Academic Appointments


All Publications

  • Targeted intraspinal injections to assess therapies in rodent models of neurological disorders. Nature protocols Chen, K. S., McGinley, L. M., Kashlan, O. N., Hayes, J. M., Bruno, E. S., Chang, J. S., Mendelson, F. E., Tabbey, M. A., Johe, K., Sakowski, S. A., Feldman, E. L. 2019


    Despite decades of research, pharmacological therapies for spinal cord motor pathologies are limited. Alternatives using macromolecular, viral, or cell-based therapies show early promise. However, introducing these substances into the spinal cord, past the blood-brain barrier, without causing injury is challenging. We describe a technique for intraspinal injection targeting the lumbar ventral horn in rodents. This technique preserves motor performance and has a proven track record of translation into phase 1 and 2 clinical trials in amyotrophic lateral sclerosis (ALS) patients. The procedure, in brief, involves exposure of the thoracolumbar spine and dissection of paraspinous muscles over the target vertebrae. Following laminectomy, the spine is affixed to a stereotactic frame, permitting precise and reproducible injection throughout the lumbar spine. We have used this protocol to inject various stem cell types, primarily human spinal stem cells (HSSCs); however, the injection is adaptable to any candidate therapeutic cell, virus, or macromolecule product. In addition to a detailed procedure, we provide stereotactic coordinates that assist in targeting of the lumbar spine and instructional videos. The protocol takes ~2 h per animal.

    View details for PubMedID 30610242

  • Impact of skull density ratio on efficacy and safety of magnetic resonance-guided focused ultrasound treatment of essential tremor. Journal of neurosurgery D'Souza, M., Chen, K. S., Rosenberg, J., Elias, W. J., Eisenberg, H. M., Gwinn, R., Taira, T., Chang, J. W., Lipsman, N., Krishna, V., Igase, K., Yamada, K., Kishima, H., Cosgrove, R., Rumià, J., Kaplitt, M. G., Hirabayashi, H., Nandi, D., Henderson, J. M., Butts Pauly, K., Dayan, M., Halpern, C. H., Ghanouni, P. 2019: 1–6


    OBJECTIVESkull density ratio (SDR) assesses the transparency of the skull to ultrasound. Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy in essential tremor (ET) patients with a lower SDR may be less effective, and the risk for complications may be increased. To address these questions, the authors analyzed clinical outcomes of MRgFUS thalamotomy based on SDRs.METHODSIn 189 patients, 3 outcomes were correlated with SDRs. Efficacy was based on improvement in Clinical Rating Scale for Tremor (CRST) scores 1 year after MRgFUS. Procedural efficiency was determined by the ease of achieving a peak voxel temperature of 54°C. Safety was based on the rate of the most severe procedure-related adverse event. SDRs were categorized at thresholds of 0.45 and 0.40, selected based on published criteria.RESULTSOf 189 patients, 53 (28%) had an SDR < 0.45 and 20 (11%) had an SDR < 0.40. There was no significant difference in improvement in CRST scores between those with an SDR ≥ 0.45 (58% ± 24%), 0.40 ≤ SDR < 0.45 (i.e., SDR ≥ 0.40 but < 0.45) (63% ± 27%), and SDR < 0.40 (49% ± 28%; p = 0.0744). Target temperature was achieved more often in those with an SDR ≥ 0.45 (p < 0.001). Rates of adverse events were lower in the groups with an SDR < 0.45 (p = 0.013), with no severe adverse events in these groups.CONCLUSIONSMRgFUS treatment of ET can be effectively and safely performed in patients with an SDR < 0.45 and an SDR < 0.40, although the procedure is more efficient when SDR ≥ 0.45.

    View details for PubMedID 31026836

  • Awake Implantation of Thoracic Spinal Cord Stimulator Paddle Electrode and Generator: 2-Dimensional Operative Video. Operative neurosurgery (Hagerstown, Md.) Chen, K. S., Sagher, O. 2018


    In this surgical video, the operative technique is presented for awake implantation of a thoracic paddle electrode for spinal cord stimulation. In the first stage, a laminotomy is performed with the patient under conscious sedation. Once the paddle is in optimal position, the patient is tested intraoperatively to confirm adequate coverage and absence of untoward side effects. This paddle electrode is used for the trial period. If the patient derives satisfactory pain relief during the trial, they are returned for the second stage implantation of pulse generator, without moving the initial paddle electrode now already placed in an optimal location. Particular attention in this video is provided toward the optimal positioning and technique for the awake laminotomy to ensure patient comfort and reliability during testing, the use of extension leads tunneled opposite the planned pulse generator site, and the method of removing extension leads to preserve the placement of the initial paddle electrode.

    View details for PubMedID 30566657

  • Human neural stem cell transplantation improves cognition in a murine model of Alzheimer's disease. Scientific reports McGinley, L. M., Kashlan, O. N., Bruno, E. S., Chen, K. S., Hayes, J. M., Kashlan, S. R., Raykin, J., Johe, K., Murphy, G. G., Feldman, E. L. 2018; 8 (1): 14776


    Stem cell transplantation offers a potentially transformative approach to treating neurodegenerative disorders. The safety of cellular therapies is established in multiple clinical trials, including our own in amyotrophic lateral sclerosis. To initiate similar trials in Alzheimer's disease, efficacious cell lines must be identified. Here, we completed a preclinical proof-of-concept study in the APP/PS1 murine model of Alzheimer's disease. Human neural stem cell transplantation targeted to the fimbria fornix significantly improved cognition in two hippocampal-dependent memory tasks at 4 and 16 weeks post-transplantation. While levels of synapse-related proteins and cholinergic neurons were unaffected, amyloid plaque load was significantly reduced in stem cell transplanted mice and associated with increased recruitment of activated microglia. In vitro, these same neural stem cells induced microglial activation and amyloid phagocytosis, suggesting an immunomodulatory capacity. Although long-term transplantation resulted in significant functional and pathological improvements in APP/PS1 mice, stem cells were not identified by immunohistochemistry or PCR at the study endpoint. These data suggest integration into native tissue or the idea that transient engraftment may be adequate for therapeutic efficacy, reducing the need for continued immunosuppression. Overall, our results support further preclinical development of human neural stem cells as a safe and effective therapy for Alzheimer's disease.

    View details for PubMedID 30283042

  • A simple, inexpensive method for subcortical stereotactic targeting in nonhuman primates. Journal of neuroscience methods Bentley, J. N., Khalsa, S. S., Kobylarek, M., Schroeder, K. E., Chen, K., Bergin, I. L., Tat, D. M., Chestek, C. A., Patil, P. G. 2018; 305: 89–97


    BACKGROUND: Many current neuroscience studies in large animal models have focused on recordings from cortical structures. While sufficient for analyzing sensorimotor systems, many processes are modulated by subcortical nuclei. Large animal models, such as nonhuman primates (NHP), provide an optimal model for studying these circuits, but the ability to target subcortical structures has been hampered by lack of a straightforward approach to targeting.NEW METHOD: Here we present a method of subcortical targeting in NHP that uses MRI-compatible titanium screws as fiducials. The in vivo study used a cellular marker for histologic confirmation of accuracy.RESULTS: Histologic results are presented showing a cellular stem cell marker within targeted structures, with mean errors ± standard deviations (SD) of 1.40 ± 1.19 mm in the X-axis and 0.9 ± 0.97 mm in the Z-axis. The Y-axis errors ± SD ranged from 1.5 ± 0.43 to 4.2 ± 1.72 mm.COMPARISON WITH EXISTING METHODS: This method is easy and inexpensive, and requires no fabrication of equipment, keeping in mind the goal of optimizing a technique for implantation or injection into multiple interconnected areas.CONCLUSION: This procedure will enable primate researchers to target deep, subcortical structures more precisely in animals of varying ages and weights.

    View details for PubMedID 29768185

  • Posterior Fossa Craniotomy for Adherent Fourth Ventricle Neurocysticercosis. Operative neurosurgery (Hagerstown, Md.) Franko, L. R., Pandian, B., Gupta, A., Savastano, L. E., Chen, K. S., Riddell, J. 4., Orringer, D. A. 2018


    BACKGROUND AND IMPORTANCE: Neurocysticercosis (NCC) is an infectious helminthic disease often presenting in patients who have immigration or travel history from areas where NCC is endemic. Fourth ventricle cysts from NCC pose a unique treatment challenge, as there is little consensus on the best treatment. This case study describes the treatment of a patient with fourth ventricle neurocysticercosis (FVNCC), examines the therapeutic decision-making, and provides a video of a posterior fossa craniotomy (PFC) resection of a degenerative cyst.CLINICAL PRESENTATION: The patient presented with headache, dizziness, nausea, and memory difficulties. A fourth ventricle cyst consistent with NCC was found on magnetic resonance imaging, and serum enzyme-linked immunosorbent assay (ELISA) confirmed the diagnosis. The cyst was removed utilizing an open PFC followed by antihelminthic therapy and corticosteroids. There was resolution of symptoms at 9 mo postoperatively.CONCLUSION: Several treatment modalities have been proposed for isolated cysts in the fourth ventricle, including medication, ventriculoperitoneal shunt, endoscopic removal, and PFC. The treatment decision is complex, and there is little guidance on the best treatment choices. In this article, we describe treatment via PFC for an adherent FVNCC cyst.

    View details for PubMedID 29905841

  • Optic neuropathy after anterior communicating artery aneurysm clipping: 3 cases and techniques to address a correctable pitfall. Journal of neurosurgery Linzey, J. R., Chen, K. S., Savastano, L., Thompson, B. G., Pandey, A. S. 2018; 128 (6): 1808–12


    Brain shifts following microsurgical clip ligation of anterior communicating artery (ACoA) aneurysms can lead to mechanical compression of the optic nerve by the clip. Recognition of this condition and early repositioning of clips can lead to reversal of vision loss. The authors identified 3 patients with an afferent pupillary defect following microsurgical clipping of ACoA aneurysms. Different treatment options were used for each patient. All patients underwent reexploration, and the aneurysm clips were repositioned to prevent clip-related compression of the optic nerve. Near-complete restoration of vision was achieved at the last clinic follow-up visit in all 3 patients. Clip ligation of ACoA aneurysms has the potential to cause clip-related compression of the optic nerve. Postoperative visual examination is of utmost importance, and if any changes are discovered, reexploration should be considered as repositioning of the clips may lead to resolution of visual deterioration.

    View details for PubMedID 28841123

  • Technique for Performing an Anterior Cervical Discectomy and Fusion With Attention to the Exposure of the Anterior Cervical Spine: 2-Dimensional Operative Video. Operative neurosurgery (Hagerstown, Md.) Buckingham, M. J., Chen, K. S. 2018; 14 (5): 596

    View details for DOI 10.1093/ons/opx199

    View details for PubMedID 28961915

  • Emerging understanding of the genotype-phenotype relationship in amyotrophic lateral sclerosis. Handbook of clinical neurology Goutman, S. A., Chen, K. S., Paez-Colasante, X., Feldman, E. L. 2018; 148: 603–23


    Amyotrophic lateral sclerosis (ALS) is a progressive, noncurable neurodegenerative disorder of the upper and lower motor neurons causing weakness and death within a few years of symptom onset. About 10% of patients with ALS have a family history of the disease; however, ALS-associated genetic mutations are also found in sporadic cases. There are over 100 ALS-associated mutations, and importantly, several genetic mutations, including C9ORF72, SOD1, and TARDBP, have led to mechanistic insight into this complex disease. In the clinical realm, knowledge of ALS genetics can also help explain phenotypic heterogeneity, aid in genetic counseling, and in the future may help direct treatment efforts.

    View details for PubMedID 29478603

  • HUMAN NEURAL STEM CELLS IMPROVE COGNITION AND DISEASE PATHOLOGY IN THE APP/PS1 ALZHEIMER's MOUSE MODEL McGinley, L. M., Kashlan, O. N., Bruno, E. S., Chen, K. S., Raykin, J., Johe, K., Murphy, G. G., Feldman, E. L. WILEY. 2018
  • Human neural stem cell transplantation into the corpus callosum of Alzheimer's mice ANNALS OF CLINICAL AND TRANSLATIONAL NEUROLOGY McGinley, L. M., Kashlan, O. N., Chen, K. S., Bruno, E. S., Hayes, J. M., Backus, C., Feldman, S., KashIan, B. N., Johe, K., Feldman, E. L. 2017; 4 (10): 749–55


    The hippocampus has been the target of stem cell transplantations in preclinical studies focused on Alzheimer's disease, with results showing improvements in histological and behavioral outcomes. The corpus callosum is another structure that is affected early in Alzheimer's disease. Therefore, we hypothesize that this structure is a novel target for human neural stem cell transplantation in transgenic Alzheimer's disease mouse models. This study demonstrates the feasibility of targeting the corpus callosum and identifies an effective immunosuppression regimen for transplanted neural stem cell survival. These results support further preclinical development of the corpus callosum as a therapeutic target in Alzheimer's disease.

    View details for PubMedID 29046883

  • Radiation dose reduction during neurointerventional procedures by modification of default settings on biplane angiography equipment JOURNAL OF NEUROINTERVENTIONAL SURGERY Kahn, E. N., Gemmete, J. J., Chaudhary, N., Thompson, B., Chen, K., Christodoulou, E. G., Pandey, A. S. 2016; 8 (8): 819–23


    Neurointerventional procedures represent a significant source of ionizing radiation. We sought to assess the effect during neurointerventional procedures of varying default rates of radiation dose in fluoroscopy (F) and image acquisition (IA) modes, and frame rates during cine acquisition (CINE) on total X-ray dose, acquisition exposures, fluoroscopy time, and complications.We retrospectively reviewed procedures performed with two radiation dose and CINE settings: a factory setting dose cohort (30 patients, F 45 nGy/pulse, IA 3.6 μGy/pulse, factory CINE frame rate) and a reduced dose cohort (30 patients, F 32 nGy/pulse, IA 1.2 μGy/pulse, with a decreased CINE frame rate). Total radiation dose, dose area product, number of acquisition exposures, fluoroscopy time, and complications were compared between the groups. Means comparisons (t tests) were employed to evaluate differences in the outcome variables between the two groups. p Value <0.05 was considered significant.The reduced dose cohort had a significant reduction in mean radiation dose (factory, 3650 mGy; reduced, 1650 mGy; p=0.005) and dose area product (factory, 34 700 μGy×m(2); reduced, 15 000 μGy×m(2); p=0.02). There were no significant differences between cohorts in acquisition exposure (p=0.73), fluoroscopy time (p=0.45), or complications.Significant reductions in radiation dose delivered by neurointerventional procedures can be achieved through simple modifications of default radiation dose in F and IA and frame rate during CINE without an increase in procedural complexity (fluoroscopy time) or rate of complications.

    View details for PubMedID 26245735

  • Minimally invasive transforaminal lumbar interbody fusion with percutaneous navigated guidewireless lumbosacral pedicle screw fixation Neurosurgical Focus Chen, K. S., Park, P. 2016; 41: 1


    This video details the minimally invasive approach for treatment of a symptomatic Grade II lytic spondylolisthesis with high-grade foraminal stenosis. In this procedure, the use of a navigated, guidewireless technique for percutaneous pedicle screw placement at the lumbosacral junction is highlighted following initial decompression and transforaminal interbody fusion. Key steps of the procedure are delineated that include positioning, exposure, technique for interbody fusion, intraoperative image acquisition, and use of a concise 2-step process for navigated screw placement without using guidewires. The video can be found here: .

    View details for PubMedID 27364422

  • Resolution of innumerable cerebral Nocardia paucivorans abscesses after medical management JOURNAL OF CLINICAL NEUROSCIENCE Delavari, N., Than, K. D., Chen, K. S., McKeever, P. E., Wang, A. C., Pandey, A. S. 2016; 27: 175–77


    Nocardia species are an infrequent cause of brain abscesses. We report a 50-year-old man with Nocardia paucivorans cerebral abscesses. Brain MRI revealed innumerable small ring-enhancing lesions. The patient initially responded to treatment with antibiotics and steroids, but experienced worsening after discontinuation of steroids. Brain biopsy performed to exclude central nervous system lymphoma produced nodular tissue with branching filaments on silver stain. Steroids were re-initiated and tapered slowly. The patient completed 1year of antibiotic therapy, after which he had no neurological symptoms and complete resolution of all brain abscesses on MRI.

    View details for PubMedID 26765763

  • Human spinal autografts of olfactory epithelial stem cells recapitulate donor site histology, maintaining proliferative and differentiation capacity many years after transplantation ACTA NEUROPATHOLOGICA Chen, K. S., McIntyre, J. C., Lieberman, A. P., Martens, J. R., Patil, P. G. 2016; 131 (4): 639–40

    View details for PubMedID 26839081

    View details for PubMedCentralID PMC5858709

  • Intraspinal Stem Cell Transplantation for Amyotrophic Lateral Sclerosis ANNALS OF NEUROLOGY Chen, K. S., Sakowski, S. A., Feldman, E. L. 2016; 79 (3): 342–53


    Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder in which the loss of upper and lower motor neurons produces progressive weakness and eventually death. In the decades since the approval of riluzole, the only US Food and Drug Administration-approved medication to moderately slow progression of ALS, no new therapeutics have arisen to alter the course of the disease. This is partly due to our incomplete understanding of the complex pathogenesis of motor neuron degeneration. Stem cells have emerged as an attractive option in treating ALS, because they come armed with equally complex cellular machinery and may modulate the local microenvironment in many ways to rescue diseased motor neurons. Various stem cell types are being evaluated in preclinical and early clinical applications; here, we review the preclinical strategies and advances supporting the recent clinical translation of neural progenitor cell therapy for ALS. Specifically, we focus on the use of spinal cord neural progenitor cells and the pipeline starting from preclinical studies to the designs of phase I and IIa clinical trials involving direct intraspinal transplantation in humans.

    View details for PubMedID 26696091

    View details for PubMedCentralID PMC4789073

  • Human Cortical Neural Stem Cells Expressing Insulin-Like Growth Factor-I: A Novel Cellular Therapy for Alzheimer's Disease STEM CELLS TRANSLATIONAL MEDICINE McGinley, L. M., Sims, E., Lunn, J., Kashlan, O. N., Chen, K. S., Bruno, E. S., Pacut, C. M., Hazel, T., Johe, K., Sakowski, S. A., Feldman, E. L. 2016; 5 (3): 379–91


    Alzheimer's disease (AD) is the most prevalent age-related neurodegenerative disorder and a leading cause of dementia. Current treatment fails to modify underlying disease pathologies and very little progress has been made to develop effective drug treatments. Cellular therapies impact disease by multiple mechanisms, providing increased efficacy compared with traditional single-target approaches. In amyotrophic lateral sclerosis, we have shown that transplanted spinal neural stem cells (NSCs) integrate into the spinal cord, form synapses with the host, improve inflammation, and reduce disease-associated pathologies. Our current goal is to develop a similar "best in class" cellular therapy for AD. Here, we characterize a novel human cortex-derived NSC line modified to express insulin-like growth factor-I (IGF-I), HK532-IGF-I. Because IGF-I promotes neurogenesis and synaptogenesis in vivo, this enhanced NSC line offers additional environmental enrichment, enhanced neuroprotection, and a multifaceted approach to treating complex AD pathologies. We show that autocrine IGF-I production does not impact the cell secretome or normal cellular functions, including proliferation, migration, or maintenance of progenitor status. However, HK532-IGF-I cells preferentially differentiate into gamma-aminobutyric acid-ergic neurons, a subtype dysregulated in AD; produce increased vascular endothelial growth factor levels; and display an increased neuroprotective capacity in vitro. We also demonstrate that HK532-IGF-I cells survive peri-hippocampal transplantation in a murine AD model and exhibit long-term persistence in targeted brain areas. In conclusion, we believe that harnessing the benefits of cellular and IGF-I therapies together will provide the optimal therapeutic benefit to patients, and our findings support further preclinical development of HK532-IGF-I cells into a disease-modifying intervention for AD.

    View details for PubMedID 26744412

    View details for PubMedCentralID PMC4807660

  • Management of recurrent aneurysms following endovascular therapy JOURNAL OF CLINICAL NEUROSCIENCE Chen, K. S., Wilson, T. J., Stetler, W. R., Davis, M. C., Giles, D. A., Kahn, E. N., Chaudhary, N., Gemmete, J. J., Thompson, B. G., Pandey, A. S. 2015; 22 (12): 1901-1906


    The aim of the current study is to describe the complication rates and clinical outcomes in patients who either underwent repeat intervention or conservative management with radiographic surveillance when presenting with aneurysmal recurrence after endovascular treatment. Since publication of the international subarachnoid aneurysm trial (ISAT), an increasing number of patients are treated with endovascular therapy. However, recurrence after endovascular therapy continues to pose a challenge, and there is minimal evidence to guide its management. We performed a retrospective review of all patients who underwent endovascular treatment of an intracranial aneurysm from January 2005 to February 2013. The patients who had an aneurysmal recurrence following the initial endovascular treatment were identified and divided into two groups: those followed with conservative management (n=24), and those who underwent reintervention (n=65). The groups were compared for complications and clinical outcomes. When a reintervention was undertaken, microsurgical clip ligation was associated with a higher rate of occlusion than additional endovascular therapy (p<0.001). When comparing conservative treatment and reintervention, there was no statistically significant difference in complications or clinical outcomes. Reintervention was more common in patients who were younger, had presented with subarachnoid hemorrhage, or had a greater degree of recurrence. We conclude that clinical outcomes and repeat subarachnoid hemorrhage are similar in patients who underwent retreatment versus those who had conservative management for their recurrent cerebral aneurysms.

    View details for DOI 10.1016/j.jocn.2015.04.012

    View details for Web of Science ID 000365370600010

    View details for PubMedID 26256068

  • The Importance of Rare Subtypes in Diagnosis and Treatment of Peripheral Neuropathy A Review JAMA NEUROLOGY Callaghan, B. C., Price, R. S., Chen, K. S., Feldman, E. L. 2015; 72 (12): 1510–18


    Peripheral neuropathy is a prevalent condition that usually warrants a thorough history and examination but has limited diagnostic evaluation. However, rare localizations of peripheral neuropathy often require more extensive diagnostic testing and different treatments.To describe rare localizations of peripheral neuropathy, including the appropriate diagnostic evaluation and available treatments.References were identified from PubMed searches conducted on May 29, 2015, with an emphasis on systematic reviews and randomized clinical trials. Articles were also identified through the use of the authors' own files. Search terms included common rare neuropathy localizations and their causes, as well as epidemiology, pathophysiology, diagnosis, and treatment.Diffuse, nonlength-dependent neuropathies, multiple mononeuropathies, polyradiculopathies, plexopathies, and radiculoplexus neuropathies are rare peripheral neuropathy localizations that often require extensive diagnostic testing. Atypical neuropathy features, such as acute/subacute onset, asymmetry, and/or motor predominant signs, are frequently present. The most common diffuse, nonlength-dependent neuropathies are Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, and amyotrophic lateral sclerosis. Effective disease-modifying therapies exist for many diffuse, nonlength-dependent neuropathies including Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, and some paraprotein-associated demyelinating neuropathies. Vasculitic neuropathy (multiple mononeuropathy) also has efficacious treatment options, but definitive evidence of a treatment effect for IgM anti-MAG neuropathy and diabetic amyotrophy (radiculoplexus neuropathy) is lacking.Recognition of rare localizations of peripheral neuropathy is essential given the implications for diagnostic testing and treatment. Electrodiagnostic studies are an important early step in the diagnostic evaluation and provide information on the localization and pathophysiology of nerve injury.

    View details for PubMedID 26437251

    View details for PubMedCentralID PMC5087804

  • Failure of a polyether-ether-ketone expandable interbody cage following transforaminal lumbar interbody fusion EUROPEAN SPINE JOURNAL Stein, I. C., Than, K. D., Chen, K. S., Wang, A. C., Park, P. 2015; 24: S555–S559


    Expandable cages are a more recent option for maintaining or restoring disc height and segmental lordosis with transforaminal lumbar interbody fusion (TLIF). Complications associated with expandable cages have not yet been widely reported. We report a case of postoperative failure of a polyether-ether-ketone (PEEK) expandable interbody device used during TLIF.A 50-year-old man presented with severe back and right leg pain after undergoing L4-5 and L5-S1 TLIFs with expandable cages and L3-S1 posterior instrumented fusion. Imaging showed retropulsion of a portion of the interbody cage into the spinal canal causing nerve compression. Displacement occurred in a delayed manner. In addition, pseudoarthrosis was present.The patient underwent re-exploration with removal of the retropulsed wafer and redo fusion.Expandable cages are a recent innovation; as such, efficacy and complication data are limited. As with any new device, there exists potential for mechanical failure, as occurred in the case presented.

    View details for PubMedID 25465905

  • Recent Advances and the Future of Stem Cell Therapies in Amyotrophic Lateral Sclerosis NEUROTHERAPEUTICS Goutman, S. A., Chen, K. S., Feldman, E. L. 2015; 12 (2): 428–48


    Amyotrophic lateral sclerosis is a progressive neurodegenerative disease of the motor neurons without a known cure. Based on the possibility of cellular neuroprotection and early preclinical results, stem cells have gained widespread enthusiasm as a potential treatment strategy. Preclinical models demonstrate a protective role of engrafted stem cells and provided the basis for human trials carried out using various types of stem cells, as well as a range of cell delivery methods. To date, no trial has demonstrated a clear therapeutic benefit; however, results remain encouraging and are the basis for ongoing studies. In addition, stem cell technology continues to improve, and induced pluripotent stem cells may offer additional therapeutic options in the future. Improved disease models and clinical trials will be essential in order to validate stem cells as a beneficial therapy.

    View details for PubMedID 25776222

    View details for PubMedCentralID PMC4404436

  • Histological Bulbar Manifestations in the ALS Rat NEURODEGENERATIVE DISEASES Kashlan, O. N., Kashlan, B. N., Oh, S., McGinley, L. M., Chen, K. S., Kupfer, R., Erman, A., Sakowski, S. A., Feldman, E. L. 2015; 15 (2): 121–26


    Almost all patients with amyotrophic lateral sclerosis (ALS) develop bulbar symptoms; therefore, it is important to have valid animal models that accurately reflect these features. While the SOD1-G93A rat is extensively used as an ALS model, bulbar symptoms in this model are not well characterized.In the present study, we aimed to better characterize bulbar dysfunction in terms of histology to determine whether the SOD1-G93A rat is a useful model for bulbar-onset ALS.Sixty-day-old SOD1-G93A rats on a Sprague-Dawley background and age-matched wild-type controls were assessed weekly for global motor function, facial nerve function, and vagal nerve function. The study endpoint was determined when an SOD1-G93A rat could not right itself within 30 s of being placed on its side. At that point, neuronal counts were assessed in different brainstem cranial nerve nuclei. In addition, the masseter muscle, posterior belly of the digastric muscle, and tongue muscle were evaluated for intact neuromuscular junctions.Our data demonstrate decreases in the number of motor neurons in the trigeminal, facial, and hypoglossal nuclei, as well as compromised neuromuscular junction integrity in the muscles they innervate.These findings suggest that, from a histological standpoint, the SOD1-G93A rat is a valid model of ALS bulbar symptoms.

    View details for PubMedID 25825172

  • Sleep apnea and cervical spine pathology EUROPEAN SPINE JOURNAL Khan, A., Than, K. D., Chen, K. S., Wang, A. C., La Marca, F., Park, P. 2014; 23 (3): 641–47


    Sleep apnea is a multi-factorial disease with a variety of identified causes. With its close proximity to the upper airway, the cervical spine and its associated pathologies can produce sleep apnea symptoms in select populations. The aim of this article was to summarize the literature discussing how cervical spine pathologies may cause sleep apnea.A search of the PubMed database for English-language literature concerning the cervical spine and its relationship with sleep apnea was conducted. Seventeen published papers were selected and reviewed.Single-lesion pathologies of the cervical spine causing sleep apnea include osteochondromas, osteophytes, and other rare pathologies. Multifocal lesions include rheumatoid arthritis of the cervical spine and endogenous cervical fusions. Furthermore, occipital-cervical misalignment pre- and post-cervical fusion surgery may predispose patients to sleep apnea.Pathologies of the cervical spine present significant additional etiologies for producing obstructive sleep apnea in select patient populations. Knowledge of these entities and their pathophysiologic mechanisms is informative for the clinician in diagnosing and managing sleep apnea in certain populations.

    View details for PubMedID 24121751

    View details for PubMedCentralID PMC3940806

  • Trigeminal Neuralgia without Vascular Conflict: Strategies and Outcomes when the Culprit Goes Missing WORLD NEUROSURGERY Chen, K. S., Sagher, O. 2013; 80 (3-4): 302–3

    View details for PubMedID 23159644

  • Minimally invasive unilateral approach for bilateral decompression of spinal stenosis and modified transforaminal lumbar interbody fusion for degenerative spondylolisthesis. Neurosurgical focus Chen, K. S., Than, K. D., Lamarca, F., Park, P. 2013; 35 (2 Suppl): 4


    This video describes a minimally invasive approach for treatment of symptomatic grade I spondylolisthesis and high-grade spinal stenosis. In this procedure, a unilateral approach for bilateral decompression is utilized in conjunction with a modified transforaminal lumbar interbody fusion and percutaneous pedicle screw fixation. The key steps in the procedure are outlined, and include positioning, fluoroscopic positioning/guidance, exposure with tubular retractor system, technique for ipsilateral and contra-lateral decompression, disc space preparation and interbody grafting, percutaneous pedicle screw and rod placement, and closure. The video can be found here:

    View details for PubMedID 23829853

  • Minimally invasive deformity correction: surgical technique. Neurosurgical focus Chen, K. S., Than, K. D., LaMarca, F., Park, P. 2013; 35 (2 Suppl): 3


    This video details a minimally invasive treatment of symptomatic adult kyphoscoliosis. Both anterior and posterior approaches are used to obtain sagittal and coronal balance. In addition, improved lumbar lordosis is achieved to closely match the patient's pelvic incidence. The key steps for the lateral transpsoas procedure are detailed in the first portion of the video and include positioning, fluoroscopic localization, exposure with tubular retractor placement, interbody preparation and grafting, and closure. The second portion of the video shows positioning, fluoroscopic positioning/guidance, exposure for percutaneous pedicle screw placement, rod insertion, and closure. The video can be found here:

    View details for PubMedID 23829852



    Monoclonal antibody (mAb) therapy is a rapidly evolving treatment immunotherapy modality for malignant gliomas. Many studies have provided evidence that the blood brain barrier-both at baseline and in the context of malignancy-is permissive for mAbs, thus providing a rationale for their use in treating intracranial malignancy. Furthermore, techniques such as convection enhanced delivery (CED) are being implemented to maximize exposure of tumor cells to mAb therapy. The mechanisms and designs of mAbs are widely varying, including unarmed immunoglobulins as well as immunoglobulins conjugated to radioisotopes, biological toxins, boronated dendrimers and immunoliposomes. The very structure of the immunoglobulin molecule has also been manipulated to generate a diverse armamentarium including single-chain Fv, bispecific T-cell engagers and chimeric antigen receptors. The targeted neutralization capacity of mAbs has been employed to modulate the immunologic milieu in hopes of optimizing other immunotherapy platforms. Many clinical trials have evaluated these mAb strategies to treat malignant gliomas, and the implementation of mAb therapy seems imminent and optimistic.

    View details for PubMedID 22639164

  • Malignant Glioma Immunotherapy: A Peptide Vaccine from Bench to Bedside TUMORS OF THE CENTRAL NERVOUS SYSTEM: GLIOMAS - GLIOBLASTOMA (PT 1) Choi, B. D., Chen, K. S., Sampson, J. H., Hayat, M. A. 2011; 1: 349–56
  • Inducible nitric oxide synthase is present in motor neuron mitochondria and Schwann cells and contributes to disease mechanisms in ALS mice BRAIN STRUCTURE & FUNCTION Chen, K., Northington, F. J., Martin, L. J. 2010; 214 (2-3): 219–34


    Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs). The molecular pathogenesis of ALS is not understood, thus effective therapies for this disease are lacking. Some forms of ALS are inherited by mutations in the superoxide dismutase-1 (SOD1) gene. Transgenic mice expressing human Gly93 --> Ala (G93A) mutant SOD1 (mSOD1) develop severe MN disease, oxidative and nitrative damage, and mitochondrial pathology that appears to involve nitric oxide-mediated mechanisms. We used G93A-mSOD1 mice to test the hypothesis that the degeneration of MNs is associated with an aberrant up-regulation of the inducible form of nitric oxide synthase (iNOS or NOS2) activity within MNs. Western blotting and immunoprecipitation showed that iNOS protein levels in mitochondrial-enriched membrane fractions of spinal cord are increased significantly in mSOD1 mice at pre-symptomatic stages of disease. The catalytic activity of iNOS was also increased significantly in mitochondrial-enriched membrane fractions of mSOD1 mouse spinal cord at pre-symptomatic stages of disease. Reverse transcription-PCR showed that iNOS mRNA was present in the spinal cord and brainstem MN regions in mice and was increased in pre-symptomatic and early symptomatic mice. Immunohistochemistry showed that iNOS immunoreactivty was up-regulated first in spinal cord and brainstem MNs in pre-symptomatic and early symptomatic mice and then later in the course of disease in numerous microglia and few astrocytes. iNOS accumulated in the mitochondria in mSOD1 mouse MNs. iNOS immunoreactivity was also up-regulated in Schwann cells of peripheral nerves and was enriched particularly at the paranodal regions of the nodes of Ranvier. Drug inhibitors of iNOS delayed disease onset and significantly extended the lifespan of G93A-mSOD1 mice. This work identifies two new potential early mechanisms for MN degeneration in mouse ALS involving iNOS at MN mitochondria and Schwann cells and suggests that therapies targeting iNOS might be beneficial in treating human ALS.

    View details for PubMedID 19888600

  • Motor neuron degeneration in amyotrophic lateral sclerosis mutant superoxide dismutase-1 transgenic mice: Mechanisms of mitochondriopathy and cell death JOURNAL OF COMPARATIVE NEUROLOGY Martin, L. J., Liu, Z., Chen, K., Price, A. C., Pan, Y., Swaby, J. A., Golden, W. 2007; 500 (1): 20–46


    The mechanisms of human mutant superoxide dismutase-1 (mSOD1) toxicity to motor neurons (MNs) are unresolved. We show that MNs in G93A-mSOD1 transgenic mice undergo slow degeneration lacking similarity to apoptosis structurally and biochemically. It is characterized by somal and mitochondrial swelling and formation of DNA single-strand breaks prior to double-strand breaks occurring in nuclear and mitochondrial DNA. p53 and p73 are activated in degenerating MNs, but without nuclear import. The MN death is independent of activation of caspases-1, -3, and -8 or apoptosis-inducing factor within MNs, with a blockade of apoptosis possibly mediated by Aven up-regulation. MN swelling is associated with compromised Na,K-ATPase activity and aggregation. mSOD1 mouse MNs accumulate mitochondria from the axon terminals and generate higher levels of superoxide, nitric oxide, and peroxynitrite than MNs in control mice. Nitrated and aggregated cytochrome c oxidase subunit-I and alpha-synuclein as well as nitrated SOD2 accumulate in mSOD1 mouse spinal cord. Mitochondria in mSOD1 mouse MNs accumulate NADPH diaphorase and inducible nitric oxide synthase (iNOS)-like immunoreactivity, and iNOS gene deletion extends significantly the life span of G93A-mSOD1 mice. Prior to MN loss, spinal interneurons degenerate. These results identify novel mechanisms for mitochondriopathy and MN degeneration in amyotrophic lateral sclerosis (ALS) mice involving blockade of apoptosis, accumulation of MN mitochondria with enhanced toxic potential from distal terminals, NOS localization in MN mitochondria and peroxynitrite damage, and early degeneration of alpha-synuclein(+) interneurons. The data support roles for oxidative stress, protein nitration and aggregation, and excitotoxicity as participants in the process of MN degeneration caused by mSOD1.

    View details for PubMedID 17099894

  • Adult motor neuron apoptosis is mediated by nitric oxide and Fas death receptor linked by DNA damage and p53 activation JOURNAL OF NEUROSCIENCE Martin, L. J., Chen, K., Liu, Z. P. 2005; 25 (27): 6449–59


    The mechanisms of injury- and disease-related degeneration of motor neurons (MNs) need clarification. Unilateral avulsion of the sciatic nerve in the mouse induces apoptosis of spinal MNs that is p53 and Bax dependent. We tested the hypothesis that MN apoptosis is Fas death receptor dependent and triggered by nitric oxide (NO)- and superoxide-mediated damage to DNA. MNs in mice lacking functional Fas receptor and Fas ligand were protected from apoptosis. Fas protein levels and cleaved caspase-8 increased in MNs after injury. Fas upregulation was p53 dependent. MNs in mice deficient in neuronal NO synthase (nNOS) and inducible NOS (iNOS) resisted apoptosis. After injury, MNs increased nNOS protein but decreased iNOS protein; however, iNOS contributed more than nNOS to basal and injury-induced levels of NADPH diaphorase activity in MNs. NO and peroxynitrite (ONOO-) fluorescence increased in injured MNs, as did nitrotyrosine staining of MNs. DNA damage, assessed as 8-hydroxy-2-deoxyguanosine and single-stranded DNA, accumulated within injured MNs and was attenuated by nNOS and iNOS deficiency. nNOS deficiency increased DNA repair protein oxoguanine DNA-glycosylase, whereas iNOS deficiency blocked diaphorase activity. MN apoptosis was blocked by the antioxidant Trolox and by overexpression of wild-type human superoxide dismutase-1 (SOD1). In contrast, injured MNs in mice harboring mutant human SOD1 had upregulated Fas and iNOS, escalated DNA damage, and accelerated and increased MN degeneration and underwent necrosis instead of apoptosis. Thus, adult spinal MN apoptosis is mediated by upstream NO and ONOO- genotoxicity and downstream p53 and Fas activation and is shifted to necrosis by mutant SOD1.

    View details for PubMedID 16000635