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BACKGROUND Currently, different postoperative predictors of chordoma recurrence have been identified. Tumor growth rate (TGR) is an image-based calculation that provides quantitative information of tumor's volume changing over time and has been shown to predict progression-free survival (PFS) in other tumor types. OBJECTIVE To explore the usefulness of TGR as a new preoperative radiological marker for chordoma recurrence. METHODS A retrospective single-institution study was carried out including patients reflecting these criteria: confirmed diagnosis of chordoma on pathological analysis, no history of previous radiation, and at least 2 preoperative thin-slice magnetic resonance images available to measure TGR. TGR was calculated for all patients, showing the percentage change in tumor size over 1 mo. RESULTS A total of 32 patients were retained for analysis. Patients with a TGR ≥ 10.12%/m had a statistically significantly lower mean PFS (P

Background Cerebrospinal fluid (CSF) leakage associated with incomplete sealing of the dura mater is a major complication of intradural procedures. Objective To compare the efficacy and safety of adjunctive TachoSil (Takeda Pharma A/S, Roskilde, Denmark) with current practice for the prevention of postoperative CSF leaks in patients undergoing elective skull base surgery involving dura mater closure. Methods Patients were intraoperatively randomized to TachoSil or current practice immediately before primary dura closure by suturing ± duraplasty. Choice of adjunctive treatment in the current practice group was at the surgeon's discretion. Primary efficacy endpoint was occurrence of clinically evident verified postoperative CSF leak or clinically evident pseudomeningocele within 7 weeks after surgery or treatment failure (third application of trial treatment or use of other treatment). Results A total of 726 patients were randomized to TachoSil (n = 361) or current practice (n = 365). More current practice patients had sutures plus duraplasty for primary dura closure compared with TachoSil (49.6% vs 35.7%) and fewer had sutures only (45.5% vs 63.2%). The primary endpoint of estimated leak rate favored TachoSil with events in 25 (6.9%) patients vs 30 (8.2%) current practice patients; however, this was not statistically significant (odds ratio: 0.82; 95% confidence interval: 0.47, 1.43; P = .485). Both treatments were well tolerated with similar frequency of adverse events. Conclusion Very low rates of postoperative CSF leaks can be achieved in patients undergoing skull base surgery of various indications. Although the study did not meet its primary endpoint, TachoSil appears to be safe and effective for the prevention of CSF leaks and associated complications.

Background Awake glioma surgery aims to maximize resection to optimize prognosis while minimizing the risk of postoperative deficits. Objective To evaluate oncological, functional, and employment outcomes in the first cohort of patients having this type of surgery at our institution and to determine the effects of any learning curve. Methods All cases of awake adult (>18 years of age) glioma surgery were recorded between the introduction of this technique in 2011 until the end of 2013. Extent of tumor resection was quantified on magnetic resonance imaging and compared with the objective prediction from a resection probability map. Cognitive status was assessed preoperatively and at 3 months postoperatively. Patients were questioned about their job and capability of working before and after surgery. Results Twenty-five patients were included in the analysis. No new motor or language deficits were noted at 6 weeks after surgery. Postoperative magnetic resonance imaging showed complete resection in 11 of 13 patients with glioblastoma and >98% resection in the other 2 patients. For patients with World Health Organization grade II glioma, 3 had total, 4 had subtotal, and 3 had partial resections. Comparison between cognitive levels before and after surgery showed no change in 4 patients, improvement in some tests in 2 patients, and deterioration in some tests in 3 patients. Of 20 patients working at the time of diagnosis, 16 returned to work. Conclusion These oncological and functional results of awake glioma surgery during the learning curve are comparable to results from established centers. The use and utility of resection probability maps are well demonstrated. The return to work level is high.

OBJECTIVE: Although an anterolateral approach is an ideal approach to the anterior part of the cervical spinal canal, it is not often used because of various technical difficulties. This article presents the case of a patient with an intradural schwannoma ventrolateral to the spinal cord and describes the technique, anterolateral surgery without fixation, that was used to remove it. CASE PRESENTATION: A 71-year-old man presented with neck pain and easy fatigability of the legs. Magnetic resonance imaging showed an intradural tumor ventrolateral to the spinal cord at the C3 level. The diagnosis was a schwannoma. TECHNIQUE: A right anterolateral approach was selected for the resection. In the dissection between the sternocleidomastoid muscle and the internal jugular vein, the accessory nerve was retracted with the fat tissue. At C3, the prevertebral aponeurosis was laterally retracted to protect the sympathetic chain. The C3 transverse process was rongeured, and the vertebral artery was shifted laterally with the venous plexus. The C2-C3 uncovertebral joint and the right third of the C3 body were removed (partial corpectomy). The tumor was easily found in the dural sac and was totally removed. The surgical wound was closed in a watertight fashion. No fixation was necessary. The symptoms improved after the operation. DISCUSSION: The anterolateral approach is one of the best approaches for resecting ventrally located intradural lesions because it allows minimally invasive surgery. Control and protection of the accessory nerve, sympathetic chain, and vertebral artery are the keys to success.

OBJECTIVE Invasive tumors involving the cavernous sinus, such as recurrent benign meningiomas or sarcomas, raise therapeutic problems that may be resolved by cavernous sinus exenteration (CSE). METHODS Our series comprises 18 patients (9 women and 9 men ranging in age from 14 to 64 yr) who underwent CSE during the past 8 years. The tumors in these patients included 12 meningiomas, 3 chondrosarcomas, 1 rhabdomyosarcoma, 1 lipomyosarcoma, and 1 epidermoid carcinoma. Preoperative occlusion of the internal carotid artery was confirmed in 15 cases by a balloon occlusion test. Three patients had a negative balloon occlusion test, and their internal carotid arteries were preserved (n = 1) or revascularized (n = 2) through an external carotid artery-to-middle cerebral artery bypass. RESULTS CSE was performed as a primary treatment in 5 patients and after one to five recurrences in 13 patients. In all patients, CSE included the internal carotid artery and Cranial Nerves III, IV, and VI and one to three branches of Cranial Nerve V. Orbital exenteration was performed in eight patients, and partial hypophysectomy was performed in five patients. Ten patients had received radiotherapy before CSE, and five patients underwent irradiation after CSE. The operative mortality includes two patients. Cerebrospinal fluid leakage was the main complication in four patients, with three patients having meningitis. Follow-up ranged from 6 months to 5 years, with three deaths from new recurrences at 2, 3, and 4 years after CSE. As compared with their clinical courses before CSE, all patients except the two who died postoperatively benefited from CSE. CONCLUSION CSE has useful indications in invasive and rapidly growing tumors, including apparently benign meningiomas. A better understanding of the biological behavior of these tumors is necessary for appropriate selection of patients for CSE.

OBJECTIVE: The goals of this investigation were to perform a detailed analysis of petroclival microanatomic features, to investigate the course of the abducens nerve in the petroclival region, and to identify potential causes of injury to neurovascular structures when anterior transpetrosal or transvenous endovascular approaches are used to treat pathological lesions in the petroclival region. METHODS: Petroclival microanatomic features were studied bilaterally in seven cadaveric head specimens, which were injected with colored silicone before microdissection. Another cadaveric head was used for histological section analyses. RESULTS: A lateral or medial location of the abducens nerve dural entrance porus, relative to the midline, was correlated with the course and angulation of the abducens nerve in the petroclival region. The angulation of the abducens nerve was greater and the nerve was closer to the petrous ridge in the lateral type, compared with the medial type. The abducens nerve exhibited three changes in direction, which represented the angulations in the petroclival region, at the dural entrance porus, the petrous apex, and the lateral wall of the internal carotid artery. The abducens nerve was covered by the dural sleeve and the arachnoid membrane, which became attenuated between the second and third angulation points. The abducens nerve was anastomosed with the sympathetic plexus and fixed by connective tissue extensions to the lateral wall of the internal carotid artery and the medial wall of Meckel's cave at the third angulation point. There were two types of trabeculations inside the sinuses around the petroclival region (tough and delicate). CONCLUSION: The petroclival part of the abducens nerve was protected in a dural sleeve accompanied by the arachnoid membrane. Therefore, the risk of abducens nerve injury during petrous apex resection via the anterior transpetrosal approach, with the use of the transvenous route through the inferior petrosal sinus to the cavernous sinus, should be lower than expected. The presence of two anatomic variations in the course of the abducens nerve, in addition to findings regarding nerve angulation and tethering points, may explain the relationships between adjacent structures and the susceptibility to nerve injury with either surgical or endovascular approaches. Venous anatomic variations may account for previously reported cases of subarachnoid hemorrhage with the endovascular approach.

OBJECTIVE: The description of the technique of multilevel oblique corpectomy (MOC) without fusion in the treatment of spondylotic myelopathy and radiculopathy and the analysis of the results of this technique from a series of 101 cases are presented. METHODS: MOC is performed using an anterolateral approach with control of the vertebral artery. The vertebral bodies are drilled obliquely from the lateral side toward the opposite posterolateral corner. More than half of the vertebral bodies are preserved, and no fusion procedure is required. The series of patients from 1992 through 1997 included 54 men and 47 women, with an average age of 57.9 years, who presented with myelopathy (n = 66) or radiculopathy (n = 35). MOC was realized on one to five levels from C2-C3 to C7-T1. Follow-up data were obtained by performing dynamic roentgenography, computed tomography, and magnetic resonance imaging 2 months, 1 year, and 3 years after surgery. RESULTS: The results (Japanese Orthopedic Association score) were improvement in 82% of the patients, worsening in 8%, and stabilization in 10%. Better results were observed in younger patients (

OBJECTIVE: Cervical neuromas with extradural components (intraextradural or strictly extradural forms) are rare. Their resection raises the problems of nerve root preservation, vertebral artery (VA) control, and spinal stability. METHODS: A series of 57 patients with neuromas (29 neurofibromas, 23 schwannomas, 4 neurofibrosarcomas, and 1 plexiform neurofibroma) was treated during the period of 1980 to 1995, using one of the lateral approaches (antero- or posterolateral approach). The VA was always controlled before resection of the tumor. In cases of intraextradural forms, the intradural component was removed by a complementary laminectomy (three patients) in the early period and then by an oblique corpectomy through the same lateral approach (five patients) in the late period. A laminectomy had been performed in 15 other patients (11 patients with intraextradural neuromas) before they were referred to us. These patients included seven with recurrent neuromas, occurring after an average period of 4.1 years (1-9 yr). RESULTS: Complete resection was achieved in all except two patients, in whom the nerve root reacted positively to intraoperative stimulation and could not be separated from the tumor. One of the patients was subsequently operated on after 2 years. Another recurrence was observed in another patient at 1 year. The four patients with sarcomas died from recurrence within 2 years. The rate of root preservation included an average of 28%, including 43.5% for schwannomas, 18% for neurofibromas, 44% for lower cervical neuromas (C4-C8), and 4.5% for upper cervical neuromas (C1-C3). Worsening of preoperative neurological deficits was observed in only two patients. The VA was always preserved, except in one patient with a sarcoma that was preoperatively occluded. No instability was observed in any of the patients. CONCLUSION: Complete resection with good neurological results can be achieved in most patients harboring cervical neuromas each with an extradural component by using a lateral approach and VA control. If the root cannot be separated from the tumor, especially in patients with neurofibromas, intraoperative stimulation can help decide whether the root may be divided without incurring postoperative deficit. The lateral approach permits the resection of the extradural as well as the intradural component by a complementary oblique corpectomy. There was no morbidity in relation to VA control as well as no postoperative instability.

A new technique of intratumoral embolization is described. An intratumoral injection of N-butylcyanoacrylate is performed either perioperatively by direct puncture of the tumor or preoperatively through the nose or through the skin. The indications for this technique are hypervascularized tumors, such as juvenile angiofibroma, hemangiopericytoma, or paraganglioma. This technique has been applied in 21 patients with excellent results in terms of devascularization.

A series of 35 patients treated for an intradural perimedullary arteriovenous fistula (AVF) between 1970 and 1990 is reported. Angiography was performed on all of the patients, leading to the diagnosis. The patients were classified into Type I (4 patients), Type II (9 patients), and Type III (22 patients). One Type I patient was not treated, two others underwent surgery, and the last one was embolized. All of the Type II AVFs were treated, two by embolization, four by direct surgery, and three by surgery after incomplete embolization. All of the Type III AVFs were treated by endovascular detachable silicone balloon. Complete occlusion of the AVF was achieved in all treated cases of Types I and II AVF and in 15 cases of Type III AVF; for the 6 other cases of Type III AVF, incomplete occlusion was achieved. In the Types I and II AVFs, partial improvement was clinically observed in only half of the patients; the others remained unchanged. The 15 patients whose Type III AVF was completely embolized recovered completely, and four patients with Type III AVF who were incompletely embolized remained unchanged; 2 other patients with Type III AVF worsened after incomplete occlusion, and 1 additional patient died a few hours after an attempt of endovascular occlusion of a cervical Type III AVF. The place of the perimedullary AVFs among the other vascular malformations involving the spinal cord is discussed according to this classification into three types. Their specific diagnostic and therapeutic difficulties are discussed, resulting in a simplified classification including two types of perimedullary AVF.

Objective En plaque sphenoid wing meningiomas are complex tumors involving the sphenoid wing, the orbit, and sometimes the cavernous sinus. Complete removal is difficult, so these tumors have high rates of recurrence and postoperative morbidity. The authors report a series of 71 patients with sphenoid wing meningiomas that were managed surgically. Methods The clinical records of 71 consecutive patients undergoing surgery for sphenoid wing meningiomas at Lariboisiere Hospital, Paris, were prospectively collected in a database during a 20-year period and analyzed for presenting symptoms, surgical technique, clinical outcome, and follow-up. Results Among the 71 patients (mean age, 52. 7 years; range, 12-79 years), 62 were females and 9 were males. The most typical symptoms recorded were proptosis in 61 patients (85.9%), visual impairment in 41 patients (57.7%), and oculomotor paresis in 9 patients (12.7%). Complete removal was achieved in 59 patients (83%). At 6 months of follow-up, magnetic resonance imaging scans revealed residual tumor in 12 patients (9 in the cavernous sinus and 3 around the superior orbital fissure). Mean follow-up was 76.8 months (range, 12-168 months). Tumor recurrence was recorded in 3 of 59 patients (5%) with total macroscopic removal. Among the patients with subtotal resection, tumor progression was observed in 3 of 12 patients (25%; 2 patients with grade III and 1 patient with grade IV resection). Mean time to recurrence was 43.3 months (range, 32-53 months). Conclusion Surgical management of patients with sphenoid wing meningiomas cannot be uniform; it must be tailored on a case-by-case basis. Successful resection requires extensive intra- and extradural surgery. We recommend optic canal decompression in all patients to ameliorate and/or preserve visual function.

OBJECTIVE: We previously reported our technique of selective microforaminotomy via an anterolateral approach for the treatment of spondylotic radiculopathy. We now report the clinical long-term results. METHODS: A retrospective study of 40 patients who consecutively underwent operation via this technique was performed. Patients' demographic, clinical presentation, and radiological and surgical data were recorded by chart review. Long-term clinical outcome was assessed by a questionnaire, office visits, and intensive telephone interviews. The results were compared with the literature. RESULTS: The study was comprised of 22 women and 18 men with a mean age of 50.6 years (age range, 33.1-75.2 yr). Preoperatively, 98% (n = 39) of the patients presented radicular pain, 88% (n = 35) of the patients presented with neck pain, 75% (n = 30) of the patients presented with a sensory deficit, and 45% (n = 18) of the patients presented with a motor deficit. Patients underwent operation at one level (n = 15), two levels (n = 23), or three levels (n = 2). One patient underwent operation bilaterally in a two-step procedure. In total, 68 cervical nerve roots were completely decompressed by this technique. On the basis of preoperative x-ray criteria of instability, two patients (5%) required graft arthrodesis, which was performed during the same surgery after the nerve root decompression. After a mean follow-up period of 4.3 years (range, 2.7-7.4 yr), 85% of the patients have no residual radicular pain, 94% of the patients have no more neck pain, 90% of the patients recovered from their sensory deficits, and 83% of the patients recovered from their motor deficits. According to Odom's criteria, 95% achieved an excellent or good outcome (Odom Grades I and II). No postoperative instability occurred. The transient and permanent morbidity rates were 7.5% (n = 3) and 2.5% (n = 1), respectively; one patient has permanent Horner's syndrome. CONCLUSION: The technique of microsurgical cervical nerve root decompression by selective microforaminotomy via an anterolateral approach is safe and efficient for the treatment of spondylotic radiculopathy. The morbidity rate is low. Clinical results are good after a long-term follow-up period. This technique allows the preservation of cervical motion and spinal stability. The results compare favorably to those of the literature.

OBJECTIVE: To detect parameters that may augment the therapeutic strategy in patients with a cerebral arteriovenous malformation (AVM) that is considered equally suitable for treatment by neurosurgery or radiosurgery, we compared the efficacy and risks of these two methods in a paired series with similar patient and AVM characteristics. PATIENTS AND METHODS: Two series of patients with AVM were studied, including a series of 39 patients treated using microsurgery (MS) and another series of 39 patients treated via radiosurgery (RS). These series were paired for age and sex, initial symptoms, size, location and Spetzler-Martin grade, and presence of embolization preceding treatment. We compared the posttreatment outcome in the two groups with respect to obliteration rate, neurological status, mortality rate, and recurrent bleeding. Statistical analysis was performed using paired Student's t test. RESULTS: The Glasgow Outcome Scale values and Modified Rankin Scores measured at discharge and 12 to 24 months were significantly better in the RS series than in the MS series. The obliteration rate tended to be higher in the MS series (91% versus 81 %; P = 0.10, not significant), whereas the rate of neurological deficit was higher in the MS series than in the RS series(P < 0.001). The mortality rate was not significantly different in the two series, but the rate of recurrent bleeding was higher in the RS group (10% versus 0%; P = 0.04). CONCLUSIONS: Although the rate of cure was similar for patients treated with MS and RS, neurological morbidity was higher after MS and recurrent bleeding was more frequent after RS.

Objective: We describe the normal anatomy, variations, and the surgical technique to expose and control the V1 segment of the vertebral artery (VA). Methods: The VA V1 segment extends classically from the subclavian artery to the C6 transverse foramen. It courses obliquely upwards and posteriorly in the cervical fat tissue, at a distance of 5 to 10 mm from the C7 vertebral body. Along its course, the VA V1 segment is crossed by the inferior thyroid artery, the thoracic duct, and the sympathetic chain. For neurosurgeons, the safest approach is to expose the distal part of the V1 segment at the C6 transverse foramen level through an antero-lateral approach. Otherwise, direct exposure of the subclavian artery requires vascular surgery expertise. Results: Surgical exposure of the VA V1 segment can be indicated on approaching the C6–C7 intervertebral disc space for degenerative disease or on treating tumoral processes in its vicinity. With developments of endovascular techniques, revascularization procedures are more rarely indicated nowadays. Conclusion: Perfect knowledge of the anatomy and of the surgical technique permits a safe exposure and control of the VA V1 segment.

OBJECTIVE: We describe our surgical technique of exposure, control, and transposition of the third segment of the vertebral artery (VA V3 segment). METHODS: The VA V3 segment extends from the C2 transverse foramen to the dura mater of the foramen magnum. It initially courses vertically between the C2 and C1 transverse foramens, then runs horizontally over the atlas groove, and finally obliquely upwards before piercing the dura mater. Exposure of the VA V3 segment through an antero-lateral approach is performed by passing medially to the ster-nomastoid muscle. After exposure and protection of the spinal accessory nerve, the C1 transverse process is identified below and in front of the mastoid tip. The small muscles that insert on it are cut to expose the C1-C2 portion. The inferior aspect of the horizontal portion is safely separated from the atlas groove by elevating the subperiosteal plane and the superior aspect is freed by a cut a few millimeters above the VA on the occipital condyle. Complete unroofing of the C1 transverse foramen is achieved by resecting the bone while leaving intact the subperiosteal plane. The VA then can be transposed. Venous bleedings during the dissection from periosteal sheath tearing can be controlled by direct bipolar coagulation. RESULTS: The control of the VA V3 segment is essentially used for lesions in the VA vicinity and to improve the surgical exposure at the craniocervical junction level. Indications therefore are tumoral removal, VA decompression, and rarely, nowadays, VA revascularization. CONCLUSION: Perfect knowledge of the anatomy and the surgical technique permits a safe exposure, control, and transposition of the VA V3 segment. This is the first step of many surgical procedures.

OBJECTIVE: To describe the advantages of a modification of the standard frontoorbitotemporozygomatic (FOTZ) approach, consisting of the forced opening of the patient's mouth (open-mouth FOTZ), for the treatment of benign tumors massively involving the splanchnocranium and neurocranium. METHODS: The modified FOTZ approach obtained by forced mouth opening is described. Such a procedure was introduce with the aim of obtaining a minimally invasive access to lesions involving both the intratemporal-parapharyngeal spaces and the anteromedial cranial fossae. The forced opening of the mouth allows the surgeon to keep the coronoid process of the mandible away from the operating field, producing a wide exposure of the infratemporal space like that of the posterior wall of the maxillary sinus, which can be penetrated from behind without adding destructive procedures on the mandibular bone. RESULTS: From a series of 45 patients affected by cranial base lesions operated on during an 8-year time period, three patients affected by juvenile nasopharyngeal angiofibromas were selected for an open-mouth FOTZ approach. In all cases, a complete eradication of both the intracranial and extracranial components of the tumor was possible by this approach. The same procedure was then used in four patients affected by extensive meningiomas and two patients harboring Vth cranial nerve schwannomas, with complete turnor removal. CONCLUSION: In our experience, the open-mouth FOTZ approach seems particularly suited for extensive benign tumors (including juvenile nasopharyngeal angiotibromas) with splanchnocranial and neurocranial involvement. No indication exists for the use of this approach in malignant tumors, in which total eradication with large tumor-free margins is required.

Objective and importance Extradural hemangioblastomas account for 8 to 12% of all spinal hemangioblastomas. Among them, intra-extradural forms with a dumbbell extension are extremely rare. We report a case of intra-extradural hemangioblastoma involving the C6 cervical nerve root. Clinical presentation The patient was a 31-year-old woman presenting with signs of myelopathy and C6 radiculopathy on the right side. A computed tomographic scan and magnetic resonance imaging demonstrated a dumbbell tumor that had developed through the C5-C6 intervertebral foramen. Angiography revealed a well-circumscribed mass with feeders from the vertebral artery and the deep cervical artery. Intervention The tumor was totally removed through the lateral approach, with control of the vertebral artery and sacrifice of the C6 cervical nerve root. Limited bone drilling to enlarge the foramen permitted us to reach and resect the intradural component. Histopathological examination confirmed the diagnosis of hemangioblastoma. Follow-up was uneventful. Conclusion This is the sixth reported case of a cervical dumbbell hemangioblastoma investigated by computed tomographic scanning and MRI but the first one resected via the lateral approach. The lateral approach seems appropriate for surgical resection because it provides primary control of the vascular feeders and access to the extradural and intradural components.

In a consecutive series of 71 cases of extrinsic lesions involving the vertebral artery (VA), 51 patients presented with external compression of this vessel. The compressive agents included 34 tumors, 4 osteophytes, 5 fibrous bands, 4 traumatic lesions, 2 neural elements, and 2 infectious processes. The main site was the second portion of the VA (C2-C6) (30 of 51 patients). Compression always induced at least significant stenosis, and in 8 patients caused complete occlusion. The compression was either permanent (44 patients) or intermittent (7 patients). Symptoms were observed in 11 patients, including 2 with permanent deficits. Surgical release of compression was performed each time symptoms could be explained by a reduction in VA flow and also when the compressing agent needed to be removed, as in the cases involving tumors. VA decompression was achieved by direct approach in 37 patients, by reduction and fixation of a traumatic dislocation in 2 patients, and by distal revascularization in 4 patients. Medical treatment or roentgenotherapy was used in the other patients. Results were excellent in all but 2 patients, who died from traumatic and ischemic lesions, respectively. Therefore, it seems important to identify external causes of compression of the VA for two reasons: 1) to suppress symptoms of vertebrobasilar insufficiency when their relation to VA compression is clearly established, and 2) to remove compressive agents like turnors safely while preserving the VA.

In 102 cases of ruptured intracranial aneurysms, the cervical as well as the cranial areas were explored by angiography. Loops in the course of the cervical vessels were present in 28 patients; features of fibromuscular dysplasia were present in 31 patients; and in 50 patients, no abnormalities were observed. In 7 patients, both cervical anomalies were present. Loops were associated with single aneurysms (95%), located primarily on the anterior communicating artery (76%), predominantly in men (M/F = 1.6). Aneurysms with fibromuscular dysplasia affected women more than men (F/M = 7), were frequently multiple (58%), and were located mainly on the intracranial part of the internal carotid and vertebral arteries (51%). These data suggest new concepts of aneurysm formation from inherited diseases and should permit the detection of some aneurysms before rupture.