Machine Learning-assisted Quantitative Mapping of Intracortical Axonal Plasticity Following a Focal Cortical Stroke in Rodents

Stroke destroys neurons and their connections leading to focal neurological deficits. Although limited, many patients exhibit a certain degree of spontaneous functional recovery. Structural remodeling of the intracortical axonal connections is implicated in the reorganization of cortical motor representation maps, which is considered to be an underlying mechanism of the improvement in motor function. Therefore, an accurate assessment of intracortical axonal plasticity would be necessary to develop strategies to facilitate functional recovery following a stroke. The present study developed a machine learning-assisted image analysis tool based on multi-voxel pattern analysis in fMRI imaging. Intracortical axons originating from the rostral forelimb area (RFA) were anterogradely traced using biotinylated dextran amine (BDA) following a photothrombotic stroke in the mouse motor cortex. BDA-traced axons were visualized in tangentially sectioned cortical tissues, digitally marked, and converted to pixelated axon density maps. Application of the machine learning algorithm enabled sensitive comparison of the quantitative differences and the precise spatial mapping of the post-stroke axonal reorganization even in the regions with dense axonal projections. Using this method, we observed a substantial extent of the axonal sprouting from the RFA to the premotor cortex and the peri-infarct region caudal to the RFA. Therefore, the machine learningassisted quantitative axonal mapping developed in this study can be utilized to discover intracortical axonal plasticity that may mediate functional restoration following stroke.

Expression of Cellular Receptors in the Ischemic Hemisphere of Mice with Increased Glucose Uptake

Many previous studies have shown reduced glucose uptake in the ischemic brain. In contrast, in a permanent unilateral common carotid artery occlusion (UCCAO) mouse model, our pilot experiments using 18F-fluorodeoxyglucose positron emission tomography (FDG PET) revealed that a subset of mice exhibited conspicuously high uptake of glucose in the ipsilateral hemisphere at 1 week post-occlusion (asymmetric group), whereas other mice showed symmetric uptake in both hemispheres (symmetric group). Thus, we aimed to understand the discrepancy between the two groups. Cerebral blood flow and histological/metabolic changes were analyzed using laser Doppler flowmetry and immunohistochemistry/Western blotting, respectively. Contrary to the increased glucose uptake observed in the ischemic cerebral hemisphere on FDG PET (p<0.001), cerebral blood flow tended to be lower in the asymmetric group than in the symmetric group (right to left ratio [%], 36.4±21.8 vs. 58.0±24.8, p=0.059). Neuronal death was observed only in the ischemic hemisphere of the asymmetric group. In contrast, astrocytes were more activated in the asymmetric group than in the symmetric group (p<0.05). Glucose transporter-1, and monocarboxylate transporter-1 were also upregulated in the asymmetric group, compared with the symmetric group (p<0.05, respectively). These results suggest that the increased FDG uptake was associated with relatively severe ischemia, and glucose transporter-1 upregulation and astrocyte activation. Glucose metabolism may thus be a compensatory mechanism in the moderately severe ischemic brain.

A Pilot Study of Endoscopic Submucosal Dissection Using an Endoscopic Assistive Robot in a Porcine Stomach Model

BACKGROUND/AIMS: Endoscopic assistive devices have been developed to reduce the complexity and improve the safety of surgeries involving the use of endoscopes. We developed an assistive robotic arm for endoscopic submucosal dissection (ESD) and evaluated its efficiency and safety in this in vitro pilot study. METHODS: ESD was performed using an auxiliary transluminal endoscopic robot. An in vitro test bed replicating the intra-abdominal environment and pig stomachs were used for the experiment. Participants were divided into skilled operators and unskilled operators. Each group performed ESD 10 times by using both conventional and robot-assisted methods. The perforation incidence, operation time, and resected mucous membrane size were measured. RESULTS: For the conventional method, significant differences were noted between skilled and unskilled operators regarding operation time (11.3 minutes vs 26.7 minutes) and perforation incidence (0/10 vs 6/10). Unskilled operators showed a large decrease in the perforation incidence with the robot-assisted method (conventional method vs robot-assisted method, 6/10 vs 1/10). However, the operation time did not differ between the conventional and robot-assisted methods. On the other hand, skilled operators did not show differences in the operation time and perforation incidence between the conventional and robot-assisted methods. Among both skilled and unskilled operators, the operation time decreased with the robot-assisted method as the experiment proceeded. CONCLUSIONS: The surgical safety of unskilled operators greatly improved with robotic assistance. Thus, our assistive robotic arm was beneficial for ESD. Our findings suggest that endoscopic assistive robots have positive effects on surgical safety.

Insulin-like Growth Factor-1 Receptor Dictates Beneficial Effects of Treadmill Training by Regulating Survival and Migration of Neural Stem Cell Grafts in the Injured Spinal Cord

Survival and migration of transplanted neural stem cells (NSCs) are prerequisites for therapeutic benefits in spinal cord injury. We have shown that survival of NSC grafts declines after transplantation into the injured spinal cord, and that combining treadmill training (TMT) enhances NSC survival via insulin-like growth factor-1 (IGF-1). Here, we aimed to obtain genetic evidence that IGF-1 signaling in the transplanted NSCs determines the beneficial effects of TMT. We transplanted NSCs heterozygous (+/−) for Igf1r, the gene encoding IGF-1 receptor, into the mouse spinal cord after injury, with or without combining TMT. We analyzed the influence of genotype and TMT on locomotor recovery and survival and migration of NSC grafts. In vitro experiments were performed to examine the potential roles of IGF-1 signaling in the migratory ability of NSCs. Mice receiving +/− NSC grafts showed impaired locomotor recovery compared with those receiving wild-type (+/+) NSCs. Locomotor improvement by TMT was more pronounced with +/+ grafts. Deficiency of one allele of Igf1r significantly reduced survival and migration of the transplanted NSCs. Although TMT did not significantly influence NSC survival, it substantially enhanced the extent of migration for only +/+ NSCs. Cultured neurospheres exhibited dynamic motility with cytoplasmic protrusions, which was regulated by IGF-1 signaling. IGF-1 signaling in transplanted NSCs may be essential in regulating their survival and migration. Furthermore, TMT may promote NSC graft-mediated locomotor recovery via activation of IGF-1 signaling in transplanted NSCs. Dynamic NSC motility via IGF-1 signaling may be the cellular basis for the TMT-induced enhancement of migration.

Toll-like Receptor 2: A Novel Therapeutic Target for Ischemic White Matter Injury and Oligodendrocyte Death

Despite paramount clinical significance of white matter stroke, there is a paucity of researches on the pathomechanism of ischemic white matter damage and accompanying oligodendrocyte (OL) death. Therefore, a large gap exists between clinical needs and laboratory researches in this disease entity. Recent works have started to elucidate cellular and molecular basis of white matter injury under ischemic stress. In this paper, we briefly introduce white matter stroke from a clinical point of view and review pathophysiology of ischemic white matter injury characterized by OL death and demyelination. We present a series of evidence that Toll-like receptor 2 (TLR2), one of the membranous pattern recognition receptors, plays a cell-autonomous protective role in ischemic OL death and ensuing demyelination. Moreover, we also discuss our recent findings that its endogenous ligand, high-mobility group box 1 (HMGB1), is released from dying OLs and exerts autocrine trophic effects on OLs and myelin sheath under ischemic condition. We propose that modulation of TLR2 and its endogenous ligand HMGB1 can be a novel therapeutic target for ischemic white matter disease.

Erratum: Cortico-Cortical Modulation Induced by 1-Hz rTMS of the Temporal Cortex

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Cortico-Cortical Modulation Induced by 1-Hz Repetitive Transcranial Magnetic Stimulation of the Temporal Cortex

BACKGROUND AND PURPOSE: Repetitive transcranial magnetic stimulation (rTMS) has potential as a noninvasive neuromodulation treatment method for various neuropsychiatric disorders, and repeated sessions of rTMS are more likely to enhance the therapeutic efficacy. This study investigated neurophysiologic and spatiodynamic changes induced by repeated 1-Hz rTMS of the temporal cortex using transcranial magnetic stimulation (TMS) indices and fluorodeoxyglucose positron emission tomography (FDG-PET). METHODS: Twenty-seven healthy subjects underwent daily 1-Hz active or sham rTMS of the right temporal cortex for 5 consecutive days. TMS indices of motor cortical excitability were measured in both hemispheres daily before and after each rTMS session, and 2 weeks after the last stimulation. FDG-PET was performed at baseline and after the 5 days of rTMS sessions. RESULTS: All subjects tolerated all of the sessions well, with only three of them (11.1%) reporting mild transient side effects (i.e., headache, tinnitus, or local irritation). One-Hz rTMS decreased motor evoked potential amplitudes and delayed cortical silent periods in the stimulated hemisphere. Statistical parametric mapping of FDG-PET data revealed a focal reduction of glucose metabolism in the stimulated temporal area and an increase in the bilateral precentral, ipsilateral superior and middle frontal, prefrontal and cingulate gyri. CONCLUSIONS: Repeated rTMS sessions for 5 consecutive days were tolerated in all subjects, with only occasional minor side effects. Focal 1-Hz rTMS of the temporal cortex induces cortico-cortical modulation with widespread functional changes in brain neural networks via long-range neural connections.

Organotypic Spinal Cord Slice Culture to Study Neural Stem/Progenitor Cell Microenvironment in the Injured Spinal Cord

The molecular microenvironment of the injured spinal cord does not support survival and differentiation of either grafted or endogenous NSCs, restricting the effectiveness of the NSC-based cell replacement strategy. Studying the biology of NSCs in in vivo usually requires a considerable amount of time and cost, and the complexity of the in vivo system makes it difficult to identify individual environmental factors. The present study sought to establish the organotypic spinal cord slice culture that closely mimics the in vivo environment. The cultured spinal cord slices preserved the cytoarchitecture consisting of neurons in the gray matter and interspersed glial cells. The majority of focally applied exogenous NSCs survived up to 4 weeks. Pre-exposure of the cultured slices to a hypoxic chamber markedly reduced the survival of seeded NSCs on the slices. Differentiation into mature neurons was severely limited in this co-culture system. Endogenous neural progenitor cells were marked by BrdU incorporation, and applying an inflammatory cytokine IL-1beta significantly increased the extent of endogenous neural progenitors with the oligodendrocytic lineage. The present study shows that the organotypic spinal cord slice culture can be properly utilized to study molecular factors from the post-injury microenvironment affecting NSCs in the injured spinal cord.

Towards the Replacement Therapy Using Neural Stem/Progenitor cells for Neurological Disorders: Strategies to Enhance Therapeutic Capacity of Transplantation Approaches

Transplantation of neural stem/progenitor cells (NPC) holds potential to improve functional outcomes in various neurological disorders. It seems more difficult than previously envisioned, however, to functionally replace the lost neural cells by grafted NPCs. A lack of appropriate developmental cues in the injured tissue contributes to the failure to guide the NPCs to survive, differentiate, grow axons, and functionally integrate to the host neural circuit. Therefore, we need to design possible strategies to recapitulate the developmental processes for the grafted NPCs to fully mature into functional neural cells. To enhance survival of NPCs following transplantation, pharmacological treatments targeting apoptosis and inflammation can be combined with transplantation. Genetic overexpression of prosurvival genes or growth factors can also improve survival. In vitro predifferentiation not only provides neural cells of a specific lineage in high purity but also greatly reduces chances of a tumor formation. Genetic overexpression of various transcription factors or manipulating molecular microenvironment of the host can also be tried to force differentiation of NPCs to a desired lineage. Pharmacological application to overcome myelin inhibition or enzymatic degradation of the inhibitory extracellular matrix will enhance axonal growth of NPC-derived neurons. Increasing synaptic activity by behavioral training or patterned electrical stimulation may promote proper development of synaptic integration and myelination of the axon. A thorough understanding of cellular and molecular aspects of neural development will help design more sophisticated strategies to enhance therapeutic capacity of NPC transplantation to reconstruct the damaged neural circuit.

Chronological Changes in the Rotational Behavior in Response to Apomorphine Administration in 6-Hydroxydopamine Parkinsonian Rat

BACKGROUND: Apomorphine-induced rotational behavior of unilateral 6-hydroxydopamine (OHDA) lesioned rat is widely used to develop anti-Parkinsonian treatments including drugs, neuroprotective therapy, and neural graft. Time course of changes in rotational behavior after lesioning, however, has not been fully elucidated. The aim of this study was to observe the chronological changes in the rotational response and to find the optimal period when this model is used for investigation of various therapies. METHODS: 6-OHDA was stereotaxically delivered to the unilateral substantia nigra in 13 rats. Rotational responses to apomorphine administrations were counted in the rotomotor on 2, 4, 8, 12, and 14 weeks after lesioning. RESULTS: The total turns for two hours increased continuously up to eight weeks, and then plateaued. CONCLUSIONS: Apomorphine-induced rotations increase until eight weeks after 6-OHDA lesioning. Therefore, this Parkinsonian model should be used at least eight weeks after lesioning. Even though priming was not excluded as an explanation in the experiment, we reason that progressive degeneration of dopaminergic neurons may explain the chronological changes in rotational behavior.

Clinicoradiologic Study on Benign and Non-benign Pontine Hemorrhage

BACKGROUND: Since prognosis of pontine hemorrhage (PH) is dependent on the initial consciousness level, prediction of outcome is not difficult in patients presenting deeply comatose mentality or mild neurologic deficits without altered consciousness. The outcome of PH accompanied by some degree of altered mentality is, however, so various and cannot be easily predicted. The aim of this study was to analyze the radiologic factors determining the prognosis in this subgroup of PH. We also tried to describe the common clinical and radiologic features in patients with benign clinical course, which have rarely been studied systematically. METHODS: Chiefly based on the initial level of consciousness, 42 patients were classified into benign (BH, n=14), non-benign (NBH, n=19), and fatal (FH, n=9) PH. We retrospectively reviewed their medical records and radiologic data. The modified Rankin score was used for evaluating long-term prognosis. In NBH group, transverse and vertical extension index of hematoma, hemorrhage volume, and presence of extrapontine extension were investigated on CT images. RESULTS: Hemiparesis with or without ocular disturbance was the most common manifestation in BH group (64%) and two patients showed neurologic signs identical to lacunar syndrome. The most common location of hemorrhage was unilateral tegmentum (64%). In NBH group, transverse extension index was significantly greater in the patients with worse prognosis, though vertical extension index and extrapontine extension did not seem to be important in predicting the prognosis. CONCLUSIONS: The clinical features simulating lacunar syndrome are frequently found in BH. The degree of transverse extension in the pons is important in predicting the prognosis of NBH subgroup.

Gait Disturbance

No abstract available.

Dissection of the vertebrobasilar artery

In spite of relatively common references as differential diagnosis in the cases of vertebrobasilar ischemia or infartion, there are only a few reports about dissections of the vertebrobasilar artery(VBA) in Korea. We reviewed medical records and radiographic findings of the 10 patients diagnosed as having dissections of the VBA at Seoul National University Hospital and Seoul City Borame Hospitall since 1994. The 10 patients, all men ranging from 15 to 58 years, did not have the usual risk factors for stroke. In 6 cases, temporally related trauma or exercise was noted. There were also 2 cases of delayed neurologic manifestations from preceeding trauma, developed 74 days and about I year later respectively. Most subjects(9 cases) showed the ischemic symptoms of posterior circulations. Subarachnold hemorrhage was manifested in 2 cases. Magnetic resonance imaging(MRD, magnetic resonance angiography(MRA) and transfemoral cerebral angiography(TFCA) showed irregular narrowing of proximal vertebral artery(VA) with non-visualization of its distal part, thrombosed VA, intramural high signal intensity in VBA, double lumen appearance or fusiform aneurysm. Until now(mean follow up period; 15 months), them are no recurrences with anticoagulation or antiplatelet therapy in the cases of vertebrobasilar ischemia. Dissections of the VBA should be included in the differential diagnosis of vertebrobasilar ischemia or infarction, especially in the young population or in the subjects without common risk factors. The diagnosis can be made on the bases of clinical features and the characteristic findings of MRI, MRA and TFCA.

A dissociation of number processing between arabic and korean numbers: A case study

The cognitive domain of number processing has been known to be separable from that of language. Further, the number processing consists of Arabic and verbal number systems which could be also separable from each other. We report a 49-year-old woman who showed a dissociation between Arabic and Korean verbal numbers. Her impairment in number processing was characterized by the defective comprehension and expression of Korean verbal umbers, without notable defects in those of Arabic numbers. A follow-up examination revealed a further dissociation within the processing of Korean numbers, showing persistent impairment of number comprehension with improvement of number expression. In dealing with numbers with more than two digits, she showed syntactic errors characterized by uttering a string of single digit numbers(I.e., 365) rather than stating them as a whole number(365). Furthermore, auditory comprehension was also more accurate when the numbers were presented as an array of single digit numbers than a whole number with units. However, these syntactic errors were not observed on an automatic counting task. The evidence of separable representation of Arabic and Korean number system could be drawn from these observations, and therefore we propose the possibility of dual number processing pathways, one for a simple numbering system without semantic mediation and the other for a complex, multidigit numbering with semantic mediation.

Three Cases of Superficial Siderosis

Superficial siderosis is a rare condition characterized by hemosiderin deposition in leptomeninges, subpial tissue, brainstem, cerebellum, spinal cord, and cranial nerves. Slowly progressive hearing loss and gait ataxia are invariable clinical manifestations. We report three patients with their clinical and radiological features. All patients presented with hearing loss and cognitive dysfunction. Two showed gait ataxia and myelopathic symptoms and signs. Decreased visual acuity, hand tremor, limb ataxia, dysarthria, and nystagmus were also present. All patients showed typical MRI findings: marked linear hypointensities around the cerebellum, brainstem, and the surface of the cerebral cortex, especially in sylvian fissures. Two patients had brain tumors : pituitary adenoma and oligodendroglioma. Another patient had no definite bleeding source. Hemosiderin deposition is caused by chronic and recurrent subarachnoid hemorrhage derived from tumor, vascular malformation, aneurysm, posthemispherectomy, and unknown bleeding sources. Diagnosis is easily made by characteristic clinical manifestations and MRI findings. The selective vulnerability of the cerebellum and the 8th cranial nerve depends upon their own histological and biochemical characteristics. Benefits of the iron chelating agents are questionable. Removal of the possible bleeding sources is the most reliable strategy to prevent the disease progression.

Progression of In Situ Thrombosis of Basilar Artery

The clinical and radiological characteristics of progressing in situ thrombosis of the basilar artery have poorly been described. Patients with such condition present with minor neurologic deficits initially, progress in the hospital over several days, and present poor outcomes. We tried to find the common features of those patients that might have been associated with progression. We investigated the clinical pictures, risk factors, possible triggering factors, managements, and radiological data of seven patients whose basilar artery thrombosis progressed in the hospital after having presented with minor neurological deficits at first. The initial clinical presentations included dysarthria plus hemiparesis in four, vertigo plus ataxia in two, and hypersomnolence without sensorimotor deficits in one. In four patients the neurological progressions were preceded by clinical events that might have caused dehydration. On MR angiography (MRA) performed in five, the basilar artery was barely visible in all. Only one patient was under adequate anticoagulation. Intraarterial thrombolysis was done in two patients with partial improvement in one. In conclusion, poor visualization of the basilar artery on MRA may be a strong indicator of early progression of in situ thrombosis. Since dehydration may play as a trigger, sufficient hydration seems to be the best strategy in addition to adequate anticoagulation when basilar artery thrombosis is suspected clinically and radiologically. Once if clinical progression occurs, Intraarterial thrombolysis may be tried.

A Case of Myoclonus Epilepsy and Ragged-red Fiber Syndrome

Myoclonus epilepsy and ragged-red fiber (MERRF) syndrome is one of the common etiologies of progressive myoclonus epilepsy. The clinical features of MERRF syndrome are myoclonus, seizure, dementia, ataxia, neuropathy, myopathy, deafness, and lipouta. The patients with MERRF syndrome have a point mutation in mitochondrial DNA at 8344 or 8356 nucleotide. We are reporting a patient who developed myoclonus and seizure at the age of eighteen. He later showed cerebellar ataxia, peripheral neuropathy, and cognitive dysfunction. Skeletal muscle biopsy failed to demonstrate ragged-red fibers. He was diagnosed as MERRF syndrome by the mitochondrial DNA analysis. He had 86% mutant mitochondrial genomes (A-)G(8%) mutation) in leukocytes, and his asymptomatic mother had 66%. The absence of ragged-red fibers does not rule out the possibility of MERRF syndrome. Demonstration of mitochondrial DNA mutation is the most convincing method for establishing the diagnosis of MERRF.