John J. Y. Zhang
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Research Interests
John J. Y. Zhang has a total of 137 co-authors. Here are the top co-authors by number of shared publications:
- Keng Siang Lee
Department of Neurosurgery, National Neuroscience Institute, Singapore, Singapore
14 shared publications Keng Siang Lee
Department of Neurological Surgery, University of California, San Francisco, California
7 shared publicationsTseng Tsai Yeo
Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Division of Neurosurgery, Department of Surgery, National University Hospital, National University Health System, Singapore
4 shared publications- Vincent Diong Weng Nga
Division of Neurosurgery, Department of Surgery, National University Hospital, Singapore 119228, Singapore
4 shared publications Kejia Teo
Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Division of Neurosurgery, Department of Surgery, National University Hospital, National University Health System, Singapore
3 shared publicationsSein Lwin
Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Division of Neurosurgery, Department of Surgery, National University Hospital, National University Health System, Singapore
3 shared publications
Latest Publications
- 17 September 2026
- Published by Springer Nature in European Spine Journal
- p. 1-8
Drain versus no drain after intradural spine surgery: a 10-year multicenter study
- 17 September 2026
- Published by Springer Nature in European Spine Journal
- p. 1-8
Drain versus no drain after intradural spine surgery: a 10-year multicenter study
- 1 May 2023
- Published by Journal of Neurosurgery Publishing Group (JNSPG) in Journal of Neurosurgery
- Vol. 138 (5) , 1242-1253
Seizure outcome after resection of insular glioma: a systematic review, meta-analysis, and institutional experience
OBJECTIVE: Gliomas arising from the insular cortex can be epileptogenic, with a significant proportion of patients having medically refractory epilepsy. The impact of surgery on seizure control for such tumors is not well established. In this study, the authors aimed to investigate seizure outcomes after resection of insular gliomas using a meta-analysis and institutional experience. METHODS: Three databases (Ovid MEDLINE, Embase, and Cochrane Central Register of Controlled Trials) were systematically searched for published studies of seizure outcomes after insular glioma resection from database inception to March 27, 2021. In addition, data were retrospectively collected on all adults (age > 17 years) who had undergone insular glioma resection between June 1997 and June 2015 at the authors’ institution. Primary outcome measures were seizure freedom rates at 1 year and the last follow-up. Secondary outcome measures consisted of persistent postoperative neurological deficit beyond 90 days, mortality, and tumor progression or recurrence. RESULTS: Eight studies reporting on 453 patients who had undergone 460 operations were included in the meta-analysis. The pooled mean age of the patients was 42 years. The pooled percentages of patients with extents of resection (EORs) ≥ 90%, 70%–89%, and < 70% were 55%, 33%, and 11%, respectively. The pooled seizure freedom rate at 1 year was 73% for Engel class IA and 78% for Engel class I. The pooled seizure freedom rate at the last follow-up was 60% for Engel class IA and 79% for Engel class I. The pooled percentage of persistent neurological deficit beyond 90 days was 3%. At the authors’ institution, 109 patients had undergone resection of insular glioma. A greater EOR was the only significant independent predictor of seizure freedom after surgery (HR 0.290, p = 0.017). The optimal threshold for seizure freedom corresponded to an EOR of 81%. Patients with an EOR > 81% had a significantly higher seizure freedom rate (OR 2.16, p = 0.048). CONCLUSIONS: Maximal safe resection can be performed with minimal surgical morbidity to achieve favorable seizure freedom rates in both the short and long term. When gross-total resection is not possible, an EOR > 81% confers the greatest sensitivity and specificity for achieving seizure freedom. Systematic review registration no.: CRD42021249404 (https://www.crd.york.ac.uk/prospero/)
- 1 May 2023
- Published by Journal of Neurosurgery Publishing Group (JNSPG) in Journal of Neurosurgery
- Vol. 138 (5) , 1242-1253
Seizure outcome after resection of insular glioma: a systematic review, meta-analysis, and institutional experience
OBJECTIVE: Gliomas arising from the insular cortex can be epileptogenic, with a significant proportion of patients having medically refractory epilepsy. The impact of surgery on seizure control for such tumors is not well established. In this study, the authors aimed to investigate seizure outcomes after resection of insular gliomas using a meta-analysis and institutional experience. METHODS: Three databases (Ovid MEDLINE, Embase, and Cochrane Central Register of Controlled Trials) were systematically searched for published studies of seizure outcomes after insular glioma resection from database inception to March 27, 2021. In addition, data were retrospectively collected on all adults (age > 17 years) who had undergone insular glioma resection between June 1997 and June 2015 at the authors’ institution. Primary outcome measures were seizure freedom rates at 1 year and the last follow-up. Secondary outcome measures consisted of persistent postoperative neurological deficit beyond 90 days, mortality, and tumor progression or recurrence. RESULTS: Eight studies reporting on 453 patients who had undergone 460 operations were included in the meta-analysis. The pooled mean age of the patients was 42 years. The pooled percentages of patients with extents of resection (EORs) ≥ 90%, 70%–89%, and < 70% were 55%, 33%, and 11%, respectively. The pooled seizure freedom rate at 1 year was 73% for Engel class IA and 78% for Engel class I. The pooled seizure freedom rate at the last follow-up was 60% for Engel class IA and 79% for Engel class I. The pooled percentage of persistent neurological deficit beyond 90 days was 3%. At the authors’ institution, 109 patients had undergone resection of insular glioma. A greater EOR was the only significant independent predictor of seizure freedom after surgery (HR 0.290, p = 0.017). The optimal threshold for seizure freedom corresponded to an EOR of 81%. Patients with an EOR > 81% had a significantly higher seizure freedom rate (OR 2.16, p = 0.048). CONCLUSIONS: Maximal safe resection can be performed with minimal surgical morbidity to achieve favorable seizure freedom rates in both the short and long term. When gross-total resection is not possible, an EOR > 81% confers the greatest sensitivity and specificity for achieving seizure freedom. Systematic review registration no.: CRD42021249404 (https://www.crd.york.ac.uk/prospero/)
- Open Access
- 8 February 2023
- Published by Springer Nature in Child's Nervous System
- Vol. 39 (5) , 1225-1243
Surgical revascularizations for pediatric moyamoya: a systematic review, meta-analysis, and meta-regression analysis
Introduction: There is no clear consensus regarding the technique of surgical revascularization for moyamoya disease and syndrome (MMD/MMS) in the pediatric population. Previous meta-analyses have attempted to address this gap in literature but with methodological limitations that affect the reliability of their pooled estimates. This meta-analysis aimed to report an accurate and transparent comparison between studies of indirect (IB), direct (DB), and combined bypasses (CB) in pediatric patients with MMD/MMS.Methods: In accordance with PRISMA guidelines, systematic searches of Medline, Embase, and Cochrane Central were undertaken from database inception to 7 October 2022. Perioperative adverse events were the primary outcome measure. Secondary outcomes were rates of long-term revascularization, stroke recurrence, morbidity, and mortality.Results: Thirty-seven studies reporting 2460 patients and 4432 hemispheres were included in the meta-analysis. The overall pooled mean age was 8.6 years (95% CI: 7.7; 9.5), and 45.0% were male. Pooled proportions of perioperative adverse events were similar between the DB/CB and IB groups except for wound complication which was higher in the former group (RR = 2.54 (95% CI: 1.82; 3.55)). Proportions of post-surgical Matsushima Grade A/B revascularization favored DB/CB over IB (RR = 1.12 (95% CI 1.02; 1.24)). There was no significant difference in stroke recurrence, morbidity, and mortality. After meta-regression analysis, year of publication and age were significant predictors of outcomes.Conclusions: IB, DB/CB are relatively effective and safe revascularization options for pediatric MMD/MMS. Low-quality GRADE evidence suggests that DB/CB was associated with better long-term angiographic revascularization outcomes when compared with IB, although this did not translate to long-term stroke and mortality benefits.
- 8 February 2023
- Published by Springer Nature in Child's Nervous System
- Vol. 39 (5) , 1225-1243
Open AccessSurgical revascularizations for pediatric moyamoya: a systematic review, meta-analysis, and meta-regression analysis
Introduction: There is no clear consensus regarding the technique of surgical revascularization for moyamoya disease and syndrome (MMD/MMS) in the pediatric population. Previous meta-analyses have attempted to address this gap in literature but with methodological limitations that affect the reliability of their pooled estimates. This meta-analysis aimed to report an accurate and transparent comparison between studies of indirect (IB), direct (DB), and combined bypasses (CB) in pediatric patients with MMD/MMS.Methods: In accordance with PRISMA guidelines, systematic searches of Medline, Embase, and Cochrane Central were undertaken from database inception to 7 October 2022. Perioperative adverse events were the primary outcome measure. Secondary outcomes were rates of long-term revascularization, stroke recurrence, morbidity, and mortality.Results: Thirty-seven studies reporting 2460 patients and 4432 hemispheres were included in the meta-analysis. The overall pooled mean age was 8.6 years (95% CI: 7.7; 9.5), and 45.0% were male. Pooled proportions of perioperative adverse events were similar between the DB/CB and IB groups except for wound complication which was higher in the former group (RR = 2.54 (95% CI: 1.82; 3.55)). Proportions of post-surgical Matsushima Grade A/B revascularization favored DB/CB over IB (RR = 1.12 (95% CI 1.02; 1.24)). There was no significant difference in stroke recurrence, morbidity, and mortality. After meta-regression analysis, year of publication and age were significant predictors of outcomes.Conclusions: IB, DB/CB are relatively effective and safe revascularization options for pediatric MMD/MMS. Low-quality GRADE evidence suggests that DB/CB was associated with better long-term angiographic revascularization outcomes when compared with IB, although this did not translate to long-term stroke and mortality benefits.
- 28 November 2022
- Published by Elsevier in World Neurosurgery
- Vol. 170, e777-e783
Clinical Application of a Stereotactic Frame–Specific 3D-Printed Attachment for Deep Brain Stimulation Surgery
- 28 November 2022
- Published by Elsevier in World Neurosurgery
- Vol. 170, e777-e783
Clinical Application of a Stereotactic Frame–Specific 3D-Printed Attachment for Deep Brain Stimulation Surgery
- Open Access
- 26 October 2022
- Published by MDPI AG in Biomedicines
- Vol. 10 (11) , 2702
Clinical Outcomes of 3D-Printed Bioresorbable Scaffolds for Bone Tissue Engineering—A Pilot Study on 126 Patients for Burrhole Covers in Subdural Hematoma
Burrhole craniostomy is commonly performed for subdural hematoma (SDH) evacuation, but residual scalp depressions are often cosmetically suboptimal for patients. OsteoplugTM, a bioresorbable polycaprolactone burrhole cover, was introduced by the National University Hospital, Singapore, in 2006 to cover these defects, allowing osseous integration and vascular ingrowth. However, the cosmetic and safety outcomes of OsteoplugTM-C—the latest (2017) iteration, with a chamfered hole for subdural drains—remain unexplored. Data were collected from a single institution from April 2017 to March 2021. Patient-reported aesthetic outcomes (Aesthetic Numeric Analog (ANA)) and quality of life (EQ-5D-3L including Visual Analog Scale (VAS)) were assessed via telephone interviews. Clinical outcomes included SDH recurrence, postoperative infections, and drain complications. OsteoplugTM-C patients had significantly higher satisfaction and quality of life compared to those without a burrhole cover (ANA: 9 [7, 9] vs. 7 [5, 8], p = 0.019; VAS: 85 [75, 90] vs. 70 [50, 80], p = 0.021), and the absence of a burrhole cover was associated with poorer aesthetic outcomes after multivariable adjustment (adjusted OR: 4.55, 95% CI: 1.09–22.68, p = 0.047). No significant differences in other clinical outcomes were observed between OsteoplugTM-C, OsteoplugTM, or no burrhole cover. Our pilot study supports OsteoplugTM-C and its material polycaprolactone as suitable adjuncts to burrhole craniostomy, improving cosmetic outcomes while achieving comparable safety outcomes.
- 26 October 2022
- Published by MDPI AG in Biomedicines
- Vol. 10 (11) , 2702
Open AccessClinical Outcomes of 3D-Printed Bioresorbable Scaffolds for Bone Tissue Engineering—A Pilot Study on 126 Patients for Burrhole Covers in Subdural Hematoma
Burrhole craniostomy is commonly performed for subdural hematoma (SDH) evacuation, but residual scalp depressions are often cosmetically suboptimal for patients. OsteoplugTM, a bioresorbable polycaprolactone burrhole cover, was introduced by the National University Hospital, Singapore, in 2006 to cover these defects, allowing osseous integration and vascular ingrowth. However, the cosmetic and safety outcomes of OsteoplugTM-C—the latest (2017) iteration, with a chamfered hole for subdural drains—remain unexplored. Data were collected from a single institution from April 2017 to March 2021. Patient-reported aesthetic outcomes (Aesthetic Numeric Analog (ANA)) and quality of life (EQ-5D-3L including Visual Analog Scale (VAS)) were assessed via telephone interviews. Clinical outcomes included SDH recurrence, postoperative infections, and drain complications. OsteoplugTM-C patients had significantly higher satisfaction and quality of life compared to those without a burrhole cover (ANA: 9 [7, 9] vs. 7 [5, 8], p = 0.019; VAS: 85 [75, 90] vs. 70 [50, 80], p = 0.021), and the absence of a burrhole cover was associated with poorer aesthetic outcomes after multivariable adjustment (adjusted OR: 4.55, 95% CI: 1.09–22.68, p = 0.047). No significant differences in other clinical outcomes were observed between OsteoplugTM-C, OsteoplugTM, or no burrhole cover. Our pilot study supports OsteoplugTM-C and its material polycaprolactone as suitable adjuncts to burrhole craniostomy, improving cosmetic outcomes while achieving comparable safety outcomes.
- 14 August 2022
- Published by Elsevier in World Neurosurgery
- Vol. 167, 184-194.e16
Impact of Intraoperative Magnetic Resonance Imaging on Short-Term and Long-Term Outcomes After Transsphenoidal Resection of Pituitary Adenoma: A Systematic Review and Meta-Analysis
- 14 August 2022
- Published by Elsevier in World Neurosurgery
- Vol. 167, 184-194.e16
Impact of Intraoperative Magnetic Resonance Imaging on Short-Term and Long-Term Outcomes After Transsphenoidal Resection of Pituitary Adenoma: A Systematic Review and Meta-Analysis
- Open Access
- 29 April 2022
- Published by Elsevier in World Neurosurgery
- Vol. 161, 291-302.e1
Tenets for the Proper Conduct and Use of Meta-Analyses: A Practical Guide for Neurosurgeons
- 29 April 2022
- Published by Elsevier in World Neurosurgery
- Vol. 161, 291-302.e1
Open AccessTenets for the Proper Conduct and Use of Meta-Analyses: A Practical Guide for Neurosurgeons
- Open Access
- 4 February 2022
- Published by Springer Nature in Scientific Reports
- Vol. 12 (1) , 1-11
A systematic review and meta-analysis of the association between cyproterone acetate and intracranial meningiomas
The influence of exposure to hormonal treatments, particularly cyproterone acetate (CPA), has been posited to contribute to the growth of meningiomas. Given the widespread use of CPA, this systematic review and meta-analysis attempted to assess real-world evidence of the association between CPA and the occurrence of intracranial meningiomas. Systematic searches of Ovid MEDLINE, Embase and Cochrane Controlled Register of Controlled Trials, were performed from database inception to 18th December 2021. Four retrospective observational studies reporting 8,132,348 patients were included in the meta-analysis. There was a total of 165,988 subjects with usage of CPA. The age of patients at meningioma diagnosis was generally above 45 years in all studies. The dosage of CPA taken by the exposed group (n = 165,988) was specified in three of the four included studies. All studies that analyzed high versus low dose CPA found a significant association between high dose CPA usage and increased risk of meningioma. When high and low dose patients were grouped together, there was no statistically significant increase in risk of meningioma associated with use of CPA (RR = 3.78 [95% CI 0.31–46.39], p = 0.190). Usage of CPA is associated with increased risk of meningioma at high doses but not when low doses are also included. Routine screening and meningioma surveillance by brain MRI offered to patients prescribed with CPA is likely a reasonable clinical consideration if given at high doses for long periods of time. Our findings highlight the need for further research on this topic.
- 4 February 2022
- Published by Springer Nature in Scientific Reports
- Vol. 12 (1) , 1-11
Open AccessA systematic review and meta-analysis of the association between cyproterone acetate and intracranial meningiomas
The influence of exposure to hormonal treatments, particularly cyproterone acetate (CPA), has been posited to contribute to the growth of meningiomas. Given the widespread use of CPA, this systematic review and meta-analysis attempted to assess real-world evidence of the association between CPA and the occurrence of intracranial meningiomas. Systematic searches of Ovid MEDLINE, Embase and Cochrane Controlled Register of Controlled Trials, were performed from database inception to 18th December 2021. Four retrospective observational studies reporting 8,132,348 patients were included in the meta-analysis. There was a total of 165,988 subjects with usage of CPA. The age of patients at meningioma diagnosis was generally above 45 years in all studies. The dosage of CPA taken by the exposed group (n = 165,988) was specified in three of the four included studies. All studies that analyzed high versus low dose CPA found a significant association between high dose CPA usage and increased risk of meningioma. When high and low dose patients were grouped together, there was no statistically significant increase in risk of meningioma associated with use of CPA (RR = 3.78 [95% CI 0.31–46.39], p = 0.190). Usage of CPA is associated with increased risk of meningioma at high doses but not when low doses are also included. Routine screening and meningioma surveillance by brain MRI offered to patients prescribed with CPA is likely a reasonable clinical consideration if given at high doses for long periods of time. Our findings highlight the need for further research on this topic.