Publications by authors named "Hoi Sang U"

Article Synopsis
  • Functional mapping during brain surgery identifies critical brain areas that can't be removed, but traditional methods are time-consuming and less precise.
  • A new technology, the iEEG-microdisplay, integrates LED arrays with electrode grids to provide real-time brain activity visualization during surgery.
  • Experiments in animal models show that this device can clearly display cortical functions and pathological activities, helping improve surgical outcomes and monitoring in clinical settings.
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Over the past decade, stereotactically placed electrodes have become the gold standard for deep brain recording and stimulation for a wide variety of neurological and psychiatric diseases. Current electrodes, however, are limited in their spatial resolution and ability to record from small populations of neurons, let alone individual neurons. Here, we report on an innovative, customizable, monolithically integrated human-grade flexible depth electrode capable of recording from up to 128 channels and able to record at a depth of 10 cm in brain tissue.

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Brain surgeries are among the most delicate clinical procedures and must be performed with the most technologically robust and advanced tools. When such surgical procedures are performed in functionally critical regions of the brain, functional mapping is applied as a standard practice that involves direct coordinated interactions between the neurosurgeon and the clinical neurology electrophysiology team. However, information flow during these interactions is commonly verbal as well as time consuming which in turn increases the duration and cost of the surgery, possibly compromising the patient outcomes.

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Article Synopsis
  • Electrophysiological recording and stimulation are essential for mapping brain function during surgeries and therapies, relying heavily on electrode materials that transmit signals between the brain and measurement systems.
  • Recent advancements in electrode array systems enhance the quality of brain activity recordings and stimulations through various materials, aimed at achieving high signal clarity and safety.
  • Discussions include the importance of electrode size for better resolution and connections, plus recent innovations in packaging and wireless monitoring for high-channel electrode arrays.
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The basic helix-loop-helix factors play a central role in neuronal differentiation and nervous system development, which involve the Notch and signal transducer and activator of transcription (STAT)/small mother against decapentaplegic signaling pathways. Neural stem cells differentiate into three nervous system lineages, and the suppressor of cytokine signaling (SOCS) and von Hippel-Lindau (VHL) proteins are involved in this neuronal differentiation. The SOCS and VHL proteins both contain homologous structures comprising the BC-box motif.

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Ectopic cerebellar tissue has only been described in isolated case reports, with only two reported cases in adult patients. We report the case of a 63-year-old woman with progressive, medically refractory headaches. A scan showed an intraosseous lesion of the midline occipital bone.

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Background: Complications of ventriculoperitoneal (VP) shunts include migration into various anatomic compartments and even extrusion through tissue layers.

Case Description: A 31-year-old female patient with a VP shunt presented with distal shunt tubing extruding through the skin at the level of the inguinal ligament. Shunt hardware was removed, and cultures grew Dermacoccus.

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Article Synopsis
  • H3K27M-mutant diffuse midline gliomas are a newly recognized type of brain tumor mainly affecting kids, with less clear characteristics in adults, often presented with severe cognitive and visual decline.
  • A 36-year-old man with progressive symptoms and MRI findings underwent surgery revealing a tumor that, despite appearing low-grade, was confirmed to have the H3K27M mutation.
  • These tumors are incurable and have a poor outlook; accurate diagnosis requires awareness of their varied features and the importance of early biopsy and molecular testing.
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Background: The thalamus has a demonstrated role in language, particularly through its connectivity to frontal language cortices.

Case Description: A 59-year-old man with transient mixed aphasia following resection of a left-sided thalamic cavernous malformation is reported. No operative complications were encountered, and there was no surgical contact with cortical language areas.

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Objective: This study discusses rare and unusual locations of primary craniopharyngiomas.

Methods: We describe a case of a craniopharyngioma in the cerebellopontine angle. As a result of this unusual location, we performed a literature review of the ectopic occurrence of craniopharyngiomas using Pubmed, Cochrane Database, Trip, and Google Scholar to search for the terms "unusual," "uncommon," and "ectopic" in combination with "craniopharyngioma.

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Venous air embolism is a devastating and potentially life-threatening complication that can occur during neurosurgical procedures. We report the development and use of the "inter-mammary sticky roll," a technique to reliably secure a precordial Doppler ultrasonic probe to the chest wall during neurosurgical cases that require lateral decubitus positioning. We have found that this noninvasive technique is safe, and effectively facilitates a constant Doppler signal with no additional risk to the patient.

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A 24-year-old male presented with eight months of increasingly severe frontal headaches, decreased right facial sensation, and periodic vertigo. Magnetic resonance imaging demonstrated a heterogeneously contrast-enhancing mass involving and expanding the right foramen ovale.  A biopsy of the lesion was performed, and the final pathologic diagnosis revealed a neoplastic rhabdomyoma.

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Introduction: Because of their relative rarity, anaplastic astrocytomas (AAs) often are grouped with glioblastomas in clinical treatment paradigms. There are reasons, however, to expect that the therapeutic response of AAs may differ from those of glioblastoma. Here, we examined the clinical benefit of gross total resection (GTR) in AA relative to glioblastoma patients.

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Inflammatory myofibroblastic tumors, also known as plasma cell granulomas or inflammatory pseudotumors, are uncommon lesions that are known to arise in many areas of the body. They are uncommonly found in the skull base region where effective treatment can be difficult. Steroids and radiation therapy with gross total excision when possible remain the treatments of choice.

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Importance: Alzheimer disease (AD) is the most common neurodegenerative disorder and lacks effective disease-modifying therapies. In 2001, we initiated a clinical trial of nerve growth factor (NGF) gene therapy in AD, the first effort at gene delivery in an adult neurodegenerative disorder. This program aimed to determine whether a nervous system growth factor prevents or reduces cholinergic neuronal degeneration in patients with AD.

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A 50-year-old male immigrant from Ethiopia presented for consultation after 3 years of hematochezia/melena requiring > 25 units of blood transfusions. Physical examination revealed severe proximal muscle wasting and weakness, central obesity, proptosis, and abdominal striae, accompanied by eosinophilia, elevated hemoglobin A1c, elevated 24-hour urinary cortisol, lack of suppression of 8 am cortisol levels by 1 mg dexamethasone, and inappropriately elevated random adrenocorticotropic hormone (ACTH) level. Histopathological examination of gastrointestinal biopsies showed large numbers of Strongyloides stercoralis, indicating Strongyloides hyperinfection.

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In adults, complete surgical resection of arteriovenous malformations (AVMs) is generally curative. Recurrence of AVMs is extremely rare and most often delayed over many years. The authors report the case of a man in his 20s with rapid AVM recurrence and dual blood supply from the dura and intracerebral vessels.

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Objectives: To evaluate whether rat fetal brain stem cells can be induced to acquire cell fates outside the nervous system, hypothesising that cell-based replacement therapy with stem cells can aid in the regeneration of penile smooth musculature and might help to attenuate organic erectile dysfunction (ED), as the degeneration of penile smooth muscle cells leading to subsequent impairment of function is important in organic ED.

Materials And Methods: Fetal brain stem cells (FBSCs) from embryonal 12-day Fisher 344 rats were isolated and characterized. For in vitro studies, undifferentiated FBSCs were cultured for 21 days in either N2 media (control) or N2 media conditioned in rat penile smooth muscle cell culture.

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Objectives: To review the literature on glossopharyngeal schwannomas with a focus on clinical presentation, radiologic/audiologic characteristics, and management options, and to propose a mechanism explaining the nature of vestibulocochlear dysfunction seen with these tumors.

Study Design: Contemporary review.

Methods: English literature search for cases of primary isolated glossopharyngeal schwannomas and chart review of two new cases.

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Object: Each region of the brain is distinguished by specific and distinct markers and functions. The authors hypothesized that each region possesses unique trophic properties that dictate and maintain its development. To test this hypothesis, they isolated central nervous system (CNS) stem cells from fetal rodents, and these rat CNS-derived stem cells (RSCs) were placed in coculture with primary cultures of the developing neonatal hippocampus and hypothalamus to determine whether region-specific primary cells would direct the differentiation of stem cells in a region-specific manner.

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Fetal brain stem cells (RSCs) have been induced to express pituitary phenotypes in vitro in co-cultures with GH(3) cells and by exposure to GH(3)-conditioned media. In the current studies, we graft RSCs into the pituitary glands of adult rat to investigate whether grafted RSCs can be induced by the native gland to acquire pituitary properties. Grafted cells survive for 4 weeks and express Pit-1, GH, FSH, LH, ACTH, TSH and to a lesser extent PRL indicating that inductive influences are operative in vivo as well.

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Although the study of the human brain is a rapidly developing and expanding science, we must take pause to examine the historical and evolutionary events that helped shape the brain of Homo sapiens. From an examination of the human lineage to a discussion of evolutionary principles, we describe the basic principles and theories behind the evolution of the human brain. Specifically, we examine several theories concerning changes in overall brain size during hominid evolution and relate them to the fossil record.

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The aim was to evaluate the potential of contrast-enhanced ultrasound to visualize the hemodynamics in intracranial aneurysms during neurosurgical intervention and to quantify the ultrasound data using digital particle image velocimetry (DPIV) technique. Aneurysms were scanned through the intact dura mater, preclipping and again postclipping after closure of the dura. After intravenous injection of Optison, angio-like views of the vascular tree surrounding the aneurysm, including the aneurysm sac, were obtained.

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Cholinergic neuron loss is a cardinal feature of Alzheimer disease. Nerve growth factor (NGF) stimulates cholinergic function, improves memory and prevents cholinergic degeneration in animal models of injury, amyloid overexpression and aging. We performed a phase 1 trial of ex vivo NGF gene delivery in eight individuals with mild Alzheimer disease, implanting autologous fibroblasts genetically modified to express human NGF into the forebrain.

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The capacity to prevent neuronal degeneration and death during the course of progressive neurological disorders such as Alzheimer disease (AD) would represent a significant advance in therapy. Nervous system growth factors are families of naturally produced proteins that, in animal models, exhibit extensive potency in preventing neuronal death due to a variety of causes, reversing age-related atrophy of neurons, and ameliorating functional deficits. The main challenge in translating growth factor therapy to the clinic has been delivery of growth factors to the brain in sufficient concentrations to influence neuronal function.

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