Intraoperative premature rupture of middle cerebral artery aneurysms: risk factors and sphenoid ridge proximation sign

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OBJECTIVE

This study was an investigation of surgical cases of a ruptured middle cerebral artery (MCA) aneurysm that was conducted to identify the risk factors of an intraoperative premature rupture.

METHODS

Among 927 patients with a ruptured intracranial aneurysm who were treated over an 8-year period, the medical records of 182 consecutive patients with a ruptured MCA aneurysm were examined for cases of a premature rupture, and the risk factors were then investigated. The risk factors considered for an intraoperative premature rupture of an MCA aneurysm included the following: patient age; sex; World Federation of Neurosurgical Societies clinical grade; modified Fisher grade; presence of an intracerebral hemorrhage (ICH); location of the ICH (frontal or temporal); volume of the ICH; maximum diameter of the ruptured MCA aneurysm; length of the preaneurysmal M1 segment between the carotid bifurcation and the MCA aneurysm; and a sign of sphenoid ridge proximation. The sphenoid ridge proximation sign was defined as a spatial proximation < 4 mm between the sphenoid ridge and the rupture point of the MCA aneurysm, such as a daughter sac, irregularity, or dome of the aneurysm, based on the axial source images of the brain CT angiography sequences.

RESULTS

A total of 11 patients (6.0%) suffered a premature rupture of the MCA aneurysm during surgery. The premature rupture occurrences were classified according to the stage of the surgery, as follows: 1) craniotomy and dural opening (n = 1); 2) aspiration or removal of the ICH (n = 1); 3) retraction of the frontal lobe (n = 1); 4) dissection of the sphenoid segment of the sylvian fissure to access the proximal vessel (n = 4); and 5) perianeurysmal dissection (n = 4). The multivariate analysis with a binary logistic regression revealed that presence of a sphenoid ridge proximation sign (p < 0.001), presence of a frontal ICH associated with the ruptured MCA aneurysm (p = 0.019), and a short preaneurysmal M1 segment (p = 0.043) were all statistically significant risk factors for a premature rupture. Plus, a receiver operating characteristic curve analysis revealed that a preaneurysmal M1 segment length ≤ 13.3 mm was the best cutoff value for predicting the occurrence of a premature rupture (area under curve 0.747; sensitivity 63.64%; specificity 81.66%).

CONCLUSIONS

Patients exhibiting a sphenoid ridge proximation sign, the presence of a frontal ICH, and/or a short preaneurysmal M1 segment are at high risk for an intraoperative premature rupture of a MCA aneurysm. Such high-risk MCA aneurysms have a superficial location close to the arachnoid in the sphenoidal compartment of the sylvian fissure and have a rupture point directed anteriorly.

ABBREVIATIONSCTA = CT angiography; ICA = internal carotid artery; ICH = intracerebral hemorrhage; MCA = middle cerebral artery; SAH = subarachnoid hemorrhage; WFNS = World Federation of Neurosurgical Societies.

Abstract

OBJECTIVE

This study was an investigation of surgical cases of a ruptured middle cerebral artery (MCA) aneurysm that was conducted to identify the risk factors of an intraoperative premature rupture.

METHODS

Among 927 patients with a ruptured intracranial aneurysm who were treated over an 8-year period, the medical records of 182 consecutive patients with a ruptured MCA aneurysm were examined for cases of a premature rupture, and the risk factors were then investigated. The risk factors considered for an intraoperative premature rupture of an MCA aneurysm included the following: patient age; sex; World Federation of Neurosurgical Societies clinical grade; modified Fisher grade; presence of an intracerebral hemorrhage (ICH); location of the ICH (frontal or temporal); volume of the ICH; maximum diameter of the ruptured MCA aneurysm; length of the preaneurysmal M1 segment between the carotid bifurcation and the MCA aneurysm; and a sign of sphenoid ridge proximation. The sphenoid ridge proximation sign was defined as a spatial proximation < 4 mm between the sphenoid ridge and the rupture point of the MCA aneurysm, such as a daughter sac, irregularity, or dome of the aneurysm, based on the axial source images of the brain CT angiography sequences.

RESULTS

A total of 11 patients (6.0%) suffered a premature rupture of the MCA aneurysm during surgery. The premature rupture occurrences were classified according to the stage of the surgery, as follows: 1) craniotomy and dural opening (n = 1); 2) aspiration or removal of the ICH (n = 1); 3) retraction of the frontal lobe (n = 1); 4) dissection of the sphenoid segment of the sylvian fissure to access the proximal vessel (n = 4); and 5) perianeurysmal dissection (n = 4). The multivariate analysis with a binary logistic regression revealed that presence of a sphenoid ridge proximation sign (p < 0.001), presence of a frontal ICH associated with the ruptured MCA aneurysm (p = 0.019), and a short preaneurysmal M1 segment (p = 0.043) were all statistically significant risk factors for a premature rupture. Plus, a receiver operating characteristic curve analysis revealed that a preaneurysmal M1 segment length ≤ 13.3 mm was the best cutoff value for predicting the occurrence of a premature rupture (area under curve 0.747; sensitivity 63.64%; specificity 81.66%).

CONCLUSIONS

Patients exhibiting a sphenoid ridge proximation sign, the presence of a frontal ICH, and/or a short preaneurysmal M1 segment are at high risk for an intraoperative premature rupture of a MCA aneurysm. Such high-risk MCA aneurysms have a superficial location close to the arachnoid in the sphenoidal compartment of the sylvian fissure and have a rupture point directed anteriorly.

During surgery for a ruptured intracranial aneurysm, intraoperative premature rerupture of the aneurysm is an ever-present, unpredictable danger leading to an unfavorable outcome. Potential causes of a premature rupture include vibration transmitted from craniotomy drilling; changes in the transmural pressure upon dural opening; removal of the intracerebral hemorrhage (ICH), with relief of a tamponade effect on the rupture point; brain retraction imparting shear stress on the aneurysm dome; and surgical dissection of the rupture point.2,8,19 In particular, a premature rupture before establishing proximal vascular control can lead to the most catastrophic bleeding. Although advances in surgical techniques and anesthetic care have reduced the incidence of premature ruptures, they can still occur unexpectedly and lead to poor outcomes.

Aneurysm surgery is performed using different strategies and tactics according to the aneurysm location. Middle cerebral artery (MCA) aneurysms draw attention as one of the most common aneurysm locations for which surgical treatment is indicated. Their wide necks with arterial branches arising at the aneurysm base and their peripheral location with straightforward surgical access generally indicate surgical clipping over endovascular coiling. Notwithstanding, the premature rupture of an MCA aneurysm remains a worrisome problem. In particular, if the aneurysm is located in the proximal or sphenoidal compartment of the sylvian fissure containing the initial, horizontal segment of the MCA and has a rupture point directed anteriorly, the risk of an early, premature rupture of the aneurysm when splitting the proximal sylvian fissure is extremely high.

Accordingly, we investigated surgically treated cases of ruptured MCA aneurysms to identify the risk factors that can predict a premature rupture and for which appropriate surgical management must be applied.

Methods

Patient Population

During an 8-year period (January 2007 to December 2014), 182 consecutive patients among a total of 927 patients with a ruptured intracranial aneurysm underwent surgical clipping for a ruptured MCA aneurysm at our institution and were enrolled in this retrospective study. The inclusion criteria for this study were as follows: 1) age > 20 years; 2) diagnosis of a subarachnoid hemorrhage (SAH) based on CT scans or spinal taps; 3) diagnosis of a ruptured MCA aneurysm based on angiographic examinations, including CT angiography (CTA) and/or catheter (conventional) angiography; and 4) treatment with surgical clipping. This study was reviewed and approved by the ethics committee at the Kyungpook National University Hospital.

Surgery for Ruptured MCA Aneurysms

All the ruptured MCA aneurysm surgeries were conducted by an experienced neurovascular surgeon (J.P.) using an emergency treatment strategy.15 Whereas a standard pterional craniotomy was commonly performed, a super-ciliary keyhole approach was applied for 6 patients.

Following the administration of 0.5 g/kg of mannitol, ventricular drainage was introduced using a modified Paine technique in most cases, and a subfrontal approach was used to open the arachnoid over the optic nerve to achieve a relaxed condition of the brain.14 After opening the carotid cistern to expose the supraclinoid internal carotid artery (ICA), the arachnoid over the sphenoidal compartment of the sylvian fissure was opened using proximal-to-distal dissection. This is preferred by many neurosurgeons for cases of ruptured MCA aneurysm, because it exposes the M1 segment of the MCA and allows early proximal vascular control with some frontal retraction.9,13,20 After dissecting the proximal sylvian fissure the dissection shifted to the distal sylvian fissure, where the superior trunk of the MCA was followed to the aneurysm in a distal-to-proximal dissection. Finally, the aneurysm was dissected and clipped permanently.

Identification of Premature Rupture

Cases of premature rupture were identified based on the operative medical records and video recordings. A premature rupture was defined as an aneurysmal rupture that occurred before securing the proximal vessel or dissecting the aneurysm neck, and that resulted in severe arterial bleeding. Minor bleeding during clip application was not included in this study.

The premature rupture occurrences were classified according to the stage of the surgery, as follows: 1) craniotomy and dural opening; 2) aspiration or removal of the ICH; 3) retraction of the frontal lobe; 4) dissection of the sphenoid segment of the sylvian fissure for access to the proximal vessel; and 5) perianeurysmal dissection.

Clinical Characteristics and Radiological Findings

The medical records were reviewed to obtain relevant clinical information, and all the radiological data used in this study were obtained using an electronic picture archiving and communication system. Clinical data, including age, sex, and clinical grade, were collected. The clinical grade was determined at admission using a World Federation of Neurosurgical Societies (WFNS) grade.

All patients for whom conventional CT scans or spinal taps confirmed the presence of an SAH underwent a brain CTA and/or catheter angiography (only CTA for 18 patients, both CTA and catheter angiography for 141 patients, and only catheter angiography for 23 patients). A postoperative angiographic evaluation using CTA was performed in all patients. The radiological findings were reviewed by neurosurgeons (J.P., W.S., and K.S.P.), and the collected data included the following variables: the modified Fisher grade, volume and location of the ICH associated with the ruptured MCA aneurysm, maximum diameter of the ruptured aneurysm, length of the preaneurysmal M1 (sphenoidal) segment extending from the bifurcation of the ICA to the MCA aneurysm, and a sign of sphenoid ridge proximation.4

The sphenoid ridge proximation sign was defined as a spatial proximation < 4 mm between the sphenoid ridge and the rupture point of the MCA aneurysm, such as a daughter sac, irregularity, or dome of the aneurysm, based on the axial source images of the brain CTA (Fig. 1). An aneurysm rupture point bordering the cortical arachnoid of the sphenoidal sylvian fissure and adjacent superficial sylvian vein was also occasionally identified. The M1 segment of the MCA parallels the course of the sphenoid ridge and is buried deep in the sphenoidal sylvian fissure. Thus, if the preaneurysmal M1 segment is short and the rupture point of the aneurysm is directed anteriorly and located superficially, these elements prompt a sphenoid ridge proximation sign. Splitting the sphenoidal sylvian fissure is a crucial step to establish proximal vascular control, yet this can incur a premature rupture in the case of a sphenoid ridge proximation sign.

FIG. 1.
FIG. 1.

Case 4. Imaging showing sphenoid ridge proximation sign observed in a patient with a premature rupture. A: Axial CTA source image showing the dome (arrow) of the ruptured MCA aneurysm bordering a superficial sylvian vein (empty arrowheads) and the proximation to the medial portion of the sphenoid ridge (solid arrowheads). B: A 3D CTA image revealing the ruptured MCA aneurysm, with a short (11.2 mm) preaneurysmal M1 segment (double-headed arrow) and rupture point (arrow) projecting anteriorly.

Statistical Analysis

The statistical analyses were performed with the aid of commercially available statistics software (SPSS version 19.0, IBM Corp.). Univariate and multivariate analyses were both performed. The following variables were investigated as potential risk factors for a premature aneurysmal rupture: age, sex, WFNS clinical grade, modified Fisher grade, presence of an ICH, frontal ICH, temporal ICH, volume of the ICH, maximum diameter of the ruptured MCA aneurysm, length of the preaneurysmal M1 segment, and the presence of a sphenoid ridge proximation sign. A 2-sample t-test was used for the quantitative variables (age, volume of the ICH, MCA aneurysm diameter, length of the preaneurysmal M1 segment), whereas a chi-square analysis was used for the categorical variables. A multivariate analysis was then performed using a binary logistic regression analysis. The results were considered significant for probability values < 0.05. Meanwhile, a receiver operating characteristic curve analysis was used to find the best cutoff length for determining whether the preaneurysmal M1 segment was affecting the occurrence of a premature aneurysmal rupture.

Results

Patient Characteristics

The clinical and radiological characteristics of the 182 patients who underwent surgical clipping for a ruptured MCA aneurysm are summarized in Table 1. The patient age ranged from 21 to 84 years (mean 55.5 ± 12.3 years; the mean is given ± SD throughout), and 56 patients (30.8%) were male. According to the clinical grading system proposed by the WFNS, Grade I was assigned to 68 patients (37.4%), Grade II to 78 patients (42.9%), Grade III to 10 patients (5.5%), Grade IV to 20 patients (11.0%), and Grade V to 6 patients (3.3%).

TABLE 1.

Clinical and radiological characteristics of 182 patients with a ruptured MCA aneurysm

CharacteristicValue*
Mean age in yrs, ± SD55.5 ± 12.3
Male sex56 (30.8)
WFNS grade
  I68 (37.4)
  II78 (42.9)
  III10 (5.5)
  IV20 (11.0)
  V6 (3.3)
Modified Fisher grade
  04 (2.2)
  163 (34.6)
  214 (7.7)
  377 (42.3)
  424 (13.2)
ICH location48 (26.4)
  Frontal lobe18 (9.9)
  Temporal lobe30 (16.5)
Mean diam of MCA aneurysm in mm, ± SD6.9 ± 4.5
Mean length of preaneurysmal M1 in mm, ± SD17.2 ± 5.1
Sphenoid ridge proximation sign11 (6.0)
Premature rupture11 (6.0)

Diam = diameter.

Unless otherwise noted, values are expressed as the number of patients (%).

Based on an examination of the preoperative CT scans, for which the modified Fisher grading scale was used to assess the severity of the SAH, Grade 0 was assigned to 4 patients (2.2%), Grade 1 to 63 patients (34.6%), Grade 2 to 14 patients (7.7%), Grade 3 to 77 patients (42.3%), and Grade 4 to 24 patients (13.2%).4 In addition, an ICH was associated with the ruptured MCA aneurysm in 48 patients, in whom the mean volume of the ICH was 25.0 ± 18.7 ml (range 2–87 ml) and the predominant location of the ICH was the frontal lobe (n = 18) and temporal lobe (n = 30).

Using the angiographic examinations, the maximum diameter of the MCA aneurysms ranged from 2.2 mm to 32.0 mm (mean 6.9 ± 4.5 mm), and the length of the preaneurysmal M1 segment ranged from 7.4 mm to 31.1 mm (mean 17.2 ± 5.1 mm). The preaneurysmal M1 segment was < 15 mm in 59 patients (32.4%). Meanwhile, the axial source images of the CTA revealed a sphenoid ridge proximation sign in 11 patients (6.0%).

Premature Rupture

A total of 11 patients (6.0%) suffered a premature rupture of the MCA aneurysm during surgery (Table 2). In 2 of these, arterial bleeding through the cerebral cortex in the frontal lobe was noticed after dural opening (Case 1), and a premature rupture was induced by aspirating an associated ICH (Case 2).

TABLE 2.

Clinical and radiological characteristics of 11 patients with intraoperative premature rupture of an MCA aneurysm

Case No.SexAge (yrs)WFNS GradeModified Fisher GradeICH Site (vol in ml)MCA Aneurysm Diam (mm)Length of Preaneurysmal M1 (mm)Sphenoid Ridge Proximation SignRupture Stage1-Mo mRS Score
1F44II3Frontal lobe (21)8.519.0014
2M64III3Frontal lobe (52)7.310.5025
3F47I2NA6.015.4131
4F51IV3NA5.511.2144
5F54II3Frontal lobe (2)13.710.1143
6F45I1NA11.015.8141
7F77II3Frontal lobe (18)12.213.3143
8F84II1NA13.115.7152
9F36I1NA7.611.0051
10M35IV4NA4.012.6051
11F69II3NA4.29.8051

mRS = modified Rankin Scale; NA = not applicable.

However, in 6 cases, a sphenoid ridge proximation sign was observed in the preoperative CTA, and the premature ruptures occurred during one of the following 3 operative stages: 1) during retraction of the frontal lobe to access the optic nerve cistern and carotid cistern for draining CSF (n = 1); 2) during opening of the sphenoidal sylvian fissure to access the proximal M1 segment and establish proximal vascular control (n = 4, Fig. 2); and 3) during perianeurysmal dissection (n = 1, Fig. 3).

FIG. 2.
FIG. 2.

Case 7. Imaging obtained in a patient with a premature rupture during the opening of the sphenoidal sylvian fissure. A: Axial CTA source image showing the ruptured MCA aneurysm (arrow) and the proximation to the medial portion of the sphenoid ridge (solid arrowheads), representing the sphenoid ridge proximation sign. B: A 3D CTA image revealing the ruptured MCA aneurysm, with an anterior-directed small outpouching (arrow) suggesting the rupture point.

FIG. 3.
FIG. 3.

Case 8. Imaging obtained in a patient with a premature rupture during perianeurysmal dissection. A: Axial CTA source image showing the ruptured MCA aneurysm (arrow) bordering a superficial sylvian vein (empty arrowheads) and the proximation of the sphenoid ridge (solid arrowheads), representing the sphenoid ridge proximation sign. B: A 3D CTA image revealing the ruptured MCA aneurysm, with the rupture point (arrow) projecting anteriorly.

For the remaining 3 cases, the premature ruptures occurred during perianeurysmal dissection.

Risk Factors for Premature Rupture

In the univariate analysis, a sphenoid ridge proximation sign (54.5% [6 of 11 patients] in the premature rupture group vs 2.9% [5 of 171 patients] in the nonpremature rupture group), frontal ICH (36.4% [4 of 11 patients] in the premature rupture group vs 8.2% [14 of 171 patients] in the nonpremature rupture group), and short preaneurysmal M1 segment (mean 13.1 ± 3.0 mm in the premature rupture group vs 17.4 ± 5.1 mm in the nonpremature rupture group) were all associated with the occurrence of a premature rupture. In contrast, the age, sex, WFNS clinical grade, modified Fisher grade, presence of a temporal ICH, volume of the ICH, and maximum diameter of the MCA aneurysm showed no between-group difference (Table 3).

TABLE 3.

Results of univariate analysis of risk factors for premature rupture in patients with MCA aneurysm*

VariablePremature Rupture, n = 11No Premature Rupture, n = 171p Value
Mean age in yrs, ± SD55.1 ± 16.355.6 ± 12.00.905
Sex0.351
  Male2 (18.2)54 (31.6)
  Female9 (81.8)117 (68.4)
WFNS grade0.818
  I3 (27.3)65 (38.0)
  II5 (45.5)73 (42.7)
  III1 (9.1)9 (5.3)
  IV2 (18.2)18 (10.5)
  V0 (0)6 (3.5)
Modified Fisher grade0.905
  00 (0)4 (2.3)
  13 (27.3)60 (35.1)
  21 (9.1)13 (7.6)
  36 (54.5)71 (41.5)
  41 (9.1)23 (13.5)
ICH0.466
  Present4 (36.4)44 (25.7)
  Absent7 (63.6)127 (74.3)
Frontal ICH0.002
  Present4 (36.4)14 (8.2)
  Absent7 (63.6)157 (91.8)
Temporal ICH0.128
  Present0 (0)30 (17.5)
  Absent11 (100.0)141 (82.5)
Mean vol of ICH in ml, ± SD8.5 ± 16.46.5 ± 14.50.666
Mean diam of MCA aneurysm in mm, ± SD8.5 ± 3.56.8 ± 4.50.249
Mean length of preaneurysmal M1 in mm, ± SD13.1 ± 3.017.4 ± 5.10.008
Sphenoid ridge proximation sign<0.001
  Present6 (54.5)5 (2.9)
  Absent5 (45.5)166 (97.1)

Values are expressed as the number of patients (%) unless noted otherwise. Boldface type indicates statistical significance.

According to the chi-square test.

According to the 2-sample t-test.

The multivariate analysis using a binary logistic regression analysis revealed that a sphenoid ridge proximation sign (p < 0.001), frontal ICH associated with the ruptured MCA aneurysm (p = 0.019), and short preaneurysmal M1 segment (p = 0.043) were all statistically significant risk factors for a premature rupture (Table 4).

TABLE 4.

Results of multivariate analysis using binary logistic regression for premature rupture in patients with MCA aneurysm*

VariableOR95% CIp Value
Presence of frontal ICH8.9361.430–55.8300.019
Length of preaneurysmal M10.7980.641–0.9930.043
Sphenoid ridge proximation sign44.9497.535–268.143<0.001

Boldface type indicates statistical significance.

Meanwhile, a receiver operating characteristic curve analysis revealed that a preaneurysmal M1 segment length ≤ 13.3 mm was the best cutoff value for predicting the occurrence of a premature rupture (area under curve 0.747). The sensitivity and specificity of the cutoff value were 63.64% (95% CI 30.8–89.1) and 81.66% (95% CI 75.0–87.2), respectively.

Surgical Results of Premature Rupture Cases

In 10 of the 11 patients (90.9%), the premature rupture was controlled and the aneurysm neck clipped without compromising the parent vessels. However, in Case 7, an extracranial-to-intracranial bypass using the great saphenous vein was performed due to perianeurysmal parent vessel damage.

In 3 patients (27.3%; Cases 1, 2, and 5), the premature aneurysmal rupture developed into an ICH with subsequent brain swelling. After clipping the ruptured aneurysm, intraoperative brain imaging was required to diagnose and demarcate the ICH. Intraoperative ultrasonography using Paine's point as an ultrasound window, which we have previously reported, was useful to diagnose and remove the ICH.16 The 3 patients with an ICH experienced a poor clinical outcome postoperatively despite successful aneurysm clipping.

The clinical outcomes for the remaining 7 patients (63.6%), who did not have a bypass and ICH removal, were favorable and unaffected by the intraoperative premature rupture.

Discussion

The reported incidence of intraoperative premature aneurysmal ruptures is 6%–20%.1,5–7,10,11 However, this has not been specifically investigated for ruptured MCA aneurysms, although the aneurysm surgery is performed using different strategies and tactics based on specific anatomical characteristics according to the aneurysm location.3,12,17,21 In the present study of ruptured MCA aneurysms, the incidence of premature rupture was 6% and the risk factors included a sphenoid ridge proximation sign, the presence of a frontal ICH, and a short preaneurysmal M1 segment.

These 3 risk factors were mainly derived from MCA aneurysms that were buried in the sphenoidal compartment of the sylvian fissure due to a short preaneurysmal M1 segment, that had a superficial location close to the arachnoid, and that had a rupture point directed anteriorly. The length of the preaneurysmal M1 segment was < 16 mm (range 10.1–15.8 mm) in the cases in which patients exhibited a sphenoid ridge proximation sign (i.e., Cases 3–8).

In the cases with a sphenoid ridge proximation sign, the steep sphenoidal compartment of the sylvian fissure was dissected along the frontal side of the superficial sylvian veins with some frontal retraction, thereby exposing an anterior aspect of the aneurysm immediately after the arachnoid opening and violating the rupture point before proximal vascular control. The shorter the preaneurysmal M1 segment, the higher the risk of a premature rupture before proximal vascular control. The source images of the CTA showed the aneurysm located medially along the sphenoid ridge and close to the anterior clinoid process in the cases with a short preaneurysmal M1 segment.

A frontal ICH associated with a ruptured MCA aneurysm is a strong sign of an anterior-directed rupture point and is a risk factor (Fig. 4). Plus, if it arises from the sphenoidal compartment of the sylvian fissure, this contributes to a sphenoid ridge proximation sign.

FIG. 4.
FIG. 4.

Case 5. Imaging obtained in a patient with a premature rupture. A: A 3D CTA image showing the MCA bifurcation aneurysm with an anterior-directed daughter sac (solid arrow) in close vicinity to the medial portion of the sphenoid ridge (sphenoid ridge proximation sign). Note a typical contralateral MCA aneurysm (empty arrow) far from the sphenoid ridge. B: Axial CT scan showing a frontal ICH (arrow) associated with the ruptured MCA aneurysm. The frontal location of the ICH strongly suggests an anterior-directed rupture point.

Thus, appropriate surgical strategies and tactics are vital in the case of a sphenoid ridge proximation sign, especially in cases of a ruptured MCA aneurysm close to the anterior clinoid process. Intraoperative external ventricular drainage is required to obtain early and sufficient brain relaxation before frontal retraction. This allows safe access to the carotid cistern and chiasmatic cistern to establish proximal control, using an ICA and A1 segment as the first step. Minimal dissection of the most proximal sylvian fissure can then be performed with minimal frontal retraction to expose the closest part of the M1 segment and place a temporary clip. Further dissection of the sylvian fissure can lead to an aneurysm rupture and back-bleeding from a distal artery. In this case, the bleeding can be controlled using a tamponade and suction, and a temporary clip can be applied to the distal artery for lesion trapping. Finally, the aneurysm can be clearly dissected and permanently clipped. Alternatively, if early proximal vascular control is established, sylvian fissure dissection provides a distal shift enabling distal-to-proximal and inside-out dissection. This minimizes the frontal lobe retraction and superficial dissection within the sphenoidal sylvian fissure compartment and can reduce the risk of a premature rupture.

If a premature rupture of an MCA aneurysm is encountered unexpectedly, the surgical management is essentially the same as for other aneurysms.8,9,18,19 The use of suction (2-mm diameter) and a tamponade (a small piece of cotton) can reduce the bleeding from the rupture point and allow sylvian fissure dissection to be performed more proximal to the aneurysm, to place a temporary clip on the proximal parent artery. The establishment of proximal vascular control is the first crucial target of the maneuver. The dissection of the more distal sylvian fissure and a temporary clip on the distal parent artery for lesion trapping then facilitate the aneurysmal dissection and permanent clipping.

The current study is limited because it is a retrospective review of a small case series from a single institution. In addition, the sylvian fissure dissection in the current cases was performed in a proximal-to-distal manner; however, distal-to-proximal dissection may also affect the occurrence of a premature rupture and lead to different risk factors. Notwithstanding, the identification of cases with the highest risk of premature rupture of an MCA aneurysm and the proposal of appropriate surgical tactics will be informative for neurosurgeons.

Conclusions

The risk factors for an intraoperative premature rupture of an MCA aneurysm were found to include a sphenoid ridge proximation sign, the presence of a frontal ICH, and a short preaneurysmal M1 segment. These risks were mainly derived from MCA aneurysms that were buried in the sphenoidal compartment of the sylvian fissure due to a short preaneurysmal M1 segment, that had a superficial location close to the arachnoid, and that had a rupture point directed anteriorly.

Acknowledgments

This research was supported by a grant from the Korea Health Technology R & D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HI15C0001).

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    Stoodley MAWeir BKASurgical treatment of middle cerebral artery aneurysms. Le Roux PDWinn HRNewell DW: Management of Cerebral Aneurysms PhiladelphiaSaunders2004. 795807

  • 21

    Zhen YYan KZhang HZhao SXu YZhang H: Analysis of the relationship between different bleeding positions on intraoperative rupture anterior circulation aneurysm and surgical treatment outcome. Acta Neurochir (Wien) 156:4814912014

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: J Park. Acquisition of data: Son, KS Park. Analysis and interpretation of data: Son, KS Park. Drafting the article: J Park. Reviewed submitted version of manuscript: Kang. Approved the final version of the manuscript on behalf of all authors: J Park. Statistical analysis: J Park, Shin. Administrative/technical/material support: Kang. Study supervision: J Park.

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Article Information

INCLUDE WHEN CITING Published online February 5, 2016; DOI: 10.3171/2015.10.JNS151586.

Correspondence Jaechan Park, Department of Neurosurgery, Kyungpook National University Hospital, 50, Samduk 2-ga, Jung-gu, Daegu 700-721, Republic of Korea. email: jparkmd@hotmail.com.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Case 4. Imaging showing sphenoid ridge proximation sign observed in a patient with a premature rupture. A: Axial CTA source image showing the dome (arrow) of the ruptured MCA aneurysm bordering a superficial sylvian vein (empty arrowheads) and the proximation to the medial portion of the sphenoid ridge (solid arrowheads). B: A 3D CTA image revealing the ruptured MCA aneurysm, with a short (11.2 mm) preaneurysmal M1 segment (double-headed arrow) and rupture point (arrow) projecting anteriorly.

  • View in gallery

    Case 7. Imaging obtained in a patient with a premature rupture during the opening of the sphenoidal sylvian fissure. A: Axial CTA source image showing the ruptured MCA aneurysm (arrow) and the proximation to the medial portion of the sphenoid ridge (solid arrowheads), representing the sphenoid ridge proximation sign. B: A 3D CTA image revealing the ruptured MCA aneurysm, with an anterior-directed small outpouching (arrow) suggesting the rupture point.

  • View in gallery

    Case 8. Imaging obtained in a patient with a premature rupture during perianeurysmal dissection. A: Axial CTA source image showing the ruptured MCA aneurysm (arrow) bordering a superficial sylvian vein (empty arrowheads) and the proximation of the sphenoid ridge (solid arrowheads), representing the sphenoid ridge proximation sign. B: A 3D CTA image revealing the ruptured MCA aneurysm, with the rupture point (arrow) projecting anteriorly.

  • View in gallery

    Case 5. Imaging obtained in a patient with a premature rupture. A: A 3D CTA image showing the MCA bifurcation aneurysm with an anterior-directed daughter sac (solid arrow) in close vicinity to the medial portion of the sphenoid ridge (sphenoid ridge proximation sign). Note a typical contralateral MCA aneurysm (empty arrow) far from the sphenoid ridge. B: Axial CT scan showing a frontal ICH (arrow) associated with the ruptured MCA aneurysm. The frontal location of the ICH strongly suggests an anterior-directed rupture point.

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Zhen YYan KZhang HZhao SXu YZhang H: Analysis of the relationship between different bleeding positions on intraoperative rupture anterior circulation aneurysm and surgical treatment outcome. Acta Neurochir (Wien) 156:4814912014

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