- Department of Neurosurgery, Klinikum Duisburg, Academic Teaching Hospital of University Essen-Duisburg, Germany
Hannah M. Ngando, Homajoun Maslehaty, Athanasios K. Petridis
Department of Neurosurgery, Klinikum Duisburg, Academic Teaching Hospital of University Essen-Duisburg, Germany
DOI:10.4103/2152-7806.119073Copyright: © 2013 Ngando HM This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Ngando HM, Maslehaty H, Schreiber L, Blaeser K, Scholz M, Petridis AK. Anatomical configuration of the Sylvian fissure and its influence on outcome after pterional approach for microsurgical aneurysm clipping. Surg Neurol Int 30-Sep-2013;4:129
How to cite this URL: Ngando HM, Maslehaty H, Schreiber L, Blaeser K, Scholz M, Petridis AK. Anatomical configuration of the Sylvian fissure and its influence on outcome after pterional approach for microsurgical aneurysm clipping. Surg Neurol Int 30-Sep-2013;4:129. Available from: http://sni.wpengine.com/surgicalint_articles/anatomical-configuration-of-the-sylvian-fissure-and-its-influence-on-outcome-after-pterional-approach-for-microsurgical-aneurysm-clipping/
Background:The sylvian fissure (SF) is the anatomical pathway used in a pterional approach, which leads to most aneurysms. There are four different anatomical variants of the SF described. In the present retrospective study the four different categories of the SF were studied in order to evaluate any correlation of these variants to surgical outcome.
Methods:Patients treated for intracranial aneurysms by a pterional transsylvian approach during 2003-2012 (N = 237) were included in the study. The SF category was determined by analysis of preoperative computed tomography (CT) scanning. Patients were grouped into unruptured intracranial aneurysms (UIA) and ruptured intracranial aneurysms with subarachnoid hemorrhage (SAH) according to the Hunt and Hess grades. Brain edema, vasospasms, ischemic lesion rate, and outcome were evaluated for possible correlation with SF anatomical variants.
Results:Postsurgically brain edema formation correlated significantly with more complex anatomical variants of the SF in patients with UIAs and in patients with Hunt and Hess 1 and 2. Ischemia rate, vasospasms, or clinical outcome was not negatively affected though.
Conclusion:The classification of the SF as proposed by Yasargil is more than a pure anatomical observation. In this retrospective study, we show that the anatomical variants of the SF can be associated to postoperative complications like formation of brain edema or ischemic lesions Preoperative knowledge of the SF anatomy and possibly consecutive adapted extend of the surgical approach can decrease procedure-related morbidity.
Keywords: Aneurysm, sylvian fissure, subarachnoid hemorrhage
The pterional approach to aneurysms of the circle of Willis is one of the most common approaches in vascular neurosurgery.[
A more complex SF anatomy could affect the surgical outcome by a pterional approach. In the present study, we aimed to analyze systematically the role of the anatomical variants of the SF and its influence on procedure-related complications like edema, ischemic lesions, and cerebral vasospasm and outcome. Furthermore, we considered the question of whether a complex SF anatomy affect postsurgical outcome and should play a role in the planning of the extend of the pterional approach to intracranial aneurysms.
In this study, we retrospectively reviewed the charts of all patients with operatively treated aneurysms at our department from 2003 to 2012 (N = 239) by a classical pterional approach. The preoperative CCTs, digital subtraction angiograms (DSA) and CT angiograms (CTA), were evaluated to specify the anatomy of the SF as characterized by Yasargil. However, we slightly modified the classification to enable categorization on the CCTs (category I-IV)[
Sylvian fissure categories. 1: Straight wide or narrow SF; 2: Wide fissure with herniation of the frontal or temporal lobe; 3: Herniation of the frontal or temporal lobe and narrow SF; 4: Herniation of temporal and frontal lobe.
TB: Temporal bone, SF: Sylvian fissue, FL: Frontal lobe, TL: Temporal lobe, Arrow: Herniation of frontal or temporal lobe
SF category I: Straight and wide or narrow, II: Wide fissure with herniation of the frontal or temporal lobe, III: Herniation of the frontal or temporal lobe and narrow SF and IV: Herniation of the temporal- and frontal-lobe into the fissure. The Fisher grade was evaluated on the CCT.[
The postoperative brain edema was categorized as 0: No edema, 1: Perifocal edema with maximum radius of 2 cm around the SF and 2: Severe edema with midline shift.[
The edema formation in patients with aneurysms treated surgically with aneurysm clipping through a pterional approach was evaluated for every SF category separately. Additionally the patients were categorized in patients with unruptured intracranial aneurysms (N = 98) (UIA) and those with SAH (HH grade 1 and 2 (N = 48), HH grade 3 (N = 17), HH grade 4 and 5 (N = 76)).
The anatomical variants of the SF were evaluated by considering the defined factors to identify the influence on postoperative imaging changes and clinical outcome.
To evaluate the distribution of patient age and SAH, the patients were categorized into different age groups: <40, 40 to <50, 50 to <60, 60 to <70, and >70 years. Aneurysm size was classified as <1, 1-2.5, and >2.5 cm.
Aneurysm shape was characterized as berry, multilobular, and fusiform.
All the patients were treated in the neuro-intensive care unit (neuro-ICU) and transcranial Doppler sonography has been performed daily for 5-14 days in cases of SAH.
All the aneurysms included in the study were clipped within 72 hours after bleeding.
Statistical analysis has been performed by Fisher's t-test, Chi-square, and analysis of variance (ANOVA). A statistical significant result represents a P < 0.001.
Anatomy of the sylvian fissure and edema formation after pterional approach to aneurysms
Patients with UIAs
In patients with UIAs (N = 98) 38 (38.8%) had a SF type I, 43 (43.9%) type II, 13 (13.3%) type III, and 5 (5.1%) patients had a type IV SF. In the SF type I group five patients had a mild edema and three suffered of severe brain edema. In SF type II group 10 patients had a mild and 1 a severe edema, in SF type III group 9 patients had a mild and 1 a severe edema, whereas in group IV none of the 5 patients had an edema. As shown in
(a) The sylvian fissure category III is significantly correlated with a postsugical brain edema. (b) The categories of the sylvian fissure do not correlate with the infarction rate. (c) The vasospasm rate does not correlate with the sylvian fissure category. (d) The glasgow outcome scale does not correlate with the sylvian fissure category. Numbers are given as percentage(**P<0.001)
Ischemic lesions occurred in four patients of group I, in nine of group II, in two of group III and zero in group IV [
The rate of transient vasospasm without occurrence of delayed cerebral ischemia (DCI) in patients operated on UIAs was low (N = 11, 11.2%): Seven in group I, four in group II. None of the patients in groups III and IV developed vasospasms. The differences between the groups were not statistically significant [
The postoperative outcome of the patients was almost similar for all four groups without any statistically significant difference. Thirty-three patients in group I had a good outcome (GOS 4 and 5) and five had a severe neurological deficit. In group II, 39 patients had a GOS of 4 and 5 and 4 a GOS of 3, in group III 12 patients had a GOS of 4 and 5 and 1 a GOS of 3. In group IV one patient had a GOS of 3 and 4 a GOS of 4 and 5 [
The edema formation was not associated with a higher incidence of ischemic lesions in the studied groups. There was a trend showing an association of severe edema (grade 2) and vasospasm but a statistical significant result could not be proven since the patients with edema and spasms or ischemia or both were very few to allow a reliable statistical analysis.
Patients with SAH, HH 1 and 2
In patients with SAH HH 1 and 2 (N = 48) 26 had a SF type I, 14 type II,7 type III and only 1 patient had a type IV SF. In the SF group I 1 patient had a mild edema and 4 suffered of severe brain edema. In category II, four patients had a mild and three a severe edema, in category III one patient had a mild, and three a severe edema, whereas in group IV the one patient had no edema. As shown in
(a) The sylvian fissure categories II and III are significantly correlated with a postsugical brain edema. (b) The categories of the sylvian fissure do not correlate with the infarction rate. (c) The vasospasm rate does not correlate with the sylvian fissure category. (d) The glasgow outcome scale does not correlate with the sylvian fissure category. Numbers are given as percentage (**P<0.001)
Four patients of group I, two of group II, two of group III, and 0 of group IV developed an ischemic stroke [
The rate of vasospasm in patients operated on ruptured aneurysms in HH 1 and 2 was higher compared with patients with UIAs (31/48 vs. 11/98, P < 0,001). Fifteen patients of group I, 11 of group II, 4 of group III, and 1of group IV had vasospasms. The differences between the groups though were not statistically significant [
The postoperative outcome of the patients was almost similar for all four groups without any statistically significant difference. Twenty-four patients of group I had a good outcome (GOS 4 and 5) and two had a severe neurological deficit. In group II, 13 patients had a GOS of 4 and 5 and 1 a GOS of 3. In group III, 12 patients had a GOS of 4 and 5 and 1 a GOS of 3 and in group IV the patient had a GOS 5 [
Similarly, in this group the edema formation was not associated with a higher incidence of ischemic lesions or vasospasms or both in the studied groups.
Patients with SAH HH 3-5
An association between the SF anatomy and edema formation, as well as ischemic and vasospasm rate could not be seen in patients with SAH HH3 (N = 17) or HH 4 and 5 (N = 76). The rate of brain edema in HH3 was 6/9 in SF group I patients, 1/2 in group II, 2/3 in group III and 1/1in group IV.
In the HH 4 and 5 group, the edema rate was high through all the SF groups indicating the severity of the initial bleeding as a crucial factor masking the anatomical variants of the SF. Twenty-one of thirty-six patients had a severe edema in SF group I, 20/24 in group II, 6/9 in group III and 5/7 in group IV. No statistical correlation between SF category and edema could be seen. Similarly, in SF category I 16/36 patients, 15/24 in category II, 4/9 in category III and 4/7 in category IV developed ischemic lesions, being statistically insignificant.
General characteristics of the patient groups UIAs, HH 1 and 2, HH 3-5
The highest incidence of diagnosed UIAs was in the age group 50 to <60 years (40/98) (P < 0.001,
Aneurysm shape and size
In all groups berry aneurysm shape was the most common (P < 0.001) [
As shown in
Vasospasms and ischemic lesions
After surgical treatment of patients with UIAs, 11.2% had vasospasms on transcranial doppler. In HH 1 and 2 the vasospasm incidence increased to 67% (P < 0.001 HH 1 and 2 vs. UIAs). In HH 3 66% of patients had vasospasms, in HH 4 81% and in HH 5 the incidence was likewise 81%. The vasospasm rate was as expected the highest in HH 4 and 5. There was a statistically significant higher number of ischemic lesions in the HH 5 patients compared with all other groups (49%, P < 0.001) [
Suppl. Figure 4
Association of SAH severity, vasospasm and infarction. The rate of vasospasm (red line) is increasing significantly when bleeding occurs. Even when vasospasm rate increases significantly in HH 1 and 2 the infarction rate in this group is similar to incidental aneurysms without bleeding which has a low number of patients with spasms. The vasospasm rate is not rising significantly from H 1 and 2 to HH 4 and 5 but the infarction rate rises significantly in HH 4 and 5 (**P<0.001). Numbers are given as percentage
In HH group 1 and 2, 22/98 patients had Fisher 3 and 4 bleeding, the remaining patients (67/98) had Fisher 1 and 2 bleeding. In HH 4 and 5 74/76 patients had Fisher 4 and 2/76 had a Fisher 3 bleeding. None had Fisher 1 or 2 bleeding (P < 0.001 for more severe bleedings and higher Fisher grade in HH 4 and 5).
Yasargil described four anatomical variants of the SF.[
In contrast, the role of neuroanesthesia helps tremendously in reducing brain tension and promoting a slack brain.[
In the present study we did not focus on the implication of SF anatomy/edema formation and different surgical approach strategies, although this is a subject, which would be interesting to study.
Another interesting point considering the anatomy of the SF is the preoperative knowledge of the anatomical variant for neurovascular surgeons in training. SF category 3 and 4 requires more brain retraction to reach the aneurysm lying in a complex SF. Hence, complex SF anatomy should not be the first surgical experience for the neurovascular rookie. SF category I is the easiest anatomical variant to approach an aneurysm and can be more suitable for a neurosurgeon who just started clipping procedures. The preoperative examination of the CCTs allows a safe identification of the SF anatomy and this anatomical variant should be always taken into consideration when planning the approach to the aneurysm in order to avoid complications.
As already shown in the pioneering reports of Fisher[
Other factors like patient age, aneurysm location, shape, and size were similar between the studied groups showing a satisfying conformity of the studied groups.
The classification of the SF as proposed by Yasargil is more than a pure anatomical observation. In this retrospective study, we show that the anatomical variants of the SF can be associated to postoperative complications like formation of brain edema or ischemic lesions. Preoperative knowledge of the SF anatomy and possibly consecutive adapted extend of the surgical approach can decrease procedure-related morbidity.
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