Cheemun Lum

University of Ottawa, Ottawa, Ontario, Canada

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Publications (83)311.96 Total impact

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    ABSTRACT: Background Hematoma expansion is a major predictor of morbidity and mortality after intracerebral hemorrhage (ICH). Both baseline hematoma volume and the CT-angiogram (CTA) spot sign predict hematoma expansion. Because the CTA spot sign may represent foci of active hemorrhage, we hypothesized that patients with smaller baseline hematoma volumes are less likely to be spot sign positive, and therefore less likely to expand.
    Full-text · Article · Feb 2016 · International Journal of Stroke
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    ABSTRACT: Purpose: Computed tomography perfusion (CTP) has been performed to predict which patients with aneurysmal subarachnoid hemorrhage are at risk of developing delayed cerebral ischemia (DCI). Patients with severe arterial narrowing may have significant reduction in perfusion. However, many patients have less severe arterial narrowing. There is a paucity of literature evaluating perfusion changes which occur with mild to moderate narrowing. The purpose of our study was to investigate serial whole-brain CTP/computed tomography angiography in aneurysm-related subarachnoid hemorrhage (aSAH) patients with mild to moderate angiographic narrowing. Methods: We retrospectively studied 18 aSAH patients who had baseline and follow-up whole-brain CTP/computed tomography angiography. Thirty-one regions of interest/hemisphere at six levels were grouped by vascular territory. Arterial diameters were measured at the circle of Willis. The correlation between arterial diameter and change in CTP values, change in CTP in with and without DCI, and response to intra-arterial vasodilator therapy in DCI patients was evaluated. Results: There was correlation among the overall average cerebral blood flow (CBF; R=0.49, p<0.04), mean transit time (R=-0.48, p=0.04), and angiographic narrowing. In individual arterial territories, there was correlation between changes in CBF and arterial diameter in the middle cerebral artery (R=0.53, p=0.03), posterior cerebral artery (R=0.5, p=0.03), and anterior cerebral artery (R=0.54, p=0.02) territories. Prolonged mean transit time was correlated with arterial diameter narrowing in the middle cerebral artery territory (R=0.52, p=0.03). Patients with DCI tended to have serial worsening of CBF compared with those without DCI (p=0.055). Conclusions: Our preliminary study demonstrates there is a correlation between mild to moderate angiographic narrowing and serial changes in perfusion in patients with aSAH. Patients developing DCI tended to have progressively worsening CBF compared with those not developing DCI.
    No preview · Article · Jan 2016 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
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    ABSTRACT: Background and purpose: Perihematomal edema volume may be related to intracerebral hemorrhage (ICH) volume at baseline and, consequently, with hematoma expansion. However, the relationship between perihematomal edema and hematoma expansion has not been well established. We aimed to investigate the relationship among baseline perihematomal edema, the computed tomographic angiography spot sign, hematoma expansion, and clinical outcome in patients with acute ICH. Methods: Predicting Hematoma Growth and Outcome in Intracerebral Hemorrhage Using Contrast Bolus CT (PREDICT) was a prospective observational cohort study of ICH patients presenting within 6 hours from onset. Patients underwent computed tomography and computed tomographic angiography scans at baseline and 24-hour computed tomography scan. A post hoc analysis of absolute perihematomal edema and relative perihematomal edema (absolute perihematomal edema divided by ICH) volumes was performed on baseline computed tomography scans (n=353). Primary outcome was significant hematoma expansion (>6 mL or >33%). Secondary outcomes were early neurological deterioration, 90-day mortality, and poor outcome. Results: Absolute perihematomal edema volume was higher in spot sign patients (24.5 [11.5-41.8] versus 12.6 [6.9-22] mL; P<0.001), but it was strongly correlated with ICH volume (ρ=0.905; P<0.001). Patients who experienced significant hematoma expansion had higher absolute perihematomal edema volume (18.4 [10-34.6] versus 11.8 [6.5-22] mL; P<0.001) but similar relative perihematomal edema volume (1.09 [0.89-1.37] versus 1.12 [0.88-1.54]; P=0.400). Absolute perihematomal edema volume and poorer outcomes were higher by tertiles of ICH volume, and perihematomal edema volume did not independently predict significant hematoma expansion. Conclusions: Perihematomal edema volume is greater at baseline in the presence of a spot sign. However, it is strongly correlated with ICH volume and does not independently predict hematoma expansion.
    No preview · Article · Dec 2015 · Stroke

  • No preview · Article · Nov 2015 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
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    ABSTRACT: Background and purpose: Nine- and 24-point prediction scores have recently been published to predict hematoma expansion (HE) in acute intracerebral hemorrhage. We sought to validate these scores and perform an independent analysis of HE predictors. Methods: We retrospectively studied 301 primary or anticoagulation-associated intracerebral hemorrhage patients presenting <6 hours post ictus prospectively enrolled in the Predicting Hematoma Growth and Outcome in Intracerebral Hemorrhage Using Contrast Bolus Computed Tomography (PREDICT) study. Patients underwent baseline computed tomography angiography and 24-hour noncontrast computed tomography follow-up for HE analysis. Discrimination and calibration of the 9- and 24-point scores was assessed. Independent predictors of HE were identified using multivariable regression and incorporated into the PREDICT A/B scores, which were then compared with existing scores. Results: The 9- and 24-point HE scores demonstrated acceptable discrimination for HE>6 mL or 33% and >6 mL, respectively (area under the curve of 0.706 and 0.755, respectively). The 24-point score demonstrated appropriate calibration in the PREDICT cohort (χ(2) statistic, 11.5; P=0.175), whereas the 9-point score demonstrated poor calibration (χ(2) statistic, 34.3; P<0.001). Independent HE predictors included spot sign number, time from onset, warfarin use or international normalized ratio >1.5, Glasgow Coma Scale, and National Institutes of Health Stroke Scale and were included in PREDICT A/B scores. PREDICT A showed improved discrimination compared with both existing scores, whereas performance of PREDICT B varied by definition of expansion. Conclusion: The 9- and 24-point expansion scores demonstrate acceptable discrimination in an independent multicenter cohort; however, calibration was suboptimal for the 9-point score. The PREDICT A score showed improved discrimination for HE prediction but requires independent validation.
    No preview · Article · Oct 2015 · Stroke
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    ABSTRACT: Background and Purpose-Hematoma expansion in intracerebral hemorrhage is associated with higher morbidity and mortality. The computed tomography (CT) angiographic spot sign is highly predictive of expansion, but other morphological features of intracerebral hemorrhage such as fluid levels, density heterogeneity, and margin irregularity may also predict expansion, particularly in centres where CT angiography is not readily available. Methods-Baseline noncontrast CT scans from patients enrolled in the Predicting Hematoma Growth and Outcome in Intracerebral Hemorrhage Using Contrast Bolus CT (PREDICT) study were assessed for the presence of fluid levels and degree of density heterogeneity and margin irregularity using previously validated scales. Presence and grade of these metrics were correlated with the presence of hematoma expansion as defined by the PREDICT study on 24-hour follow-up scan. Results-Three hundred eleven patients were included in the analysis. The presence of fluid levels and increasing heterogeneity and irregularity were associated with 24-hour hematoma expansion (P=0.021, 0.003 and 0.049, respectively) as well as increases in absolute hematoma size. Fluid levels had the highest positive predictive value (50%; 28%-71%), whereas margin irregularity had the highest negative predictive value (78%; 71%-85). Noncontrast metrics had comparable predictive values as spot sign for expansion when controlled for vitamin K, antiplatelet use, and baseline National Institutes of Health Stroke Scale, although in a combined area under the receiver-operating characteristic curve model, spot sign remained the most predictive. Conclusions-Fluid levels, density heterogeneity, and margin irregularity on noncontrast CT are associated with hematoma expansion at 24 hours. These markers may assist in prediction of outcomes in scenarios where CT angiography is not readily available and may be of future help in refining the predictive value of the CT angiography spot sign.
    No preview · Article · Oct 2015 · Stroke

  • No preview · Article · Oct 2015 · The Canadian journal of cardiology
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    ABSTRACT: Objective: We derived and validated a method to screen all hospital admissions for 1° subarachnoid hemorrhage by retrospectively implementing recognized diagnostic criteria. Study design and setting: A screen for 1° subarachnoid hemorrhage was developed using two previously created registries. Screen-positive cases underwent diagnosis confirmation with primary record review. A review of all patient hospital encounters with the diagnostic code for 1° subarachnoid hemorrhage and cross-referencing with an existing subarachnoid hemorrhage registry was undertaken to identify missed cases. Results: Three sub-screens were combined to form the 1° subarachnoid hemorrhage screen (sensitivity: 98.4% [95% CI: 91.7-99.7%], specificity: 93.4% [95% CI: 90.4-95.4%], n=455 patients in validation sample). From 1699 screen-positive admissions between 1 July 2002 and 30 June 2011, we identified 831 true cases of subarachnoid hemorrhage of which 632 patients had 1° subarachnoid hemorrhage from ruptured aneurysm/AVM (sensitivity: 96.5% [95% CI: 94.8%-97.8%]; specificity: 40.3% [95% CI: 38.1%-42.6%]). A review of all encounters with a diagnostic code for 1° subarachnoid hemorrhage yielded an additional 22 true cases. Conclusion: When positive, our 1° subarachnoid hemorrhage screen significantly increases the probability of this diagnosis in a particular hospitalization. The addition of patient hospitalizations encoded with the diagnostic code for 1° subarachnoid hemorrhage improved sensitivity. Together, these methods represent the best way to retrospectively identify all cases of 1° subarachnoid hemorrhage within an extensive sampling frame.
    No preview · Article · Sep 2015 · Journal of clinical epidemiology
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    ABSTRACT: There is a paucity of literature on early discharge after elective aneurysm treatment. We hypothesize that patient discharge on the next day is not associated with an increase in post-discharge adverse events. We retrospectively reviewed elective coiling procedures between 2009 and 2013. The primary outcome measure was 30-day adverse events (emergency department visits, readmission or prolonged admission >30 days, and death). We evaluated the association between early and standard discharge for the primary outcome using the Fisher exact test. We also assessed the association of the primary outcome with other patient and technical variables as well as findings on pre-discharge diffusion weighted imaging. We included 97 patients. Median length of hospital stay (LOS) was 2.52 days, and in 26 patients (26.8%) LOS was <2 days. There was no significant difference in post-discharge adverse outcome rates between early and standard discharge groups (19.2% vs 18.3%; p=1.000). The primary outcome was significantly associated with the use of flow diverters (p=0.0287) and change in modified Rankin Scale category at discharge (p=0.0329). No significant association was noted between the outcome and the other variables including the presence of diffusion restriction pre-discharge (p>0.05). Patient discharge the next day after elective intracranial aneurysm coiling is not associated with an increase in 30-day adverse outcomes. A prospective study investigating early discharge in elective treatment is warranted. OHSN-REB #20130786-01H. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    No preview · Article · Sep 2015 · Journal of Neurointerventional Surgery

  • No preview · Article · Sep 2015 · International Journal of Stroke
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    Full-text · Dataset · Jul 2015
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    ABSTRACT: The purpose of this article is to prospectively test the hypothesis that time-resolved CT angiography (TRCTA) on a Toshiba 320-slice CT scanner enables the same characterization of cerebral vascular malformation (CVM) including arteriovenous malformation (AVM), dural arteriovenous fistula (DAVF), pial arteriovenous fistula (PAVF) and developmental venous anomaly (DVA) compared to digital subtraction angiography (DSA). Eighteen (eight males, 10 females) consecutive patients (11 AVM, four DAVF, one PAVF, and two DVA) underwent 19 TRCTA (Aquillion one, Toshiba) for suspected CVM diagnosed on routine CT or MRI. One patient with a dural AVF underwent TRCTA and DSA twice before and after treatment. Of the 18 patients, 13 were followed with DSA (Artis, Siemens) within two months of TRCTA. Twenty-three sequential volume acquisitions of the whole head were acquired after injection of 50 ml contrast at the rate of 4 ml/sec. Two patients with DVA did not undergo DSA. Two TRCTA were not assessed because of technical problems.TRCTAs were independently reviewed by two neuroradiologists and DSA by two other neuroradiologists and graded according to the Spetzler-Martin classification, Borden classification, overall diagnostic quality, and level of confidence. Weighted kappa coefficients (k) were calculated to compare reader's assessment of DSA vs TRCTA. There was excellent (k = 0.83 and 1) to good (k = 0.56, 0.61, 0.65 and 0.67) agreement between the different possible pairs of neuroradiologists for the assessment of vascular malformations. TRCTA may be a sufficient noninvasive substitute for conventional DSA in certain clinical situations. © The Author(s) 2015.
    Full-text · Article · Jun 2015
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    ABSTRACT: Despite the increasing use of stent-assisted coiling (SAC), data on its long-term clinical and angiographic results are limited. The objective of this article is to assess the long-term clinical and angiographic outcomes in SAC in our single-center practice. We conducted a retrospective analysis of intracranial aneurysms treated with detachable coils during the period 2003-2012. Patients were divided into SAC and non-SAC groups and were analyzed for aneurysm occlusion, major recurrence and clinical outcome. Logistic regression analyses identified factors associated with clinical/angiographic outcomes (p value <0.05 was statistically significant). A total of 516 procedures met inclusion criteria: Sixty-three (12.2%) patients underwent SAC, of whom 56 (89%) had an elective procedure whereas 286 (63.1%) aneurysms from the non-SAC group were ruptured. In the unruptured subcohort, baseline class I was achieved in 24 (38%, p = 0.91), and predischarge modified Rankin scale score (mRS) 0-2 was obtained in 96.4% of cases in the SAC group versus 90.4% in the non-stent group. The major recurrence was 9.5% versus 11.3% in the SAC and non-SAC group, respectively (p = 0.003). At last clinical assessment, 98.2% of the patients from the unruptured SAC group had mRS 0-2 (mean follow-up, 58 months) versus 93.6% (mean follow-up, 56 months) in the unruptured non-SAC group (p = 0.64). Periprocedural vasospasm was associated with long-term poor outcome in the unruptured SAC subcohort (p = 0.0008). SAC and non-SCA techniques show comparable safety and clinical outcome. The SAC technique significantly decreases retreatment rates. Periprocedural vasospasm resulting from vessel manipulation is associated with poor outcome in SAC of unruptured aneurysms. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
    Full-text · Article · May 2015 · Interventional Neuroradiology
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    ABSTRACT: Whole-slide scanning of tissue sections spatially informed by imaging studies offers the opportunity to reconstruct specimens for co-registration to 3D imaging data. Digital image analysis algorithms can be designed to analyze and reconstruct such specimens via electronic “pipelines”. Methods: A goal of the Canadian Atherosclerosis Imaging Network (CAIN) is to improve the assessment of carotid atheromatous disease through studies that inform clinical imaging with gold-standard data (plaque pathology). To achieve this, sectioned atheromas are manually annotated and analyzed by electronic algorithm for pathological features of interest. Resulting images are then reassembled in 3D for registration to ultrasound, CT, PET-CT and MRI studies. Results: Carotid endarterectomy specimens were sub-serially sectioned, stained, digitized and annotated manually and by electronic algorithms. Resulting 2D images were successfully rendered, reassembled and analyzed in 3D using ex-vivo micro-CT as a spatial reference. Furthermore, histology quantification using colour deconvolution was found to be preferred over hue-saturation-intensity methods 94.7-100% of the time in a blinded multiple rater study. Conclusion: Automated “pipelines” greatly facilitate 3D reconstruction in comparison to traditional slice-by-slice methods. Transformations spatially guided by pre-existing imaging data is not only faster, but has superior objectivity and fidelity. With embedded annotations, 3D pathology maps become a rich, micron-level, permanent digital pathological database for correlative studies.
    No preview · Article · May 2015 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
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    ABSTRACT: It has been hypothesized that [18F]-sodium fluoride (NaF) uptake imaged with positron emission tomography (PET) binds to hydroxyapatite molecules expressed in regions with active calcification. Therefore, we aimed to validate NaF as a marker of hydroxyapatite expression in high-risk carotid plaque. Methods: Eleven patients (69 ± 5 years, 3 female) scheduled for carotid endarterectomy were prospectively recruited for NaF PET/CT. One patient received a second contralateral endarterectomy; two patients were excluded (intolerance to contrast media and PET/CT misalignment). The bifurcation of the common carotid was used as the reference point; NaF uptake (tissue to blood ratio - TBR) was measured at every PET slice extending 2 cm above and below the bifurcation. Excised plaque was immunostained with Goldner’s Trichrome and whole-slide digitized images were used to quantify hydroxyapatite expression. Pathology was co-registered with PET. Results: NaF uptake was related to the extent of hydroxyapatite expression (r=0.45, p<0.001). Upon classifying bilateral plaque for symptomatology, symptomatic plaque was associated with cerebrovascular events (3.75±1.1 TBR, n=9) and had greater NaF uptake than clinically silent asymptomatic plaque (2.79±0.6 TBR, n=11) (p=0.04). Conclusion: NaF uptake is related to hydroxyapatite expression and is increased in plaque associated with cerebrovascular events. NaF may serve as a novel biomarker of active calcification and plaque vulnerability.
    Full-text · Article · May 2015 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
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    ABSTRACT: ESCAPE is a prospective, multicenter, randomized clinical trial that will enroll subjects with the following main inclusion criteria: less than 12 h from symptom onset, age > 18, baseline NIHSS >5, ASPECTS score of >5 and CTA evidence of carotid T/L or M1 segment MCA occlusion, and at least moderate collaterals by CTA. The trial will determine if endovascular treatment will result in higher rates of favorable outcome compared with standard medical therapy alone. Patient populations that are eligible include those receiving IV tPA, tPA ineligible and unwitnessed onset or wake up strokes with 12 h of last seen normal. The primary end-point, based on intention-to-treat criteria is the distribution of modified Rankin Scale scores at 90 days assessed using a proportional odds model. The projected maximum sample size is 500 subjects. Randomization is stratified under a minimization process using age, gender, baseline NIHSS, baseline ASPECTS (8–10 vs. 6–7), IV tPA treatment and occlusion location (ICA vs. MCA) as covariates. The study will have one formal interim analysis after 300 subjects have been accrued. Secondary end-points at 90 days include the following: mRS 0–1; mRS 0–2; Barthel 95–100, EuroQOL and a cognitive battery. Safety outcomes are symptomatic ICH, major bleeding, contrast nephropathy, total radiation dose, malignant MCA infarction, hemicraniectomy and mortality at 90 days.
    Full-text · Article · Apr 2015 · International Journal of Stroke

  • No preview · Article · Apr 2015 · International Journal of Stroke

  • No preview · Conference Paper · Feb 2015
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    ABSTRACT: Background: Recurrence after intracranial aneurysm coiling is a highly prevalent outcome, yet to be understood. We investigated clinical, radiological and procedural factors associated with major recurrence of coiled intracranial aneurysms. Methods: We retrospectively analyzed prospectively collected coiling data (2003-12). We recorded characteristics of aneurysms, patients and interventional techniques, pre-discharge and angiographic follow-up occlusion. The Raymond-Roy classification was used; major recurrence was a change from class I or II to class III, increase in class III remnant, and any recurrence requiring any type of retreatment. Identification of risk factors associated with major recurrence used univariate Cox Proportional Hazards Model followed by multivariate regression analysis of covariates with P<0.1. Results: A total of 467 aneurysms were treated in 435 patients: 283(65%) harboring acutely ruptured aneurysms, 44(10.1%) patients died before discharge and 33(7.6%) were lost to follow-up. A total of 1367 angiographic follow-up studies (range: 1-108 months, Median [interquartile ranges (IQR)]: 37[14-62]) was performed in 384(82.2%) aneurysms. The major recurrence rate was 98(21%) after 6(3.5-22.5) months. Multivariate analysis (358 patients with 384 aneurysms) revealed the risk factors for major recurrence: age>65 y (hazard ratio (HR): 1.61; P=0.04), male sex (HR: 2.13; P<0.01), hypercholesterolemia (HR: 1.65; P=0.03), neck size ≥4 mm (HR: 1.79; P=0.01), dome size ≥7 mm (HR: 2.44; P<0.01), non-stent-assisted coiling (HR: 2.87; P=0.01), and baseline class III (HR: 2.18; P<0.01). Conclusion: Approximately one fifth of the intracranial aneurysms resulted in major recurrence. Modifiable factors for major recurrence were choice of stent-assisted technique and confirmation of adequate baseline occlusion (Class I/II) in the first coiling procedure.
    No preview · Article · Jan 2015 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
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    ABSTRACT: Background and Purpose: Carotid artery stenting (CAS) has been, historically, an alternative to open endarterectomy (CEA) for stroke prevention in high risk patients with carotid atherosclerosis. We sought to determine the rates of periprocedural and long-term stroke or death and the risk factors for complications after CAS in our high risk patient population. Methods: Clinical and treatment variables of consecutive CAS procedures performed between 2002 and 2011 were analyzed. Using univariate and multivariate logistic regression analyses we examined how patient characteristics influenced outcomes and changes in modified Rankin Score (mRS). Results: In 152 patients, the composite total of periprocedural death, stroke, transient ischemic attack (TIA) and myocardial infarction (MI) rate was 3.95% (6/152). Chronic kidney disease (CKD) was strongly associated with periprocedural complications (p<0.001). Coronary artery disease/peripheral vascular disease (CAD/PVD) (p=0.03), dyslipidemia (p=0.02), CKD (p=0.01), and contralateral internal carotid artery stenosis (p=0.02) were non-modifiable risk factors for mRS increase. There were 25 deaths, 8 strokes, 11 TIAs, and 1 MI (mean follow-up 38.4 months, range 0-116 months). The presence of CAD/PVD (p=0.009) and dyslipidemia (p=0.002) were significantly associated with long-term complications. Conclusion: CAS was performed with low periprocedural complications in high-risk patients. Our rates compare very favorably to large-scale trials that have ideal patients. This data encourages the consideration of CAS in patients considered high risk for CEA and provides possible patient characteristics (CKD) to help with periprocedural risk stratification.
    No preview · Article · Jan 2015 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques

Publication Stats

560 Citations
311.96 Total Impact Points

Institutions

  • 2006-2015
    • University of Ottawa
      • • Department of Radiology
      • • Division of Medical Oncology
      • • Department of Medicine
      Ottawa, Ontario, Canada
  • 2004-2015
    • The Ottawa Hospital
      • Department of Medical Imaging
      Ottawa, Ontario, Canada
  • 2009-2014
    • The Ottawa Hospital
      Ottawa, Ontario, Canada