Research
Electrophysiology in Temporal Lobe Epilepsy
Our lab is interested in the pathophysiology of temporal lobe epilepsy. In particular, we investigate the electrodynamics in the hippocampal circuits and the roles of different types of neurons in the hippocampus in seizure generation and propagation. The techniques we employ include optogenetics, chemogenetics, calcium imaging, intracranial recordings, and immunohistochemistry. We also apply digital signal processing and computational algorithms to EEG signals to help unlock the relationship between neuronal activities and changes in electrophysiological signals.
Recent publications:
Unilateral optogenetic kindling of hippocampus leads to more severe impairments of the inhibitory signaling in the contralateral hippocampus. F.C. Tescarollo, D. Valdivia, S. Chen, H. Sun*. Frontiers in Molecular Neuroscience, 2023.
Ictogenesis proceeds through discrete phases in hippocampal CA1 seizures in mice. JS. Mueller, F.C. Tescarollo, T. Huynh, D. Brenner, D. Valdivia, K. Olagbegi, S. Sangappa, S. Chen, H. Sun. Nature Communications, 2023.
DREADDs in Epilepsy Research: Network-Based Review. JS. Mueller†, F.C. Tescarollo†, H. Sun*. Frontiers in Molecular Neuroscience, 2022.
Evaluation of pathological changes in brain connectivity using neuroimaging
Our lab is interested in using advanced magnetic resonance imaging (MRI) techniques to study the brain networks involving in human cognition and how these networks are affected by diseases. The MRI techniques we employ include anatomical studies, diffuse tensor imaging (DTI), functional MRI (fMRI), and resting state functional MRI (rsfMRI). These imaging studies can also be combined with electrophysiological studies such as EEG and neuropsychological testing results to understand the brain networks in both physiological states and pathological states.
One of the ongoing projects in the lab is to recruit subjects with moderate and severe traumatic brain injuries and follow them over time with imaging, EEG, and neuropsychological testing results. These results will be compared to studies obtained from healthy controls. The goal is to identify biomarkers that can predict the development of post-traumatic epilepsy (PTE) among these individuals. This study is the US Dept. of Defense, Congressional Directed Medical Research Program (CDMRP): W81XWH-18-1-0655. URL: https://app.dimensions.ai/details/grant/grant.7749737
We also plan to apply these techniques to patients affected by diseases such as movement disorders, Alzheimer’s disease, and epilepsy.
Recent publications:
Biomarkers of Seizure Activity in Patients with Intracranial Metastases and Glioma: a Wide Range Study of Correlated Region of Interest, P. Kalakoti, A. Edwards, C. Ferrier, K. Sharma, T. Huynh, C. Ledbetter, E. Gozalez-Toledo, A. Nanda, and H. Sun, Frontiers in Neurology, 2020.
Focal epilepsy caused by single cerebral cavernous malformation (CCM) is associated with regional and global resting state functional connectivity (FC) disruption. J. D'Cruz, M. Hefner, C. Ledbetter, C. Frilot, B. Howard, P. Zhu, R. Riel-Romero, C. Notarianni, E. Gonzalez-Toledo, A. Nanda, and H. Sun. Neuroimage Clin. 2019.
Differentiation of High-Grade Glioma and Intracranial Metastasis Using Volumetric Diffusion Tensor Imaging Tractography. Holly, J. Fitz-Gerald, B. Barker, D. Murcia, R. Daggett, C. Ledbetter, E. Gonzalez-Toledo, and H. Sun. World Neurosurgery. 2018.
High-grade Gliomas Exhibit Higher Peritumoral Fractional Anisotropy and Lower Mean Diffusivity than Intracranial Metastases. K. Holly, B. Barker, D. Murcia, R. Bennett, P. Kalakoti, C. Ledbetter, E. Gonzalez-Toledo, A. Nanda, and, H. Sun. Frontiers Surgery. 2017.
Brain Computer Interface
As a neurosurgeon specializing in epilepsy surgery, I am privileged to have direct contact with the brain. For example, during the workup for patients undergoing evaluation for epilepsy surgery, we obtained brain signals by performing electroencephalogram (EEG) or intracranial recordings including electrocorticography (ECOG) to identify the origin of the seizures, which are abnormal neuronal activities. The recordings obtained from these studies give us a tremendous amount of information on how the brain works. How does the brain control our motor movements? How does the brain generate and understand speech? Furthermore, these brain signals can be used to design and control robotic devices to perform important functions for a patient who has lost these functions from stroke or spinal cord injuries. Our goal is to use brain computer interface devices to help design periprosthetic devices to improve the lives of these patients.
Recent publication:
Sequential activation of premotor, primary somatosensory and primary motor areas in humans during cued finger movements, H. Sun, T. Blakely, F. Darvas, J. Wander, L. Johnson, D. Su, K. Miller, E. Fetz, J. Ojemann, Clinical Neurophysiology. 2015.
Novel treatment and clinical outcomes of cerebrovascular neurosurgery
I am a dual-trained cerebrovascular neurosurgeon, which means that I employ both open microsurgical and minimally invasive endovascular approaches to treat patients with diseases affecting blood vessels in the brain, which can result from either ischemic or hemorrhagic strokes. In the basic science arena, I collaborate with scientists who study the pathophysiology of these diseases. In the clinical arena, I evaluate the efficacy and outcomes of the current treatments of these diseases by reviewing my own practice and the practice of my colleagues nationally and internationally. By doing so, I hope to improve the standard of care and usher new treatment paradigms for these patients.
Recent publications:
Cerebral Revascularization for Moyamoya Syndrome Associated with Sickle Cell Disease: A Systematic Review of the Literature on the Role of Extracranial-Intracranial Bypass in in Treating Neurologic Manifestations of Pediatric Patients with Sickle Cell Disease, D Terrell, AR Savardekar, SG Whipple, RH Dossani, RF Spetzler, H Sun, World Neurosurgery. 2020.
Targeted Stereotactic Radiosurgery for Arteriovenous Malformation Downgrading Followed by Microsurgical Resection: A Case Report and Review of the Literature, E Wild, J Barry, H Sun, World Neurosurgery. 2019.
Timing of carotid endarterectomy for symptomatic carotid stenosis: a snapshot of current trends and systematic review of literature on changing paradigm towards early surgery, AR Savardekar, V Narayan, DP Patra, RF Spetzler, H Sun, Neurosurgery. 2019.
Novel role for the AnxA1-Fpr2/ALX signaling axis as a key regulator of platelet function to promote resolution of inflammation, EY Senchenkova, J Ansari, F Becker, SA Vital, Z Al-Yafeai, H Sun et al., Circulation. 2019.
Major Cerebral Artery Injury during Skull Base Meningioma Resection: Critical Video Analysis of Institutional Experience and Systematic Review of Literature, JD Thakur, N Adeeb, A Savardekar, B Guthikonda, H Sun, Journal of Neurological Surgery Part B: Skull Base. 2019.
Novel use of pipeline stent device after inadvertent microcatheter rupture during arteriovenous fistula embolization, H Cuellar, T Maiti, V Narayan, D Patra, R Dossani, H Sun, A Nanda, World Neurosurgery. 2018.
Pulmonary Complications After Spontaneous Aneurysmal Subarachnoid Hemorrhage: Experience from Barrow Neurological Institute, C Cavallo, S Safavi-Abbasi, MYS Kalani, S Gandhi, H Sun, et al., World Neurosurgery. 2018.
Perioperative complications and long-term outcomes after bypasses in adults with moyamoya disease: a systematic review and meta-analysis. Sun H, Wilson C, Ozpinar A, Safavi-Abbasi S, Zhao Y, Nakaji P, Wanebo J, Spetzler R. World Neurosurg. 2016.
Socioeconomics of Neurosurgical Care
I am interested in the socioeconomics of diagnoses and treatments of neurosurgical conditions including access to care, resource utilization, and value-based assessment. This is an important aspect of patient care that is worth investigating especially because we are faced with challenges including the rapid increase in healthcare cost, inequality in the healthcare access, and regional variability of cost and outcomes.
Recent publications:
Proposing a Validated Clinical App Predicting Hospitalization Cost for Extracranial-Intracranial Bypass Surgery. Sun H, Kalakoti P, Sharma K, Thakur JD, Dossani RH, Patra DP, Phan K, Farokhi F, Notarianni C, Guithikonda B, Nanda A. PLOS One. 2017.
Impact of Prehospital Transportation on Survival in Skiers and Snowboarders with Traumatic Brain Injury. Sun H, Samra NS, Kalakoti P, Sharma K, Patra DP, Dossani RH, Thakur JD, Disbrow EA, Phan K, Veeranki SP, Pabaney A, Notarianni C, Owings JT, Nanda A. World Neurosurg. 2017.
Revisiting racial disparities in access to surgical management of drug-resistant temporal lobe epilepsy post implementation of Affordable Care Act. Sharma K, Kalakoti P, Henry M, Mishra V, Riel-Romero RM, Notarianni C, Nanda A, Sun H. Clin Neurol Neurosurg. 2017.