Computed Tomography- and Magnetic Resonance Image-based Analysis of the Anatomical Variations of the Sylvian Fissure and Characteristics of the Middle Cerebral Artery

A Novel Surgical Classification of the Sylvian Fissure and Its Implications on the Clinical and Radiological Outcomes of Patients Undergoing Clipping for Unruptured Middle Cerebral Artery Aneurysms

BACKGROUND

The main access route for middle cerebral artery (MCA) aneurysms is the transsylvian approach. Although Sylvian fissure (SF) variations have been assessed, none have examined how this affects MCA aneurysm surgery. The objective of this study is to investigate how SF variants affect clinical and radiological outcomes for surgically-treated unruptured MCA aneurysms.

METHODS

This retrospective study examined consecutive unruptured MCA aneurysms in 101 patients undergoing SF dissection and aneurysm clipping. SF anatomical variants were categorized using a novel functional anatomical classification: Type I: Wide straight, Type II: Wide with frontal and/or temporal opercula herniation, Type III: Narrow straight, and Type IV: Narrow with frontal and/or temporal opercula herniation. The relationships between SF variants and postoperative edema, ischemia, hemorrhage, vasospasm, and Glasgow Outcome Scale (GOS) were analyzed.

RESULTS

Study included 101 patients (53.5% women), 60.9 ± 9.4 (range 24-78) years. SF types were 29.7% Type I, 19.8% Type II, 35.6% Type III, and 14.9% Type IV. The SF type with the highest proportion of females was Type IV (n = 11, 73.3%), while it was Type III for males (n = 23, 63.9%) (P = 0.03). There were significant differences between SF types, ischemia, and edema (P < 0.001, P = 0.008, respectively). Although narrow SF types had poorer GOS scores (P = 0.055), there were no significant differences between SF types and GOS, postoperative hemorrhage, vasospasm, or hospital stay.

CONCLUSIONS

Sylvian fissure variants may impact intraoperative complications during aneurysm surgery. Thus, presurgical determination of SF variants can predict surgical difficulties, thereby potentially reducing morbidity for patients with MCA aneurysms and other pathologies requiring SF dissection.

The role of the Sylvian fissure configuration and the vascular anatomy on different bleeding patterns in ruptured middle cerebral artery aneurysms

OBJECTIVE

Ruptured middle cerebral artery (MCA) aneurysms are one of the causes of subarachnoid (SAH) or intracerebral hemorrhage (ICH) but the factors associated with the bleeding type are unknown. The aim of the study was to analyze the association of the morphological variations of the Sylvian fissure (SF) and vascular parameters on occurrence of different bleeding patterns in patients with ruptured MCA aneurysms.

PATIENTS AND METHODS

The data of consecutive 202 patients with ruptured MCA aneurysm of two centers were included for analysis. Patients were divided into three groups: Group 1 with SAH, Group 2 with accompanying ICH and Group 3 with intrasylvian hemorrhage (ISH). The SF was divided into five types according to the previously described classification. Analyzed vascular parameters were aneurysm size, localization, presence of a daughter aneurysm, shape, and angulation of the aneurysm sac.

RESULTS

A total of 202 patients (141 female, 61 male, mean age 52.4 yr) were included in this study. 67 patients (33.2%) had a SAH, 122 (60.4%) an ICH and 13 (6.4%) presented with ISH. Statistical analysis showed a significant association of narrow and twisted SF types 4 and 5 (p < 0.001) and temporal angulation of the aneurysm (p = 0.030) for occurrence of ICH. All other vascular parameters showed no significant association for any kind of hemorrhage.

CONCLUSION

Our results allow the conclusion that the complex SF types 4 and 5, as well as the temporal angulation of the aneurysm sac are associated with the occurrence of ICH in ruptured MCA aneurysms.

Morphology of the lateral fossa of the brain (sylvian valley): anatomo-radiological aspects and surgical application

INTRODUCTION

The knowledge acquired on the lateral fossa of the brain (LFB) is heterogeneous and incomplete. Our goal was to provide a morphological description of the LFB and analyze the impact of these descriptions on the surgical approach of the region.

METHODS

The morphology of LFB was studied on 40 cerebral hemispheres of 20 right-handed subjects aged 18-55 years with an MRI of 1.5 T. The anatomo-radiological identification of the two section levels preceded the description of the shapes of the LFB. From these landmarks, the forms presented by the LFB were identified and described on each of the transverse, sagittal and frontal planes. The comparison of the proportion of shapes made it possible to identify the typical shapes at each section level and on each section plane.

RESULTS

The average age of the subjects was 33 years with extremes of 19 and 54 years including 7 women and 13 right-handed men. According to the plane and the level of section, 6 typical morphologies of the LFB have been described, 2 of which were identical. The forms did not vary according to the cerebral hemisphere or the sex of the subject. The set of typical morphologies made it possible to determine a reference subject called NSK which presented the greatest number of typical morphological characteristics.

CONCLUSION

Knowledge of LFB anatomical imaging is of paramount importance in the pre-surgical evaluation of pathologies in this region. The reference subject will be used for our future biometric and three-dimensional manual reconstruction work in this region.