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Nirav J. Patel and Michael K. Morgan

This video shows the surgical repair of a 2.3 cm ICA aneurysm found in a 58-year-old woman, who presented for right eye vision changes. The patient underwent a right modified orbitozygomatic craniotomy and saphenous vein bypass from the common carotid to the temporal M2. The aneurysm was then opened and repaired. However, since the anterior choroidal artery was not filling, a salvage bypass between the anterior choroidal and the PCOM was done. Both bypasses were patent and the patient has done well with a mRS of 1 for vision symptoms.

The video can be found here: http://youtu.be/ciMyzfXgo8I.

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Michael K. Morgan and W. Richard Marsh

✓ Dura-based spinal arteriovenous malformations (AVM's) are being diagnosed with increasing frequency. The optimal management of such lesions remains a topic of discussion. In an effort to guide this discussion, the authors review their experience with 17 cases of spinal dural AVM treated between January, 1984, and July, 1987. All patients presented with a slowly progressive paraparesis. The abnormalities were initially identified on myelography and confirmed by selective spinal angiography. Fourteen patients underwent endovascular embolization as a primary treatment, and a total of 18 embolization procedures were performed. After all but two of these, obliteration was confirmed at angiography. Patients' symptoms improved following 15 or these procedures but early improvement was not sustained in 10 instances; patients were unchanged after two procedures and worse after one. Follow-up angiography was performed at varying intervals after 15 of the 18 procedures, and recanalization of the previously obliterated spinal dural AVM was demonstrated in 13 instances. Eight patients ultimately underwent surgical treatment of their dura-based spinal AVM. No patient suffered deterioration of symptoms following operation. While embolization may allow angiographic obliteration of a spinal dural AVM and early clinical improvement, for the majority of patients these are not sustained. The average time to treatment failure was 5 months. Newer embolization materials will be necessary to effect permanent treatment in many of these patients.

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Mohamed Samy Elhammady and Roberto C. Heros

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Michael K. Morgan and Lali H. S. Sekhon

✓ The management of carotid or vertebral artery dissections has generally been either conservative (with anticoagulation) or surgical (by proximal ligation or trapping procedures). However, identification and management of those patients with a high risk of stroke recurrence have been difficult. Six patients with carotid or vertebral artery dissections underwent a total of seven surgical procedures involving intracranial interpositional saphenous vein bypass grafts anastomosed distally beyond the point of dissection with trapping of the intermediate diseased section of the artery. It is suggested that this procedure be used in patients who have bilateral carotid or vertebral artery disease, persistent angiographic abnormalities (particularly aneurysms), or recurring ischemic events while undergoing anticoagulation therapy, or in whom anticoagulation is undesirable. This procedure has benefits over current surgical options because of the maintenance of high flow, the avoidance of abnormal watershed areas of flow, and the elimination of the risk of emboli. The procedure is compared to previous techniques of extracranial-intracranial bypass.

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Manuri Gunawardena, Jeffrey M. Rogers, Marcus A. Stoodley and Michael K. Morgan

OBJECTIVE

Previous trials rejected a role of extracranial-to-intracranial bypass surgery for managing symptomatic atheromatous disease. However, hemodynamic insufficiency may still be a rationale for surgery, provided the bypass can be performed with low morbidity and patency is robust.

METHODS

Consecutive patients undergoing bypass surgery for symptomatic non-moyamoya intracranial arterial stenosis or occlusion were retrospectively identified. The clinical course and surgical outcomes of the cohort were evaluated at 6 weeks, 6 months, and annually thereafter.

RESULTS

From 1992 to 2017, 112 patients underwent 127 bypasses. The angiographic abnormality was arterial occlusion in 80% and stenosis in 20%. Procedures were performed to prevent future stroke (76%) and stroke reversal (24%), with revascularization using an arterial pedicle graft in 80% and venous interposition graft (VIG) in 20%. A poor outcome (bypass occlusion, new stroke, new neurological deficit, or worsening neurological deficit) occurred in 8.9% of patients, with arterial pedicle grafts (odds ratio [OR] 0.15), bypass for prophylaxis against future stroke (OR 0.11), or anterior circulation bypass (OR 0.17) identified as protective factors. Over the first 8 years following surgery the 66 cases exhibiting all three of these characteristics had minimal risk of a poor outcome (95% confidence interval 0%–6.6%).

CONCLUSIONS

Prophylactic arterial pedicle bypass surgery for anterior circulation ischemia is associated with high graft patency and low stroke and surgical complication rates. Higher risks are associated with acute procedures, typically for posterior circulation pathology and requiring VIGs. A carefully selected subgroup of individuals with hemodynamic insufficiency and ischemic symptoms is likely to benefit from cerebral revascularization surgery.

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Michael K. Morgan, Markus K. Hermann Wiedmann, Marcus A. Stoodley and Gillian Z. Heller

OBJECTIVE

The purpose of this study was to adapt and apply the extended definition of favorable outcome established for Gamma Knife radiosurgery (GKRS) to surgery for brain arteriovenous malformations (bAVMs). The aim was to derive both an error around the point estimate and a model incorporating angioarchitectural features in order to facilitate comparison among different treatments.

METHODS

A prospective microsurgical cohort was analyzed. This cohort included patients undergoing embolization who did not proceed to microsurgery and patients denied surgery because of perceived risk of treatment. Data on bAVM residual and recurrence during long-term follow-up as well as complications of surgery and preoperative embolization were analyzed. Patients with Spetzler-Ponce Class C bAVMs were excluded because of extreme selection bias. First, patients with a favorable outcome were identified for both Class A and Class B lesions. Patients were considered to have a favorable outcome if they were free of bAVM recurrence or residual at last follow-up, with no complication of surgery or preoperative embolization, and a modified Rankin Scale score of more than 1 at 12 months after treatment. Patients who were denied surgery because of perceived risk, but would otherwise have been candidates for surgery, were included as not having a favorable outcome. Second, the authors analyzed favorable outcome from microsurgery by means of regression analysis, using as predictors characteristics previously identified to be associated with complications. Third, they created a prediction model of favorable outcome for microsurgery dependent upon angioarchitectural variables derived from the regression analysis.

RESULTS

From a cohort of 675 patients who were either treated or denied surgery because of perceived risk of surgery, 562 had Spetzler-Ponce Class A or B bAVMs and were included in the analysis. Logistic regression for favorable outcome found decreasing maximum diameter (continuous, OR 0.62, 95% CI 0.51–0.76), the absence of eloquent location (OR 0.23, 95% CI 0.12–0.43), and the absence of deep venous drainage (OR 0.19, 95% CI 0.10–0.36) to be significant predictors of favorable outcome. These variables are in agreement with previous analyses of microsurgery leading to complications, and the findings support the use of favorable outcome for microsurgery. The model developed for angioarchitectural features predicts a range of favorable outcome at 8 years following microsurgery for Class A bAVMs to be 88%–99%. The same model for Class B bAVMs predicts a range of favorable outcome of 62%–90%.

CONCLUSIONS

Favorable outcome, derived from GKRS, can be successfully used for microsurgical cohort series to assist in treatment recommendations. A favorable outcome can be achieved by microsurgery in at least 90% of cases at 8 years following microsurgery for patients with bAVMs smaller than 2.5 cm in maximum diameter and, in the absence of either deep venous drainage or eloquent location, patients with Spetzler-Ponce Class A bAVMs of all diameters. For patients with Class B bAVMs, this rate of favorable outcome can only be approached for lesions with a maximum diameter just above 6 cm or smaller and without deep venous drainage or eloquent location.

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Michael K. Morgan and Michael T. Biggs

✓ The case is presented of a 27-year-old man who developed a basilar artery bifurcation embolus encompassing Hilal microcoil as a complication following therapeutic embolization. An immediate direct surgical approach to the basilar artery bifurcation enabled the microcoil and associated thrombus to be removed and flow to be restored in the basilar artery and its distal branches. Postoperatively, the patient made a good recovery and on discharge was neurologically normal with the exception of a right third nerve palsy. This case suggests that in selected patients a direct surgical approach to the top of the basilar artery may be possible for treatment of emboli.

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Tor Ingebrigtsen, Michael K. Morgan, Ken Faulder, Linda Ingebrigtsen, Trygve Sparr and Henrik Schirmer

Object. The angles of arterial bifurcations are governed by principles of work minimization (optimality principle). This determines the relationship between the angle of a bifurcation and the radii of the vessels. Nevertheless, the model is predicated on an absence of significant communication between these branches. The circle of Willis changes this relationship because the vessels proximal to the ring of vessels have additional factors that determine work minimization compared with more distal branches. This must have an impact on understanding of the relationship between shear stress and aneurysm formation. The authors hypothesized that normal bifurcations of cerebral arteries beyond the circle of Willis would follow optimality principles of minimum work and that the presence of aneurysms would be associated with deviations from optimum bifurcation geometry. Nevertheless, the vessels participating in (or immediately proximal to) the circle of Willis may not follow the geometric model as it is generally applied and this must also be investigated.

Methods. One hundred seven bifurcations of the middle cerebral artery (MCA), distal internal carotid artery (ICA), and basilar artery (BA) were studied in 55 patients. The authors analyzed three-dimensional reconstructions of digital subtraction angiography images with respect to vessel radii and bifurcation angles. The junction exponent (that is, a calculated measure of the division of flow at the bifurcation) and the difference between the predicted optimal and observed branch angles were used as measures of deviation from the geometry thought best to minimize work.

The mean junction exponent for MCA bifurcations was 2.9 ± 1.2 (mean ± standard deviation [SD]), which is close to the theoretical optimum of 3, but it was significantly smaller (p < 0.001; 1.7 ± 0.8, mean ± SD) for distal ICA bifurcations. In a multilevel multivariate logistic regression analysis, only the observed branch angles were significant independent predictors for the presence of an aneurysm. The odds ratio (OR) (95% confidence interval) for the presence of an aneurysm was 3.46 (1.02–11.74) between the lowest and highest tertile of the observed angle between the parent vessel and the largest branch. The corresponding OR for the smallest branch was 48.06 (9.7–238.2).

Conclusions. The bifurcation beyond the circle of Willis (that is, the MCA) closely approximated optimality principles, whereas the bifurcations within the circle of Willis (that is, the distal ICA and BA) did not. This indicates that the confluence of hemodynamic forces plays an important role in the distribution of work at bifurcations within the circle of Willis. In addition, the observed branch angles were predictors for the presence of aneurysms.

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M. Sean Grady

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Michael K. Morgan, Burton M. Onofrio and Claire E. Bender

✓ A familial asymptomatic os odontoideum with a Klippel-Feil type II fusion of C-2 and C-3 is reported. The pattern of inheritance within this family is consistent with that of autosomal dominance. The index case, a 16-year-old boy, was studied with plain cervical spine x-ray films, lateral cervical tomography in flexion and extension, fluoroscopic evaluation of the subluxation, and magnetic resonance (MR) imaging of the spine in flexion and extension. In spite of the subluxation noted on flexion and extension, there was no evidence of cord compression on MR imaging. The etiology and management of this condition are discussed.