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OBJECTIVE Anatomical taxonomy is a practical tool to successfully guide clinical decision-making for patients with brain arteriovenous malformations and brainstem cavernous malformations (CMs). Deep cerebral CMs are complex, difficult to access, and highly variable in size, shape, and position. The authors propose a novel taxonomic system for deep CMs in the thalamus based on clinical presentation (syndromes) and anatomical location (identified on MRI). METHODS The taxonomic system was developed and applied to an extensive 2-surgeon experience from 2001 through 2019. Deep CMs involving the thalamus were identified. These CMs were subtyped on the basis of the predominant surface presentation identified on preoperative MRI. Six subtypes among 75 thalamic CMs were defined: anterior (7/75, 9%), medial (22/75, 29%), lateral (10/75, 13%), choroidal (9/75, 12%), pulvinar (19/75, 25%), and geniculate (8/75, 11%). Neurological outcomes were assessed using modified Rankin Scale (mRS) scores. A postoperative score ≤ 2 was defined as a favorable outcome and > 2 as a poor outcome. Clinical and surgical characteristics and neurological outcomes were compared among subtypes. RESULTS Seventy-five patients underwent resection of thalamic CMs and had clinical and radiological data available. Their mean age was 40.9 (SD 15.2) years. Each thalamic CM subtype was associated with a recognizable constellation of neurological symptoms. The common symptoms were severe or worsening headaches (30/75, 40%), hemiparesis (27/75, 36%), hemianesthesia (21/75, 28%), blurred vision (14/75, 19%), and hydrocephalus (9/75, 12%). The thalamic CM subtype determined the selection of surgical approach. A single approach was associated with each subtype for most patients. The main exception to this paradigm was that in the surgeons’ early experience, pulvinar CMs were resected through a superior parietal lobule–transatrial approach (4/19, 21%), which later evolved to the paramedian supracerebellar-infratentorial approach (12/19, 63%). Relative outcomes implied by mRS scores were unchanged or improved in most patients (61/66, 92%) postoperatively. CONCLUSIONS This study confirms the authors’ hypothesis that this taxonomy for thalamic CMs can meaningfully guide the selection of surgical approach and resection strategy. The proposed taxonomy can increase diagnostic acumen at the patient bedside, help identify optimal surgical approaches, enhance the clarity of clinical communications and publications, and improve patient outcomes.

The "weekend effect" is the negative effect on disease course and treatment resulting from being admitted to the hospital during a weekend. Whether the weekend effect is associated with worse outcomes for patients treated for aneurysmal subarachnoid hemorrhage (aSAH) is unknown. We assessed neurologic outcomes of patients with aSAH admitted during the weekend versus during the week.A retrospective database was reviewed to identify all patients with aSAH who received open or endovascular treatment from August 1, 2007, to July 31, 2019, at a quaternary center. The primary outcome was a poor neurologic outcome (modified Rankin Scale score2). Propensity adjustment included age, sex, treatment type, Hunt and Hess grade, and Charlson Comorbidity Index.A total of 1014 patients (women, 703 [69.3%]; men, 311 [30.7%]; mean age, 56 [standard deviation, 14]) met inclusion criteria; 726 (71.6%) had weekday admissions, and 288 (28.4%) had weekend admissions. There was no significant difference between patients with a weekday versus a weekend admission in mean (standard deviation) time to treatment (0.85 [1.29] vs. 0.93 [1.30] days, P = 0.10) or length of stay (19 [9] vs. 19 [9] days, P = 0.04). Total cost and rates of delayed cerebral ischemia and vasospasm were similar between the admission groups, both overall and within the open and endovascular treatment cohorts. After propensity adjustment, weekend admission was not a significant predictor of a modified Rankin Scale score greater than 2 (odds ratio [95% confidence interval]; 1.12 [0.85-1.49]; P = 0.4).No difference in neurologic outcomes was associated with weekend admission among this cohort of patients with aSAH.

OBJECTIVE Giant cerebral cavernous malformations (GCCMs) are rare vascular malformations. Unlike for tumors and aneurysms, there is no clear definition of a "giant" cavernous malformation (CM). As a result of variable definitions, working descriptions and outcome data of patients with GCCM are unclear. A new definition of GCCM related to surgical outcomes is needed. METHODS An institutional database was searched for all patients who underwent resection of CMs > 1 cm in diameter. Patient information, surgical technique, and clinical and radiographic outcomes were assessed. A systematic review was performed to augment an earlier published review. RESULTS In the authors’ institutional cohort of 183 patients with a large CM, 179 with preoperative and postoperative modified Rankin Scale (mRS) scores were analyzed. A maximum CM diameter of ≥ 3 cm was associated with greater risk of severe postoperative decline (≥ 2-point increase in mRS score). After adjustment for age and deep versus superficial location, size ≥ 3 cm was strongly predictive of severe postoperative decline (OR 4.5, 95% CI 1.2–16.9). A model with CM size and deep versus superficial location was developed to predict severe postoperative decline (area under the receiver operating characteristic curve 0.79). Thirteen more patients with GCCMs have been reported in the literature since the most recent systematic review, including some patients who were treated earlier and not discussed in the previous review. CONCLUSIONS The authors propose that cerebral CMs with a diameter ≥ 3 cm be defined as GCCMs on the basis of the inflection point for functional and neurological outcomes. This definition is in line with the definitions for other giant lesions. It is less exclusive than earlier definitions but captures the rarity of these lesions (approximately 1% incidence) and variation in outcomes. GCCMs remain operable with potentially favorable outcomes. The term "giant" is not meant to deter or contraindicate surgery.

Intramedullary spinal cord cavernous malformations (SCCMs) account for only 5% of overall cavernous malformations (CMs). The occurrence of recurrent or residual SCCMs has not been well discussed, nor have the technical nuances of resection.To assess the characteristics of residual SCCMs and surgical outcomes and describe the techniques to avoid leaving lesion remnants during primary resection.Demographic, radiologic, intraoperative findings and surgical outcomes data for a cohort of surgically managed intramedullary SCCMs were obtained from an institutional database and retrospectively analyzed. A systematic literature review was performed using PRISMA guidelines.Of 146 SCCM resections identified, 17 were for residual lesions (12%). Patients with residuals included 13 men and 4 women, with a mean age of 43 years (range 16-70). All patients with residual SCCMs had symptomatic presentations: sensory deficits, paraparesis, spasticity, and pain. Residuals occurred between 3 and 264 months after initial resection. Approaches for 136 cases included posterior midline myelotomy (28.7%, n = 39), pial surface entry (37.5%, n = 51), dorsal root entry zone (27.9%, n = 38), and lateral entry (5.9%, n = 8). Follow-up outcomes were similar for patients with primary and residual lesions, with the majority having no change in modified Rankin Scale score (63% [59/93] vs 75% [9/12], respectively, P = .98).SCCMs may cause significant symptoms. During primary resection, care should be taken to avoid leaving residual lesion remnants, which can lead to future hemorrhagic events and neurological morbidity. However, satisfactory results are achievable even with secondary or tertiary resections.

Dural arteriovenous fistulas (dAVFs) located at craniocervical junction are extremely rare (1%-2% of intracranial/spinal dAVFs). Their angio-architectural complexity renders endovascular embolization to be challenging given multiple small feeders with risk of embolysate reflux into vertebral artery and limited transvenous access. The available literature discussing microsurgery for these lesions is limited to few case reports.To report a multicenter experience assessing microsurgery safety/efficacy.Prospectively maintained registries at 13 North American centers were queried to identify craniocervical junction dAVFs treated with microsurgery (2006-2021).Thirty-eight patients (median age 59.5 years, 44.7% female patients) were included. The most common presentation was subarachnoid/intracranial hemorrhage (47.4%) and myelopathy (36.8%) (92.1% of lesions Cognard type III-V). Direct meningeal branches from V3/4 vertebral artery segments supplied 84.2% of lesions. All lesions failed (n = 5, 13.2%) or were deemed inaccessible/unsafe to endovascular treatment. Far lateral craniotomy was the most used approach (94.7%). Intraoperative angiogram was performed in 39.5% of the cases, with angiographic cure in 94.7% of cases (median imaging follow-up of 9.2 months) and retreatment rate of 5.3%. Favorable last follow-up modified Rankin Scale of 0 to 2 was recorded in 81.6% of the patients with procedural complications of 2.6%.Craniocervical dAVFs represent rare entity of lesions presenting most commonly with hemorrhage or myelopathy because of venous congestion. Microsurgery using a far lateral approach provides robust exposure and visualization for these lesions and allows obliteration of the arterialized draining vein intradurally as close as possible to the fistula point. This approach was associated with a high rate of angiographic cure and favorable clinical outcomes.

OBJECTIVE Part 2 of this 2-part series on pontine cavernomas presents the taxonomy for subtypes 4–6: inferior peduncular (IP) (subtype 4), rhomboid (5), and supraolivary (6). (Subtypes 1–3 are presented in Part 1.) The authors have proposed a novel taxonomy for pontine cavernous malformations based on clinical presentation (syndromes) and anatomical location (MRI findings). METHODS The details of taxonomy development are described fully in Part 1 of this series. In brief, pontine lesions (323 of 601 [53.7%] total lesions) were subtyped on the basis of predominant surface presentation identified on preoperative MRI. Neurological outcomes were assessed according to the modified Rankin Scale, with score ≤ 2 defined as favorable. RESULTS The 323 pontine brainstem cavernous malformations were classified into 6 distinct subtypes: basilar (6 [1.9%]), peritrigeminal (53 [16.4%]), middle peduncular (100 [31.0%]), IP (47 [14.6%]), rhomboid (80 [24.8%]), and supraolivary (37 [11.5%]). Subtypes 4–6 are the subject of the current report. IP lesions are located in the inferolateral pons and are associated with acute vestibular syndrome. Rhomboid lesions present to the fourth ventricle floor and are associated with disconjugate eye movements. Larger lesions may cause ipsilateral facial weakness. Supraolivary lesions present to the surface at the ventral pontine underbelly. Ipsilateral abducens palsy is a strong localizing sign for this subtype. A single surgical approach and strategy were preferred for subtypes 4–6: for IP cavernomas, the suboccipital craniotomy and telovelar approach predominated; for rhomboid lesions, the suboccipital craniotomy and transventricular approach were preferred; and for supraolivary malformations, the far lateral craniotomy and transpontomedullary sulcus approach were preferred. Favorable outcomes were observed in 132 of 150 (88%) patients with follow-up. There were no significant differences in outcomes between subtypes. CONCLUSIONS The neurological symptoms and signs associated with a hemorrhagic pontine subtype can help define that subtype clinically with key localizing signs. The proposed taxonomy for pontine cavernous malformation subtypes 4–6 meaningfully guides surgical strategy and may improve patient outcomes.

The additional hospital costs associated with delayed cerebral ischemia (DCI) have not been well investigated in prior literature. In this study, the total hospital cost of DCI in aneurysmal subarachnoid hemmorhage (aSAH) patients treated at a single quaternary center was analyzed.All patients in the Post-Barrow Ruptured Aneurysm Trial treated for an aSAH between January 1, 2014, and July 31, 2019, were retrospectively analyzed. DCI was defined as cerebral infarction identified on computed tomography, magnetic resonance imaging, or autopsy after exclusion of procedure-related infarctions. The primary outcome was the difference in total cost (including hospital, discharge facility, and all follow-up) using a propensity-adjusted analysis. Propensity score covariate-adjusted linear regression analysis included age, sex, open versus endovascular treatment, Hunt and Hess score, and Charlson Comorbidity Index score.Of the 391 patients included, 144 (37%) had DCI. Patients with DCI had a significantly greater cost compared to patients without DCI (mean standard deviation $112,081 [$54,022] vs. $86,159 [$38,817]; P 0.001) and a significantly greater length of stay (21 days [11] vs. 18 days [8], P = 0.003, respectively). In propensity-adjusted linear regression analysis, both DCI (odds ratio, $13,871; 95% confidence interval, $7558-$20,185; P 0.001) and length of stay (odds ratio, $3815 per day; 95% confidence interval, $3480-$4149 per day; P 0.001) were found to significantly increase the cost.The significantly higher costs associated with DCI further support the evidence that adverse effects associated with DCI in aSAH pose a significant burden to the health care system.

Liver cirrhosis is associated with an increased risk of aneurysmal subarachnoid hemorrhage (aSAH). However, large studies analyzing the prognosis of cirrhotic patients after aSAH treatment are lacking. This study explores factors associated with inpatient mortality among aSAH patients with cirrhosis.All patients who underwent open or endovascular treatment for an aSAH at a large quaternary center between January 1, 2003, and July 31, 2019, were retrospectively reviewed. Patients were grouped into cirrhosis versus noncirrhosis groups. Univariate analysis determined variables associated with inpatient mortality. Variables with P0.20 were included in a propensity-adjusted multivariable logistic regression analysis to predict inpatient mortality.A total of 1419 patients were treated for aSAH; 17 (1.2%) had confirmed cirrhosis. Inpatient mortality was significantly higher among cirrhotic patients than noncirrhotic patients (35.3% vs. 6.8%; P0.001). In the univariate analysis for inpatient mortality, the variables cirrhosis, age65 years, Charlson Comorbidity Index4, aneurysm size ≥10 mm, Hunt and Hess grade3, Fisher grade 4, delayed cerebral ischemia (DCI), and posterior circulation aneurysm had P0.20 and were included in the multivariable analysis. The propensity-adjusted stepwise multivariable logistic regression analysis showed that cirrhosis (odds ratio [OR]: 12.7, 95% confidence interval [CI]: 3.3-48.7), Hunt and Hess grade3 (OR: 3.9, 95% CI: 2.3-6.4), Fisher grade 4 (OR: 3.7, 95% CI: 1.3-10.7), and DCI (OR: 2.4, 95% CI: 1.5-3.9) were associated with inpatient mortality (P ≤ 0.01).Cirrhosis was a predictor of inpatient mortality among aSAH patients and was a stronger predictor than DCI or a poor Hunt and Hess grade among patients in this study.

OBJECTIVE Safe entry zones (SEZs) enable safe tissue transgression to lesions beneath the brainstem surface. However, evidence for the safety of SEZs is scarce and is based on anatomical studies, case reports, and small series. METHODS A cohort of 154 patients who underwent microsurgical brainstem cavernous malformation (BSCM) treatment during a 23-year period and who had preoperative MR images and intraoperative photographs or videos was retrospectively examined. This study assessed the safety of SEZs for access to deep BSCMs, preoperative MRI to predict BSCM surface proximity, and the relationships between BSCM subtype, surgical approach, and SEZs. Lesions were characterized as exophytic, superficial, or deep on the basis of preoperative MRI and intraoperative inspection. Outcomes were scored as good (modified Rankin Scale [mRS] score ≤ 2) or poor (mRS score > 2) and relative outcomes as stable/improved or worse relative to baseline (± 1 point). RESULTS Resections included 34 (22%) in the midbrain, 102 (66%) in the pons, and 18 (12%) in the medulla. Of those, 23 (15%) were exophytic, 57 (37%) were superficial, and 74 (48%) were deep. Established SEZs were used for 97% (n = 72) of deep lesions; the preferred SEZ associated with its subtype was used for 91% (n = 67). MR images accurately depicted exophytic BSCMs that did not require SEZ approaches (sensitivity, 96%) but overestimated the proximity of lesions superficial to brainstem surfaces (specificity, 67%), resulting in unanticipated SEZ use. Final neurological outcomes were good in 80% of patients with follow-up data (119/149), and relative outcomes were stable/improved in 93% (139/149). Outcomes for patients with brainstem transgression through an SEZ did not differ from outcomes for patients with superficial or exophytic lesions that did not require SEZ use (final mRS score ≤ 2 in 72% of all patients with deep lesions vs 82% of all patients with superficial or exophytic lesions [p = 0.10]). Among patients with follow-up, the rates of permanent new cranial nerve deficits in patients with deep BSCMs and superficial or exophytic BSCMs were 21% and 20%, respectively (p = 0.81), with no significant change in overall cranial nerve deficit (0 and −1, p = 0.65). CONCLUSIONS Neurological outcomes for patients with deep BSCMs were equivalent to those for superficial or exophytic BSCMs, validating the safety of SEZs for deep BSCMs. Preoperative T1-weighted MR images overestimated the lesion’s surface proximity, necessitating detailed knowledge of SEZs and readiness to use them in cases of radiological-microsurgical discordance. Most patients achieved favorable outcomes despite the transgression of eloquent brainstem tissue in and around SEZs.

OBJECTIVE Brainstem cavernous malformations (BSCMs) are complex, difficult to access, and highly variable in size, shape, and position. The authors have proposed a novel taxonomy for pontine cavernous malformations (CMs) based upon clinical presentation (syndromes) and anatomical location (findings on MRI). METHODS The proposed taxonomy was applied to a 30-year (1990–2019), 2-surgeon experience. Of 601 patients who underwent microsurgical resection of BSCMs, 551 with appropriate data were classified on the basis of BSCM location: midbrain (151 [27%]), pons (323 [59%]), and medulla (77 [14%]). Pontine lesions were then subtyped on the basis of their predominant surface presentation identified on preoperative MRI. Neurological outcomes were assessed according to the modified Rankin Scale, with a score ≤ 2 defined as favorable. RESULTS The 323 pontine BSCMs were classified into 6 distinct subtypes: basilar (6 [1.9%]), peritrigeminal (53 [16.4%]), middle peduncular (MP) (100 [31.0%]), inferior peduncular (47 [14.6%]), rhomboid (80 [24.8%]), and supraolivary (37 [11.5%]). Part 1 of this 2-part series describes the taxonomic basis for the first 3 of these 6 subtypes of pontine CM. Basilar lesions are located in the anteromedial pons and associated with contralateral hemiparesis. Peritrigeminal lesions are located in the anterolateral pons and are associated with hemiparesis and sensory changes. Patients with MP lesions presented with mild anterior inferior cerebellar artery syndrome with contralateral hemisensory loss, ipsilateral ataxia, and ipsilateral facial numbness without cranial neuropathies. A single surgical approach and strategy were preferred for each subtype: for basilar lesions, the pterional craniotomy and anterior transpetrous approach was preferred; for peritrigeminal lesions, extended retrosigmoid craniotomy and transcerebellopontine angle approach; and for MP lesions, extended retrosigmoid craniotomy and trans–middle cerebellar peduncle approach. Favorable outcomes were observed in 123 of 143 (86%) patients with follow-up data. There were no significant differences in outcomes between the 3 subtypes or any other subtypes. CONCLUSIONS The neurological symptoms and key localizing signs associated with a hemorrhagic pontine subtype can help to define that subtype clinically. The proposed taxonomy for pontine CMs meaningfully guides surgical strategy and may improve patient outcomes.

OBJECTIVE Vertebrobasilar dissecting (VBD) aneurysms are rare, and patients with these aneurysms often present with thromboembolic infarcts or subarachnoid hemorrhage (SAH). The morphological nature of VBD aneurysms often precludes conventional clip reconstruction or coil placement and encourages parent artery exclusion or endovascular stenting. Treatment considerations include aneurysm location along the vertebral artery (VA), the involvement of the posterior inferior cerebellar artery (PICA), and collateral blood flow. Outcomes after endovascular treatment have been well described in the neurosurgical literature, but microsurgical outcomes have not been detailed. Patient outcomes from a large, single-surgeon, consecutive series of microsurgically managed VBD aneurysms are presented, and 3 illustrative case examples are provided. METHODS The medical records of patients with dissecting aneurysms affecting the intracranial VA (V4), basilar artery, and PICA that were treated microsurgically over a 19-year period were reviewed. Patient demographics, aneurysm characteristics, surgical procedures, and clinical outcomes (according to modified Rankin Scale [mRS] scores at last follow-up) were analyzed. RESULTS Forty-two patients with 42 VBD aneurysms were identified. Twenty-six aneurysms (62%) involved the PICA, 14 (33%) were distinct from the PICA origin on the V4 segment of the VA, and 2 (5%) were located at the vertebrobasilar junction. Thirty-four patients (81%) presented with SAH with a mean Hunt and Hess grade of 3.2 at presentation. Six (14%) of the 42 patients had been previously treated using endovascular techniques. Nineteen aneurysms (45%) underwent clip wrapping, 17 (40%) were treated with bypass trapping, and 6 (14%) underwent parent artery sacrifice. The complete aneurysm obliteration rate was 95% (n = 40), and the surgical complication rate was 7% (n = 3). The 8 patients with unruptured VBD aneurysms were significantly more likely to be discharged home (n = 6, 75%) compared with 34 patients with ruptured aneurysms (n = 9, 27%; p = 0.01). Good outcomes (mRS score ≤ 2) were observed in 20 patients (48%). Eight patients (19%) died. CONCLUSIONS These data demonstrate that patients with VBD aneurysms often present after a rupture in poor neurological condition, but favorable results can be achieved with open microsurgical repair in almost half of such cases. Microsurgery remains a viable treatment option, with the choice between bypass trapping and clip wrapping largely dictated by the specific location of the aneurysm and its relationship to the PICA.

OBJECTIVE The Barrow Ruptured Aneurysm Trial (BRAT) was a single-center trial that compared endovascular coiling to microsurgical clipping in patients treated for aneurysmal subarachnoid hemorrhage (aSAH). However, because patients in the BRAT were treated more than 15 years ago, and because there have been advances since then—particularly in endovascular techniques—the relevance of the BRAT today remains controversial. Some hypothesize that these technical advances may reduce retreatment rates for endovascular intervention. In this study, the authors analyzed data for the post-BRAT (PBRAT) era to compare microsurgical clipping with endovascular embolization (coiling and flow diverters) in the two time periods and to examine how the results of the original BRAT have influenced the practice of neurosurgeons at the study institution. METHODS In this retrospective cohort study, the authors evaluated patients with saccular aSAHs who were treated at a single quaternary center from August 1, 2007, to July 31, 2019. The saccular aSAH diagnoses were confirmed by cerebrovascular experts. Patients were separated into two cohorts for comparison on the basis of having undergone microsurgery or endovascular intervention. The primary outcome analyzed for comparison was poor neurological outcome, defined as a modified Rankin Scale (mRS) score > 2. The secondary outcomes that were compared included retreatment rates for both therapies. RESULTS Of the 1014 patients with aSAH during the study period, 798 (79%) were confirmed to have saccular aneurysms. Neurological outcomes at ≥ 1-year follow-up did not differ between patients treated with microsurgery (n = 451) and those who received endovascular (n = 347) treatment (p = 0.51). The number of retreatments was significantly higher among patients treated endovascularly (32/347, 9%) than among patients treated microsurgically (6/451, 1%) (p < 0.001). The retreatment rate after endovascular treatment was lower in the PBRAT era (9%) than in the BRAT (18%). CONCLUSIONS Similar to results from the BRAT, results from the PBRAT era showed equivalent neurological outcomes and increased rates of retreatment among patients undergoing endovascular embolization compared with those undergoing microsurgery. However, the rate of retreatment after endovascular intervention was much lower in the PBRAT era than in the BRAT.

Background Longitudinal mouse models of brain arteriovenous malformations (AVMs) are crucial for developing novel therapeutics and pathobiological mechanism discovery underlying brain AVM progression and rupture. The sustainability of existing mouse models is limited by ubiquitous Cre activation, which is associated with lethal hemorrhages resulting from AVM formation in visceral organs. To overcome this condition, we developed a novel experimental mouse model of hereditary hemorrhagic telangiectasia (HHT) with CreER-mediated specific, localized induction of brain AVMs. Methods Hydroxytamoxifen (4-OHT) was stereotactically delivered into the striatum, parietal cortex, or cerebellum of R26CreER; Alk12f/2f (Alk1-iKO) littermates. Mice were evaluated for vascular malformations with latex dye perfusion and 3D time-of-flight magnetic resonance angiography (MRA). Immunofluorescence and Prussian blue staining were performed for vascular lesion characterization. Results Our model produced two types of brain vascular malformations, including nidal AVMs (88%, 38/43) and arteriovenous fistulas (12%, 5/43), with an overall frequency of 73% (43/59). By performing stereotaxic injection of 4-OHT targeting different brain regions, Alk1-iKO mice developed vascular malformations in the striatum (73%, 22/30), in the parietal cortex (76%, 13/17), and in the cerebellum (67%, 8/12). Identical application of the stereotaxic injection protocol in reporter mice confirmed localized Cre activity near the injection site. The 4-week mortality was 3% (2/61). Seven mice were studied longitudinally for a mean (SD; range) duration of 7.2 (3; 2.3−9.5) months and demonstrated nidal stability on sequential MRA. The brain AVMs displayed microhemorrhages and diffuse immune cell invasion. Conclusions We present the first HHT mouse model of brain AVMs that produces localized AVMs in the brain. The mouse lesions closely resemble the human lesions for complex nidal angioarchitecture, arteriovenous shunts, microhemorrhages, and inflammation. The model’s longitudinal robustness is a powerful discovery resource to advance our pathomechanistic understanding of brain AVMs and identify novel therapeutic targets.

In this review, we describe the pathophysiology, diagnosis, and treatment of spinal dorsal intradural arteriovenous fistulae (DI-AVFs), focusing on novel research areas. DI-AVFs compose the most common subgroup of spinal arteriovenous lesions and most commonly involve the thoracic spine, followed by lumbar and sacral segments. The pathogenesis underlying DI-AVFs is an area of emerging understanding, thought to be attributable to venous congestion and hypertension that precipitate ascending myelopathy. Patients with DI-AVFs typically present with motor, sensory, or urinary dysfunction, although a wide swath of other less common symptoms has been reported. DI-AVFs can be subdivided by spinal region, which in turn is associated with 4 distinct clinical phenotypes: craniocervical junction (CCJ), subaxial cervical, thoracic, and lumbosacral. Patients with CCJ and lumbosacral DI-AVFs have particularly interesting presentations and treatment considerations. High-value diagnostic findings on magnetic resonance imaging include flow voids, missing-piece sign, and T2-weighted intramedullary hyperintensity. However, digital subtraction angiography is the gold standard for diagnosis and localization of DI-AVFs, as well as for definitive treatment planning. Surgical disconnection of DI-AVFs is almost universally curative and frontline treatment especially for CCJ and lumbosacral DI-AVFs. Endovascular techniques evolve in promising ways, such as improved visualization, distal access, and liquid embolic techniques. The pathophysiology of DI-AVFs is better understood using newly identified radiological diagnostic markers. Despite new techniques and devices introduced in the endovascular field, surgery remains the gold-standard treatment for DI-AVFs.

In specialized neurosurgical centers, open microsurgery is routinely performed for aneurysmal subarachnoid hemorrhage (aSAH).To compare the cost of endovascular vs microsurgical treatment for aSAH at a single quaternary center.All patients undergoing aSAH treatment from July 1, 2014, to July 31, 2019, were retrospectively reviewed. Patients were grouped based on primary treatment (microsurgery vs endovascular treatment). The primary outcome was the difference in total cost (including hospital, discharge facility, and all follow-up) using a propensity-adjusted analysis.Of 384 patients treated for an aSAH, 234 (61%) were microsurgically treated and 150 (39%) were endovascularly treated. The mean cost of index hospitalization for these patients was marginally higher ($9504) for endovascularly treated patients ($103 980) than for microsurgically treated patients ($94 476) ( P = .047). For the subset of patients with follow-up data available, the mean total cost was $45 040 higher for endovascularly treated patients ($159 406, n = 59) than that for microsurgically treated patients ($114 366, n = 105) ( P.001). After propensity scoring (adjusted for age, sex, comorbidities, Glasgow Coma Scale score, Hunt and Hess grade, Fisher grade, aneurysms, and type/size/location), linear regression analysis of patients with follow-up data available revealed that microsurgery was independently associated with healthcare costs that were $37 244 less than endovascular treatment costs ( P.001). An itemized cost analysis suggested that this discrepancy was due to differences in the rates of aneurysm retreatment and long-term surveillance.Microsurgical treatment for aSAH is associated with lower total healthcare costs than endovascular therapy. Aneurysm surveillance after endovascular treatments, retreatment, and device costs warrants attention in future studies.

Intraoperative neuromonitoring (IONM) is useful during spinal cord operations, but whether IONM is necessary for posterior cervical surgeries for degenerative conditions is unknown. We evaluated the utility of somatosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring as a tool for predicting new postoperative neurologic deficits during posterior decompression and fusion for degenerative cervical spine conditions.We retrospectively reviewed posterior cervical operations performed at our institute over a 4-year period. Patients with postoperative neurologic deficits were identified, and a detailed analysis performed to ascertain whether SSEP or MEP monitoring accurately predicted the onset of new postoperative deficits.Overall, 498 patients were included in the analysis (median age 66 years; range: 22-93 years). SSEP monitoring was performed in all patients, and both SSEP and MEP monitoring were performed in 121 patients (24%). Twenty-one patients (4.2%) had new postoperative neurologic deficits. SSEP had significantly higher specificity (90%) but lower sensitivity (33%) than MEP (74% specificity [P = 0.008], 50% sensitivity [P = 0.01]) for detecting neurologic compromise intraoperatively. For SSEP, the positive predictive value (PPV) and negative predictive value (NPV) in detecting intraoperative changes that translated to new postoperative neurological deficits were 12% and 97%, respectively, whereas for MEP, the PPV and NPV were 6% (P = 0.009) and 98% (P = 0.20), respectively.IONM during posterior cervical operations for degenerative conditions of the spine is not reliable at predicting new postoperative neurologic deficits in patients treated for degenerative conditions, but may provide peace of mind to the surgeon intraoperatively when no abnormalities are detected.

OBJECTIVE Anatomical taxonomy is a practical tool that has successfully guided clinical decision-making for patients with brain arteriovenous malformations. Brainstem cavernous malformations (BSCMs) are similarly complex lesions that are difficult to access and highly variable in size, shape, and position. The authors propose a novel taxonomy for midbrain cavernous malformations based on clinical presentation (syndromes) and anatomical location (identified with MRI). METHODS The taxonomy system was developed and applied to an extensive 2-surgeon experience over a 30-year period (1990–2019). Of 551 patients with appropriate data who underwent microsurgical resection of BSCMs, 151 (27.4%) had midbrain lesions. These lesions were further subtyped on the basis of predominant surface presentation identified on preoperative MRI. Five distinct subtypes of midbrain BSCMs were defined: interpeduncular (7 lesions [4.6%]), peduncular (37 [24.5%]), tegmental (73 [48.3%]), quadrigeminal (27 [17.9%]), and periaqueductal (7 [4.6%]). Neurological outcomes were assessed using modified Rankin Scale (mRS) scores. A postoperative score ≤ 2 was defined as a favorable outcome; a score > 2 was defined as a poor outcome. Clinical and surgical characteristics and neurological outcomes were compared among subtypes. RESULTS Each midbrain BSCM subtype was associated with a recognizable constellation of neurological symptoms. Patients with interpeduncular lesions commonly presented with ipsilateral oculomotor nerve palsy and contralateral cerebellar ataxia or dyscoordination. Peduncular lesions were associated with contralateral hemiparesis and ipsilateral oculomotor nerve palsy. Patients with tegmental lesions were the most likely to present with contralateral sensory deficits, whereas those with quadrigeminal lesions commonly presented with the features of Parinaud syndrome. Periaqueductal lesions were the most likely to cause obstructive hydrocephalus. A single surgical approach was preferred (> 90% of cases) for each midbrain subtype: interpeduncular (transsylvian-interpeduncular approach [7/7 lesions]), peduncular (transsylvian-transpeduncular [24/37]), tegmental (lateral supracerebellar-infratentorial [73/73]), quadrigeminal (midline or paramedian supracerebellar-infratentorial [27/27]), and periaqueductal (transcallosal-transchoroidal fissure [6/7]). Favorable outcomes (mRS score ≤ 2) were observed in most patients (110/136 [80.9%]) with follow-up data. No significant differences in outcomes were observed between subtypes (p = 0.92). CONCLUSIONS The study confirmed the authors’ hypothesis that taxonomy for midbrain BSCMs can meaningfully guide the selection of surgical approach and resection strategy. The proposed taxonomy can increase diagnostic acumen at the patient bedside, help identify optimal surgical approaches, enhance the consistency of clinical communications and publications, and improve patient outcomes.

Dural arteriovenous fistulas (DAVFs) of the sphenoparietal sinus or sphenoid wing region are uncommon lesions with unique and interesting angioarchitecture. Understanding appropriate anatomy and recognizing patterns provide important treatment implications.To describe a single surgeon's experience with open surgical treatment of sphenoparietal sinus DAVFs, the surgical indications for this uncommon lesion, and the microsurgical techniques related to its treatment and to review the literature on its surgical treatment.Consecutive cases of sphenoparietal sinus DAVF treatment conducted by a single surgeon over 24 years (1997-2020) were retrospectively reviewed. Published reports of similar cases were reviewed.Of 202 surgically treated DAVFs, 10 lesions in 10 patients were sphenoparietal sinus DAVFs. Four patients presented with intracranial hemorrhage, 3 with headache, and 2 with pulsatile tinnitus; 1 patient was incidentally identified as having a DAVF during treatment for a ruptured aneurysm. Most patients (7 of 10) had undergone endovascular embolization previously. Nine patients had Borden type III DAVFs and one had a Borden type II fistula. Surgery in all 10 patients resulted in angiographically confirmed fistula obliteration. Clinical outcomes at the last follow-up, measured by a modified Rankin Scale (mRS) score, were excellent in 6 patients (mRS ≤ 2) and poor in 1 patient (mRS ≥ 3); late outcomes were not available for 3 patients.Sphenoparietal sinus DAVFs are an uncommon anatomic subtype. Careful attention to angiographic detail leads to identification of the site of venous interruption and results in a high rate of surgical cure with excellent clinical outcomes.

OBJECTIVE Ophthalmic artery (OA) aneurysms are surgically challenging lesions that are now mostly treated using endovascular procedures. However, in specialized tertiary care centers with experienced neurosurgeons, controversy remains regarding the optimal treatment of these lesions. This study used propensity adjustment to compare microsurgical and endovascular treatment of unruptured OA aneurysms in experienced tertiary and quaternary settings. METHODS The authors retrospectively reviewed the medical records of all patients who underwent microsurgical treatment of an unruptured OA aneurysm at the University of California, San Francisco, from 1997 to 2017 and either microsurgical or endovascular treatment at Barrow Neurological Institute from 2011 to 2019. Patients were categorized into two cohorts for comparison: those who underwent open microsurgical clipping, and those who underwent endovascular flow diversion or coil embolization. Outcomes included neurological or visual outcomes, residual or recurrent aneurysms, retreatment, and severe complications. RESULTS A total of 345 procedures were analyzed: 247 open microsurgical clipping procedures (72%) and 98 endovascular procedures (28%). Of the 98 endovascular procedures, 16 (16%) were treated with primary coil embolization and 82 (84%) with flow diversion. After propensity adjustment, microsurgical treatment was associated with higher odds of a visual deficit (OR 8.5, 95% CI 1.1–64.9, p = 0.04) but lower odds of residual aneurysm (OR 0.06, 95% CI 0.01–0.28, p < 0.001) or retreatment (OR 0.12, 95% CI 0.02–0.58, p = 0.008) than endovascular therapy. No difference was found between the two cohorts with regard to worse modified Rankin Scale score, modified Rankin Scale score greater than 2, or severe complications. CONCLUSIONS Compared with endovascular therapy, microsurgical clipping of unruptured OA aneurysms is associated with a higher rate of visual deficits but a lower rate of residual and recurrent aneurysms. In centers experienced with both open microsurgical and endovascular treatment of these lesions, the treatment choice should be based on patient preference and aneurysm morphology.

The Woven EndoBridge (WEB) device (Terumno Corp. [parent company of Microvention]) was approved by the U.S. Food and Drug Administration as the first intrasaccular device for intracranial aneurysm treatment in December 2018. Its use has become more common since then, but both trial results and postmarket experiences have raised questions about the efficacy in achieving complete aneurysm obliteration. Retreatment after WEB embolization has not been extensively discussed. OBJECTIVE: To discuss the incidence and retreatment of aneurysms after initial WEB embolization. METHODS: Retrospective review across 13 institutions identified all occurrences of WEB retreatment within neurovascular databases. Details regarding demographics, aneurysm characteristics, treatment considerations, clinical outcomes, and aneurysm occlusion were obtained and analyzed. RESULTS: Thirty aneurysms were retreated in 30 patients in a cohort of 342 WEB-treated aneurysms. The retreatment rate was 8.8%. Endovascular methods were used for 23 cases, and 7 were treated surgically. Two aneurysms presented with rehemorrhage after initial WEB embolization. Endovascular treatments included stent-assisted coiling (12), flow diversion (7), coiling (2), PulseRider (Johnson & Johnson)–assisted coiling (1), and additional WEB placement (1). Surgical treatments included primary clipping (6) and Hunterian ligation (1). There were no major complications within the study group. CONCLUSION: WEB retreatments were successfully performed by a variety of techniques, including stent-assisted coiling, clipping, and flow diversion as the most common. These procedures were performed safely with subsequent obliteration of most aneurysms. The potential need for retreatment of aneurysms should be considered during primary WEB treatments.

Despite advances in endovascular techniques, microsurgery continues to play an important role in the treatment of cerebral aneurysms. This article reviews the history of surgical treatment of intracranial aneurysms and the evolving role of microsurgery in the endovascular era. Although endovascular tools and techniques have changed significantly since the placement of the first Guglielmi coils in 1990, with the development of endoluminal flow-diverting stents and now endosaccular flow-diverting devices, microsurgical treatment of aneurysms has also continued to evolve. Since the first treatment with Hunterian ligation by Horsley in the 1800s, surgical treatment of intracranial aneurysms has advanced significantly beginning with the introduction of the microscope and microsurgical techniques in the 1950s. More recent advances in microsurgical treatment of aneurysms include microsurgical adjuncts, such as indocyanine green angiography, adenosine, and the exoscope, as well as tailored craniotomies, retractorless surgery, and novel bypass constructs for complex aneurysms. Microsurgery continues to play an important role in the endovascular era.