Facial pain refractory to medical treatments may benefit from neurosurgical interventions. Only a few studies have reported on the efficacy of peripheral trigeminal stimulation and more specifically supraorbital nerve (SON) and infraorbital nerve (ION) stimulation for the treatment of facial pain.

PATIENTS AND METHODS

In the present study, we identified all patients at our institution who underwent SON and/or ION stimulation for treatment of facial pain due to post-herpetic, traumatic or idiopathic etiology. Relevant pre and post-operative outcomes were analyzed.

RESULTS

We identified 15 patients who underwent SON and/or ION stimulation. Among them, 12 (80 %) endorsed >50 % pain relief during the trial stimulation period. After a median follow-up of 5.8 months with permanent implantation, 1 patient (8.3 %) was diagnosed with lead erosion and IPG migration, two patients had lead infections (16.7 %) and one (8.3 %) had wound dehiscence. No lead migrations were identified during the long-term follow-up. The VAS score showed a statistically significant reduction from a median pre-operative score of 7 to a post-operative score of 1.8 (p = 0.011), which corresponded to a 74.3 % average pain reduction.

CONCLUSION

SON and/or ION stimulation can be an effective treatment for intractable facial pain due to post-herpetic, traumatic or idiopathic etiology; however the complication rate is relatively high. Future prospective studies with longer follow-up periods are warranted.

Clinical outcomes of globus pallidus deep brain stimulation for Parkinson disease: a comparison of intraoperative MRI- and MER-guided lead placement

OBJECTIVE

Deep brain stimulation (DBS) lead placement is increasingly performed with the patient under general anesthesia by surgeons using intraoperative MRI (iMRI) guidance without microelectrode recording (MER) or macrostimulation. The authors assessed the accuracy of lead placement, safety, and motor outcomes in patients with Parkinson disease (PD) undergoing DBS lead placement into the globus pallidus internus (GPi) using iMRI or MER guidance.

METHODS

The authors identified all patients with PD who underwent either MER- or iMRI-guided GPi-DBS lead placement at Emory University between July 2007 and August 2016. Lead placement accuracy and adverse events were determined for all patients. Clinical outcomes were assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) part III motor scores for patients completing 12 months of follow-up. The authors also assessed the levodopa-equivalent daily dose (LEDD) and stimulation parameters.

RESULTS

Seventy-seven patients were identified (MER, n = 28; iMRI, n = 49), in whom 131 leads were placed. The stereotactic accuracy of the surgical procedure with respect to the planned lead location was 1.94 ± 0.21 mm (mean ± SEM) (95% CI 1.54-2.34) with frame-based MER and 0.84 ± 0.007 mm (95% CI 0.69-0.98) with iMRI. The rate of serious complications was similar, at 6.9% for MER-guided DBS lead placement and 9.4% for iMRI-guided DBS lead placement (RR 0.71 [95% CI 0.13%-3.9%]; p = 0.695). Fifty-seven patients were included in clinical outcome analyses (MER, n = 16; iMRI, n = 41). Both groups had similar characteristics at baseline, although patients undergoing MER-guided DBS had a lower response on their baseline levodopa challenge (44.8% ± 5.4% [95% CI 33.2%-56.4%] vs 61.6% ± 2.1% [95% CI 57.4%-65.8%]; t = 3.558, p = 0.001). Greater improvement was seen following iMRI-guided lead placement (43.2% ± 3.5% [95% CI 36.2%-50.3%]) versus MER-guided lead placement (25.5% ± 6.7% [95% CI 11.1%-39.8%]; F = 5.835, p = 0.019). When UPDRS III motor scores were assessed only in the contralateral hemibody (per-lead analyses), the improvements remained significantly different (37.1% ± 7.2% [95% CI 22.2%-51.9%] and 50.0% ± 3.5% [95% CI 43.1%-56.9%] for MER- and iMRI-guided DBS lead placement, respectively). Both groups exhibited similar reductions in LEDDs (21.2% and 20.9%, respectively; F = 0.221, p = 0.640). The locations of all active contacts and the 2D radial distance from these to consensus coordinates for GPi-DBS lead placement (x, ±20; y, +2; and z, -4) did not differ statistically by type of surgery.

CONCLUSIONS

iMRI-guided GPi-DBS lead placement in PD patients was associated with significant improvement in clinical outcomes, comparable to those observed following MER-guided DBS lead placement. Furthermore, iMRI-guided DBS implantation produced a similar safety profile to that of the MER-guided procedure. As such, iMRI guidance is an alternative to MER guidance for patients undergoing GPi-DBS implantation for PD.

CRISPR-mediated gene correction links the ATP7A M1311V mutations with amyotrophic lateral sclerosis pathogenesis in one individual

Amyotrophic lateral sclerosis (ALS) is a severe disease causing motor neuron death, but a complete cure has not been developed and related genes have not been defined in more than 80% of cases. Here we compared whole genome sequencing results from a male ALS patient and his healthy parents to identify relevant variants, and chose one variant in the X-linked ATP7A gene, M1311V, as a strong disease-linked candidate after profound examination. Although this variant is not rare in the Ashkenazi Jewish population according to results in the genome aggregation database (gnomAD), CRISPR-mediated gene correction of this mutation in patient-derived and re-differentiated motor neurons drastically rescued neuronal activities and functions. These results suggest that the ATP7A M1311V mutation has a potential responsibility for ALS in this patient and might be a potential therapeutic target, revealed here by a personalized medicine strategy.

Frameless Stereotactic Targeting of the Cerebellar Dentate Nucleus in Nonhuman Primates: Translatable Model for the Surgical Delivery of Gene Therapy

BACKGROUND

Stereotactic targeting techniques in nonhuman primate (NHP) models are often utilized in the preclinical investigation of new drug therapies with the goal of demonstrating accurate and reliable delivery of a therapy to the target tissue. However, targeting certain neuroanatomical structures can be challenging. The deep cerebellar nuclei, specifically the dentate nucleus, are potential stereotactic targets for the treatment of certain ataxias. Currently, there are no detailed techniques describing frameless targeting of these structures in a NHP model. A well-defined, accurate, and reliable stereotactic surgical approach to the dentate in these animal models is critical to prove the feasibility and safety of drug delivery in order to develop clinical protocols.

METHODS

Frameless stereotactic neuronavigation was employed to target the bilateral dentate nuclei of the cerebellum in four healthy juvenile Cynomolgus monkeys via a suboccipital, transcerebellar approach. The precision and accuracy of the targeting were evaluated radiologically and histologically.

RESULTS

Using the described surgical methodology, we were successful in hitting the target deep cerebellar nuclei seven out of eight times.

CONCLUSION

Frameless stereotactic targeting of the cerebellar dentate nuclei in NHPs for future investigational drug delivery is feasible, safe, and accurate as described by this report. Potential areas for improving the technique are discussed.

Lot-to-Lot Variation in Adeno-Associated Virus Serotype 9 (AAV9) Preparations

Viral vectors are complex drugs that pose a particular challenge for manufacturing. Previous studies have shown that, unlike small-molecule drugs, vector preparations do not yield a collection of identical particles. Instead, a mixture of particles that vary in capsid stoichiometry and impurities is created, which may differ from lot to lot. The consequences of this are unclear, but conflicting reports regarding the biological properties of vectors, including transduction patterns, suggest that this variability may have an effect. However, other variables, including differences in animal strains and techniques, make it difficult to identify a cause. Here, we report lot-to-lot variation in spinal cord gray matter transduction following intrathecal delivery of self-complementary adeno-associated virus serotype 9 vectors. Eleven lots of vector were evaluated from six vector cores, including one preclinical/Good Laboratory Practice lot. Eight of the lots, including the preclinical lot, failed to transduce the gray matter, whereas the other three provided robust transduction. The cause for this variation is unknown, but it did not correlate with vector titer, buffer, or purification method. These results highlight the need to identify the cause of this variation and to develop improved production and quality control methods to ensure lot-to-lot consistency of vector potency.

Clinical outcomes of pallidal deep brain stimulation for dystonia implanted using intraoperative MRI

OBJECTIVE

Lead placement for deep brain stimulation (DBS) using intraoperative MRI (iMRI) relies solely on real-time intraoperative neuroimaging to guide electrode placement, without microelectrode recording (MER) or electrical stimulation. There is limited information, however, on outcomes after iMRI-guided DBS for dystonia. The authors evaluated clinical outcomes and targeting accuracy in patients with dystonia who underwent lead placement using an iMRI targeting platform.

METHODS

Patients with dystonia undergoing iMRI-guided lead placement in the globus pallidus pars internus (GPi) were identified. Patients with a prior ablative or MER-guided procedure were excluded from clinical outcomes analysis. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) scores and Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) scores were assessed preoperatively and at 6 and 12 months postoperatively. Other measures analyzed include lead accuracy, complications/adverse events, and stimulation parameters.

RESULTS

A total of 60 leads were implanted in 30 patients. Stereotactic lead accuracy in the axial plane was 0.93 ± 0.12 mm from the intended target. Nineteen patients (idiopathic focal, n = 7; idiopathic segmental, n = 5; DYT1, n = 1; tardive, n = 2; other secondary, n = 4) were included in clinical outcomes analysis. The mean improvement in BFMDRS score was 51.9% ± 9.7% at 6 months and 63.4% ± 8.0% at 1 year. TWSTRS scores in patients with predominant cervical dystonia (n = 13) improved by 53.3% ± 10.5% at 6 months and 67.6% ± 9.0% at 1 year. Serious complications occurred in 6 patients (20%), involving 8 of 60 implanted leads (13.3%). The rate of serious complications across all patients undergoing iMRI-guided DBS at the authors' institution was further reviewed, including an additional 53 patients undergoing GPi-DBS for Parkinson disease. In this expanded cohort, serious complications occurred in 11 patients (13.3%) involving 15 leads (10.1%).

CONCLUSIONS

Intraoperative MRI-guided lead placement in patients with dystonia showed improvement in clinical outcomes comparable to previously reported results using awake MER-guided lead placement. The accuracy of lead placement was high, and the procedure was well tolerated in the majority of patients. However, a number of patients experienced serious adverse events that were attributable to the introduction of a novel technique into a busy neurosurgical practice, and which led to the revision of protocols, product inserts, and on-site training.

<p>High cervical spinal cord stimulation for occipital neuralgia: a case series and literature review</p>

Background

Occipital neuralgia (ON) is defined as paroxysmal pain in the distribution of the greater, lesser, and/or third occipital nerves. ON can be refractory to conservative management and minimally invasive interventions. Neuromodulatory procedures can potentially treat refractory ON and include occipital nerve stimulation and the sparsely reported high cervical spinal cord stimulation (SCS).

Objective

To report our experience and conduct a systematic literature review of studies evaluating the effect of high cervical SCS as a treatment modality for refractory ON.

Methods

A retrospective review of patients with refractory ON who underwent high cervical SCS was conducted. In addition, a systematic literature review was performed according to the PRISMA guidelines.

Results

Five patients with refractory ON were treated with high cervical (C1–C3) SCS in our institution. Two out of five (40%) patients reported a successful trial stimulation (>50% pain reduction) and received permanent implantation. During the follow-up, the visual analog scale score decreased from 7.5 to 4 and from 6.5 to 5 in these patients. No complications were reported for any of the patients. The systematic literature review, identified two eligible studies, comprising 18 patients overall who underwent cervicomedullary junction SCS. Nine out of 18 patients (50%) had a successful trial and received permanent implantation.

Conclusion

High cervical or cervicomedullary junction SCS is associated with a 40–50% successful trial rate in refractory ON. No major complications were noted during the follow-up. Future studies are needed to compare the different neurosurgical options, in order to identify the optimal treatment strategy for refractory ON.

Treatment of neurofibromatosis 1-associated malignant peripheral nerve sheath tumors: a systematic review

Malignant peripheral nerve sheath tumors (MPNST) are a rare and aggressive group of tumors that are challenging to treat. Neurofibromatosis type 1 (NF-1)-associated MPNSTs have been associated with poorer clinical outcomes. The treatment options for NF-1-associated MPNSTs broadly include surgery (SG), chemotherapy (CT), and adjuvant radiotherapy (RT). Overall, the role and efficacy of CT and RT are unclear. Examination of existing literature for studies reporting on NF-1-associated MPNSTs and respective treatment-related outcomes was conducted. We conducted a systematic review according to PRISMA guidelines in PubMed/Medline and Cochrane databases of studies which reported treatment-specific outcomes in NF-1-associated MPNSTs. The literature search found 444 records after removal of duplicates. The present study included 50 patients across 12 observational studies. All of the included studies reported data on overall survival (OS 52%, n = 26/50) but mean follow-up in months among the studies and among patients varied widely, between 10.85 (SD, ± 10.38) and 192 (SD, ± 98.22). From the included studies, patients underwent either SG alone (n = 21), SG + CT (n = 10), SG + RT (n = 7), or SG + CT + RT (n = 12). The quality of evidence in the literature regarding optimal treatment options for NF-1-associated MPNSTs remains tenuous. Future retrospective and prospective comparative trials should consider adherence to a set of reporting guidelines to improve the quality of evidence in the literature with respect to individual treatment-related outcomes. The need for prospective multi-institutional efforts cannot be overstated.

Results from Phase I Clinical Trial with Intraspinal Injection of Neural Stem Cells in Amyotrophic Lateral Sclerosis: A Long-Term Outcome

The main objective of this phase I trial was to assess the feasibility and safety of microtransplanting human neural stem cell (hNSC) lines into the spinal cord of patients with amyotrophic lateral sclerosis (ALS). Eighteen patients with a definite diagnosis of ALS received microinjections of hNSCs into the gray matter tracts of the lumbar or cervical spinal cord. Patients were monitored before and after transplantation by clinical, psychological, neuroradiological, and neurophysiological assessment. For up to 60 months after surgery, none of the patients manifested severe adverse effects or increased disease progression because of the treatment. Eleven patients died, and two underwent tracheotomy as a result of the natural history of the disease. We detected a transitory decrease in progression of ALS Functional Rating Scale Revised, starting within the first month after surgery and up to 4 months after transplantation. Our results show that transplantation of hNSC is a safe procedure that causes no major deleterious effects over the short or long term. This study is the first example of medical transplantation of a highly standardized cell drug product, which can be reproducibly and stably expanded ex vivo, comprising hNSC that are not immortalized, and are derived from the forebrain of the same two donors throughout this entire study as well as across future trials. Our experimental design provides benefits in terms of enhancing both intra‐ and interstudy reproducibility and homogeneity. Given the potential therapeutic effects of the hNSCs, our observations support undertaking future phase II clinical studies in which increased cell dosages are studied in larger cohorts of patients. stem cells translational medicine2019;8:887&897

Dorsal Root Ganglion Stimulation for Thoracic Neuralgia: A Report of Six Cases

Objective: Thoracic neuralgia (TN) is a chronic pain syndrome that can be refractory to pharmacologic intervention and management by pain specialists. Dorsal root ganglion (DRG) stimulation has shown promise as a targeted and effective modality compared to traditional therapies for several indications but has not yet been applied in the thoracic region. This study aims to report the outcomes of off-label thoracic DRG stimulation in patients with refractory TN.

Methods: A retrospective chart review was performed at Emory University Hospital for patients who underwent thoracic DRG stimulation in a two-year period. Relevant outcomes for safety and efficacy were evaluated.

Results: Six patients were identified that underwent thoracic DRG stimulation for various etiologies of TN, including post-mastectomy, post-herpetic, and post-abdominoplasty neuralgia. All patients initially underwent trial DRG stimulation with a mean pre-operative visual analogue scale (VAS) (0-10) of 6.8 ± 1.6 (range: 4-8). Four of six patients (67%) were non-responders and did not pursue permanent implantation; two experienced pain with stimulation during the trial, and two patients experienced no significant benefit. In addition, all three patients with post-herpetic neuralgia did not respond to treatment. Two of six patients (33%) responded well to stimulation, elected to receive permanent leads, and reported significant pain relief with VAS scores of 0/10 and 1/10, and 100% reduction in morphine equivalent use. Complications included lead migration and need to reset stimulator programming.

Conclusions: DRG stimulation may be an effective therapy for patients experiencing chronic TN as a result of peripheral nerve injury; however, post-herpetic neuralgia may be unresponsive to this treatment. Future prospective studies are warranted to evaluate the feasibility of this procedure in patients with refractory TN.

Case Series: A Minimally Invasive Tunneling Approach for Cubital Tunnel Syndrome

Background

Cubital tunnel syndrome (CuTS) is the second most common peripheral neuropathy in the United States. All three current surgical treatment approaches, consisting of in situ decompression, medial epicondylectomy, and transposition, require large curvilinear incisions and dissections that cross the medial epicondyle. However, the use of a large curvilinear incision may not be necessary for in situ decompression and may be achieved with small incisions proximal and distal to the medial epicondyle. This may limit the risk of peri-incisional pain and numbness, similar to the benefits provided by endoscopy.

Objective

The aim of this study is to evaluate a minimally invasive tunneling approach for in situ ulnar nerve decompression utilizing 2 cm incisions proximal and distal to the medial epicondyle.

Methods

A retrospective chart review was performed for patients at Emory University Hospital with CuTS who underwent minimally invasive tunneling for in situ decompression. Seven cases were identified. Patient demographics and data on post-operative complications were collected. Pre-operative severity was graded as a Modified McGowan severity. The primary outcome was evaluated using the post-surgical Messina Criterion. Secondary outcomes were reports of peri-incisional pain or numbness evaluated at follow-up. Descriptive statistics are presented.

Results

Pre-operatively, one of the seven cases was Grade I McGowan and the remaining six were Grade 2a or 2b. Post-operatively, on the Messina Criterion, four of seven patients were rated as having “Good” outcomes, two of seven had “Fair”, while one of seven had “Poor.” There was one post-operative surgical site infection. Among the other six cases, there were no reports of peri-incisional pain or numbness.

Conclusions

The use of less-invasive tunneling approach to in situ decompression yielded positive outcomes in this case series with no reports of peri-incisional pain or numbness. A prospective trial may be useful to explore the theoretical benefits of this novel tunneling approach.

Double Fascicular Nerve Transfer to Musculocutaneous Branches for Restoration of Elbow Flexion in Brachial Plexus Injury

Background

Restriction of elbow flexion significantly limits upper extremity function following brachial plexus injuries. In recent years, the double fascicular nerve transfer procedure utilizing ulnar and median nerve transfer to musculocutaneous branches has shown promising functional outcomes.

Objective

To evaluate restoration of elbow flexion following a double fascicular transfer in patients with brachial plexus injuries and identify predictors of poor outcomes.

Methods

This retrospective review included 10 consecutive patients with brachial plexus injuries involving C5-C6 root avulsions who underwent the double nerve transfer procedure. The mean follow-up was 12 months and the primary outcome was assessment of elbow flexion with the use of the Medical Research Council (MRC) scale.

Results

This procedure achieved elbow flexion of MRC grade M3 or higher in 50% of our cohort. Time interval from injury to surgery showed a statistically significant inverse association with functional recovery (r = -0.73, p = 0.016). Patients who had the surgery within six months of the injury, demonstrated higher MRC grades during the follow-up (p = 0.048). There was no association between elbow flexion recovery and age, body mass index (BMI), gender, hypertension, diabetes or smoking status.

Conclusions

The double fascicular transfer to musculocutaneous may be a safe and effective treatment for restoration of elbow flexion. The procedure is associated with superior functional outcomes when performed within the first six months from the injury.

Supraorbital Occipital Circumferential Stimulation for the Treatment of Refractory Chronic Primary Headache: A Case Series

BACKGROUND

Patients with refractory chronic primary headache disorders have extremely debilitating symptoms, severe comorbidities (e.g., anxiety, depression), and a significant reduction in quality of life. The headaches are extremely difficult to treat, as they are often refractory to pharmacologic and procedural interventions. Neuromodulation with stimulation of the occipital and supraorbital nerves has been proposed as a viable treatment for these refractory headaches. We retrospectively review the long-term (33.5 ± 20 months) results of supraorbital occipital nerve circumferential stimulation (SOCS) in patients with chronic primary headache disorders.

METHODS

We retrospectively review 25 patients who were evaluated for SOCS for chronic primary headache disorders from 2010 to 2017 at a single institution with a single neurosurgeon.

RESULTS

Of these 25 patients, 14 saw benefits to their trial stage of stimulation and underwent full implantation. A total 3 patients were excluded from further analysis because of having <2 months of follow-up or discordant data. Of the 11 patients analyzed, there was an overall response rate (≥50% pain reduction) of 82%. The average preoperative 10-point pain score dropped from 7.1 ± 1.6 to a postoperative score of 3.3 ± 2.1. However, there was a high rate of complications including infection, erosion, and loss of effect.

CONCLUSIONS

The results (82% response) suggest that SOCS may be an effective treatment and should be studied more extensively. Occipital nerve stimulation alone has shown 40% to 50% response rate in published studies. However, the relatively high complication rate highlights an obstacle for the approach for the treatment of refractory headache disorders and room for device optimization.

Combined Radial to Axillary and Spinal Accessory Nerve (SAN) to Suprascapular Nerve (SSN) Transfers May Confer Superior Shoulder Abduction Compared with Single SA to SSN Transfer

BACKGROUND

The restoration of shoulder function after brachial plexus injury is a high priority. Shoulder abduction and stabilization can be achieved by nerve transfer procedures including spinal accessory nerve (SAN) to suprascapular nerve (SSN) and radial to axillary nerve transfer. The objective of this study is to compare functional outcomes after SAN to SSN transfer versus the combined radial to axillary and SA to SSN transfer.

METHODS

This retrospective chart review included 14 consecutive patients with brachial plexus injury who underwent SAN to SSN transfer, 4 of whom had both SA to SSN and radial to axillary nerve transfer.

RESULTS

SAN to SSN transfer achieved successful shoulder abduction (≥M3) in 64.3% of this cohort (9/14). During the long-term follow-up, patients achieved an average increase of 67.5° in shoulder abduction. There was no association between motor recovery and time from injury to surgery, age, body mass index (BMI), sex, or smoking status. The 4 patients who had SAN to SSN combined with radial to axillary nerve transfer demonstrated a statistically significant increase in the range of abduction (median, 90° vs. 42.5°, respectively; P = 0.022) compared with those who had SAN to SSN transfer alone; however, the difference in Medical Research Council (MRC) grades (MRC > M3) did not reach statistical significance (P = 0.07).

CONCLUSIONS

Patients with brachial plexus injury and an intact C7 root could benefit from radial to axillary transfer in addition to SAN to SSN transfer. There was no association between recovery of shoulder abduction and time interval from injury to surgery, age, sex, smoking, and BMI.

Phantom Sensation-Underreported Sensory Outcome Following Intercostal-to-Musculocutaneous Nerve Transfer

BACKGROUND

Intercostal-to-musculocutaneous nerve transfer is commonly performed in patients with brachial plexus avulsion injuries. As techniques have improved since its inception in 1963, most patients now experience some level of motor function improvement of their affected arm. While motor outcomes are well described, there is a paucity of literature describing sensory outcomes. It is thus difficult to gauge surgical success with respect to sensory function, and there is a necessity to share clear expectations with patients regarding intended or unintended postoperative sensation.

CASE DESCRIPTION

In this case report, we describe an unintended sensory outcome of this procedure. Three years after the operation, our patient experiences a "phantom sensation" on his chest when he is touched on the lateral forearm in the distribution of the lateral antebrachial cutaneous nerve. This outcome can be explained with review of the anatomy before and after the operation. The persistence of this adverse outcome suggests limitations in sensory cortical neuroplasticity.

CONCLUSIONS

It is important to be aware of potential sensory complications in intercostal-to-musculocutaneous nerve transfer. Although this complication is known, it is often overlooked and underreported. Complications such as this should be emphasized in order to set expectations for patients and guide evaluation of sensory outcomes in a future study.