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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 31  |  Issue : 4  |  Page : 1402-1409

Aneurysm geometrics impact on microsurgical modality of ruptured and unruptured middle cerebral artery aneurysms


1 Department of Neurosurgery, Faculty of Medicine, Menoufia University, Alexandria, Egypt
2 Department of Neurosurgery, Faculty of Medicine, Alexandria University, Alexandria, Egypt

Date of Submission05-Jun-2017
Date of Acceptance23-Aug-2017
Date of Web Publication14-Feb-2019

Correspondence Address:
Ahmed Mansour
Department of Neurosurgery, Faculty of Medicine, Menoufia University, 2 Salah Abo El-Kher Street, Shebeen El-Kom 32511, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_371_17

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  Abstract 


Objective
The aim of this study was to evaluate the influence of study of parent vessel and aneurysm geometry in modifying surgical therapeutic modalities of cerebral aneurysms.
Background
Saccular aneurysms are localized bulging of intracranial blood vessels. Imaging technologies have improved our understanding of the three-dimensional orientation of cerebral aneurysms. The localization, size, and morphology of middle cerebral artery (MCA) aneurysms are recognized as essential for the rupture risk prediction.
Patients and methods
Forty-one patients who underwent surgical treatment of at least one MCA aneurysm (nine patients in the ruptured group and 32 patients in the unruptured group) were analyzed for information on aneurysm morphology: shape, diameters, neck width, parent vessel diameter, location of the aneurysm [ first part of the MCA (M1) or the bifurcation segment], and the presence of branching vessels. Aneurysm occlusion and parent artery patency were assessed by intraoperative indocyanine green angiography. Postprocedural assessment included assessment of the patient's clinical condition and radiological follow-up.
Results
Forty-one aneurysms were clipped (100%) and nine aneurysms were wrapped and clipped (21%). The frequency of multilobulated aneurysms and aneurysms with bleb were significantly different in the subrachnoidal hemorrhage (SAH) group versus the non-SAH group. Branching vessels out of the aneurismal neck were registered and the frequency of aneurysms with the branch vessel was significantly different in the SAH versus the non-SAH group.
Conclusion
In MCA aneurysms, independent predictors for the risk of rupture and for the postsurgical outcome are the presence of SAH, location on the bifurcation segment, multilobulation, blebs, size, and finger-shaped aneurysm.

Keywords: angiography, indocyanine green, intracranial aneurysm, rupture risk


How to cite this article:
Mansour A, Alemam S, Albeltagy H, Hassan T, Gaber E. Aneurysm geometrics impact on microsurgical modality of ruptured and unruptured middle cerebral artery aneurysms. Menoufia Med J 2018;31:1402-9

How to cite this URL:
Mansour A, Alemam S, Albeltagy H, Hassan T, Gaber E. Aneurysm geometrics impact on microsurgical modality of ruptured and unruptured middle cerebral artery aneurysms. Menoufia Med J [serial online] 2018 [cited 2024 Mar 28];31:1402-9. Available from: http://www.mmj.eg.net/text.asp?2018/31/4/1402/252052




  Introduction Top


Saccular aneurysms are localized bulging of intracranial blood vessels, commonly at bifurcation or branching arteries. Most aneurysms stay asymptomatic, but rupture causes subarachnoid hemorrhage (SAH), with subsequent morbidity and mortality[1],[2].

Improvements in imaging technologies have enhanced our understanding of the three-dimensional (3D) orientation of cerebral aneurysms, which has further influenced therapeutic modalities, and aids neurosurgeons in the diagnosis, planning, and effective evaluation of the treatment procedures[3].

Comparisons of standardized classifications enable assessment of treatment techniques of different aneurysms, thus aiding in their management and approaches; this classification can enable comparisons of different treatment techniques and decision-making, and also provides information on cerebral vasculature computer models to obtain 3D morphological classifications[4].

The risk factors for aneurysm rupture include aneurysm-related factors, location, size, and morphological features such as the shape, and also patient-related factors such as genetics, sex, age, hypertension, and smoking. Assessment of all these factors and others can help to link the clinical events and pathophysiology behind aneurysm genesis, growth, and rupture[5].

The localization, size, and morphology of middle cerebral artery (MCA) aneurysms are recognized as essential for the rupture risk prediction vessel identification, in addition, considered as indicators of intraoperative complications. Nowadays, these factors are commonly associated with preoperative planning and decision-making[6]. Preoperative planning of aneurysm surgery should be integrated with the process of aneurysm formation, progression, and rupture; thus, comparisons of the risks and benefits of therapeutic modalities can be performed[6],[7],[8],[9],[10].

The aim of this study was to evaluate the influence of the study of the parent vessel and aneurysm geometry in modifying surgical therapeutic modalities of cerebral aneurysms.


  Patients and Methods Top


This was a case-series study in which we analyzed the preoperative angiography and the preoperative and postoperative computed tomography scans, as well as patient data, of 41 patients who underwent surgical treatment of at least one MCA aneurysm (nine patients in the ruptured group and 32 patients in the unruptured group) who presented to Menoufia University Hospitals, Alexandria University Hospitals, and Tohoku University Hospitals during the period from October 2015 to October 2016.

The study was approved by the Ethical Committee of Menoufia Faculty of Medicine and informed consent was obtained from each patient.

From 2015 to 2016, 41 patients were referred for microsurgical treatment of MCA aneurysms: nine patients with ruptured aneurysms and 32 with unruptured aneurysms. These included 30 women and 11 men with a mean age of 61.6 ± 8.25 years. Patients were classified according to age, sex, presenting symptoms, aneurysm exact location and side, aneurysm characteristics, size, presence of the branch vessel in relation to the aneurysm dome or neck, or bleb at the wall of the aneurysm; also, for ruptured aneurysms, we used the Hunt and Hess, and Fisher grading systems. Personal history information on hypertension, dyslipidemia, diabetes mellitus (DM), and trauma was obtained. Family history of stroke, SAH, hypertension, and DM was also recorded. Patients were asked about their symptoms, including headache, vomiting, failure of visual acuity, double vision, epileptic fits, neck pain or stiffness, facial weakness, motor weakness, and sphincter disturbance. Patients were assessed using the Hunt and Hess grading system and neurological examination.

For all aneurysms, we analyzed the geometric data including the diameter, aspect ratio (AR), and neck width of the aneurysms. Also, statuses of the parent artery (PA) and the branch vessel or perforators in relation to the aneurysms were analyzed.

Special attention was focused on the techniques used for surgery in terms of the number of clips used to secure aneurysm occlusion and techniques for preservation of the PA, and branch vessel or perforators. Further assessment was performed by indocyanine green (ICG) and electrophysiological studies for confirmation of aneurysm occlusion and patency of PA, and changes in brain function, respectively.

Finally, the clinical and radiological outcomes were assessed after surgery and 6-month follow-up using the Modified Rankin Scale (MRS), and other radiological methods such as magnetic resonance angiography, computed tomography angiography (CTA), and in some cases by digital subtraction angiography.

Inclusion criteria

We specifically studied patients with MCA aneurysms because of their superficial location within the Sylvain fissure and because easy exposure of the entire aneurysm wall is possible during surgery.

Exclusion criteria

To prevent the generation of false results in the geometric representation, we did not include any patient in whom radiological studies indicated severe vasospasm.

Patients were scanned. Then, the data were reconstructed 3D from rotational angiographic images. To increase visualization of the vasculature, a contrast was used; quantification of vascular dimensions was performed.

All patients were assessed for information on aneurysm morphology, shape, diameters, neck width, parent vessel diameter, location of the aneurysm [ first part of the MCA (M1) or the bifurcation segment], and the presence of branching vessels.

Two-dimensional size indices were defined: neck width, aneurysm diameter, and aneurysm depth. Neck width is the diameter of the curve in the point that is considered the beginning of the aneurysm. Aneurysm diameter is the maximal distance between the walls of the aneurysm. Aneurysm depth is the maximal perpendicular distance between the top of the aneurysm dome and the plane of the surface of the neck. The determination of neck width and aneurysm depth values enabled the calculation of the aneurysm volume, area, and the neck area.

The AR proposed to represent the shape of an aneurysm in a single parameter; it was assessed for a better description of the aneurysm than only the size. It was calculated with the maximum distance from the neck to the dome divided by the width of the neck.

In all patients, aneurysm clipping was performed using the peritoneal approach in the microsurgical technique. Aneurysm occlusion and PA patency were assessed by ICG angiography. All patients were transferred to the neurosurgical ICU, where treatment was administered.

Timing of the procedure, anesthesia used, and the type of procedure, materials used, and procedural complications were assessed. Surgical techniques were identified, and orientation of the clip across the aneurysm neck, number and type of clips, and special techniques for large and complex aneurysms were determined.

Postprocedural assessment included assessment of the patient's clinical condition using the Hunt and Hess grading scale and evaluation of the clinical outcome using the postoperative and late follow-up MRS.

Radiological follow-up of the cases with 3D CTA or digital subtraction angiography assessed the benefit of geometric studies of the parent vessel and aneurysm on the technique to improve the long-term effectiveness and safety of patients' therapy. The mean follow-up period after treatment was 6 months.

Statistical analysis

Ruptured and unruptured aneurysm groups were analyzed separately. The risk of aneurysm rupture was tested statistically for all parameters. Data were collected, tabulated, and analyzed statistically using an IBM personal computer using the statistical package for the social science (IBM SPSS, version 20; IBM Corp., Armonk, New York, USA), where the following statistics were calculated.

Descriptive statistics

Quantitative data were presented in the form of mean, SD, and range; qualitative data were presented in the form of numbers and percentages.

Analytical statistics

  1. The χ2-test was used to study the association between two qualitative variables
  2. The Mann–Whitney U-test is a test of significance used for comparison between two non-normally distributed groups with quantitative variables
  3. Fisher's exact test was used for 2 × 2 tables when the expected cell count of more than 25% of cases was less than 5
  4. Spearman's correlation coefficient test (r-test) is a test of significance used to study the correlation between nonparametric quantitative variables. Correlation coefficient test (r-test) results may have a positive (+) or a negative (−) correlation. It is used to quantify the strength of the linear relationship between two variables
  5. A P value of more than 0.05 was considered not statistically significant
  6. A P value of less than or equal to 0.05 was considered statistically significant
  7. A P value of less than or equal to 0.001 was considered highly statistically significant.



  Results Top


We included 11 men and 30 (41 patients) women. The mean age of the patients was 61.6 years (range: 33–73 years). Nine patients presented with SAH. Of all patients, 34 (83%) had a relevant accompanying disease or a major risk factor; arterial hypertension was present in 25 (60%) patients, dyslipidemia in 22 (53.6%) patients, and DM in six (14.6%) patients. Family history of aneurysm surgery or SAH was found in 32 (78%) patients. Of all patients, 38 (92.6%) had a presenting symptom; headache was present in 31 (75%) patients, stroke in two (0.04%) patients, and epilepsy in one (0.02%) patient. No statistically significant difference was detected in age and sex distribution, comorbidity, family history, and presenting symptoms between the SAH and the non-SAH groups [Table 1].
Table 1: Demographics, comorbidities, and clinical presentation

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In terms of the qualitative morphological geometric parameters, in the entire population, 15 (36.5%) aneurysms had a bleb in the dome of aneurysm, which had a relation with SAH. The frequency of aneurysms with bleb was significantly different in the SAH versus the non-SAH group (P < 0.001). In 19 (46.5%) patients, branching vessels out of the aneurismal neck were found; the frequency of aneurysms with the branch vessel was significantly different in the SAH group versus the non-SAH group (P < 0.001). Forty (97%) aneurysms were saccular with a single berry whereas 12 (29%) aneurysms had a multilobulated configuration. The frequency of multilobulated aneurysms was significantly different in the SAH group versus the non-SAH group (P < 0.001). A total of aneurysms 24 (58.5%) originated from the M1-segment, whereas 18 (43.9%) aneurysms were found in the bifurcation segment; significantly more patients presented with a bifurcation segment aneurysm in the SAH group compared with the non-SAH group (P < 0.05). In terms of quantitative morphological geometric parameters, 38 aneurysms were 5–10 mm in diameter (92.6%), whereas three (7.4%) aneurysms were larger than 10 mm in diameter; nonruptured aneurysms showed significantly smaller aneurysm diameter than ruptured group (P = 0.008). A total of 11 aneurysms had neck width more than or equal to 4 mm (wide neck) (26.8%), whereas 29 (73.2%) aneurysms had less than 4 mm neck width; no significant difference was noted between the SAH and the non-SAH group in the neck width. There were 26 aneurysms with AR more than or equal to 1.6 (63%), whereas 14 (37%) aneurysms had AR less than 1.6. There were 11 aneurysms with AR more than or equal to 2 (27.5%), whereas 29 (72.5%) aneurysms had AR less than 2; no significant difference was noted between the SAH and the non-SAH group in the AR more than 1.6, whereas a significant difference was noted in AR more than 2 (P = 0.03) [Table 2].
Table 2: Aneurysm and parent vessel morphologic and geometric measures

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In terms of outcomes, intraoperative rupture of the aneurysm occurred in seven (17%) patients; aneurysms ruptured significantly more often intraoperatively in patients with SAH than in patients with non-SAH aneurysms. This difference was statistically significant (P < 0.001). Postoperative new morbidity also appeared in four (0.1%) patients, with significant frequency in SAH compared with the non-SAH group (P = 0.028). The neurological outcome was classified using the MRS; few days after aneurysm clipping (MRS post), and 6 months during the follow-up visits (MRS follow-up) were assessed and showed that postoperative and follow up morbidity scores had significant positive correlation with rupture status of aneurysms. P = 0.001 and P less than 0.001, respectively [Table 3].
Table 3: Clinical outcome assessment

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A significant correlation was found between MRS post with bleb and multilobulated aneurysms independently (P = 0.016 and P < 0.001); additionally with MRS follow up, same correlation was noted, P = 0.008 and P less than 0.001, respectively. Moreover, MRS follow-up as an outcome measure showed a significant correlation with AR less than 2 than more than 2 (P = 0.005), proving that round-shaped aneurysms rather than oblong-shaped aneurysms showed a better outcome during follow-up [Table 4].
Table 4: Correlation between aneurysm geometry and special characteristics of the aneurysm wall with postoperative and follow-up Modified Rankin Scale

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Accordingly, we assessed independent morphological features that influence the surgical modality of the aneurysm. The use of multiple clips rather than a single clip was significantly influenced by whether the diameter of the aneurysm was larger than 10 mm (P = 0.027) and also by the shape of the aneurysm, represented by AR more than 1.6 and more than 2 (P < 0.001), meaning that oblong-shaped aneurysms needed more clips to occlude the neck of the aneurysm and to achieve complete aneurysm obliteration. Other factors such as bleb, branch vessel, or multilobulated aneurysms required more frequent usage of multiple clips, but this was not statistically significant. Surgical wrapping combined with clipping was used in nine patients and wrapping alone was not used in our series of surgical cases; use of this technique was affected significantly only by AR more than 1.6 (P = 0.026) [Table 5].
Table 5: Impact on technique (multiple clipping and wrapping)

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A model case was presented with the preoperative clinical and radiological data. An intraoperative technique with dissection, aneurysm, and parent vessel identification, and a plan for surgery were established (1-5-5, Otemachi, Chiyoda-ku, Tokyo 100-8176, Japan). A Sugita vascular clip (Mizuho medical Co., Ltd., Tokyo, Japan), and a Yasargil vascular clip (Aesculap AG, Tuttlingen, Germany), were used; the orientation of the clip used was monitored, and finally, the ICG monitor of blood flow to assess the patency of PA and complete aneurysm occlusion were recorded [Figure 1]a,[Figure 1]b,[Figure 1]c.
Figure 1: (a) Case presentation: preoperative clinical and radiological data. (b) Case presentation: Intraoperative technique with dissection, aneurysm, and parent vessel identification, and plan for surgery. (c) Case presentation: clipping technique, orientation and type of clip used, and indocyanine green (ICG) monitoring of patency of the parent artery and complete aneurysm occlusion.

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  Discussion Top


Family history, hypertension, dyslipidemia, and DM are, respectively, associated with aneurysms, but did not significantly affect the SAH status. Headache and progressively enlarging aneurysms, respectively, were the frequent presentations for aneurysms in our series.

The majority of MCA aneurysms are nongiant and localized in the M1 and/or the bifurcation segment[11]. More variable surgical modalities are needed for complex aneurysms. Nevertheless, some MCA aneurysms with complex characteristics may require multiple clipping or other different techniques, aiming to avoid intraoperative rupture, postoperative morbidity, and to enable complete aneurysm occlusion[12].

The presence of SAH is an obvious factor that is indicative for urgent treatment of the aneurysm; also, it requires more preparation and affects the outcome[13]. Accordingly, we found an increased rate of intraoperative aneurysm rupture in patients with SAH and a statistically significantly higher rate of a new morbidity immediately postoperatively in patients in the SAH group compared with the non-SAH group[12].

Other factors that can affect MCA aneurysm treatment are the size, shape, location, and the related vasculature[14],[15],[16],[17]. Several authors have described a significantly larger size of ruptured MCA aneurysms compared with asymptomatic ones. Van Dijk et al.[11] retrospectively reviewed 151 patients with MCA aneurysms; 77 of these patients had SAH. In two-thirds of these patients, the aneurysm size was larger than 6 mm. Güresir et al.[14] found a mean diameter of 8.8 mm in the SAH group, whereas the other group had a significantly smaller mean size of 6.5 mm.

In our study, most of represented aneurysms were in the 5-10 mm diameter group. Moreover, when evaluating the AR, this difference was even more obvious. Thus, it may be assumed that oblong-shaped aneurysms with larger AR more than 1.6 and more than 2 tend to be at a higher risk for initial rupture compared with ballooned or round-shaped aneurysms.

In addition, an oblong-shaped configuration of aneurysms requires more experienced surgical skills secondary to flow-related factors than in ballooned aneurysms[18],[19]. Our data support this theory as the AR was associated significantly with increased use of special techniques, multiple clips, or clips combined with wrapping.

Moreover, in relation to outcomes with the use of the MRS, we found that worse outcome was detected with aneurysms larger than 10 mm and with AR more than 2; thus, oblong-shaped or finger-shaped aneurysms have a higher risk of rupture and worse outcome.

Many authors have reported that aneurysm rupture is associated with multilobulated shapes[11],[14] and our data support these findings. In our population, we significantly more frequently detected a multilobulated shape of aneurysms in the SAH group. Also, we detected more frequent aneurysms with bleb in the SAH group. Moreover, worse outcome was detected with multilobulated and bleb using the MRS; however, no significant effect on surgical modality was found. Intraoperative rupture can be avoided by proximal control in almost every case of a ruptured, multilobulated aneurysm[12],[20],[21],[22]. In our series, intraoperative rupture and the appearance of new morbidity postoperatively were significantly and independently related to SAH.

Previous reports did not clearly define a Wide neck aneurysm[14],[23],[24],[25]. In our series, we determined the neck diameter quantitatively; a larger neck width was associated with greater surgery-related difficulty and need for the use of different configurations and types of multiple clips, However, detailed preoperative planning using aneurysm geometric analysis and in some cases hemodynamic assessment allowed for better outcome even in complex cases.

Branching vessels were found to affect the risk of rupture and the difficulty of surgery, in addition, incorporation of aneurysm neck with the M1 and/or bifurcation segments is significantly more often present in ruptured MCA aneurysms[14],[26]. In our study, aneurismal localization on the bifurcation segment and the presence of branching vessels were associated independently with a higher risk of SAH, but this was not statistically significant.

Treatment of MCA aneurysms remains the domain of operative vascular neurosurgery. However, in addition to the presence of subarachnoid hemorrhage, the identification of significant morphological features of the aneurysm itself and of its direct anatomical environment strongly influence the surgical strategy. Our results show that a detailed preoperative angiographic evaluation is useful to obtain valuable data on the complexity of the aneurysm and surgical difficulty. The key features of size, shape, and branching vessels should always be considered during surgical planning.


  Conclusion Top


For MCA aneurysms, SAH, location on the Bifurcation segment, multilobulation, blebs, and aneurysm size and shape were independent predictors for the risk of rupture and for the postsurgical outcomes. These important morphological features can be assessed easily by CTA and rotational angiography. Thus, a preoperative standardized assessment of these morphological features is recommended.

Financial support and sponsorship

Egyptian ministry of higher education supported the 1st and corresponding authour with a joint supervision program to complete part of the study, and scholarship with neurosurgery department, Tohoku university graduate school of medicine, Sendai, Japan.

Conflicts of interest

There are no conflicts of interest.



 
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