Ana Rodríguez-Hernández

Cerebellar Arteriovenous Malformations: Anatomic Subtypes, Surgical Results, and Increased Predictive Accuracy of the Supplementary Grading System

BACKGROUND Anatomic diversity among cerebellar arteriovenous malformations (AVMs) calls for a classification that is intuitive and surgically informative. Selection tools like the Spetzler-Martin grading system are designed to work best with cerebral AVMs but have shortcomings with cerebellar AVMs. OBJECTIVE To define subtypes of cerebellar AVMs that clarify anatomy and surgical management, to determine results according to subtypes, and to compare predictive accuracies of the Spetzler-Martin and supplementary systems. METHODS From a consecutive surgical series of 500 patients, 60 had cerebellar AVMs, 39 had brainstem AVMs and were excluded, and 401 had cerebral AVMs. RESULTS Cerebellar AVM subtypes were as follows: 18 vermian, 13 suboccipital, 12 tentorial, 12 petrosal, and 5 tonsillar. Patients with tonsillar and tentorial AVMs fared best. Cerebellar AVMs presented with hemorrhage more than cerebral AVMs (P < .001). Cerebellar AVMs were more likely to drain deep (P = .04) and less likely to be eloquent (P < .001). The predictive accuracy of the supplementary grade was better than that of the Spetzler-Martin grade with cerebellar AVMs (areas under the receiver-operating characteristic curve, 0.74 and 0.59, respectively). The predictive accuracy of the supplementary system was consistent for cerebral and cerebellar AVMs, whereas that of the Spetzler-Martin system was greater with cerebral AVMs. CONCLUSION Patients with cerebellar AVMs present with hemorrhage more often than patients with cerebral AVMs, justifying an aggressive treatment posture. The supplementary system is better than the Spetzler-Martin system at predicting outcomes after cerebellar AVM resection. Key components of the Spetzler-Martin system such as venous drainage and eloquence are distorted by cerebellar anatomy in ways that components of the supplementary system are not.

Distal Aneurysms of Intracranial Arteries: Application of Numerical Nomenclature, Predilection for Cerebellar Arteries, and Results of Surgical Management

BACKGROUND Distal intracranial aneurysms are rare, have unclear origins, and are frequently nonsaccular. Published clinical experience with these aneurysms is limited. OBJECTIVE To examine differences between distal aneurysms of cerebral and cerebellar arteries and to examine results associated with surgical therapy in 140 patients. METHODS Distal aneurysms in the cerebral arteries were defined as outside the circle of Willis, on or beyond the A2 anterior cerebral artery, M2 middle cerebral artery, or P2 posterior cerebral segments. Distal aneurysms in the cerebellar arteries were on or beyond the s2 superior cerebellar artery, a2 anterior inferior cerebellar artery, or p2 posterior inferior cerebellar artery segments. Clinical data, microsurgical technique, and patient outcomes were reviewed. RESULTS The incidence of distal cerebellar artery aneurysms was 4.3 times greater than distal cerebral artery aneurysms (6.5% vs. 28.6%; P< 0.01). The A3 anterior cerebral artery segment and the p2 and p3 posterior inferior cerebellar artery segments were the most common sites. Presentation with aneurysm rupture was more frequent with cerebellar aneurysms (65% vs. 40%; P< 0.05). Distal cerebellar artery aneurysms were less likely than distal cerebral artery aneurysms to be clipable (40% vs. 72%; P< 0.01), with 42% treated with trapping alone. Overall, 14% required a bypass. CONCLUSIONS Distal intracranial aneurysms have a predilection for cerebellar arteries and are not as rare as the literature suggests. Application of standardized nomenclature for segmental anatomy to these lesions will increase the precision of anatomic description and clarity of clinical discourse. Although technically difficult, good clinical results can be expected with surgical management.

Segmental anatomy of cerebellar arteries: a proposed nomenclature. Laboratory investigation.

OBJECT The conceptual division of intracranial arteries into segments provides a better understanding of their courses and a useful working vocabulary. Segmental anatomy of cerebral arteries is commonly cited by a numerical nomenclature, but an analogous nomenclature for cerebellar arteries has not been described. In this report, the microsurgical anatomy of the cerebellar arteries is reviewed, and a numbering system for cerebellar arteries is proposed. METHODS Cerebellar arteries were designated by the first letter of the arterys name in lowercase letters, distinguishing them from cerebral arteries with the same first letter of the arterys name. Segmental anatomy was numbered in ascending order from proximal to distal segments. RESULTS The superior cerebellar artery was divided into 4 segments: s(1), anterior pontomesencephalic segment; s(2), lateral pontomesencephalic segment; s(3), cerebellomesencephalic segment; and s(4), cortical segment. The anterior inferior cerebellar artery was divided into 4 segments: a(1), anterior pontine segment; a(2), lateral pontine segment; a(3), flocculopeduncular segment; and a(4), cortical segment. The posterior inferior cerebellar artery was divided into 5 segments: p(1), anterior medullary segment; p(2), lateral medullary segment; p(3), tonsillomedullary segment; p(4), telovelotonsillar segment; and p(5), cortical segment. CONCLUSIONS The proposed nomenclature for segmental anatomy of cerebellar artery complements established nomenclature for segmental anatomy of cerebral arteries. This nomenclature is simple, easy to learn, and practical. The nomenclature localizes distal cerebellar artery aneurysms and also localizes an anastomosis or describes a grafts connections to donor and recipient arteries. These applications of the proposed nomenclature with cerebellar arteries mimic the applications of the established nomenclature with cerebral arteries.

Anatomical triangles defining surgical routes to posterior inferior cerebellar artery aneurysms

OBJECT Surgical routes to posterior inferior cerebellar artery (PICA) aneurysms are opened between the vagus (cranial nerve [CN] X), accessory (CN XI), and hypoglossal (CN XII) nerves for safe clipping, but these routes have not been systematically defined. The authors describe 3 anatomical triangles and their relationships with PICA aneurysms, routes for surgical clipping, outcomes, and angiographically demonstrated anatomy. METHODS The vagoaccesory triangle is defined by CN X superiorly, CN XI laterally, and the medulla medially. It is divided by CN XII into the suprahypoglossal triangle (above CN XII) and the infrahypoglossal triangle (below CN XII). From a consecutive surgical series of 71 PICA aneurysms in 70 patients, 51 aneurysms were analyzed using intraoperative photographs. RESULTS Forty-three PICA aneurysms were located inside the vagoaccessory triangle and 8 were outside. Of the aneurysms inside the vagoaccessory triangle, 22 (51%) were exposed through the suprahypoglossal triangle and 19 (44%) through the infrahypoglossal triangle; 2 were between triangles. The lesions were evenly distributed between the anterior medullary (16 aneurysms), lateral medullary (19 aneurysms), and tonsillomedullary zones (16 aneurysms). Neurological and CN morbidity linked to aneurysms in the suprahypoglossal triangle was similar to that associated with aneurysms in the infrahypoglossal triangle, but no morbidity was associated with PICA aneurysms outside the vagoaccessory triangle. A distal PICA origin on angiography localized the aneurysm to the suprahypoglossal triangle in 71% of patients, and distal PICA aneurysms were localized to the infrahypoglossal triangle or outside the vagoaccessory triangle in 78% of patients. CONCLUSIONS The anatomical triangles and zones clarify the borders of operative corridors to PICA aneurysms and define the depth of dissection through the CNs. Deep dissection to aneurysms in the anterior medullary zone traverses CNs X, XI, and XII, whereas shallow dissection to aneurysms in the lateral medullary zone traverses CNs X and XI. Posterior inferior cerebellar artery aneurysms outside the vagoaccessory triangle are frequently distal and superficial to the lower CNs, and associated surgical morbidity is minimal. Angiography may preoperatively localize a PICA aneurysms triangular anatomy based on the distal PICA origin or distal aneurysm location.

Flash fluorescence with indocyanine green videoangiography to identify the recipient artery for bypass with distal middle cerebral artery aneurysms: operative technique.

BACKGROUND: Distal middle cerebral artery (MCA) aneurysms frequently have nonsaccular morphology that necessitates trapping and bypass. Bypasses can be difficult because efferent arteries lie deep in the opercular cleft and may not be easily identifiable. OBJECTIVE: We introduce the “flash fluorescence” technique, which uses videoangiography with indocyanine green (ICG) dye to identify an appropriate recipient artery on the cortical surface for the bypass, enabling a more superficial and easier anastomosis. METHODS: Flash fluorescence requires 3 steps: (1) temporary clip occlusion of the involved afferent artery; (2) videoangiography demonstrating fluorescence in uninvolved arteries on the cortical surface; and (3) removal of the temporary clip with flash fluorescence in the involved efferent arteries on the cortical surface, thereby identifying a recipient. Alternatively, temporary clips can occlude uninvolved arteries, and videoangiography will demonstrate initial fluorescence in efferent arteries during temporary occlusion and flash fluorescence in uninvolved arteries during reperfusion. RESULTS: From a consecutive series of 604 MCA aneurysms treated microsurgically, 22 (3.6%) were distal aneurysms and 11 required a bypass. The flash fluorescence technique was used in 3 patients to select the recipient artery for 2 superficial temporal artery-to-MCA bypasses and 1 MCA-MCA bypass. The correct recipient was selected in all cases. CONCLUSION: The flash fluorescence technique provides quick, reliable localization of an appropriate recipient artery for bypass when revascularization is needed for a distal MCA aneurysm. This technique eliminates the need for extensive dissection of the efferent artery and enables a superficial recipient site that makes the anastomosis safer, faster, and less demanding. ABBREVIATIONS: ICG, indocyanine green MCA, middle cerebral artery STA, superficial temporal artery

Superior cerebellar artery-posterior cerebral artery bypass: in situ bypass for posterior cerebral artery revascularization.

Iatrogenic pseudoaneurysms are rare but serious complications of transsphenoidal surgery, and an iatrogenic pseudoaneurysm of the posterior cerebral artery (PCA) has been reported just once in the literature. The authors encountered such a case with a new P1 segment PCA pseudoaneurysm after endoscopic transsphenoidal resection of a pituitary adenoma. The aneurysm proved ideal for a novel intracranial-intracranial bypass in which the superior cerebellar artery (SCA) was used as an in situ donor artery to revascularize the recipient P2 segment. The bypass allowed aneurysm trapping without causing ischemic stroke or neurological morbidity. This case represents the first reported surgical treatment of an iatrogenic PCA pseudoaneurysm. Endovascular occlusion with coils was an option, but dolichoectatic morphology requires sacrifice of the P1 segment, with associated risks to the thalamoperforators and circumflex perforators. The SCA-PCA bypass was ideal because of low-flow demands. Like other in situ bypasses, it requires no dissection of extracranial arteries, no second incision for harvesting interposition grafts, and has a high likelihood of long-term patency. The SCA-PCA bypass is also applicable to fusiform SCA aneurysms requiring revascularization with trapping. This case demonstrates a dangerous complication that results from the limited view of the posterolateral surgical field through the endoscope and the imprecision of endoscopic instruments.

Contralateral clipping of middle cerebral artery aneurysms: rationale, indications, and surgical technique.

BACKGROUND: Contralateral clipping of middle cerebral artery (MCA) aneurysms seems dangerous and ill advised but could become an important technique because of the prevalence of MCA aneurysms, the limitations of endovascular therapy, and increasing interest in less invasive techniques. OBJECTIVE: To define patient selection, surgical technique, and results with contralateral MCA aneurysm clipping. METHODS: Forty-two patients with bilateral MCA aneurysms were treated either in 1 stage with a single craniotomy and contralateral aneurysm clipping (group 1, 11 patients) or in 2 stages with bilateral craniotomy (group 2, 31 patients). Surgical technique consisted of ipsilateral sylvian fissure split, subfrontal dissection, contralateral sylvian fissure split, mobilization of medial orbital gyrus, and contralateral aneurysm clipping. RESULTS: Group 1 patients were older than group 2 patients (60.3 vs 55.4 years, respectively). Clinical presentation with subarachnoid hemorrhage was less common in group 1. Nine group 1 patients (82%) had left-sided craniotomies, and the ipsilateral aneurysm was larger than the contralateral aneurysm. All aneurysms were clipped without intraoperative complications (136 aneurysms). Mean neurosurgical charges were decreased by contralateral MCA aneurysm clipping:

Aneurysms associated with non-moyamoya collateral arterial networks: report of three cases and review of literature

39 297 in group 1 vs

Bypass for the Prevention of Ischemic Stroke

57 977 in group 2. CONCLUSION: Contralateral MCA aneurysm clipping can be viewed as an extreme microsurgical technique or as a less invasive technique that spares patients a second craniotomy in the management of bilateral aneurysms. This technique is acceptable in selected patients with contralateral aneurysms that are unruptured, have simple necks, project inferiorly or anteriorly, are associated with short M1 segments, and reside in older patients with sylvian fissures widened by brain atrophy. ABBREVIATIONS: ACA, anterior cerebral artery ICA, internal carotid artery MCA, middle cerebral artery mRS, modified Rankin Scale

Rescue Bypass for Revascularization After Ischemic Complications in the Treatment of Giant or Complex Intracranial Aneurysms

IntroductionMoyamoya disease is characterized by the gradualocclusion of distal internal carotid artery and thedevelopment of a collateral network of arteries torevascularize middle and anterior cerebral artery territo-ries. Similar collateral networks have also been describedin response to other occlusive vasculopathies differentfrom moyamoya disease. Rarely, aneurysms can formwithin these non-moyamoya collateral networks andpresent with hemorrhage. Overall, 12 cases of non-moyamoya occlusions revascularized by collateral arterialnetworks with an associated aneurysm have beenreported [1, 3–6, 9–14]. We report a case of a middlecerebral artery (MCA) occlusion with a collateral networkaneurysm. We also report two cases of aneurysm within acollateral arterial network arising from distal posteriorinferior cerebellar artery (PICA), which have not previ-ously been described. We present our management strategyand results in these three cases.Case reportsCase 1History and examinationA previously healthy 52-year-old man awoke with a severeright-sided headache, left-sided weakness, and difficultyambulating. His past medical history was not relevant. Onneurological exam, he was alert and oriented. He had a leftfacial droop and left hemiparesis with 4/5 strength in hisarm and leg.Diagnostic studiesHead CT scan revealed a right-sided 2.5-cm basal gangliahemorrhage. Cerebral angiography revealed a proximalocclusion of the right M1 MCA segment. A tangle of smallcaliber, tortuous arteries originating from the right A1anterior cerebral artery (ACA) segment reconstituted theM1 segment distally. The distal MCA and its branches hadnormalcaliberandcourse.A2-mmaneurysmwasseenwithinthat collateral network (Fig. 1a). Left internal carotid artery(ICA) angiography demonstrated normal left-sided vascula-ture with filling of the right-sided collateral network via apatent anterior communicating artery. Bilateral P1 segmentswere patent, and no arteriovenous shunting was observed.ManagementThe surgical plan was to perform a superficial temporalartery (STA) to MCA bypass to augment flow to the right