32 e-Letters

published between 2015 and 2018

  • Reply to: Decreasing incidence of subarachnoid hemorrhage

    We would like to congratulate Nicholson et al. on their highly interesting work on the declining rate of SAH in the Irish population. This will certainly provide some very interesting points. Also in Germany there is - at least subjectively - the phenomenon of the declining rate of SAH. The authors can establish a clear correlation to the decline in the smoking rate. Now the question arises whether this is the only relevant correlation. In particular, it would certainly be necessary to investigate whether there has been an increased rate of detection of unruptered Aneurysma and an increasing rate of treatment of those during the study period and whether this may also have a relevant influence on the decrease in SAH.

  • Using an intermediate catheter triaxial system for Direct Aspiration first Pass Technique: the easiest way for thrombectomy?

    Dear Editor,
    we read with great interest the paper from Sallustio et al 1 regarding the use of new thromboaspiration catheter, AXS Catalyst 6 (Stryker Neurovascular, Mountain View, CA, USA), for endovascular treatment (EVT) of large vessel stroke (LVS) with A Direct Aspiration first Pass Technique (ADAPT)2.
    In our center, a team composed by 4 vascular interventional radiologists, two physicians with certified experience in stroke treatment and two physicians with large carotid stent experience, and 4 stroke neurologist with large experience in intravenous thrombolysis, started to perform EVT in patients with LVS of anterior or posterior circulation from September 2017.
    Given the wide availability of different systems of neurothrombectomy we decided to use AXS Catalyst 6 both for its technical features, as reported by Sallustio et al, both for its lower costs than the others available (6F SOFIA plus catheter, MicroVention, Tustin, CA, USA; the X Penumbra ACE catheters, Penumbra Inc., Alameda, CA, USA).
    Between September 2017 and May 2018, 24 patients (72.1 ± 13.2 years old) affected by acute ischemic stroke with LVS underwent to EVT in our center. Median baseline NIHSS was 18 (range: 7-24). Intravenous thrombolysis was used in 5 patients.
    The most frequent site of occlusion was the middle cerebral artery (MCA) (70.8%), while in 16.7% of cases was basilar artery. Tandem occlusions occurred in 12.5% of patients and the most frequent stroke etiolo...

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  • Repeatability when measuring porosity and pore density of flow diverters: can we measure in vivo?

    The paper by Farzin et al.[1] shows interesting results about measuring porosity of fully expanded flow diverter stents using (photographic) images of the stent being assessed. In their study, authors used 3 different methods and repeated measurements by different observers to assess the porosity of stents. According to their results, the variability when measuring porosity is so large that previous works assessing it should be questioned. On the other hand, they indicate that pore density seems to be more reliable and repeatable. The study highlights the difficulty of measuring such parameter in a controlled in vitro environment. After carefully reading the article, it became clear that the most reproducible way of measuring porosity, from the 3 options studied, was M3 (based on measuring the width and length of the struts and number of struts per reference square). Furthermore, some simple assumptions should improve the results and substantially reduce errors and variability:
    1. Wire width: the value for wire width, indicated by the manufacturer, is likely to be more accurate. If this value is no to be trusted, at least in average, then the reproducibility of the manufacturing process could not be trusted. Measuring wire width directly on the images is likely to introduce error as it might be affected by reflection/refraction of light on the wire material and wire coating, as well as lens imperfections or optical aberrations in some cases.
    2. Calculating poro...

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  • Response to “Impact of balloon guiding catheter on technical and clinical outcomes: a systematic review and meta-analysis”

    I read with great interest the meta-analysis by Brinjikji et al.1 which evaluated outcomes after mechanical thrombectomy for acute ischemic stroke by using a balloon guiding catheter (BGC) device. In that study, the authors documented that patients who underwent mechanical thrombectomy with BGC had better clinical and angiographic outcomes than those without BGC. However, there were some issues which should be addressed and discussed.
    First, the number of successful recanalizations, shown as 2b/3 of Thrombolysis In Cerebral Infarction (TICI) grade in Fig.3 in the article,1 might be not accurately described. The events of successful recanalization were noted in 113 of 149 in the BGC group and 133 of 189 in the non-BGC group according to Nguyen et al.2 However, the events were presented as 112 of 149 in the BGC group and 135 of 189 in the non-BGC group.1 Accordingly, the forest plot can be changed as in Fig. 1 below. Mechanical thrombectomy using BGC exhibited significantly higher successful recanalizations than did non-BGC use (OR, 1.710; 95% CI: 1.099-2.662). Second, there was no specific explanation for the publication bias of Fig. 4 in the result section.1 Although the authors reported a p value of 0.49 using Egger’s regression, we are not sure what publication bias meant to represent, successful recanalization or clinical outcome or other variables.
    In this letter, we made a funnel plot for successful recanalization based on the revised number of events we h...

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  • Reduction of ghost infarct core with TMax/CBF mismatch in CT perfusion

    TO THE EDITOR: We read with interest the recent paper by Boned and colleagues.1 The authors conclude that “CT perfusion may overestimate final infarct core, especially in the early time window. Selecting patients for reperfusion therapies based on the CTP mismatch concept may deny treatment to patients who might still benefit from reperfusion”. We completely agree with this consideration, mainly when, as in this article, the core volume is assessed according to the classical CT perfusion (CTP) mismatch mean transit time (MTT)/cerebral blood volume (CBV)2 by measuring the lesion on CBV maps generated with a one-phase CT perfusion (CTP) acquisition protocol. In fact, it is well-known that a short CTP scan duration often produces a truncation of the perfusion curves resulting in an overestimation of CBV lesion that can frequently reverse.3 In addition, it has recently been demonstrated that relative cerebral blood flow (CBF) < 30% and time to peak of the residual function (Tmax) > 6 seconds is more reliable than CBV < 2.0 ml/100gr and relative MTT > 145% in identifying infarct core and ischemic penumbra at admission, respectively.4,5 As a consequence, the new CTP mismatch model Tmax/CBF was successfully used to include acute ischemic stroke (AIS) patients in the last trials showing the efficacy of endovascular treatment.6-9 We recently treated with combined intravenous thrombolysis and with mechanical thrombectomy patients imaged within 1.5 hour from symptom onset...

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  • Comments on Impact of balloon guide catheter on technical and clinical outcomes: a systematic review and meta-analysis

    We read with interest the meta-analysis conducted by our colleague Dr Waleed Brinjikji (1). In the text (section "Limitations", he stated: "Data from the Interest of Direct Aspiration First Pass Technique (ADAPT) for Thrombectomy Revascularization of Large Vessel Occlusion in Acute Ischemic Stroke (ASTER) trial suggest that there were no statistically significant differences in revascularization rates when performing the ADAPT technique compared with using a stent retriever. However, it is unclear at this time whether BGCs were used in this trial."
    Nevertheless in our publication of the ASTER trial results (2), we clearly stated in the Results section that a balloon-guide catheter was used to allow proximal flow arrest during stent retriever removal in 92% of patients treated with the stent retriever technique.
    1. Brinjikji W, Starke RM, Murad MH, et al. Impact of balloon guide catheter on technical and clinical outcomes: a systematic review and meta-analysis. J Neurointerv Surg 2018;10:335–339.
    2. Lapergue B, Blanc R, Gory B, et al. JAMA. 2017;318:443-452.

  • Letter to the Editor

    We read with interest the editorial by Darsaut and colleagues entitled, “PHASES and the natural history of unruptured aneurysms: science or pseudoscience?”[1]. Beginning with references to Aristotle and Pliny the Elder (always impressive), the authors launch a critique of studies of the natural history of unruptured aneurysms. With attention to ISUIA and the PHASES system, the contributors from Quebec call attention to limitations in both prospective and retrospective studies of the risk of rupture and associated risk factors for rupture of intracranial aneurysms. In their view, these imperfect studies are so deeply flawed that they are essentially useless as tools to inform decision-making with patients with unruptured intracranial aneurysms. Ending with the umpteenth call for a randomized trial, the authors create the impression that, for all patients with all kinds, sizes and locations of intracranial aneurysms, clinicians are powerless to use data from the available studies, condensed in the PHASES Score, to guide decision-making.

    The PHASES score, developed from a pooled analysis of six prospective cohort studies of patients with unruptured intracranial aneurysms, was designed to use existing natural history data (limited though that may be), to provide some estimate of future rupture risk and to aid in identifying risk factors for rupture that may push clinician and patient past the treatment threshold. Several lines of evidence support the use of PHASES...

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  • Prediction of hyperperfusion phenomenon after carotid artery stenting and carotid angioplasty using quantitative DSA with cerebral circulation time imaging; methodological issues

    I was interested to read the paper by Yamauchi K and colleagues published in J Neurointerv Surg 2017 Sep. Hyperperfusion syndrome after carotid interventions has a low incidence but it can lead to morbidity and mortality. The aim of the authors was to evaluate the usefulness of quantitative DSA for predicting hyperperfusion phenomenon (HPP) after carotid artery stenting and angioplasty. Thirty-three consecutive patients with carotid stenosis treated with carotid artery stenting or angioplasty between February 2014 and August 2016 were included. The cerebral circulation time (CCT) was defined as the difference in the relative time to maximum intensity between arterial and venous regions of interest set on the angiograms. HPP was diagnosed straight after the procedure with qualitative 123I-IMP single-photon emission CT (SPECT). Cut-off points for detecting HPP for preprocedural CCT and periprocedural change of CCT were assessed by receiver operating characteristic analysis using 123I-IMP SPECT as reference standard. Differences between patients with and without HPP were analyzed by Student's t test for continuous variables and Fisher`s exact test for categorical variables. A p value of <0.05 was considered statistically significant. Receiver operating characteristic curve analysis of preprocedural CCT and ΔCCT was performed for the prediction of HPP, with 123I-IMP SPECT as standard of reference. They reported that the optimal cut-off points of preprocedural CCT and c...

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  • Venous Sinus Pressure Measurement Technique

    We read with interest the recent paper looking at venous sinus pressure gradients prior to stenting (1), and commend the authors for their work on this interesting topic. We also share an interest in the subject, and recently published our experience looking at venous stenting in a similar patient population (2). The authors of the current paper documented significant differences in trans-stenotic venous pressure-gradients measured under general anaesthesia (GA), and suggested that pressure measurements should be performed with patients awake to counteract this. Another paper published in this issue of JNIS also documented the disparities between pressure measurements performed under GA versus those performed under conscious sedation (CS) (3). The pressure differences in our paper were significantly more marked in those patients who underwent measurements under local anaesthesia alone versus under CS. We can therefore hypothesise that even the use of CS can result in changes in the measured venous pressures in these patients, and indeed in the current paper the authors noted that the use of midazolam in their awake patients had a statistically significant effect on the pressures obtained. Since the decision to treat often hinges on this all-important measurement, we thus propose that venous sinus pressure measurements should be always performed using local anaesthesia alone, in an effort to minimise this variability.

    1: Fargen KM, Spiotta AM, Hyer M, et al, Comparis...

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  • The Authors' response to "Intra-arterial vasodilators for vasospasm following aneurysmal subarachnoid hemorrhage"

    We appreciate the interest shown by Drs. Yao and You (1) in our paper (2) and find it our pleasure to address their concerns.

    The first point raised by Drs. Yao and You is that our search strategy missed two articles, namely those of Mortimer et al (2015) (3) and Morgan et al (1996) (4). We would like to reassure Drs. Yao and You that we did screen these articles, and decided against including them in our meta-analysis based on our inclusion criteria. The article by Mortimer et al (2015) (3) describes a patient population where balloon angioplasty, verapamil, and papaverine infusions were used separately or in various combinations. They did not break down their results by the specific intra-arterial vasodilator (IAD) used, and therefore we decided not to include this information. The paper by Morgan et al (1996) (4) describes a patient population which overlapped with that described by the same group in another paper, Morgan et al (2000) (5). We had personally communicated with the authors in 2016 regarding the multiple papers from this group, such as Little et al (1994) (6) and Morgan et al (2000)
    (5) that described papaverine infusions for vasospasm. We found out that there were overlaps in these study populations, and that the cohort in the 2000 paper(5) was the most complete. Therefore, only this paper was included in our meta-analysis, while the earlier ones were excluded.

    The second suggestion by Drs. Yao and You was to perform a regression ana...

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