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Hugo Andrade-Barazarte, Krunal Patel, Mazda K. Turel, Francesco Doglietto, Anne Agur, Fred Gentili, Rachel Tymianski, Vitor Mendes Pereira, Michael Tymianski and Ivan Radovanovic

OBJECTIVE

The evolution of microsurgical and endoscopic techniques has allowed the development of less invasive transcranial approaches. The authors describe a purely endoscopic transpterional port craniotomy to access lesions involving the cavernous sinus and the anterolateral skull base.

METHODS

Through single- or dual-port incisions and with direct endoscopic visualization, the authors performed an endoscopic transpterional port approach (ETPA) using a 4-mm straight endoscope in 8 sides of 4 formalin-fixed cadaveric heads injected with colored latex. A main working port incision is made just below the superior temporal line and behind the hairline. An optional 0.5- to 1-cm second skin port incision is made on the lateral supraorbital region, allowing multiangle endoscopic visualization and maneuverability. A 1.5- to 2-cm craniotomy centered over the pterion is done through the main port, which allows an extradural exposure of the cavernous sinus region and extra/intradural exposure of the frontal and temporal cranial fossae. The authors present a pilot surgical series of 17 ETPA procedures and analyze the surgical indications and clinical outcomes retrospectively.

RESULTS

The initial stage of this work on cadavers provided familiarity with the technique, standardized its steps, and showed its anatomical limits. The clinical ETPA was applied to gain access into the cavernous sinus, as well as for aneurysm clipping and meningioma resection. Overall, perioperative complications occurred in 1 patient (6%), there was no mortality, and at last follow-up all patients had a modified Rankin Scale score of 0 or 1.

CONCLUSIONS

The ETPA provides a less invasive, focused, and direct route to the cavernous sinus, and to the frontal and temporal cranial fossae, and it is feasible in clinical practice for selected indications with good results.

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Amir R. Dehdashti, Leodante B. Da Costa, Karel G. terBrugge, Robert A. Willinsky, Michael Tymianski and M. Christopher Wallace

Dural arteriovenous fistulas are the most common vascular malformations of the spinal cord. These benign vascular lesions are considered straightforward targets of surgical treatment and possibly endovascular embolization, but the outcome in these cases depends mainly on the extent of clinical dysfunction at the time of the diagnosis. A timely diagnosis is an equally important factor, with early treatment regardless of the type more likely to yield significant improvements in neurological functioning. The outcomes after surgical and endovascular treatment are similar if complete obliteration of the fistulous site is obtained. In the present study, the authors evaluated the current role of each modality in the management of these interesting lesions.

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Susanna Bacigaluppi, Amir R. Dehdashti, Ronit Agid, Timo Krings, Michael Tymianski and David J. Mikulis

The aim of this review was to evaluate the imaging tools used in diagnosis and perioperative assessment of moyamoya disease, with particular attention to the last decade.

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Dittapong Songsaeng, Sasikhan Geibprasert, Karel G. ter Brugge, Robert Willinsky, Michael Tymianski and Timo Krings

Object

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.

Methods

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.

Results

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 A1 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).

Conclusions

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.

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Daipayan Guha, Benjamin Davidson, Mustafa Nadi, Naif M. Alotaibi, Michael G. Fehlings, Fred Gentili, Taufik A. Valiante, Charles H. Tator, Michael Tymianski, Abhijit Guha and Gelareh Zadeh

OBJECTIVE

A surgical series of 201 benign and malignant peripheral nerve sheath tumors (PNSTs) was assessed to characterize the anatomical and clinical presentation of tumors and identify predictors of neurological outcome, recurrence, and extent of resection.

METHODS

All surgically treated PNSTs from the Division of Neurosurgery at Toronto Western Hospital from 1993 to 2010 were reviewed retrospectively. Data were collected on patient demographics, clinical presentation, surgical technique, extent of resection, postoperative neurological outcomes, and recurrence.

RESULTS

One hundred seventy-five patients with 201 tumors had adequate follow-up for analysis. There were 182 benign and 19 malignant PNSTs. Of the benign lesions, 133 were schwannomas, 21 of which were associated with a diagnosis of schwannomatosis. There were 49 neurofibromas, and 26 were associated with neurofibromatosis Type 1 (NF1). Patients presenting with schwannomas were significantly older than those with neurofibromas. Schwannomas were more readily resected than neurofibromas, with the extent of resection of the former influenced by tumor location. Patients with benign PNSTs typically presented with a painful mass and less frequently with motor deficits. The likelihood of worsened postoperative motor function was decreased in patients with fully resected tumors or preoperative deficits. Recurrence of schwannomas and neurofibromas were seen more frequently in patients diagnosed with NF3 and NF1, respectively. Subtotal resection was associated with the increased recurrence of all benign lesions.

CONCLUSIONS

Outcomes following resection of benign PNSTs depend on tumor histopathology, tumor location, and genetic predisposition syndrome. Gross-total resection should be attempted for benign lesions where possible. The management of malignant PNSTs remains challenging, requiring a multimodal approach.

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Amir R. Dehdashti, Laurent Thines, Robert A. Willinsky, Karel G. terBrugge, Michael L. Schwartz, Michael Tymianski and M. Christopher Wallace

Object

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.

Methods

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.

Results

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.

Conclusions

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.

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Jorn Fierstra, Stephanie Spieth, Leanne Tran, John Conklin, Michael Tymianski, Karel G. ter Brugge, Joseph A. Fisher, David J. Mikulis and Timo Krings

Object

Cerebral proliferative angiopathy (CPA) has been morphologically distinguished from classically appearing brain arteriovenous malformations (AVMs) by exhibition of functional brain parenchyma that is intermingled with abnormal vascular channels. The presence of oligemia in this intralesional brain tissue may suggest ischemia, which is not detected in classic brain AVMs. The authors hypothesized that patients with CPA would exhibit a greater impairment of cerebrovascular reserve in neuronal tissue surrounding the true nidus compared with those with brain AVMs.

Methods

Four patients with CPA, 10 patients with brain AVMs and seizures, and 12 young healthy individuals were studied. The 4 patients with CPA underwent blood oxygen level–dependent MR imaging examinations while applying normoxic step changes in end-tidal CO2 to obtain quantitative cerebrovascular reactivity measurements.

Results

Patients with a CPA lesion exhibited severely impaired perilesional cerebrovascular reserve in comparison with patients with brain AVMs and seizures (0.10 ± 0.03 vs 0.16 ± 0.03, respectively; p < 0.05), and young healthy individuals (0.10 ± 0.03 vs 0.21 ± 0.06, respectively; p < 0.01)

Conclusions

This study demonstrated severely impaired cerebrovascular reserve in the perilesional brain tissue surrounding the abnormal vessels of patients with CPA. This finding may provide an additional means to distinguish CPA from classic brain AVMs.

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Hengwei Jin, Stephanie Lenck, Timo Krings, Ronit Agid, Yibin Fang, Youxiang Li, Alex Kostynskyy, Michael Tymianski, Vitor Mendes Pereira and Ivan Radovanovic

OBJECTIVE

The goal of this study was to describe changes in the angioarchitecture of brain arteriovenous malformations (bAVMs) between acute and delayed cerebral digital subtraction angiography (DSA) obtained after hemorrhage, and to examine bAVM characteristics predicting change.

METHODS

This is a retrospective study of a prospective institutional bAVM database. The authors included all patients with ruptured bAVMs who had DSA in both acute and delayed phases, with no interval treatment of their bAVM, between January 2000 and April 2017. The authors evaluated the existence or absence of angioarchitectural changes. Demographic data, radiological characteristics of hemorrhages, and angioarchitectural features of the bAVMs of the two patients’ groups were analyzed. Univariate and multivariate logistic analyses were performed to identify predictors of angioarchitectural change.

RESULTS

A total of 42 patients were included in the series. Seventeen (40.5%) patients had angioarchitectural changes including bAVM only visible on the delayed DSA study (n = 8), spontaneous thrombosis of the AVM (n = 3), or alteration of the size or the opacification of the nidus (n = 6). The factors associated with angioarchitectural changes were a small nidus (3.8 ± 7.9 ml vs 6.1 ± 9.5 ml, p = 0.046), a superficial location (94.1% vs 5.9%, p = 0.016), and a single superficial draining vein (58.8% vs 24.0%, p = 0.029).

CONCLUSIONS

Angioarchitectural changes can be seen in 40% of ruptured bAVMs between the acute- and delayed-phase DSA. A small nidus, a superficial location, and a single superficial draining vein were statistically associated with the occurrence of angioarchitectural changes. These changes included either enlargement or spontaneous occlusion of the bAVM, as well as subsequent diagnosis of a bAVM following an initial negative DSA study.

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David J. Mikulis, Gregory Krolczyk, Hubert Desal, William Logan, Gabrielle deVeber, Peter Dirks, Michael Tymianski, Adrian Crawley, Alex Vesely, Andrea Kassner, David Preiss, Ron Somogyi and Joseph A. Fisher

Object. The ability to map cerebrovascular reactivity (CVR) at the tissue level in patients with moyamoya disease could have considerable impact on patient management, especially in guiding surgical intervention and assessing the effectiveness of surgical revascularization. This paper introduces a new noninvasive magnetic resonance (MR) imaging—based method to map CVR. Preoperative and postoperative results are reported in three cases to demonstrate the efficacy of this technique in assessing vascular reserve at the microvascular level.

Methods. Three patients with angiographically confirmed moyamoya disease were evaluated before and after surgical revascularization. Measurements of CVR were obtained by rapidly manipulating end-tidal PCO2 between hypercapnic and hypocapnic states during MR imaging. The CVR maps were then calculated by comparing the percentage of changes in MR signal with changes in end-tidal PCO2.

Presurgical CVR maps showed distinct regions of positive and negative reactivity that correlated precisely with the vascular territories supplied by severely narrowed vessels. Postsurgical reactivity maps demonstrated improvement in the two patients with positive clinical outcome and no change in the patient in whom a failed superficial temporal artery—middle cerebral artery bypass was performed.

Conclusions. Magnetic imaging—based CVR mapping during rapid manipulation of end-tidal PCO2 is an exciting new method for determining the location and extent of abnormal vascular reactivity secondary to proximal large-vessel stenoses in moyamoya disease. Although the study group is small, there seems to be considerable potential for guiding preoperative decisions and monitoring efficacy of surgical revascularization.

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Amir R. Dehdashti, Laurent Thines, Leodante B. Da Costa, Karel G. terBrugge, Robert A. Willinsky, M. Christopher Wallace and Michael Tymianski

Object

The purpose of this study was to evaluate the authors' initial experience with the integration of high-resolution rotational and biplanar angiography during neurovascular operative procedures.

Methods

Eight patients with intracerebral arteriovenous malformations (AVMs) and aneurysms underwent surgical treatment of their lesions in a combined endovascular surgical suite. After initial head positioning, preoperative biplane and rotational angiography was performed. Resection of the AVM or clipping of the aneurysm was then performed. Further biplane and rotational 3D angiograms were obtained intraoperatively to confirm satisfactory treatment.

Results

One small residual AVM identified intraoperatively necessitated further resection. One aneurysm was clipped during endovascular inflation of an intracarotid balloon for temporary proximal control. The completeness of treatment was confirmed on intraoperative 3D rotational angiography in all cases, and there were no procedure-related complications.

Conclusions

Intraoperative rotational angiography performed in an integrated biplane angiography/surgery suite is a safe and useful adjunct to surgery and may enable combining endovascular and surgical procedures for the treatment of complex vascular lesions.