Spontaneous thrombosis of unruptured small saccular intracranial aneurysm.

Aneurysmal subarachnoid hemorrhage (SAH), despite improvements in surgical and medical treatment, is still a serious disease with high rates of case fatality (40% to 50%) and morbidity.1–3 Incidence rates of SAH have not changed during the CT era, and outcome of SAH has only modestly improved during the past few decades. Outcome is still determined mainly by severity of initial bleeding or early rebleeding.1–4 It seems that identification of preventive treatment methods for aneurysm rupture and of modifiable risk factors for SAH are important as means to influence incidence and outcome of this serious disease. Unruptured aneurysms, when incidentally discovered or found in connection with diagnosis of ruptured aneurysm (multiple aneurysm cases), have been operated on for 2 to 3 decades in western countries. In this way, the high case fatality and morbidity associated with a possible severe initial bleed can be eliminated by preventive surgical intervention. However, the natural history as well as risks of surgery of unruptured intracranial aneurysms are poorly known as are the risk factors for rupture because of lack of studies with sufficient number of patients and follow-up years. The Table shows cohorts of largest studies of rupture risk of unruptured intracranial aneurysms.4–8 The recently published prospective part of The International Study of Unruptured Intracranial Aneurysms (ISUIA; patient enrollment in 61 centers between 1991 and 1998)5 shows somewhat different results as compared with those of the retrospective part of ISUIA (in 53 centers between 1970 and 1991).7 In the prospective study,5 overall incidence of aneurysm rupture was higher (0.8% versus 0.3% per year); risk for rupture of vertebrobasilar aneurysms was lower (relative risk 2.3 versus 5.1 to 13.8 as compared with other aneurysms); mean follow-up time per patient was shorter (3.9 versus 8.3 years); there was a lower limit …

It is foolhardy to remove from consideration of treatment any aneurysm solely because its maximal size is <10 mm or 7 mm. Annually, ≥15 000 American patients have subarachnoid hemorrhage (SAH) from aneurysms with a maximum diameter <7 mm and consequently experience irreparable morbidity and severe mortality. The majority of their aneurysms were, of course, unruptured, single, asymptomatic, and even smaller at some point before rupture. If the rupture rates for <10-mm aneurysms in International Study of Unruptured Intracranial Aneurysm (ISUIA) I1 or <7 mm in ISUIA II2 are used with the known number of ruptured aneurysms of these sizes admitted each year to calculate the prevalence of such small aneurysms in American adults, there is an unbelievably high result: in the range of 7% to 14%. Previous best estimates of prevalence on the basis of retrospective and prospective, radiological and pathological data have been ≈2% for all sizes of aneurysms and for those <10 mm, less than 1%. In autopsy studies, unruptured aneurysms have not outnumbered ruptured ones; the reverse is the case.3 Between ISUIA I1 and ISUIA II,2 the rupture rate …

Magnitude and Role of Wall Shear Stress on Cerebral Aneurysm. Computational Fluid Dynamic Study of 20 Middle Cerebral Artery Aneurysms

Aneurysmal subarachnoid hemorrhage (SAH) has a 30-day mortality rate of 45%, with approximately half the survivors sustaining irreversible brain damage.1 On the basis of an annual incidence of 6 per 100 000, ≈15 000 Americans will have an aneurysmal SAH each year. Population-based incidence rates vary considerably from 6 to 16 per 100 000, with the highest rates reported from Japan and Finland.2 3 4 5 Approximately 5% to 15% of stroke cases are secondary to ruptured saccular aneurysms. Although the prevention of hemorrhage has been advocated as the most effective strategy aimed at lowering mortality rates,6 the optimal management of patients with unruptured intracranial aneurysms (UIAs) remains controversial. Management decisions require an accurate assessment of the risks of various treatment options compared with the natural history of the condition. The natural history of UIAs and treatment outcomes are influenced by (1) patient factors, such as previous aneurysmal SAH, age, and coexisting medical conditions; (2) aneurysm characteristics, such as size, location, and morphology; and (3) factors in management, such as the experience of the surgical team and the treating hospital. These many influences have contributed to considerable variability in the reported risks for aneurysmal SAH and the treatment of UIAs. There are no prospective randomized trials of treatment interventions versus conservative management to date, and it is possible that no such studies will be carried out in the future. According to a classification system suggested by Cook et al,7 randomized clinical trials with low likelihoods of false-positive and false-negative errors provide the highest level of evidence (level I) that can be applied to a clinical recommendation. Randomized trials with high likelihoods of false-negative and positive errors provide level II evidence. Level III evidence is generated with nonrandomized concurrent cohort comparisons between contemporaneous patients who did and …

Cerebrovascular neurosurgery is a field where the highs are high and the lows are low. The successful cerebrovascular neurosurgeon gets to save lives and restore neurological function but must also to attend families and patients who are facing stroke and death. Patients generally fall into 2 categories: those who have had hemorrhagic or ischemic strokes, and those who are at risk for stroke but are so far unscathed. Patients in the first group have experienced a catastrophe. The neurosurgeon typically meets the patient and their family in the hospital. Morbidity and mortality within this group is common and can be devastating. The able neurosurgeon must be able to assess the situation and act rapidly to prevent worsening of neurological damage and decide how best to keep the patient from further harm. Those in the second group have often received a diagnosis after medical imaging for an unrelated complaint. While the vascular lesion may be asymptomatic, these patients are fearful and anxious about the possibility of experiencing a stroke. For these patients, neurosurgeons must be able to summarize the available evidence, provide comfort, and recommend the safest treatment option. Sometimes the safest course is not surgery, but instead, reassurance and medical management. Within the following 6 chapters, the authors lay out practical information all physicians should be familiar with. These chapters cover some of the more common diagnoses that we confront and should help to familiarize students with how to analyze, understand, and treat these problems. This is an exciting field and the authors share a passion for doing everything we can to care for our patients and to keep them from harm. It is hoped that these chapters will help to introduce the next generation of physicians to the satisfaction we enjoy when we are able to shepherd patients safely through the risks that they face. Institutional Review Board approval was not necessary for this study. Patient consent for the cases in each chapter was obtained directly from the patients; in instances in which consent could not be obtained, patient information has been anonymized. CHAPTER 1: MICROSURGERY FOR UNRUPTURED INTRACRANIAL ANEURYSMS Case Presentation A female in her mid-fifties without a significant past medical history presented with double vision. Her neurological examination revealed left ptosis, a dilated, nonreactive left pupil, and the inability to adduct and supraduct her left eye. Magnetic resonance imaging (MRI) and computed tomography angiography (CTA) imaging showed a large left internal carotid artery (ICA) aneurysm arising at the origin of the posterior communicating artery (Figure 1). (See discussion at end of chapter.)FIGURE 1.: Axial A, coronal B, and sagittal C CTA revealing a wide-necked, large left posterior communicating artery aneurysm.Questions The relative rupture risk of a posterior communicating artery aneurysm to a cavernous aneurysm is: The same Higher Lower No relationship Of the following aneurysms which has the highest rupture risk (refer to Figure 2): A 12-mm cavernous aneurysm A 12-mm posterior communicating artery aneurysm A 12-mm middle cerebral artery (MCA) bifurcation aneurysm A 12-mm superior hypophyseal artery aneurysm A 12-mm ophthalmic artery aneurysm Which craniotomy is most suitable for clipping a posterior communicating artery bifurcation aneurysm: Far lateral Subtemporal Interhemispheric Pterional Suboccipital A posterior communicating artery aneurysm can cause double vision related to compression of which cranial nerve: 2nd cranial nerve 3rd cranial nerve 5th cranial nerve 7th cranial nerve 8th cranial nerve FIGURE 2.: Location distributions of intracranial aneurysms across the neurovasculature. Abbreviations: Acomm = anterior communicating artery; MCA = middle cerebral artery; Pcomm = posterior communicating artery; PICA = posterior inferior cerebellar artery; SCA = superior cerebellar artery; VB = vertebral/basilar.Epidemiology Approximately 1% of adults have an intracranial aneurysm, most of which are not congenital. Aneurysms are quite rare in children and become more common with age. Perhaps those individuals with aneurysms are born with a weak area in the wall of their vessel and the aneurysm many develop later in life, but it is not fully known. For example, intracranial aneurysms occur in both sexes, but are distinctly more common in females. While most intracranial aneurysms are thought to be sporadic, about 15% run in families. We presume, therefore, there is a genetic basis for this and is inherited, but those genes have not yet been identified. Smoking, hypertension, family history of intracranial aneurysms, polycystic kidney disease, connective tissue diseases, and possibly aortic aneurysms are all correlated with the presence of an intracranial aneurysm; further, these factors also increase the risk of aneurysm rupture. The presence of multiple factors can magnify risk in a synergistic and multiplicative fashion. Patients with familial aneurysms tend to rupture a decade younger than those with sporadic aneurysms. The incidence is higher in families with genetic risk factors, including those with polycystic kidney disease and various connective tissue disorders (ie, Marfan's syndrome, Ehler-Danlos syndrome, etc). In such families where one individual has an aneurysm, the chance of another first-degree family member having an aneurysm may be as high as 30%. It is estimated that 30 000 patients suffer aneurysmal rupture each year. Approximately 50 to 75% of patients who have an aneurysm rupture reach a hospital in time to receive medical care. Of those who attain medical attention, approximately 50% die and another 25% suffer significant complications. Of those patients who receive timely medical care, 25% can have a good outcome. Due to this high mortality rate, it is reasonable to consider treatment in a patient diagnosed with an unruptured intracranial aneurysm. Morphology Ninety percent of intracranial aneurysms are saccular and 10% are fusiform. Most saccular aneurysms occur at bifurcations, but small percentages are sidewall aneurysms. Aneurysms are classified as small (<10 mm), large (10-24 mm), and giant (>24 mm). Infectious aneurysms (also known as mycotic aneurysms) tend to occur on distal intracranial vessels. Saccular aneurysms can have small or wide necks, which can influence treatment difficulty and strategy. As they enlarge, the sac may become filled with thrombosed blood, causing mass effect on surrounding neural tissue. Natural History Several studies have been published that attempted to quantify the risk of rupture of asymptomatic unruptured intracranial aneurysms. It is important that one keep in mind that these studies only address asymptomatic aneurysms. Symptomatic aneurysms almost always necessitate urgent intervention. These studies suffer from relatively short follow-up periods (typically 5 yr or less). These time periods are considered short because for most patients, the question of risk exposure to rupture is one of decades. The most prominent of the natural history studies is the International Study of Unruptured Intracranial Aneurysms (ISUIA) study (Wiebers DO, Whisnant JP, Huston J 3rd, et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet. 2003 Jul 12;362(9378):103-110). Table 1, which is reproduced from the ISUIA study, shows the relationship between aneurysm location, size, and risk of rupture. The study also showed that larger size, prior history of subarachnoid hemorrhage, and posterior circulation (including posterior communicating artery aneurysms) had a higher risk of rupture. While this suggests low rupture risk for anterior circulation aneurysms <7 mm in diameter, it should be noted that the median size of aneurysm rupture is about 6 mm. Pericallosal and anterior communicating artery aneurysms tend to rupture at smaller sizes than other aneurysms. The median rupture size of this type of an aneurysm is about 3 mm. Certain morphological features have been associated with the risk of rupture, including irregular dome shape and the presence of daughter sacs on the dome. TABLE 1. - Five-Year Annual Cumulative Risk of Aneurysmal Rupture According to Size and Location Within the Intracranial Vasculature (Reproduced from the ISUIA Trial) < 7 mm No Hx of SAH Hx of SAH 7–12 mm 13–24 mm ≥25 mm Cavernous carotid artery 0% 0% 0% 3.0% 6.4% Anterior circulation 0% 1.5% 2.6% 14.5% 40% Posterior circulation 2.5% 3.4% 14.5% 18.4% 50% Hx = history; SAH = subarachnoid hemorrhage. Clinical Presentation Due to the growing utilization of MRI and magnetic resonance angiography (MRA), there is an increasing number of incidentally discovered aneurysms diagnosed when patients are evaluated for unrelated symptoms. Unruptured aneurysms can cause a myriad of symptoms, including cranial neuropathies, seizures, headaches, and cognitive decline due to mass effect. Rarely, an intracranial aneurysm can cause ischemic symptoms due to emboli that result from turbulent flow within an aneurysm. Anatomy and Distribution Figure 2 outlines the location of the most common types of intracranial aneurysms. Eighty percent of aneurysms occur in the anterior circulation and 20% occur in the posterior circulation. Decision Making The decision of whether to treat an aneurysm or not can be complex. Several parameters must be considered, including age, the health of the patient, an assessment of the natural history of the aneurysm, and the technical capabilities of the treating surgeon. One of the most important determinants of the risk of a nonruptured aneurysm is the patient's age and health. Younger age and a longer life expectancy expose the patient to greater cumulative risk than a patient with a more limited life expectancy. Therefore, younger patients have a graver natural history favoring treatment while advanced age accompanied by lower rupture risk favors observation with serial imaging. Despite a growing body of literature on aneurysm behavior and natural history, aneurysm rupture remains unpredictable. Any absolute statements on aneurysm natural history are largely conjecture, and it is important to share this uncertainty with patients. Studies have suggested that outcomes tend to be better at high volume centers. The advent and evolution of endovascular options over the past several decades have increased the neurosurgeon's repertoire of aneurysm treatment modalities. More options may have made decision making more complicated, but it has also allowed a greater number of aneurysms to be treated. Microsurgical and endovascular treatments are associated with inherent benefits and disadvantages. Surgical clipping remains the most definitive way to treat intracranial aneurysms with a proven track record of durability and versatility. Almost all aneurysms can be treated surgically. Endovascular therapies have the advantage of being less invasive and for unruptured aneurysms, patients generally have shorter hospitalizations and recoveries. The disadvantages include risks of the treatment, greater risk of recurrence, and the fact that some aneurysms cannot be treated by current endovascular therapies. Factors that favor clipping as opposed to endovascular treatment include young patient age, wide aneurysm neck, incorporation of outflow branches into the dome, and larger aneurysm size. Surgical Techniques Aneurysm clipping involves exposing the aneurysm along with its inflow and outflow vessels. This technique requires a carefully planned surgical approach that minimizes brain manipulation and takes advantage of the subarachnoid space. With careful planning and positioning, a skilled microsurgeon can navigate atraumatically through the subarachnoid cisterns to first expose the inflow branch to an aneurysm, thus achieving proximal control. Establishing proximal control is an important tenet in aneurysm surgery. The surgeon then carefully exposes outflow vessels, which assures complete control of the circulation related to the aneurysm. This control is important for 3 reasons. First, if the aneurysm leaks during manipulation, flow can be arrested with temporary clips until the aneurysm can be clipped. Flow can be arrested for 20 to 30 min with special anesthetic techniques in most cases, which gives the surgeon time to complete the dissection and clip the aneurysm safely. Second, certain aneurysms with wide necks are best clipped after they are trapped and deflated. Finally, flow arrest may be needed if a bypass is required as part of the aneurysm treatment strategy. During flow arrest, anesthesiologists can give sufficient doses of anesthetic to suppress the electroencephalogram. This is referred to as “burst suppression.” This reduces the metabolic needs of neuronal cells thus increasing the tolerance to temporary flow arrest. Instruments used in aneurysm clipping are shown in Figure 3.FIGURE 3.: A, Various styles of aneurysm clip appliers. B, Different clip styles, both permanent and temporary. C, Clip applier opening a clip.Case Discussion This patient with a cranial nerve III palsy raised concern for an intracranial aneurysm; an awake patient with acute third nerve palsy with pupillary dilation should be assumed to have an aneurysm until proven otherwise. A posterior communicating artery aneurysm is the most likely aneurysm to cause compressive third nerve palsy. Diabetes can also be associated with this deficit and is the most common because of noncompressive third nerve paresis. Diabetes induced third nerve palsy, however, is usually pupil sparring (ie, the pupil is not asymmetrically dilated). In this case, the CTA revealed a wide-necked, large left posterior communicating artery aneurysm (Figure 1). Given the relatively young age of the patient, the mass effect on the third nerve, and the wide neck of the aneurysm, surgical clipping was recommended. At surgery, the wide neck of the aneurysm required trapping and deflation prior to successful clipping. The case is narrated in Video 1. Other clipping cases are discussed in Videos 2 and 3. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1.","caption":"Trapping and deflation to clip a large Pcomm artery aneurysm. This video can be accessed in the HTML version of the article. Please visit www.operativeneurosurgery-online.com to view this article in HTML and play the video.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_xpznvs9a"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 2.","caption":"Miscrosurgical clipping of paraclinoid aneurysms in 3 patients. This video can be accessed in the HTML version of the article. Please visit www.operativeneurosurgery-online.com to view this article in HTML and play the video.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_rgt2vrwb"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 3.","caption":"Surgical clipping of an unruptured MCA aneurysm. This video can be accessed in the HTML version of the article. Please visit www.operativeneurosurgery-online.com to view this article in HTML and play the video.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_lfhih4hy"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} Answers to Questions B. The cavernous segment of the ICA is extradural and surrounded by bone and dura. These aneurysms have very low risk of subarachnoid hemorrhage. B. Posterior communicating artery aneurysms have a higher risk of hemorrhage than the other locations listed. D. The pterional or frontotemporal craniotomy is the ideal exposure used for most carotid segment aneurysms. B. The anatomic relationship of the posterior communicating artery to the oculomotor nerve makes this the most common cranial nerve compressed by an enlarging aneurysm at that site. Pearls ✓ Larger aneurysm size, location in posterior circulation (including posterior communicating artery aneurysms), family history of aneurysms, smoking, connective tissue disease, and a history of SAH increase the annual risk of rupture of intracranial aneurysms. ✓ Aneurysm rupture carries significant morbidity and mortality, thus justifying the treatment of many intracranial aneurysms. ✓ Aneurysm clipping is associated with very high rates of durability when compared with endovascular coiling. Patient selection for aneurysm clipping depends on careful analysis of anatomic features, an understanding of the natural history, and an honest appraisal of surgeon expertise. ✓ Endovascular treatment of aneurysms is a less-invasive approach to aneurysm treatment and may be preferable form select patients and select aneurysms. ✓ There are many new techniques arising for diagnosis and treatment of aneurysms, including emerging neurosurgical modalities and technological advancements to care. Care should be individualized and take aneurysm and patient characteristics into account. SUGGESTED READING Murayama Y, Takao H, Ishibashi T, et al. Risk analysis of unruptured intracranial aneurysms: prospective 10-year cohort study. Stroke. 2016;47(2):365-371. Wiebers DO, Whisnant JP, Huston J 3rd, et al. International Study of Unruptured Intracranial Aneurysms Investigators. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet. 2003;362(9378):103-110. Juvela S, Porras M, Poussa K. Natural history of unruptured intracranial aneurysms: probability of and risk factors for aneurysm rupture. J Neurosurg. 2000;93(3):379-387. Rhoton AL Jr. Anatomy of saccular aneurysms. Surg Neurol. 1980;14(1):59-66. Samson D, Batjer HH, White J, et al. Intracranial Aneurysm Surgery: Basic Principles and Techniques. New York: Thieme; 2011. Bendok BR, Sattur MG, Welz ME, et al. Patient selection and technical nuances for microsurgical clipping of carotid-ophthalmic aneurysms: 2-dimensional operative video. Oper Neurosurg. 2018;15(2):245. CHAPTER 2: RUPTURED BRAIN ARTERIOVENOUS MALFORMATIONS Case Presentation An otherwise healthy pediatric patient slightly older than the age of 10 presented with sudden onset of severe headache, emesis, and confusion. Initial imaging demonstrated intracerebral hemorrhage (ICH) involving the mesial parietal and occipital lobes with extension into the ventricles (intraventricular hemorrhage [IVH]), and ventriculomegaly (Figure 4). CTA demonstrated an abnormal, periventricular tangle of vessels within the ICH.FIGURE 4.: A, CTA demonstrates an abnormal tangle of blood vessels (white arrow) adjacent to the ICH and IVH (*). B, DSA (lateral view, left vertebral artery). DSA demonstrates a small (1.5 cm), diffuse nidus (arrow), supplied by PCA branches, and arterial feeder has a flow-related aneurysm (arrowhead) proximal to the nidus. Venous drainage is both deep (*) and superficial. The Spetzler–Martin classification is grade II (S1E0V1). C, After embolization, the Onyx cast is demonstrated. D, The portion of the Onyx cast is seen intraoperatively. E, The main draining vein has been cauterized after disconnection of the arterial supply. F, Postoperative DSA demonstrates no residual BAVM.(See discussion at end of chapter.) Questions After stabilizing the patient, initial management would include which of the following: Emergent decompressive craniectomy Evacuation of the ICH Intracranial pressure (ICP) management with external ventricular drain (EVD) placement Diagnostic cerebral angiography After initial management, which of the following would be the next step in Microsurgical of the Diagnostic cerebral angiography would be the grade of this with a 2 diameter, both and deep and II III A brain is a vascular by an abnormal tangle of and known as a nidus. This nidus and vessels that the of blood flow from the arterial to the circulation. can with hemorrhage, seizures, neurological and headache, or as during for other reasons. Patient and anatomic features of help the risk of hemorrhage and risks of treatment. options include microsurgical endovascular embolization, or over management, for unruptured asymptomatic however, treatment with microsurgical or is generally for most with the type of treatment on patient and have a low but are an important cause of The of has been estimated at 50 cases 000 on several the incidence of is case 000 for the incidence is cases 000 year. can patients of age, but most are between 20 and The most common is hemorrhage 50% of by 25% and headache, neurological or which for the The rupture risk of unruptured is to which to 3 to with a history of hemorrhage. have a 2 to risk of hemorrhage year. age, history of hemorrhage, deep brain location, and deep drainage increase the risk of hemorrhage with annual risk of hemorrhage from for patients with of these features to for patients with all The presence of associated aneurysms can risk double the annual risk of hemorrhage. The of size, posterior location, and have not been demonstrated as as prior hemorrhage. is but they have been thought to be a of definitive and as as genetic may to their and and not directly and are by but in of blood between and and the vessels that this tangle of blood vessels are and to rupture. aneurysms can form due to these (ie, proximal and distal flow-related aneurysms), as as within the abnormal (ie, These aneurysms may often be the of hemorrhage. become due to these and and as a result they may develop an or These features may not the risk of hemorrhage, but they are important in treatment planning and as of these will increase pressure and to hemorrhage. In to rupture and the of hemorrhage with brain and increased unruptured the surrounding brain due to and which can to cognitive and and Initial of or SAH are generally diagnosed on computed tomography imaging. CTA is which often demonstrates the and draining it may also associated aneurysms. With the initial special is to IVH or large with of mass brain as as hemorrhage in the posterior because these may treatment with placement or decompressive the patient's examination with these imaging will their management. Patients with are to the neurosurgical care for of their neurological and medical cerebral angiography angiography is to further the DSA will anatomic features that will help management, including the number and location of associated aneurysms and of size and of or of drainage and presence of or ICH from a may or the nidus and flow is typically during of unruptured and can assess the and brain MRI can of prior hemorrhage with imaging to blood and of with increased imaging. with CTA and is also used for planning treatment. are important for the of as as management The most used is the Spetzler–Martin grade The Spetzler–Martin grade is also used The and the are used to risk of treatment from but are less used during the initial management of a TABLE - and grade 2 3 location location Venous drainage only Any deep drainage grade grade yr yr 2 yr 3 history Unruptured of nidus TABLE 3. - of for the Most of Aneurysms Anterior cerebral artery Anterior communicating artery cerebral artery Posterior communicating artery carotid artery TABLE - The and = 2 location History of hemorrhage = = 1. receive to 5 in the Spetzler–Martin on size drainage or and location One is for an aneurysm size 2 for a size 3 to 6 and 3 for a size One is for deep and is for Venous drainage is considered if the into and then to deep drainage through the vein of is anatomic and as internal cerebellar and deep cerebellar This has been into 3 on surgical morbidity and mortality (ie, A, B, and C for and Surgical morbidity and mortality increase with increased such that outcomes occur in of A, of B, and of C patients. The Spetzler–Martin grade was on the observation that age, hemorrhage, and of the nidus also outcomes obtained from age, hemorrhage, and are to the Spetzler–Martin < 20 and yr are 1, and 3 on unruptured carries more surgical risk and has a higher of from than for A diffuse nidus is more likely to have brain within the nidus and is more to than a with a nidus The Spetzler–Martin grade from 2 to and risk of surgical treatment with higher Patients with unruptured are

With the increased investigation of cerebral arteries using magnetic resonance angiography in the general population, the detection of unruptured intracranial aneurysms (UIAs) has increased. Understanding the distribution and factors associated with UIAs might be helpful for understanding the pathomechanism. Subjects who underwent magnetic resonance angiography with a health examination at the Health Screening and Promotion Center were enrolled. The incidence and risk factors of UIAs (age, sex, hypertension, diabetes mellitus, smoking, alcohol, and coronary artery disease) were investigated by comparing patients with and without UIAs. These risk factors were also investigated by the UIA location, distal internal carotid artery, anterior cerebral artery and middle cerebral artery (MCA), MCA bifurcation, anterior and posterior communicating artery, and posterior circulation. Among 187 166 subjects who received health examination, 18 954 underwent magnetic resonance angiography. Of them, 367 (1.93%) had UIAs. Age (odds ratio [OR], 1.02; P=0.003), women (OR, 2.00; P<0.001), hypertension (OR, 2.21; P<0.001), smoking (OR, 1.66; P=0.001), and coronary artery disease (OR, 0.23; P<0.001) were independently associated with the presence of UIAs. Hypertension was associated with most UIAs, except for those located at sidewalls (anterior cerebral artery and MCA). MCA aneurysms were associated with old age and smoking. Distal internal carotid artery, posterior communicating artery, and MCA-bifurcation aneurysms were associated with female sex. Anterior communicating artery aneurysms were associated with smoking and alcohol. Posterior circulation UIAs were only associated with hypertension. Coronary artery disease was negatively associated with anterior circulation aneurysms. The risk factors for UIAs differ by their location, compared with the control. Interestingly, the presence of coronary artery disease was protective against the presence of UIAs.

Spontaneous radiographic disappearance of cerebral aneurysms is often observed under special conditions such as giant aneurysms. However, spontaneous disappearance of an unruptured and nongiant intracranial saccular aneurysms is rare. We describe two cases of this rare vascular phenomenon. The first patient is a 64-year-old female diagnosed with a small unruptured aneurysm arising from the distal anterior cerebral artery. Spontaneous disappearance of the aneurysm on magnetic resonance angiography (MRA) was observed 5 years after the initial diagnosis. Continuous imaging surveillance also revealed spontaneous reappearance of the aneurysm 2 years later. The second patient is a 57-year-old female harboring a small unruptured saccular aneurysm arising from the M1–M2 bifurcation of the middle cerebral artery. The aneurysm showed spontaneous disappearance on MRA 13 years after the initial diagnosis. These cases provide a new insight into this natural dynamic process even in cases of a small unruptured intracranial saccular aneurysm.

BackgroundTo examine the effect of stenting on progressive occlusion of small and incompletely occluded unruptured intracranial aneurysms (UIAs) ≤10 mm in size using a propensity score matched case controlled analysis.Methods715...

Unruptured Intracranial Aneurysms.

The Natural Course of Unruptured Cerebral Aneurysms

Objective To explore and compare the hemodynamic factors in small,medium and large unruptured lateral intracranial saccular aneurysms at the Internal Carotid Artery.Method 27 patient -specific unruptured lateral intracranial saccular aneurysms at the Internal Carotid Artery were divided into small,medium and large groups based on their diameters.Results models were retrospectively constructed and analyzed by computational fluid dynamic(CFD) method.Results All these three groups displayed typical lateral aneurismal flow patterns.Larger - sized group displayed more unstable flow patterns,significantly lower wall shear stress(WSS) and higher oscillatory shear index( OSI ).Conclusions These observations indicated that more unstable flow patterns,lower WSS and higher OSI in the aneurysms might be involved in increasing the risk of rupture for larger - sized unruptured lateral intracranial saccular aneurysms. Key words: Intracranial aneurysms; Lateral type; Hemodynamics; Computational fluid dynamics; Size

To determine the morphological features distinguishing small unruptured saccular intracranial aneurysms (sIAs) with high and low wall strength (WS) in post mortem subjects. Subarachnoid haemorrhage caused by sIA rupture is associated with increased mortality and morbidity. Analysis of the morphology and biomechanical properties of sIAs might facilitate the identification of clinically relevant risk factors for sIA rupture. Eight single unruptured sIAs were found among eight subjects during 184 post mortem examinations. After assessment of the dimensions, aspect ratio (AR), size ratio (SR), height/width ratio (HW), bottleneck factor (BNF), and shape, sIAs with adjacent cerebral arteries were subjected to quasi-static increasing pressure until the wall of the cerebral artery or sIA ruptured. In three specimens, the sIA ruptured at a significantly lower average pressure than the other cases, in which the rupture occurred within the wall of the adjacent cerebral artery (769 vs. 1,259 mmHg; p = 0.035). The sIAs with low WS, i.e. sIAs that ruptured during experiments, were characterised by significantly increased dome dimensions compared to sIAs with high WS (p < 0.05). At the same time, no significant differences were observed between high and low WS categories regarding AR, SR, HW, and BNF, or the presence of an irregular dome shape. Dome dimension was the only feature that distinguished unruptured sIAs as having low or high WS, and this supports observations that sIAs with increased dome dimensions are characterised by an increased risk of rupture. Thus, dome dimension may be more useful than other morphometric parameters, such as AR, SR, HW and BNF, in assessing the rupture risk assessment of small unruptured sIAs.

The long-term history and management of unruptured intracranial aneurysms is not well understood. Our aim was to determine current practice patterns in the management of unruptured intracranial aneurysms, especially regarding imaging surveillance for conservatively managed aneurysms of this type. An on-line survey was designed to examine physician practice and preference regarding the management of small unruptured intracranial aneurysms (≤7 mm in diameter). The survey was circulated to members of the American Society of Neuroradiology. Participation was voluntary, and all responses were anonymous. A total of 227 individual survey responses were obtained and included in the analysis with 54.6% (124/227) from diagnostic neuroradiologists (practicing >50% neuroradiology) and one-third (29%) from neurointerventional radiologists. One hundred seventy-three of 227 responded that routine, periodic imaging surveillance would be appropriate for conservatively managed unruptured intracranial aneurysms, and 84% of respondents recommended surveillance frequency of at least once a year. Fifty-nine percent favored indefinite, life-long follow-up for small unruptured intracranial aneurysms, and a similar number of respondents favored noncontrast MR angiography for aneurysm follow-up. Significant heterogeneity was found in size measurements used to assess aneurysms and criteria used to define growth on surveillance imaging. The natural history of intracranial aneurysms is not well-understood. A large proportion of incidentally detected, unruptured aneurysms are small (<7 mm). The survey results show significant heterogeneity in practice even among neuroradiologists and underlies the need to standardize imaging practice. Further studies are needed to assess the optimal frequency and duration of surveillance imaging for unruptured intracranial aneurysms. The criteria used to measure aneurysms and define growth on imaging also need to be standardized.

Prevalence and risk factors of unruptured intracranial saccular aneurysms in hospital population by 3D-TOF-MRA with VR reconstruction

For effective management of patients with unruptured intracranial aneurysms, prognostic criteria for rupture are needed, of which aneurysm size is a key factor. However, the critical size at which an aneurysm becomes hazardous is not known. During the last 5 years, 1558 aneurysm patients have been operated on in our centre. Of these 1248 presented with a subarachnoid haemorrhage (ruptured aneurysms) and 310 without a subarachnoid haemorrhage (unruptured aneurysms). Of the ruptured aneurysms 475 (38%) were small in size with a maximum diameter 6 mm. Most of these small ruptured aneurysms were located on the anterior communicating artery. Of the 310 patients with unruptured aneurysms 253 (81.6%) had single aneurysms; 113 (44.7%) of those were small in size. Most of these small unruptured aneurysms were located on the middle cerebral artery. The remaining 57 patients with unruptured aneurysms harboured multiple aneurysms totalling 116 aneurysms; 50% of them were small in size. Out of 160 patients with multiple aneurysms presenting with subarachnoid haemorrhage, 34 patients had small aneurysm(s) accompanied with medium or large sized aneurysm(s); in nine (26.5%) of these 34 patients the small aneurysm was the ruptured one. These data suggest that small aneurysms 6 mm in diameter are not innocuous and hazardous, and surgical treatment should be considered for small unruptured aneurysms even if they are less than 6 mm in diameter.