Publications by authors named "Michel Kliot"

80 Publications

James Tate Goodrich MD/PhD: a renaissance man for all seasons April 16, 1946-March 30, 2020.

Acta Neurochir (Wien) 2020 06 29;162(6):1215-1216. Epub 2020 Apr 29.

Division of Pediatric Neurosurgery, UT Southwest, Dallas, TX, USA.

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http://dx.doi.org/10.1007/s00701-020-04349-yDOI Listing
June 2020

Promises and Perils of Artificial Intelligence in Neurosurgery.

Neurosurgery 2020 07;87(1):33-44

Department of Neurosurgery, Houston Methodist Hospital, Houston, Texas.

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.
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http://dx.doi.org/10.1093/neuros/nyz471DOI Listing
July 2020

Thread common peroneal nerve release-a cadaveric validation study.

Acta Neurochir (Wien) 2019 09 4;161(9):1931-1936. Epub 2019 Jul 4.

Department of Neurosurgery, Stanford University, 300 Pasteur Dr, Palo Alto, CA, 94304, USA.

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.
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http://dx.doi.org/10.1007/s00701-019-03998-yDOI Listing
September 2019

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

J Hand Surg Eur Vol 2019 Nov 12;44(9):920-924. Epub 2019 Jun 12.

Aurora/BayCare Health, BayCare Clinic Pain & Rehab Medicine, Green Bay, WI, USA.

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.
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http://dx.doi.org/10.1177/1753193419856591DOI Listing
November 2019

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

Acta Neurochir (Wien) 2019 10 23;161(10):2133-2139. Epub 2019 May 23.

Department of Neurosurgery, Stanford University, 300 Pasteur Dr, Palo Alto, CA, 94304, USA.

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.
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http://dx.doi.org/10.1007/s00701-019-03944-yDOI Listing
October 2019

In Reply: Neurosurgery and Manned Spaceflight.

Neurosurgery 2019 07;85(1):E159-E160

Department of Neurosurgery King's College Hospital London, United Kingdom.

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http://dx.doi.org/10.1093/neuros/nyz107DOI Listing
July 2019

Artificial Intelligence and the Future of Surgical Robotics.

Ann Surg 2019 08;270(2):223-226

Department of Neurosurgery, Stanford University, Stanford, CA.

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http://dx.doi.org/10.1097/SLA.0000000000003262DOI Listing
August 2019

Neurosurgery and Manned Spaceflight.

Neurosurgery 2020 03;86(3):317-324

Department of Neurosurgery, King's College Hospital, London, United Kingdom.

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.
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http://dx.doi.org/10.1093/neuros/nyy531DOI Listing
March 2020

Predictive value of a diagnostic block in focal nerve injury with neuropathic pain when surgery is considered.

PLoS One 2018 12;13(9):e0203345. Epub 2018 Sep 12.

Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands.

Object: In patients with focal nerve injury and neuropathic pain cutting the nerve to obtain permanent pain reduction can be considered. Surgery is indicated only if a diagnostic nerve block provides temporary pain relief. We evaluated the predictive value of a block on the outcome of surgery.

Methods: In total, three blocks were performed at two week intervals. Patients were blinded to injections containing lidocaine 1% and a placebo was included. Surgery was offered regardless of the effect of the blocks. Twenty-four patients received 72 blocks. Sixteen patients opted for surgery, 5 patients refrained from surgery, and in 3 the blocks provided permanent pain relief. The predictive ability of the block on the outcome of surgery was assessed by calculating the area under a Receiver Operating Characteristic curve (AUC).

Results: The AUC of the first lidocaine block was 0.35 with a 95% confidence interval from 0.077 to 0.62. At 95% confidence (two-sided), the AUC is less than 0.62, and hence the predictive ability of the block was poor. The outcome of the second lidocaine block and saline block did not change the conclusion of the first block.

Conclusions: We conclude that the use of blocks to select patients for surgery should be critically appraised.

Perspective: A pain relieving response to one open block is currently considered mandatory before patients with focal nerve injury and neuropathic pain are offered surgery. Blinded blocks including a placebo show that responses for selection should be carefully interpreted because they may not be as predictive as generally presumed.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0203345PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135496PMC
February 2019

Mariano Socolovsky, Lukas Rasulic, Rajiv Midha, and Debora Garozzo (eds): Manual of peripheral nerve surgery: from the basics to complex procedures.

Authors:
Michel Kliot

Acta Neurochir (Wien) 2018 03 6;160(3):663. Epub 2018 Jan 6.

Stanford University Medical Center, Stanford, CA, 94305, USA.

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http://dx.doi.org/10.1007/s00701-017-3450-3DOI Listing
March 2018

Intraoperative monitoring of neuromuscular function with soft, skin-mounted wireless devices.

NPJ Digit Med 2018 23;1. Epub 2018 May 23.

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Peripheral nerves are often vulnerable to damage during surgeries, with risks of significant pain, loss of motor function, and reduced quality of life for the patient. Intraoperative methods for monitoring nerve activity are effective, but conventional systems rely on bench-top data acquisition tools with hard-wired connections to electrode leads that must be placed percutaneously inside target muscle tissue. These approaches are time and skill intensive and therefore costly to an extent that precludes their use in many important scenarios. Here we report a soft, skin-mounted monitoring system that measures, stores, and wirelessly transmits electrical signals and physical movement associated with muscle activity, continuously and in real-time during neurosurgical procedures on the peripheral, spinal, and cranial nerves. Surface electromyography and motion measurements can be performed non-invasively in this manner on nearly any muscle location, thereby offering many important advantages in usability and cost, with signal fidelity that matches that of the current clinical standard of care for decision making. These results could significantly improve accessibility of intraoperative monitoring across a broad range of neurosurgical procedures, with associated enhancements in patient outcomes.
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http://dx.doi.org/10.1038/s41746-018-0023-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6419749PMC
May 2018

Erratum to: an update on addressing important peripheral nerve problems: challenges and potential solutions.

Acta Neurochir (Wien) 2017 09;159(9):1775

Department of Neurosurgery, Stanford University School of Medicine, Palo Alto, CA, 94304, USA.

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http://dx.doi.org/10.1007/s00701-017-3232-yDOI Listing
September 2017

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

Acta Neurochir (Wien) 2017 Sep 12;159(9):1765-1773. Epub 2017 May 12.

Department of Neurosurgery, Stanford University School of Medicine, Palo Alto, CA, 94304, USA.

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.
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http://dx.doi.org/10.1007/s00701-017-3203-3DOI Listing
September 2017

Peripheral nerve diffusion tensor imaging as a measure of disease progression in ALS.

J Neurol 2017 May 6;264(5):882-890. Epub 2017 Mar 6.

Brain and Mind Centre, Sydney Medical School, University of Sydney, Camperdown, NSW, Australia.

Clinical trial design in amyotrophic lateral sclerosis (ALS) remains hampered by a lack of reliable and sensitive biomarkers of disease progression. The present study evaluated peripheral nerve diffusion tensor imaging (DTI) as a surrogate marker of axonal degeneration in ALS. Longitudinal studies were undertaken in 21 ALS patients studied at 0 and 3 months, and 19 patients at 0, 3 and 6 months, with results compared to 13 age-matched controls. Imaging metrics were correlated across a range of functional assessments including amyotrophic lateral sclerosis functional rating scale revised (ALSFRS-R), lower limb muscle strength (Medical Research Council sum score, MRCSS-LL), compound muscle action potential amplitudes and motor unit number estimation (MUNE). Fractional anisotropy was reduced at baseline in ALS patients in the tibial (p < 0.05), and peroneal nerve (p < 0.05). Fractional anisotropy and axial diffusivity declined in the tibial nerve between baselines, 3- and 6-month scans (p < 0.01). From a functional perspective, ALSFRS-R correlated with fractional anisotropy values from tibial (R = 0.75, p < 0.001) and peroneal nerves (R = 0.52, p = 0.001). Similarly, peroneal nerve MUNE values correlated with fractional anisotropy values from the tibial (R = 0.48, p = 0.002) and peroneal nerve (R = 0.39, p = 0.01). There were correlations between the change in ALSFRS-R and tibial nerve axial diffusivity (R = 0.38, p = 0.02) and the change in MRCSS-LL and peroneal nerve fractional anisotropy (R = 0.44, p = 0.009). In conclusion, this study has demonstrated that some peripheral nerve DTI metrics are sensitive to axonal degeneration in ALS. Further, that DTI metrics correlated with measures of functional disability, strength and neurophysiological measures of lower motor neuron loss.
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http://dx.doi.org/10.1007/s00415-017-8443-xDOI Listing
May 2017

Whole Exome Sequencing of Growing and Non-Growing Cutaneous Neurofibromas from a Single Patient with Neurofibromatosis Type 1.

PLoS One 2017 18;12(1):e0170348. Epub 2017 Jan 18.

Department of Neurosurgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.

The growth behaviors of cutaneous neurofibromas in patients with Neurofibromatosis type 1 are highly variable. The role of the germline NF1 mutation, somatic NF1 mutation and mutations at modifying loci, are poorly understood. We performed whole exome sequencing of three growing and three non-growing neurofibromas from a single individual to assess the role of acquired somatic mutations in neurofibroma growth behavior. 1-11 mutations were identified in each sample, including two deleterious NF1 mutations. No trends were present between the types of somatic mutations identified and growth behavior. Mutations in the HIPPO signaling pathway appeared to be overrepresented.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170348PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5242532PMC
August 2017

Epigenetic mechanisms drive the progression of neurofibromas to malignant peripheral nerve sheath tumors.

Surg Neurol Int 2016 14;7(Suppl 33):S797-S800. Epub 2016 Nov 14.

Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.

Thinking Outside The Box: The polycomb repressive complex 2 (PRC2) is a histone methyltransferase complex known to repress gene expression. There is a large body of experimental evidence that supports its role in promoting tumorigenicity by suppressing tumor suppressor genes. Here, we discuss the surprising findings that, in neurofibromas, it may have a completely different role as a tumor suppressor; mutations of PRC2 lead to conversion of benign neurofibromas into malignant peripheral nerve sheath tumors (MPNSTs) by de-repressing and thereby activating genes driving cell growth and development. These findings have potentially powerful clinical applications in both diagnosing and treating MPNSTs.

Hypothesis: PRC2 loss drives malignant transformation of neurofibromas.
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http://dx.doi.org/10.4103/2152-7806.194058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5122817PMC
November 2016

Developing an algorithm for cost-effective, clinically judicious management of peripheral nerve tumors.

Surg Neurol Int 2016 26;7:80. Epub 2016 Aug 26.

Department of Neurological Surgery, Northwestern University, Chicago, Illinois, USA.

Peripheral nerve tumors such as neurofibromas and schwannomas have become increasingly identified secondary to improved imaging modalities including magnetic resonance neurogram and ultrasound. Given that a majority of these peripheral nerve tumors are benign lesions, it becomes important to determine appropriate management of such asymptomatic masses. We propose a normal cost-effective management paradigm for asymptomatic peripheral nerve neurofibromas and schwannomas that has been paired with economic analyses. Specifically, our management paradigm identifies patients who would benefit from surgery for asymptomatic peripheral nerve tumors, while providing cost-effective recommendations regarding clinical exams and serial imaging for such patients.
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http://dx.doi.org/10.4103/2152-7806.189299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5009575PMC
September 2016

Peripheral nerve imaging.

Handb Clin Neurol 2016 ;136:811-26

Department of Neurological Surgery, Northwestern Feinberg School of Medicine, Chicago, IL, USA. Electronic address:

Disorders of peripheral nerve have been traditionally diagnosed and monitored using clinical and electrodiagnostic approaches. The last two decades have seen rapid development of both magnetic resonance imaging (MRI) and ultrasound imaging of peripheral nerve, such that these imaging modalities are increasingly invaluable to the diagnosis of patients with peripheral nerve disorders. Peripheral nerve imaging provides information which is supplementary to clinical and electrodiagnostic diagnosis. Both MRI and ultrasound have particular benefits in specific clinical circumstances and can be considered as complementary techniques. These technologic developments in peripheral nerve imaging will usher in an era of multimodality assessment of peripheral nerve disorders, with clinical evaluations supported by anatomic information from imaging, and functional information from electrodiagnostic studies. Such a multimodality approach will improve the accuracy and efficiency of patient care.
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http://dx.doi.org/10.1016/B978-0-444-53486-6.00040-5DOI Listing
February 2017

Visualizing nerve fibers surrounding a brachial plexus tumor using MR diffusion tensor imaging.

Neurology 2016 Feb;86(6):582-3

From the Departments of Radiology (T.A.G.) and Neurosurgery (T.A.G., M.K.), Northwestern University Feinberg School of Medicine, Chicago, IL; Prince of Wales Clinical School (N.G.S.), University of New South Wales; and Department of Neurology (N.G.S.), St. Vincent's Hospital, Darlinghurst, Australia.

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http://dx.doi.org/10.1212/WNL.0000000000002360DOI Listing
February 2016

The impact of a patient education bundle on neurosurgery patient satisfaction.

Surg Neurol Int 2015 16;6(Suppl 22):S567-72. Epub 2015 Nov 16.

Department of Neurological Surgery, University of California at San Francisco, San Francisco, CA, USA ; Department of Neurological Surgery, Northwestern University, Chicago, IL, USA.

Background: As reimbursements and hospital/physician performance become ever more reliant on Hospital Consumer Assessment of Health Care Providers and Systems (HCAHPS) and other quality metrics, physicians are increasingly incentivized to improve patient satisfaction.

Methods: A faculty and resident team at the University of California, San Francisco (UCSF) Department of Neurological Surgery developed and implemented a Patient Education Bundle. This consisted of two parts: The first was preoperative expectation letters (designed to inform patients of what to expect before, during, and after their hospitalization for a neurosurgical procedure); the second was a trifold brochure with names, photographs, and specialty/training information about the attending surgeons, resident physicians, and nurse practitioners on the neurosurgical service. We assessed patient satisfaction, as measured by HCAHPS scores and a brief survey tailored to our specific intervention, both before and after our Patient Education Bundle intervention.

Results: Prior to our intervention, 74.6% of patients responded that the MD always explained information in a way that was easy to understand. After our intervention, 78.7% of patients responded that the MD always explained information in a way that was easy to understand. "Neurosurgery Patient Satisfaction survey" results showed that 83% remembered receiving the preoperative letter; of those received the letter, 93% found the letter helpful; and 100% thought that the letter should be continued.

Conclusion: Although effects were modest, we believe that patient education strategies, as modeled in our bundle, can improve patients' hospital experiences and have a positive impact on physician performance scores and hospital ratings.
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http://dx.doi.org/10.4103/2152-7806.169538DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4653328PMC
December 2015

Central Adaptation following Brachial Plexus Injury.

World Neurosurg 2016 Jan 25;85:325-32. Epub 2015 Sep 25.

Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. Electronic address:

Brachial plexus trauma (BPT) often affects young patients and may result in lasting functional deficits. Standard care following BPT involves monitoring for clinical and electrophysiological evidence of muscle reinnervation, with surgical treatment decisions based on the presence or absence of spontaneous recovery. Data are emerging to suggest that central and peripheral adaptation may play a role in recovery following BPT. The present review highlights adaptive and maladaptive mechanisms of central and peripheral nervous system changes following BPT that may contribute to functional outcomes. Rehabilitation and other treatment strategies that harness or modulate these intrinsic adaptive mechanisms may improve functional outcomes following BPT.
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http://dx.doi.org/10.1016/j.wneu.2015.09.027DOI Listing
January 2016

Peripheral nerve diffusion tensor imaging is reliable and reproducible.

J Magn Reson Imaging 2016 Apr 23;43(4):962-9. Epub 2015 Sep 23.

Brain and Mind Research Institute, University of Sydney, Australia.

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.
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http://dx.doi.org/10.1002/jmri.25056DOI Listing
April 2016

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

Neurosurg Focus 2015 Sep;39(3):E2

Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois;

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.
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http://dx.doi.org/10.3171/2015.6.FOCUS15220DOI Listing
September 2015

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

Neurosurg Focus 2015 Sep;39(3):E16

Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois.

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.
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http://dx.doi.org/10.3171/2015.6.FOCUS15235DOI Listing
September 2015

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

Neurosurg Focus 2015 Sep;39(3):E10

Neurosurgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois;

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.
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http://dx.doi.org/10.3171/2015.6.FOCUS15211DOI Listing
September 2015

Introduction: Imaging of peripheral nerves.

Neurosurg Focus 2015 Sep;39(3):E1

Neurosurgery, Mayo Clinic, Rochester, Minnesota;

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http://dx.doi.org/10.3171/2015.6.FOCUS15314DOI Listing
September 2015

The Presto 1000: A novel automated transcranial Doppler ultrasound system.

J Clin Neurosci 2015 Nov 31;22(11):1771-5. Epub 2015 Jul 31.

Department of Neurological Surgery, University of California, 505 Parnassus Avenue, M-779, San Francisco, CA 94143, USA.

We examined the reliability and ease of use of a novel automated transcranial Doppler (TCD) system in comparison to a conventional TCD system. TCD ultrasound allows non-invasive monitoring of cerebral blood flow, and can predict arterial vasospasm after a subarachnoid hemorrhage (SAH). The Presto 1000 TCD system (PhysioSonics, Bellevue, WA, USA) is designed for monitoring flow through the M1 segment of the middle cerebral artery (MCA) via temporal windows. The Presto 1000 system was tested across multiple preclinical and clinical settings in parallel with a control predicate TCD system. In a phantom flow generating device, both the Presto 1000 and Spencer system (Spencer Technologies, Redmond, WA, USA) were able to detect velocities with high accuracy. In nine volunteer patients, the Presto system was able to locate the MCA in 14 out of 18 temporal windows, in an average of 12.5s. In the SAH cohort of five patients with a total of 25 paired measurements, the mean absolute difference in flow velocities of the M1 segment, as measured by the two systems, was 17.5 cm/s. These data suggest that the Presto system offers an automated TCD that can reliably localize and detect flow of the MCA, with relative ease of use. The system carries the additional benefit of requiring minimal training for the operator, and can be used by many providers across multiple bedside settings. The mean velocities that were generated warrant further validation across an extended group of patients, and the predictive value for vasospasm should be checked against the current standard of angiography.
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http://dx.doi.org/10.1016/j.jocn.2015.05.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5240787PMC
November 2015

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

J Neurol Neurosurg Psychiatry 2016 Feb 28;87(2):198-208. Epub 2015 Apr 28.

Department of Neurological Surgery, Northwestern Feinberg School of Medicine, Chicago, Illinois, USA.

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.
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http://dx.doi.org/10.1136/jnnp-2014-310175DOI Listing
February 2016

Diffusion weighted MRI and tractography for evaluating peripheral nerve degeneration and regeneration.

Neural Regen Res 2014 Dec;9(24):2122-4

Department of Neurological Surgery, Northwestern Feinberg School of Medicine, Chicago, IL, USA.

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http://dx.doi.org/10.4103/1673-5374.147941DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4316443PMC
December 2014
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