Publications by authors named "Ady Thien"

8 Publications

  • Page 1 of 1

The National Neuroscience Institute External Ventricular Drain Study: A Pragmatic Multisite Risk-Stratification Pathway to Reduce Ventriculostomy-Related Infection.

World Neurosurg 2020 Mar 19;135:e126-e136. Epub 2019 Nov 19.

Department of Neurosurgery, National Neuroscience Institute, Singapore, Singapore; Duke-NUS Medical School, Singapore, Singapore. Electronic address:

Objective: Ventriculostomy-related infection (VRI) is associated with potential serious morbidity, extended hospitalization duration, increased health care costs, and mortality. We assessed the effectiveness of a pragmatic risk-stratification pathway for external ventricular drain (EVD) management, allowing for surgical decision making, in reducing the rate of VRIs.

Methods: Two studies were performed concurrently. A retrospective audit of EVD infection rates and outcomes in our unit across 3 hospitals was conducted from January to December 2014. The second prospective study compared the same variables during the implementation of the EVD pathway across the 3 sites from January 2015 to December 2016.

Results: The number of patients requiring EVDs increased from 2014 to 2016 (165 vs. 189 vs. 197 patients, respectively), with a significant increase in patients with intraventricular hemorrhage (P = 0.009). Despite increasing risk, overall EVD infections decreased during the implementation period, from 4.8% (8/165) in 2014 to 3.7% in 2015 (7/189) and 2.0% in 2016 (4/197, P = 0.33). In 2 sites (site 1, 2.0% vs. 2.1% vs. 1.9%, and site 2, 4.7% vs. 5.0% vs. 5.3%), transition to the EVD risk-stratification pathway maintained already low infection rates; in site 3, EVD infections decreased from 6.8% (5/73) to 3.9% (4/102) and 0% (0/86, P = 0.06).

Conclusions: The introduction of a pragmatic evidence-based risk-stratification pathway, in which different options for EVD management are incorporated, results in low EVD infection rates across a multisite institutional practice. Our results are comparable to published protocols involving the implementation of standard care bundles and/or antibacterial EVDs alone, in reducing VRIs.
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http://dx.doi.org/10.1016/j.wneu.2019.11.070DOI Listing
March 2020

Investigation of the usefulness of fluorescein sodium fluorescence in stereotactic brain biopsy.

Acta Neurochir (Wien) 2018 02 23;160(2):317-324. Epub 2017 Dec 23.

Department of Neurosurgery, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore.

Background: Intraoperative frozen section assessment, to confirm acquisition of pathological tissues, is used in stereotactic brain biopsy to minimise sampling errors. Limitations include the dependence on dedicated neuro-oncology pathologists and an increase in operative duration. We investigated the use of intraoperative fluorescein sodium, and compared it to frozen section assessment, for confirming pathological tissue samples in the stereotactic biopsy of gadolinium-contrast-enhancing brain lesions.

Methods: This prospective observational study consisted of 18 consecutive patients (12 men; median age, 63 years) who underwent stereotactic biopsy of gadolinium-contrast-enhancing brain lesions with intravenous fluorescein sodium administration. Twenty-three specimens were obtained and examined for the presence of fluorescence using a microscope with fluorescence visualisation capability. Positive and negative predictive values were calculated based on the fluorescence status of the biopsy samples with its corresponding intraoperative frozen section and definitive histopathological diagnosis.

Results: Nineteen specimens (83%) were fluorescent and four (17%) were non-fluorescent. All 19 fluorescent specimens were confirmed to be lesional on intraoperative frozen section assessment and were suitable for histopathological diagnosis. Three of the non-fluorescent specimens were confirmed to be lesional on intraoperative frozen section assessment. One non-fluorescent specimen was non-diagnostic on frozen section and histological assessments. The positive predictive value was 100% and the negative predictive value was 25%.

Conclusions: Fluorescein sodium fluorescence is as accurate as frozen section assessment in confirming sampling of pathological tissue in the stereotactic biopsy of gadolinium-contrast-enhancing brain lesions. Fluorescein sodium fluorescence-guided stereotactic biopsy is a useful addition to the neurosurgical armamentarium.
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http://dx.doi.org/10.1007/s00701-017-3429-0DOI Listing
February 2018

Post-operative diffusion weighted imaging as a predictor of posterior fossa syndrome permanence in paediatric medulloblastoma.

Childs Nerv Syst 2017 Mar 11;33(3):457-465. Epub 2017 Feb 11.

Neurosurgical Service, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore, 229899, Singapore.

Purpose: Posterior fossa syndrome (PFS) is a serious complication faced by neurosurgeons and their patients, especially in paediatric medulloblastoma patients. The uncertain aetiology of PFS, myriad of cited risk factors and therapeutic challenges make this phenomenon an elusive entity. The primary objective of this study was to identify associative factors related to the development of PFS in medulloblastoma patient post-tumour resection.

Methods: This is a retrospective study based at a single institution. Patient data and all related information were collected from the hospital records, in accordance to a list of possible risk factors associated with PFS. These included pre-operative tumour volume, hydrocephalus, age, gender, extent of resection, metastasis, ventriculoperitoneal shunt insertion, post-operative meningitis and radiological changes in MRI. Additional variables included molecular and histological subtypes of each patient's medulloblastoma tumour. Statistical analysis was employed to determine evidence of each variable's significance in PFS permanence.

Results: A total of 19 patients with appropriately complete data was identified. Initial univariate analysis did not show any statistical significance. However, multivariate analysis for MRI-specific changes reported bilateral DWI restricted diffusion changes involving both right and left sides of the surgical cavity was of statistical significance for PFS permanence.

Conclusion: The authors performed a clinical study that evaluated possible risk factors for permanent PFS in paediatric medulloblastoma patients. Analysis of collated results found that post-operative DWI restriction in bilateral regions within the surgical cavity demonstrated statistical significance as a predictor of PFS permanence-a novel finding in the current literature.
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http://dx.doi.org/10.1007/s00381-017-3356-7DOI Listing
March 2017

The Fluoropen: a simple low-cost device to detect intraoperative fluorescein fluorescence in stereotactic needle biopsy of brain tumors.

Acta Neurochir (Wien) 2017 02 10;159(2):371-375. Epub 2016 Dec 10.

Department of Neurosurgery, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore.

Background: The use of fluorescein fluorescence-guided stereotactic needle biopsy has been shown to improve diagnostic accuracy and to expedite operative procedure in the stereotactic needle biopsy of high-grade gliomas. We developed a device (Fluoropen) for detecting fluorescence in brain tumor tissues obtained by fluorescein fluorescence-guided stereotactic needle biopsy.

Methods: The Fluoropen is a device consisting of a light source fitted with color filters to create the required emission and visualization wavelengths. The proof-of-concept study consisted of four consecutive patients who underwent fluorescein fluorescence-guided frameless stereotactic biopsy of brain tumor. Each sample was examined for the presence of fluorescence using the Fluoropen and compared with a microscope with fluorescence visualization capability.

Results: A total of six samples were obtained from four stereotactic needle biopsy procedures. Four out of five samples (80%) taken from the contrast-enhancing part of the tumors were shown to be fluorescent under the microscope fitted with fluorescence module and the Fluoropen. One non-contrast enhancing lesion was non-fluorescent using both the microscope fitted with fluorescence module and the Fluoropen. The Fluoropen was shown to have 100% concordance with the microscope fitted with fluorescence module.

Conclusions: The Fluoropen is a low-cost and simple standalone device for the detection of fluorescein fluorescence that can expedite stereotactic needle biopsy by providing instant confirmation of the diagnostic sample and therefore avoid the need for an intraoperative frozen section. In patients with non-contrast enhancing tumors and those who were pre-treated with dexamethasone prior to surgery, fluorescein fluorescence-guided stereotactic needle biopsy will need to be used with caution.
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http://dx.doi.org/10.1007/s00701-016-3041-8DOI Listing
February 2017

Prevalence of Asymptomatic Unruptured Intracranial Aneurysms in a Southeast Asian Population.

World Neurosurg 2017 Jan 12;97:326-332. Epub 2016 Oct 12.

Department of Neurosurgery, National Neuroscience Institute, Singapore.

Background: The prevalence of asymptomatic unruptured intracranial aneurysms (AUIA) in a Southeast Asian population has not been previously studied. Knowing the disease burden and population at risk can assist us in making informed decisions when managing AUIAs. We aimed to determine if the local prevalence of AUIAs differed from other populations in the published literature.

Methods: Magnetic resonance angiography radiology reports and images for 4572 patients between January 2013 and January 2014 were reviewed for AUIAs.

Results: The overall prevalence of AUIAs was 3.5% (160/4572). It was significantly higher in women (4.5%) compared with men (2.6%) (P < 0.001). The mean aneurysm size was 3.2 ± 1.7 mm. Of the aneurysms, 88.5% (146/165) measured less than 5 mm, 9.7% (16/165) measured 5-9 mm, and 1.8% (3/165) measured more than 9 mm. Most of the aneurysms were located in the cavernous segment (72/165, 43.6%) and ophthalmic segment (34/165, 20.6%) of the internal carotid artery, followed by the middle cerebral artery (16/165, 9.7%). The posterior circulation contributed 9.1% (15/165) of the AUIAs. During the study period, 1 aneurysm ruptured and the rest of the aneurysms did not show any growth.

Conclusions: In this large cohort of a Southeast Asian population, the prevalence of AUIA was 3.5%. Most of the AUIAs were less than 5 mm and did not require intervention at time of discovery and did not progress within the year of follow-up.
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http://dx.doi.org/10.1016/j.wneu.2016.09.118DOI Listing
January 2017

Computed tomographic morphometric analysis of cervical pedicles in a multi-ethnic Asian population and relevance to subaxial cervical pedicle screw fixation.

Eur Spine J 2015 Jan 26;24(1):120-6. Epub 2014 Aug 26.

Department of Neurosurgery, National Neuroscience Institute, 11, Jalan Tan Tock Seng, Singapore, 308433, Singapore,

Purpose: Pedicle screw instrumentation provides optimal stabilization of the cervical spine complex, but is associated with risk of neurovascular injury. Sex and ethnic disparities may compromise safe and accurate screw placement. Therefore, a comprehensive analysis of pedicle dimensions derived from computed tomography scans is pertinent for our multi-ethnic population.

Methods: Cervical spine CT of 50 patients without significant cervical spine pathology was selected. Pedicle width (PW), pedicle height (PH) and pedicle transverse angle (PTA) from C3 to C7 were measured and subsequently analyzed for sex and ethnic differences.

Results: The smallest mean PW was at C4 in males and C3 in females. Mean PW for males was significantly greater than females at all levels (P < 0.05). 8 % of our population had at least one PW < 4.00 mm. At C5, C6 and C7 there is zero percent incidence of PW < 4.00 mm. The mean PH in males was significantly greater than females at all levels (P < 0.05), but no statistically significant sex differences in mean PTA values were found. There were significant ethnic differences in mean PW of males at C4, C5 and C7 (P < 0.05) and mean PH of females at C3, C4 and C7 (P < 0.05).

Conclusions: Transpedicular screw fixation is generally feasible in our population except for 8 % with at least one PW < 4.00 mm. However, in view of significant sex and ethnic morphometric variability, pre-operative CT evaluation together with image-guided screw placement is highly advised to ensure safety and accuracy.
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http://dx.doi.org/10.1007/s00586-014-3526-1DOI Listing
January 2015

Comparison of polyetheretherketone and titanium cranioplasty after decompressive craniectomy.

World Neurosurg 2015 Feb 5;83(2):176-80. Epub 2014 Jun 5.

Department of Neurosurgery, National Neuroscience Institute, Singapore.

Objective: To characterize complication and failure rates and outcomes of patients who underwent cranioplasty with polyetheretherketone (PEEK) and titanium implants and to compare complication and failure rates between the 2 implants.

Methods: A retrospective cohort study of patients who underwent cranioplasty with PEEK patient-specific implant (PEEK Optima-LT) and preformed titanium mesh at the National Neuroscience Institute, Singapore, between January 2001 and February 2012 was performed. Data related to initial decompressive craniectomy and cranioplasty, associated complications after cranioplasty, and indication for revision or removal of implants were collected. Cranioplasty failure was defined as revision or removal of a patient's implant.

Results: Overall complication rates for PEEK and titanium cranioplasty were 25.0% and 27.8%, respectively. The combined complication rate was 27.3%. A trend toward increase in exposed implant in titanium cranioplasty compared with PEEK cranioplasty was observed (P = 0.074). There were 3 of 24 (12.5%) cranioplasty failures with PEEK, and 27 of 108 (25%) cranioplasty failures with titanium (P = 0.129). Previous deep infection in patients after decompressive craniectomy was associated with cranioplasty complications (odds ratio, 23.3; confidence interval, 3.00-180.5; P = 0.003) and failure (odds ratio, 22.5; confidence interval, 2.82-179.0; P = 0.003).

Conclusions: The findings from this study highlight that cranioplasty is associated with significant complications, including the necessity for reoperation. It is hoped that the information in this study will provide better understanding of the risks associated with PEEK and titanium cranioplasty and contribute to decision making by the clinician and patient.
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http://dx.doi.org/10.1016/j.wneu.2014.06.003DOI Listing
February 2015

Soft tissue chondroma mimicking "dumbbell" neurogenic tumour: a rare cause of lumbar radiculopathy.

J Clin Neurosci 2014 Jun 13;21(6):1073-4. Epub 2013 Nov 13.

Department of Neurosurgery, National Neuroscience Institute, Singapore.

Soft tissue chondromas are rare, benign extra-skeletal tumours of cartilaginous origin, which may rarely occur within the spinal canal. We report a patient who presented with left lumbar radiculopathy, and a peripherally-enhancing dumbbell shaped soft tissue mass involving both the intraspinal and extraspinal compartments on MRI. This was misdiagnosed as a neurogenic tumour and the patient underwent surgical removal. Histological examination revealed cartilaginous tissue. Although rare, soft tissue chondromas should be considered in the differential diagnosis of spinal dumbbell shaped tumours, especially if MRI shows peripheral contrast enhancement.
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http://dx.doi.org/10.1016/j.jocn.2013.09.011DOI Listing
June 2014