A cadaveric study using the ultra-minimally invasive thread transection technique to decompress the superficial peroneal nerve in the lower leg.

BACKGROUND: After successful applications of the ultra-minimally invasive thread transecting technique (Guo Technique) for both thread carpal tunnel release and thread trigger finger release, we hypothesized that this technique could be used for superficial peroneal nerve release in the lower leg by selective crural fasciectomy. This study is aimed at testing the operative feasibility of performing the thread superficial peroneal nerve release (TSPNR) procedure in cadavers. METHODS: The TSPNR procedure was performed on 15 fresh frozen cadaveric lower-extremity specimens under ultrasound guidance. All cadaveric specimens were dissected and visually assessed immediately after the procedures. RESULTS: All 15 legs demonstrated a complete transection of the crural fasciae along the course of the superficial peroneal nerve (SPN) including where it penetrated and traversed the crural fascia. There was no evidence of any iatrogenic damage to the neurovascular bundle or adjacent tendons. The average operating time was less than 20 min. CONCLUSION: This cadaveric study demonstrated that the technique of TSPNR was accurate, reliable, and feasible while causing no injury to adjacent neurovascular structures and avoiding having to make a skin incision. Further studies are warranted to verify the results of this study before implementing this new technique in the clinical setting.

Thread common peroneal nerve release-a cadaveric validation study.

OBJECTIVE: To determine if the thread release technique can be applied to common peroneal nerve entrapment at the fibular neck. METHODS: The thread common peroneal nerve release was performed on 15 fresh frozen cadaveric lower extremity specimens. All procedures were performed under ultrasound guidance and immediately underwent post-procedural gross anatomic inspection for completeness of decompression and presence or absence of iatrogenic neurovascular injury. RESULTS: All 15 specimens demonstrated complete transection of the deep fascia of the peroneus longus overlying the common peroneal nerve. The transections extended to the bifurcation of the superficial peroneal and deep peroneal nerves. There was no evidence of any iatrogenic damage to the neurovascular bundle or adjacent tendons. The average operating time was less than 30 min. CONCLUSION: This cadaveric validation study demonstrates the accuracy of the thread common peroneal nerve release. Future pilot studies are warranted to ensure the safety of this procedure in the clinical setting.

An update on addressing important peripheral nerve problems: challenges and potential solutions.

From time to time it is thoughtful and productive to review a medical field and reflect upon what are the major issues that need to be addressed and what is being done to do so. This review article is not meant to be all-inclusive but rather focuses on four evolving areas in the field of peripheral nerve disorders and treatments: (1) nerve surgery under ultrasound guidance using a new ultra-minimally invasive thread technique; (2) evolving magnetic resonance imaging (MRI) and ultrasound imaging techniques that are helping to both diagnose and treat a variety of peripheral nerve problems including entrapment neuropathies, traumatic nerve injuries, and masses arising from nerves; (3) promoting recovery after nerve injury using electrical stimulation; and (4) developing animal models to reproduce a severe nerve injury (neurotmetic grade in continuity) that requires a surgical intervention and repair. In each area we first describe the current challenges and then discuss new and emerging techniques and approaches. It is our hope that this article will bring added attention and resources to help better address peripheral nerve problems that remain a challenge for both patients and physicians.

Advances in the neurological and neurosurgical management of peripheral nerve trauma.

Peripheral nerve trauma frequently affects younger people and may result in significant and long-lasting functional disability. Currently, diagnosis and monitoring of peripheral nerve injury relies on clinical and electrodiagnostic information, supplemented by intraoperative electrophysiological studies. However, in a significant proportion of nerve injuries, the likelihood of spontaneous regeneration resulting in good functional outcome remains uncertain and unnecessary delays to treatment may be faced while monitoring for recovery. Advances in non-invasive imaging techniques to diagnose and monitor nerve injury and regeneration are being developed, and have the potential to streamline the decision-making process. In addition, advances in operative and non-operative treatment strategies may provide more effective ways to maximise functional outcomes following severe peripheral nerve trauma. This review discusses these advances in light of the current state of the art of management of peripheral nerve trauma.

Peripheral nerve diffusion tensor imaging is reliable and reproducible.

PURPOSE: To determine the reliability and reproducibility of peripheral nerve diffusion tensor imaging (DTI) in healthy subjects. MATERIALS AND METHODS: We assessed the test-retest and interrater reliability studies of peripheral nerve DTI in a cohort of 12 healthy subjects (mean age 44.0 years, range 26-71 years). Magnetic resonance imaging (MRI) studies were performed on a 3T scanner (MR750, GE Healthcare). DTI and T1 -weighted sequences were performed on the tibial and peroneal nerves in the knee. Each subject was scanned on three separate occasions. Image analyses were performed at two anatomic positions: the level of the lateral femoral condyle (position 1), and the superior pole of the patella (position 2). Analysis was performed using three software packages ("raters"): FuncTools, FSL, and Diffusion Toolkit. Metrics obtained included fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD). RESULTS: DTI metrics were not significantly different between each measurement position, except peroneal nerve AD and tibial nerve RD were higher at position 1 (P = 0.02 and 0.04, respectively). There was no significant difference in DTI metrics between male and female subjects (P = 0.10-0.99). The test-retest reliability of DTI metrics was high, maximal for FA (intraclass correlation coefficient [ICC] = 0.96). ICC values for individual DTI metrics were similar between each measurement position, except that tibial nerve AD was significantly higher at position 2 (P = 0.03). Interrater reliability was also high (ICC = 0.95-0.96). CONCLUSION: We found peripheral nerve DTI to be reliable and reproducible, with few effects related to the postprocessing package used.

Quantitative ultrasound of denervated hand muscles.

INTRODUCTION: Presentations to the neuromuscular clinic commonly involve hand muscle denervation, but few studies have evaluated hand muscle ultrasound. METHODS: Ultrasound studies of abductor pollicis brevis, first dorsal interosseous, and abductor digit minimi were prospectively performed in a cohort of 34 patients (77 muscles) with electromyography (EMG)-confirmed denervation, compared with 58 healthy control subjects. RESULTS: In control subjects, muscle thickness was highly reproducible [intraclass correlation coefficient (ICC) = 0.88-0.98], and echogenicity was moderately reproducible (ICC = 0.542-0.686). Age, gender, and body mass index influenced muscle thickness and echogenicity. Ultrasound changes in denervated muscles correlated with the severity of EMG abnormalities. A z-score cutoff of 0 identified denervated muscles with a sensitivity of 100% and 89% for echogenicity and muscle thickness, respectively. CONCLUSIONS: Hand muscle ultrasound provides a noninvasive method to quantify muscle denervation and may be useful as a screening tool before EMG studies.

Diffusion tensor imaging to visualize axons in the setting of nerve injury and recovery.

Successful management of peripheral nerve trauma relies on accurate localization of the injury and grading of the severity of nerve injury to determine whether surgical intervention is required. Existing techniques, such as electrodiagnostic studies and conventional imaging modalities, provide important information, but are limited by being unable to distinguish severe nerve lesions in continuity that will recover from those that will not. Diffusion tensor imaging (DTI) and tractography of peripheral nerves provide a novel technique to localize and grade nerve injury, by assessing the integrity of the nerve fibers across the site of nerve injury. Diffusion tensor imaging and tractography also hold promise as markers of early nerve regeneration, prior to clinical and electrodiagnostic evidence of recovery. In the present review, the techniques of peripheral nerve DTI and tractography are discussed with respect to peripheral nerve trauma, with illustrative cases demonstrating potential roles of these novel approaches.

Visualization of nerve fibers and their relationship to peripheral nerve tumors by diffusion tensor imaging.

OBJECT The majority of growing and/or symptomatic peripheral nerve tumors are schwannomas and neurofibromas. They are almost always benign and can usually be resected while minimizing motor and sensory deficits if approached with the proper expertise and techniques. Intraoperative electrophysiological stimulation and recording techniques allow the surgeon to map the surface of the tumor in an effort to identify and thus avoid damaging functioning nerve fibers. Recently, MR diffusion tensor imaging (DTI) techniques have permitted the visualization of axons, because of their anisotropic properties, in peripheral nerves. The object of this study was to compare the distribution of nerve fibers as revealed by direct electrical stimulation with that seen on preoperative MR DTI. METHODS The authors conducted a retrospective chart review of patients with a peripheral nerve or nerve root tumor between March 2012 and January 2014. Diffusion tensor imaging and intraoperative data had been prospectively collected for patients with peripheral nerve tumors that were resected. Preoperative identification of the nerve fiber location in relation to the nerve tumor surface as seen on DTI studies was compared with the nerve fiber's intraoperative localization using electrophysiological stimulation and recordings. RESULTS In 23 patients eligible for study there was good correlation between nerve fiber location on DTI and its anatomical location seen intraoperatively. Diffusion tensor imaging demonstrated the relationship of nerve fibers relative to the tumor with 95.7% sensitivity, 66.7% specificity, 75% positive predictive value, and 93.8% negative predictive value. CONCLUSIONS Preoperative DTI techniques are useful in helping the peripheral nerve surgeon to both determine the risks involved in resecting a nerve tumor and plan the safest surgical approach.

Ultrasound-guided percutaneous injection of methylene blue to identify nerve pathology and guide surgery.

OBJECT The objective of this study was to provide a technique that could be used in the preoperative period to facilitate the surgical exploration of peripheral nerve pathology. METHODS The authors describe a technique in which 1) ultrasonography is used in the immediate preoperative period to identify target peripheral nerves, 2) an ultrasound-guided needle electrode is used to stimulate peripheral nerves to confirm their position, and then 3) a methylene blue (MB) injection is performed to mark the peripheral nerve pathology to facilitate surgical exploration. RESULTS A cohort of 13 patients with varying indications for peripheral nerve surgery is presented in which ultrasound guidance, stimulation, and MB were used to localize and create a road map for surgeries. CONCLUSIONS Preoperative ultrasound-guided MB administration is a promising technique that peripheral nerve surgeons could use to plan and execute surgery.

Intense focused ultrasound preferentially stimulates subcutaneous and focal neuropathic tissue: preliminary results.

OBJECTIVE: Potential peripheral sources of pain from subcutaneous tissue can require invasive evocative tests for their localization and assessment. Here, we describe studies whose ultimate goal is development of a noninvasive evocative test for subcutaneous, painful tissue. DESIGN: We used a rat model of a focal and subcutaneous neuroma to test the hypothesis that intense focused ultrasound can differentiate focal and subcutaneous neuropathic tissue from control tissue. To do so, we first applied intense focused ultrasound (2 MHz, with individual pulses of 0.1 second in duration) to the rat's neuroma while the rat was under light anesthesia. We started with low values of intensity, which we increased until intense focused ultrasound stimulation caused the rat to reliably flick its paw. We then applied that same intense focused ultrasound protocol to control tissue away from the neuroma and assayed for the rat's response to that stimulation. RESULTS: Intense focused ultrasound of sufficient strength (I(SATA) of 600 +/- 160 W/cm(2) ) applied to the neuroma caused the rat to flick its paw, while the same intense focused ultrasound applied millimeters to a centimeter away failed to induce a paw flick. CONCLUSION: Successful stimulation of the neuroma by intense focused ultrasound required colocalization of the neuroma and intense focused ultrasound supporting our hypothesis.

Rapid ultrasonic stimulation of inflamed tissue with diagnostic intent.

Previous studies have observed that individual pulses of intense focused ultrasound (iFU) applied to inflamed and normal tissue can generate sensations, where inflamed tissue responds at a lower intensity than normal tissue. It was hypothesized that successively applied iFU pulses will generate sensation in inflamed tissue at a lower intensity and dose than application of a single iFU pulse. This hypothesis was tested using an animal model of chronic inflammatory pain, created by injecting an irritant into the rat hind paw. Ultrasound pulses were applied in rapid succession or individually to rats' rear paws beginning at low peak intensities and progressing to higher peak intensities, until the rats withdrew their paws immediately after iFU application. Focused ultrasound protocols consisting of successively and rapidly applied pulses elicited inflamed paw withdrawal at lower intensity and estimated tissue displacement values than single pulse protocols. However, both successively applied pulses and single pulses produced comparable threshold acoustic dose values and estimates of temperature increases. This raises the possibility that temperature increase contributed to paw withdrawal after rapid iFU stimulation. While iFU-induction of temporal summation may also play a role, electrophysiological studies are necessary to tease out these potential contributors to iFU stimulation.

Surgery versus non-surgical therapy for carpal tunnel syndrome: a randomised parallel-group trial.

BACKGROUND: A previous randomised controlled trial reported greater efficacy of surgery than of splinting for patients with carpal tunnel syndrome. Our aim was to compare surgical versus multi-modality, non-surgical treatment for patients with carpal tunnel syndrome without denervation. We hypothesised that surgery would result in improved functional and symptom outcomes. METHODS: In this parallel-group randomised controlled trial, we randomly assigned 116 patients from eight academic and private practice centres, using computer-generated random allocation stratified by site, to carpal tunnel surgery (n=57) or to a well-defined, non-surgical treatment (including hand therapy and ultrasound; n=59). The primary outcome was hand function measured by the Carpal Tunnel Syndrome Assessment Questionnaire (CTSAQ) at 12 months assessed by research personnel unaware of group assignment. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00032227. FINDINGS: 44 (77%) patients assigned to surgery underwent surgery. At 12 months, 101 (87%) completed follow-up and were analysed (49 of 57 assigned to surgery and 52 of 59 assigned to non-surgical treatment). Analyses showed a significant 12-month adjusted advantage for surgery in function (CTSAQ function score: Delta -0.40, 95% CI 0.11-0.70, p=0.0081) and symptoms (CTSAQ symptom score: 0.34, 0.02-0.65, p=0.0357). There were no clinically important adverse events and no surgical complications. INTERPRETATION: Symptoms in both groups improved, but surgical treatment led to better outcome than did non-surgical treatment. However, the clinical relevance of this difference was modest. Overall, our study confirms that surgery is useful for patients with carpal tunnel syndrome without denervation. FUNDING: NIH/NIAMS 5P60AR048093 and the Intramural Research Program of the NIH Clinical Center.

Neurosurgery and Manned Spaceflight.

There has been a renewed interest in manned spaceflight due to endeavors by private and government agencies. Publicized goals include manned trips to or colonization of Mars. These missions will likely be of long duration, exceeding existing records for human exposure to extra-terrestrial conditions. Participants will be exposed to microgravity, temperature extremes, and radiation, all of which may adversely affect their physiology. Moreover, pathological mechanisms may differ from those of a terrestrial nature. Known central nervous system (CNS) changes occurring in space include rises in intracranial pressure and spinal unloading. Intracranial pressure increases are thought to occur due to cephalad re-distribution of body fluids secondary to microgravity exposure. Spinal unloading in microgravity results in potential degenerative changes to the bony vertebrae, intervertebral discs, and supportive musculature. These phenomena are poorly understood. Trauma is of highest concern due to its potential to seriously incapacitate crewmembers and compromise missions. Traumatic pathology may also be exacerbated in the setting of altered CNS physiology. Though there are no documented instances of CNS pathologies arising in space, existing diagnostic and treatment capabilities will be limited relative to those on Earth. In instances where neurosurgical intervention is required in space, it is not known whether open or endoscopic approaches are feasible. It is obvious that prevention of trauma and CNS pathology should be emphasized. Further research into neurosurgical pathology, its diagnosis, and treatment in space are required should exploratory or colonization missions be attempted.

Promises and Perils of Artificial Intelligence in Neurosurgery.

Artificial intelligence (AI)-facilitated clinical automation is expected to become increasingly prevalent in the near future. AI techniques may permit rapid and detailed analysis of the large quantities of clinical data generated in modern healthcare settings, at a level that is otherwise impossible by humans. Subsequently, AI may enhance clinical practice by pushing the limits of diagnostics, clinical decision making, and prognostication. Moreover, if combined with surgical robotics and other surgical adjuncts such as image guidance, AI may find its way into the operating room and permit more accurate interventions, with fewer errors. Despite the considerable hype surrounding the impending medical AI revolution, little has been written about potential downsides to increasing clinical automation. These may include both direct and indirect consequences. Directly, faulty, inadequately trained, or poorly understood algorithms may produce erroneous results, which may have wide-scale impact. Indirectly, increasing use of automation may exacerbate de-skilling of human physicians due to over-reliance, poor understanding, overconfidence, and lack of necessary vigilance of an automated clinical workflow. Many of these negative phenomena have already been witnessed in other industries that have already undergone, or are undergoing "automation revolutions," namely commercial aviation and the automotive industry. This narrative review explores the potential benefits and consequences of the anticipated medical AI revolution from a neurosurgical perspective.

Percutaneous cubital tunnel release with a dissection thread: a cadaveric study.

This cadaveric study tested the feasibility of decompressing the ulnar nerve across the elbow percutaneously with a commercially available surgical dissection thread, a guiding needle, hydrodissection and ultrasound guidance. We performed the procedure in 19 fresh-frozen cadaveric upper extremities. Subsequently, we did an anatomical dissection of the specimens to visualize the extent of ulnar nerve decompression and the extent of damage to surrounding structures. The cubital tunnel and deep across the medial elbow were completely transected leaving the ulnar nerve fully decompressed in all cases. There was no evidence of direct injury to the ulnar nerve or adjacent neurovascular structures. A prerequisite knowledge of sonographic anatomy and experience with interventional ultrasound is essential. Future clinical studies should evaluate this technique's safety and efficacy compared with conventional ones.