Robert A Willinsky

Toronto Western Hospital, Toronto, Ontario, Canada

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Publications (99)302.99 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of our study was to compare the clinical characteristics and preferential localization of aneurysms in three patient groups: single aneurysm, non-mirror multiple aneurysms, and mirror aneurysms.
    Neuroradiology 10/2014; · 2.70 Impact Factor
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    ABSTRACT: Management of unruptured fusiform intracranial aneurysms is controversial because of the paucity of natural history data. We studied their natural history and outcome after treatment.
    Stroke 09/2014; · 6.16 Impact Factor
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    ABSTRACT: To report the epidemiological features, clinical presentation, angiographic characteristics and therapeutic options, success and complication rates in patients with dural carotid cavernous fistulas (dural CCFs).
    European Radiology 07/2014; · 4.34 Impact Factor
  • I-Chang Su, Robert A Willinsky, Noel F Fanning, Ronit Agid
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    ABSTRACT: Perianeurysmal edema and aneurysm wall enhancement are previously described phenomenon after coil embolization attributed to inflammatory reaction. We aimed to demonstrate the prevalence and natural course of these phenomena in unruptured aneurysms after endovascular treatment and to identify factors that contributed to their development. We performed a retrospective analysis of consecutively treated unruptured aneurysms between January 2000 and December 2011. The presence and evolution of wall enhancement and perianeurysmal edema on MRI after endovascular treatment were analyzed. Variable factors were compared among aneurysms with and without edema. One hundred thirty-two unruptured aneurysms in 124 patients underwent endovascular treatment. Eighty-five (64.4 %) aneurysms had wall enhancement, and 9 (6.8 %) aneurysms had perianeurysmal brain edema. Wall enhancement tends to persist for years with two patterns identified. Larger aneurysms and brain-embedded aneurysms were significantly associated with wall enhancement. In all edema cases, the aneurysms were embedded within the brain and had wall enhancement. Progressive thickening of wall enhancement was significantly associated with edema. Edema can be symptomatic when in eloquent brain and stabilizes or resolves over the years. Our study demonstrates the prevalence and some appreciation of the natural history of aneurysmal wall enhancement and perianeurysmal brain edema following endovascular treatment of unruptured aneurysms. Aneurysmal wall enhancement is a common phenomenon while perianeurysmal edema is rare. These phenomena are likely related to the presence of inflammatory reaction near the aneurysmal wall. Both phenomena are usually asymptomatic and self-limited, and prophylactic treatment is not recommended.
    Neuroradiology 03/2014; · 2.70 Impact Factor
  • I-Chang Su, Karel G Terbrugge, Robert A Willinsky, Timo Krings
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    ABSTRACT: Despite improvements of embolization agents and techniques, endovascular treatment of spinal dural arterovenous fistula (SDAVF) is still limited by inconsistent success. The aim of embolization is to occlude initial portion of the draining vein by liquid embolic materials. This study investigates factors that contribute to the success of embolization treatments among SDAVF patients. We performed a retrospective analysis on consecutive SDAVF patients who received N-butyl cyanoacrylate (NBCA) glue embolization between January 1992 and June 2012. Univariable and multivariable logistic regression analyses were performed to calculate the probability of successful draining vein occlusion for variable procedure-related factors. We attempted endovascular approach as the first intention treatment in 66 out of 90 consecutive patients. Among them, a total of 43 NBCA glue injections were performed in 40 patients. Successful embolization was achieved in 24 patients (60 %). In multivariable analyses, antegrade flow during microcatheter test injection (OR 13.2, 95 % CI 1.7 to 105.4) and use of glue concentration ≥30 % (OR 0.1, 95 % CI 0.01 to 0.8) were detected as significant positive and negative predictors of successful venous penetration, respectively. With persistent antegrade flow, the success rates using a glue mixture of more than 30 % dropped significantly from 85.0 to 42.9 % (p = 0.049). If contrast stagnated during microcatheter injections, success rates were low regardless of glue concentrations. Presence of antegrade flow toward the draining vein and injection of NBCA glue less than 30 % are associated with higher chance of draining vein penetration and, therefore, successful endovascular SDAVF obliteration.
    Neuroradiology 10/2013; · 2.70 Impact Factor
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    ABSTRACT: Cystic parenchymal lesions may pose an important diagnostic challenge, particularly when encountered in unexpected locations. Dilated perivascular spaces, which may mimic cystic neoplasms, are known to occur in the inferior basal ganglia and mesencephalothalamic regions; a focal preference within the subcortical white matter has not been reported. This series describes 15 cases of patients with cystic lesions within the subcortical white matter of the anterior superior temporal lobe, which followed a CSF signal; were located adjacent to a subarachnoid space; demonstrated variable surrounding signal change; and, in those that were followed up, showed stability. Pathology study results obtained in 1 patient demonstrated chronic gliosis surrounding innumerable dilated perivascular spaces. These findings suggest that dilated perivascular spaces may exhibit a regional preference for the subcortical white matter of the anterior superior temporal lobe. Other features-lack of clinical symptoms, proximity to the subarachnoid space, identification of an adjacent vessel, and stability with time-may help in confidently making the prospective diagnosis of a dilated perivascular space, thereby preventing unnecessary invasive management.
    American Journal of Neuroradiology 08/2013; · 3.17 Impact Factor
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    ABSTRACT: BACKGROUND AND PURPOSE:Flow-diverting stents are increasingly being used for the treatment of complex intracranial aneurysms, but the indications for their use in lieu of traditional endovascular PVO have yet to be precisely defined. The purpose of this study was to review the clinical and imaging outcomes of patients with intracranial aneurysms treated by PVO.MATERIALS AND METHODS:A total of 28 patients with intracranial aneurysms, treated by PVO between July 1992 and December 2009, were reviewed. Aneurysms arising from peripheral arteries were excluded. Clinical and imaging data were retrospectively analyzed from a prospectively maintained data base.RESULTS:There were 28 patients with 28 aneurysms treated by PVO. Aneurysms of the anterior circulation presenting with mass effect (n = 11) or discovered incidentally (n = 1), and dissecting-type VB aneurysms presenting with subarachnoid hemorrhage (n = 6) faired the best with high obliteration rates (83.3% and 83.6%, respectively) and no permanent major ischemic complications. In contrast, VB aneurysms presenting with mass effect (n = 7) demonstrated the lowest obliteration rate (57.1%), the highest rate of permanent major ischemic complications (28.6%), and a high mortality rate (28.6%).CONCLUSIONS:PVO is a safe and effective treatment for complex intracranial aneurysms of the carotid artery and dissecting-type VB aneurysms presenting with SAH. In contrast, PVO for aneurysms of the VB circulation presenting with mass effect is less efficacious and associated with significant morbidity and mortality. It is hoped that flow diverters may represent a better treatment technique for these most difficult-to-treat lesions.
    American Journal of Neuroradiology 05/2012; · 3.17 Impact Factor
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    ABSTRACT: Prospective differentiation between reversible cerebral vasoconstriction syndrome and central nervous system vasculitis can be challenging. We hypothesized that high-resolution vessel wall MRI would demonstrate arterial wall enhancement in central nervous system vasculitis but not in reversible cerebral vasoconstriction syndrome. We identified all patients with multifocal segmental narrowing of large intracranial arteries who had high-resolution vessel wall MRI and follow-up angiography at our institute over a 4-year period and performed a detailed chart review. Three patients lacked arterial wall enhancement, and these all had reversal of arterial narrowing within 3 months. Four patients demonstrated arterial wall enhancement, and these had persistent or progressive arterial narrowing at a median follow-up of 17 months (range, 6-36 months) with final diagnoses of central nervous system vasculitis (3) and cocaine vasculopathy (1). Preliminary results suggest that high-resolution contrast-enhanced vessel wall MRI may enable differentiation between reversible cerebral vasoconstriction syndrome and central nervous system vasculitis.
    Stroke 12/2011; 43(3):860-2. · 6.16 Impact Factor
  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 09/2011; 38(5):760-1. · 1.33 Impact Factor
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    ABSTRACT: Brainstem arteriovenous malformations are challenging lesions, and benefits of treatment are uncertain. To study the clinical course of Brainstem arteriovenous malformations and the influence of treatments on outcome. We reviewed a prospective series of 31 brainstem arteriovenous malformations. Demographic, morphological, and clinical characteristics were recorded. Factors determining initial and final outcomes (modified Rankin Scale), results of treatments (cure rates, complications), and disease course were analyzed. Brainstem arteriovenous malformations were symptomatic and bled in 93% and 61% of cases, respectively. Examination was abnormal and initial modified Rankin Scale score was < 3 in 71% and 86% of patients, respectively. The average follow-up time was 6.2 years, and 26% of patients rebled (5.9 %/y). Treatment modalities included conservative, radiosurgical, endovascular, surgical, and multimodality treatment in 13%, 58%, 35%, 16%, and 26% of cases, respectively. The obliteration rate was 60% overall and 39% after radiosurgery, 40% after embolization, and 75% after microsurgery, with respective complication-free cure rates of 71%, 50%, and 0%. Overall procedural mortality and morbidity were 2.3% and 18.6%, respectively. Final modified Rankin Scale score was < 3 in 77% of cases. Neurological deterioration (35%) was related to treatment complications in 74% of cases with a negative impact of surgery (P = .04), palliative embolization (odds ratio = 16), and multimodality treatments (odds ratio = 24). Radiosurgery was inversely associated with worsening (odds ratio = 0.06). Brainstem arteriovenous malformations require individualized treatment decisions. Single-modality treatments with a reasonable chance of complete cure and low complication rate (such as radiosurgery) should be favored.
    Neurosurgery 05/2011; 70(1):155-61; discussion 161. · 2.53 Impact Factor
  • Source
    I Y L Tan, R F Agid, R A Willinsky
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    ABSTRACT: The aim of this study was to retrospectively assess the recanalization rate, factors associated with and time taken for recanalization to occur in a matched ruptured and unruptured aneurysm population that were treated with endovascular coiling.Ruptured and unruptured aneurysms treated between 2002 and 2007 were matched for aneurysm location, diameter and neck size. Recanalization rate, time to recanalize, re-treatment rate and clinical outcome were analysed. Ninety-eight matched ruptured and unruptured aneurysms (49 aneurysms in each group) were studied. 46.8% of aneurysms in the ruptured group achieved complete obliteration on the initial post treatment angiogram versus 34.7% in the unruptured group. The ruptured group had a higher rate of recanalization (40.4% versus 20.4%). 25.5% of aneurysms had significant recanalization in the ruptured group versus 6.1% in the unruptured group (p=0.009). The retreatment rate was higher in the ruptured group (21.3% versus 6%). Ruptured aneurysms took a shorter time to recanalize with a mean time of 5.3±3.8 months versus 12.4±7.7months (p=0.003). Multivariate logistic regression analysis found neck size (p=0.0098), wide neck morphology (p=0.0174), aneurysm diameter (p< 0.0001) and ruptured aneurysms (p=0.0372) were significant predictors of recanalization. The majority of patients in both groups had a good outcome with GOS=5 (85.7% and 83.7%) but two deaths occurred in the ruptured group.Ruptured and unruptured aneurysms showed significant differences in rate, degree and timing of recanalization, thus requiring different protocols for imaging follow-up post endovascular treatment. Earlier and more frequent imaging follow-up is recommended for ruptured aneurysms.
    Interventional Neuroradiology 03/2011; 17(1):27-35. · 0.77 Impact Factor
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    ABSTRACT: To evaluate the effectiveness and safety of transarterial glue embolization of intracranial dural arteriovenous shunts (DAVS). Institutional review board approval was obtained, with waiver of informed consent, for this retrospective study. From a single-center database of information on 371 intracranial DAVS, data in 115 consecutive patients treated with transarterial glue embolization were identified and assessed. Clinical and angiographic features, including cure rate, complications, and outcome, were evaluated. The treatment results were also compared between the patients in the first half of the consecutive series and those in the second half. The mean glue concentrations used were compared between the first and second halves of the patient series by using the Student t test. One hundred twenty-one lesions were treated with transarterial glue embolization. There were 31 (25.6%) Borden type I lesions, 39 (32.2%) Borden type II lesions, and 51 (42.1%) Borden type III lesions. Angiographic cure with glue embolization was achieved for 36 lesions (29.8%); 17 (14.0%) lesions were cured immediately, and 19 (15.7%) showed progressive thrombosis at follow-up. The angiographic cure rate for Borden type III lesions improved from 10% to 55% in the later group of patients as compared with the earlier group. The mean concentration of glue was significantly lower in the later group of patients. One (0.9%) of the 115 patients suffered permanent morbidity from aggravation of left extremity weakness due to venous thrombosis. Eight patients experienced nonpermanent morbidities, including transient worsening of neurologic status due to venous thrombosis (n = 4), alopecia (n = 2), scalp ulcer (n = 1), and pulmonary embolism (n = 1). Overall, improvement (n = 65) or stabilization (n = 32) of symptoms was seen in 84.3% of the patients. Transarterial glue embolization is a safe and effective method of primary treatment for intracranial DAVS, especially Borden type III lesions. Improvement of cure rates in the latter half of this study suggest that technical advances and experience may enhance outcomes.
    Radiology 02/2011; 258(2):554-61. · 6.34 Impact Factor
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    ABSTRACT: In this study, the authors evaluated how an appropriate allocation of patients with occipital arteriovenous malformations (AVMs) who were treated according to different strategies would affect nonhemorrhagic headache, visual function, and hemorrhage risk levels. Of the 712 patients with brain AVMs in the Toronto Western Hospital prospective database, 135 had occipital AVMs. The treatment decision was based on patients' characteristics, presentation, and morphology of the AVM. The management modalities were correlated with their outcomes. The mean follow-up period was 6.78 years. Nonhemorrhagic headache was the most frequent symptom (82 [61%] of 135 patients). Ninety-four patients underwent treatment with one or a combination of embolization, surgery, or radiosurgery, and 41 were simply observed. Of the 40 nontreated patients with nonhemorrhagic headache, only 12 (30%) showed improvement. In the observation group 2 patients (22%) had worsening of visual symptoms, and 2 experienced hemorrhage, for an annual hemorrhage rate of 0.7% per year; 1 patient died. In the treatment group, the improvement in nonhemorrhagic headache in 35 patients (83%) was significant (p < 0.0001). Visual deficit at presentation worsened in 2 (8%), and there were 8 new visual field deficits (9%). The visual worsening was not significantly different. There were 2 other neurological deficits (2%) and 2 deaths (2%) related to the AVM treatment. One AVM hemorrhaged. The annual hemorrhage rate was 0.1% per year. The hemorrhage risk in the observation and treatment groups was lower than the observed hemorrhage risk of all patients with AVMs (4.6%) at the authors' institution. Appropriate selection of patients with occipital AVMs for one or a combination of treatment modalities yields a significant decrease in nonhemorrhagic headache without significant visual worsening. The multidisciplinary care of occipital AVMs can aim for an apparent decrease in hemorrhage risk.
    Journal of Neurosurgery 10/2010; 113(4):742-8. · 3.15 Impact Factor
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    ABSTRACT: The goal was to investigate whether morphological features of aneurysms can be identified that determine initial success and recurrence rates of coiled aneurysms of the basilar artery tip, the posterior communicating artery (PCoA), and the anterior communicating artery. The authors evaluated 202 aneurysms in connection with their pretreatment morphological features including size, neck-to-dome ratio, angulation of the aneurysm in relation to the parent artery, orientation of the aneurysm dome, and associated anatomical variations. The mean follow-up was 19 months (range 6-96 months) after endovascular coil occlusion. Using multivariate logistic regression, probabilities for initial complete occlusion and long-term stability of the treatment were calculated. Recanalization occurred in 49 of 202 cases. Favorable factors for long-term stability included small aneurysms with small necks. However, additional factors related to local hemodynamic forces could be identified for the different aneurysm locations, which may influence initial success rates and long-term stability of aneurysm treatment with endovascular coiling. These factors were a medial dome orientation and a symmetrical disposition of both A(1) segments (for the anterior communicating artery), a posteroinferior dome orientation and a small-size PCoA (for the PCoA), and a cranial symmetrical fusion (for the basilar artery tip). A detailed pretreatment analysis of morphological features of aneurysms may help to determine those aneurysms that are more prone to recurrence, which could add to the treatment decision and the follow-up algorithm.
    Journal of Neurosurgery 10/2010; 114(4):994-1002. · 3.15 Impact Factor
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    ABSTRACT: Multidetector computerized tomography angiography (MDCTA) is now a widely accepted technique for the management of intracranial aneurysms. To evaluate its accuracy for the postoperative assessment of clipped intracranial aneurysms. We analyzed a consecutive series of 31 patients that underwent direct surgical clipping procedures of 38 aneurysms. A 64 slice MDCT scanner (Aquilion 64, Toshiba) was used and results were compared with digital subtraction angiographies (DSA). Two independent neuroradiologists analyzed the following data: examination quality, artifacts, aneurysm remnant, and patency of collateral branches. Interobserver agreement, sensitivity, and specificity were calculated. Seventy-nine percent of the aneurysms were located in the anterior circulation. Significant artifacts were found with multiple and cobalt-alloy clips. According to DSA, remnants >2 mm were found in 21% of the cases, and 2 patients had one collateral branch occluded. Sensitivity and specificity of 64-MDCTA for the detection of aneurysm remnants were 50% and 100%, respectively. Sensitivity and specificity of 64-MDCTA for the detection of a significant remnant (>2 mm) and the detection of the occlusion of a collateral branch were, respectively, 67% and 100% and 50% and 100%. No relationship was found with the location, type, shape, size, or number of clips, but missed remnants tended to be larger with cobalt-alloy clips. 64-MDCTA is a valuable technique to assess the presence of a significant postoperative remnant in single titanium clip application cases and might be useful for long-term follow-up. DSA remains the most accurate postoperative radiological examination.
    Neurosurgery 09/2010; 67(3):844-53; discussion 853-4. · 2.53 Impact Factor
  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 09/2010; 37(5):681-3. · 1.33 Impact Factor
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    ABSTRACT: Dural arteriovenous shunt (DAVS) is a disease in which abnormal arteriovenous communications develop within the dura. Some case series have suggested DAVS may evolve over time, but the natural history is poorly understood. In this study, we aimed to define the incidence and clinical characteristics of patients with DAVS showing spontaneous angiographic pattern conversion. We assessed clinical and angiographic features of patients with angiographic conversion without any treatment from a single center database consisting of 335 DAVS cases. Spontaneous angiographic conversion was defined as complete occlusion of a pre-existing DAVS or conversion of a benign into an aggressive lesion on follow-up diagnostic subtraction angiography. One hundred twelve patients were followed without treatment after the initial diagnosis of DAVS. Overall, we saw pattern conversion on angiography in 18 of the 112 cases (16.1%). Fourteen patients showed spontaneous occlusion of the shunt (12.5%); the most common locations of spontaneous obliteration were the transverse and cavernous sinuses. Four patients showed conversion to an aggressive lesion from benign DAVS (4.0%); all of these cases were associated with occlusion of the ipsilateral draining vein. DAVS is a dynamic disorder, which will show chronological progression. Spontaneous angiographic obliteration or conversion into an aggressive type may occur on follow-up of untreated DAVSs.
    Stroke 07/2010; 41(7):1489-94. · 6.16 Impact Factor
  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 07/2010; 37(4):532-4. · 1.33 Impact Factor
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    ABSTRACT: Middle ear aneurysms are rare and difficult to treat. An innovative, parent vessel-preserving, aneurysm occlusion stent is a treatment alternative. It redirects blood flow away from the aneurysm, resulting in stasis within, and ultimate aneurysm thrombosis. Concurrent coiling is not needed with this stent, eliminating the risk of coils extruding or migrating, or acting as a nidus for infection in the middle ear. We review a successful treatment using this device.
    The Laryngoscope 03/2010; 120(4):796-9. · 1.98 Impact Factor
  • Source
    The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 03/2010; 37(2):286-8. · 1.33 Impact Factor

Publication Stats

2k Citations
302.99 Total Impact Points


  • 1990–2014
    • Toronto Western Hospital
      Toronto, Ontario, Canada
  • 2013
    • Cathay General Hospital
      T’ai-pei, Taipei, Taiwan
  • 2011
    • Yonsei University Hospital
      Sŏul, Seoul, South Korea
  • 1997–2011
    • University of Toronto
      • • Division of Neuroradiology
      • • Division of Neurosurgery
      • • Department of Medical Imaging
      Toronto, Ontario, Canada
  • 2010
    • University of Lille Nord de France
      Lille, Nord-Pas-de-Calais, France
    • The Neurosciences Institute
      La Jolla, California, United States
  • 2009
    • Gyeongsang National University
      • Department of Radiology
      Chinju, South Gyeongsang, South Korea
    • University of Groningen
      • Department of Neurosurgery
      Groningen, Province of Groningen, Netherlands
  • 2006
    • McMaster University
      • Division of Neurosurgery
      Hamilton, Ontario, Canada
  • 2003
    • Leiden University Medical Centre
      • Department of Neurosurgery
      Leiden, South Holland, Netherlands
    • Karolinska University Hospital
      Tukholma, Stockholm, Sweden
    • University Health Network
      • Department of Medical Imaging
      Toronto, Ontario, Canada
  • 1999
    • University of British Columbia - Vancouver
      • Department of Surgery
      Vancouver, British Columbia, Canada
    • Lantheus Medical Imaging
      Lowell, Massachusetts, United States