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Extra-Axial and Clear Cell Type Ependymoma, Mimicking a Convexity Meningioma
( Stephen Ahn ),( Young Joo Kim ),( Youn Soo Lee ),( Sin-soo Jeun ) 대한뇌종양학회·대한신경종양학회·대한소아뇌종양학회 2017 Brain Tumor Research and Treatment Vol.5 No.2
A 33-year-old woman presented with tingling and paresthesia on left extremity for 2 months. Magnetic resonance imaging revealed that the tumor was iso- and hypo-intensity on T1-weighted image, mixed iso- and high-signal intensity on T2-weighted images and heterogeneously enhanced with rim en-hancement. Neither arachnoid cleft nor dural tail was certain but mass was located extra-axially so meningioma was suspected. During operation, tumor wasn’t attached to dura at all but arachnoid at-tachment was seen. Pathologically, clear cell type ependymoma was confirmed. Details of diagnosis and treatment of this tumor is described.
HLA and Disease Associations in Koreans
Ahn, Stephen,Choi, Hee-Back,Kim, Tai-Gyu The Korean Association of Immunobiologists 2011 Immune Network Vol.11 No.6
The human leukocyte antigen (HLA), the major histocompatibility complex (MHC) in humans has been known to reside on chromosome 6 and encodes cell-surface antigen-presenting proteins and many other proteins related to immune system function. The HLA is highly polymorphic and the most genetically variable coding loci in humans. In addition to a critical role in transplantation medicine, HLA and disease associations have been widely studied across the populations worldwide and are found to be important in prediction of disease susceptibility, resistance and of evolutionary maintenance of genetic diversity. Because recently developed molecular based HLA typing has several advantages like improved specimen stability and increased resolution of HLA types, the association between HLA alleles and a given disease could be more accurately quantified. Here, in this review, we have collected HLA association data on some autoimmune diseases, infectious diseases, cancers, drug responsiveness and other diseases with unknown etiology in Koreans and attempt to summarize some remarkable HLA alleles related with specific diseases.
Stephen Ahn,Seung Ho Yang,Jae Hoon Sung,Sang Won Lee 대한두개저학회 2016 대한두개저학회지 Vol.11 No.2
The middle fossa approach has undergone several modifications to expand its exposure along the cerebellopontine angle, petrous apex, tentorium and clivus. The middle fossa anterior transpetrosal approach, so called Kawase’s approach, is designed for the anterior cerebellopontine angle, the ventral surface of pons, and the upper clivus. The purpose of the study is to summarize the surgical experiences of anterior petrosal approach for the treatment of skull base tumor performed by a neurosurgeon. Eight patients (6 women and 2 men) underwent frontotemporal craniotomy and anterior petrosal approach for skull base tumor resection. They included 3 trigeminal schwannomas, 3 meningiomas, 1 chondroma, and 1 metastasis. The median age was 57.5 years (range, 43-72). Three patients with trigeminal schwannomas and 1 patient with chondroma achieved total resection using the classic anterior petrosectomy without dura opening. For petroclival meningioma, opening of posterior fossa dura and coagulation of petrosal sinus was additionally performed. However, surgical corridor was limited anteriorly by mandibular nerve, laterally by internal auditory canal, and posteriorly by tentorium. Neurological deterioration developed postoperatively in 2 patients with petroclival meningioma. It is suggested that anterior petrosal approach is suited for accessing middle fossa lesions with smaller petroclival components.
Molecular and clinical characteristics of hepatitis B virus in Korea
Ahn, Sang Hoon,Yuen, Lilly,Han, Kwang-Hyub,Littlejohn, Margaret,Chang, Hye Young,Damerow, Hans,Ayres, Anna,Heo, Jeong,Locarnini, Stephen,Revill, Peter A. Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of Medical Virology Vol.82 No.7
<P>Korea is an endemic area of hepatitis B virus (HBV) infection but very little is known about the molecular characteristics of HBV isolates from Korean patients or the association with disease progression. The complete HBV genome sequences from 53 Korean patients with chronic hepatitis B, advanced cirrhosis, or hepatocellular carcinoma (HCC) were analyzed to identify (i) subgenotype distribution and genetic diversity and (ii) signature mutations associated with liver disease progression. With the exception of 1 patient infected with HBV/B, all 52 patients (98.1%) were infected with HBV/C, subgenotype C2. These strains were 98.4% identical and the frequency of amino acid substitutions occurring within key immunological epitopes increased with disease severity. A number of amino acid/nucleotide substitutions were associated with HCC, namely sR24K (HBsAg), SI126T (HBsAg), and pcA1846T (precore gene) mutations (P = 0.029, 0.001, and 0.008, respectively). HBV harboring deletions in the pre-S region were also associated with increased liver disease severity (chronic hepatitis B vs. cirrhosis, P = 0.040; chronic hepatitis B vs. HCC, P = 0.040). Despite the high degree of sequence conservation, several key HBV mutations were associated with disease progression. Prospective studies with larger cohorts of patients are required to evaluate further the clinical manifestation of HBV/C2 in Korea. J. Med. Virol. 82: 1126–1134, 2010. © 2010 Wiley-Liss, Inc.</P>
( Changik Lee ),( Stephen Ahn ),( Jae-sung Park ),( Jin Ho Song ),( Yong-kil Hong ),( Sin-soo Jeun ) 대한뇌종양학회 대한신경종양학회 2020 Brain Tumor Research and Treatment Vol.8 No.2
Background Lymphopenia frequently occurs after concomitant chemoradiation (CCRT) in patients with glioblastoma (GBM) and is associated with worse overall survival (OS). A few studies have tried to identify risk factors for lymphopenia; however, the results were not clear. We aimed to identify potential risk factors for lymphopenia, focusing on the use of dexamethasone to control cerebral edema in patients with GBM. Methods The electronic medical records of 186 patients with newly diagnosed GBM treated at our institution between 2009 and 2017 were retrospectively examined. Acute lymphopenia was defined as total lymphocyte count less than 1,000 cells/μL at 4 weeks after completion of CCRT. Multivariate logistic regression analysis was used to identify independent risk factors for lymphopenia, and Cox regression analysis was used to identify independent risk factors for OS. Results Of the 125 eligible patients, 40 patients (32.0%) developed acute lymphopenia. Female sex and median daily dexamethasone dose ≥2 mg after initiation of CCRT were independent risk factors for acute lymphopenia on multivariate analysis. Acute lymphopenia, extent of surgical resection, and performance status were associated with OS; however, dexamethasone use itself was not an independent risk factor for poor OS. Conclusion Female sex, median daily dexamethasone dose ≥2 mg after initiation of CCRT until 4 weeks after completion of CCRT may be associated with acute lymphopenia. However, dexamethasone use itself did not affect OS in patients newly diagnosed with GBM. These results should be validated by further prospective studies controlling for other confounding factors.
Rare Intramedullary Myeloid Sarcoma Mistaken as Acute Transverse Myelitis
이민기,허정우,Ahn Stephen 대한말초신경학회 2018 The Nerve Vol.4 No.2
Myeloid sarcoma is a rare extramedullary tumor of immature myeloid cells. It more often develops with the underlying acute myeloid leukemia, but it can also occur with chronic myeloid leukemia (CML), myelodysplastic syndrome and rarely even with the absence of marrow involvement. Spinal epidural myeloid sarcoma is uncommon, and intramedullary presentation is exceptionally rare. In this report the authors report an unusual case of spinal intramedullary myeloid sarcoma after completer remission from CML several years ago. He was mistakenly diagnosed as acute transverse myelitis and treated with high-dose steroid and plasmaparesis without improvement. Magnetic resonance imaging revealed intramedullary mass-like lesion with hyper-intensity in T2-weighted image and mild homogeneous enhancement. Myeloid sarcoma should be considered as a possible differential diagnosis when patient with history of myeloid leukemia present intramedullary tumor and pathologic confirmation with open biopsy is mandatory for the exact diagnosis.
Jin Eun,Stephen Ahn,Min Ho Lee,Jin-Gyu Choi,Jae-Sung Park,Chul Bum Cho,김영일 대한신경외과학회 2023 Journal of Korean neurosurgical society Vol.66 No.6
Objective : Chronic subdural hematoma (CSDH) patients using antithrombotic agents (AT) at high risk for cardiovascular disease are increasing. The authors aimed to analyze the factors influencing outcome by targeting patients using AT and to establish a desirable treatment strategy. Methods : A retrospective analysis was performed on data from 462 patients who underwent burr hole trephination (BHT) surgery for CSDH at five hospitals from March 2010 to June 2021. Outcomes included incidence of postoperative acute bleeding, recurrence rate, and morbidity or mortality rate. Patients were divided into the following four groups based on their history of AT use : no AT. Only antiplatelet agents (AP), only anticoagulants (AC), both of AP and AC. In addition, a concurrent literature review was conducted alongside our cohort study. Results : Of 462 patients, 119 (119/462, 25.76%) were using AT. AP prescription did not significantly delay surgery (p=0.318), but AC prescription led to a significant increase in the time interval from admission to operation (p=0.048). After BHT, AP or AC intake significantly increased the period required for an in-dwelling drain (p=0.026 and p=0.037). The use of AC was significantly related to acute bleeding (p=0.044), while the use of AP was not (p=0.808). Use of AP or AC had no significant effect on CSDH recurrence (p=0.517 and p=1.000) or reoperation (p=0.924 and p=1.000). Morbidity was not statistically correlated with use of either AP or AC (p=0.795 and p=0.557, respectively), and there was no significant correlation with mortality for use of these medications (p=0.470 and p=1.000). Conclusion : Elderly CSDH patients may benefit from maintenance of AT therapy during BHT due to reduced thromboembolic risk. However, the use of AC necessitates individualized due to potential postoperative bleeding. Careful post-operative monitoring could mitigate prognosis and recurrence impacts.