Dissection of the Sylvian Fissure in the Trans-sylvian Approach Based on the Morphological Classification of the Superficial Middle Cerebral Vein

Abstract

The superficial middle cerebral vein (SMCV) is one of the main factors that can impede a wide opening of the sylvian fissure. To reveal the most efficient SMCV dissection for a wide operative field while preserving the veins in the trans-sylvian approach, we retrospectively investigated the SMCVs through intraoperative video images. We characterized the SMCV as composed of the frontosylvian trunk (FST; receiving frontosylvian veins [FSVs] or parietosylvian veins [PSVs]), the temporosylvian trunk (TST; receiving temporosylvian veins [TSVs]), and the superficial middle cerebral common trunk (SMCCT; receiving both FSV/PSV and TSV), and classified the SMCVs of the 116 patients into 5 types based on the morphological classification of the SMCV. Type A SMCV (60.4%) with the SMCCT anastomosed to the frontal side had few bridging veins (BVs) between the SMCCT and the temporal side during dissection. Type B (7.8%) had the SMCCT with no anastomoses to the frontal side. In Type C (17.2%) consisting of the FST and TST and Type D (12.9%) with a merging of the vein of Trolard and Labbé posteriorly and the SMCVs dividing into the FST and the TST again proximally, there were few BVs between the FST and the TST during dissection. Finally, in Type E (1.7%) showing an undeveloped SMCV, there were no BVs between the frontal and the temporal lobes. Postoperative venous infarction occurred in 2.6%. Morphological classification of the SMCV can inform appropriate dissection line to create a wide operative field while preserving the veins in the trans-sylvian approach.

Keywords: frontosylvian vein; superficial middle cerebral vein; temporosylvian vein; trans-sylvian approach.

Fig. 1

FST is the SMCV that receives the FSV or the PSV. TST is the SMCV that receives the TSV. SMCCT is the SMCV that receives both the FSV (or PSV) and the TSV at the posterior end of the Sylvian fissure. FST: frontosylvian trunk, FSV: frontosylvian veins, PSV: parietosylvian veins, SMCCT: superficial middle cerebral common trunk, SMCV: superficial middle cerebral vein, TST: temporosylvian trunk, TSV: temporosylvian veins.

Fig. 2

(A) Intraoperative view of a case of Type A SMCVs (left IC–Acho A unruptured aneurysm; 71 year-old woman) and the schema of dissection of Type A SMCVs based on our classification of the SMCV. Red arrows show the dissecting line. (B) Intraoperative view of Type B SMCVs (right side) and the schema of dissection of Type B SMCVs based on our classification of the SMCV. Red arrows show the dissecting line. (C) Intraoperative view of a case of Type C SMCVs (right IC–P com A URAN; 56 year-old man) and the schema of dissection of Type C SMCVs based on our classification of the SMCV. This case seemed to have no SMCCT, and the FST and TST were recognized in parallel along the Sylvian fissure and coursed toward the skull base. Red arrows show the dissecting line. (D) Intraoperative view of a case of Type D SMCVs and the schema of dissection of Type D SMCVs based on our classification of the SMCV. Type D SMCVs can show a complex morphology at the first glance. Red arrows show the dissecting line. (E) Intraoperative view of Type E SMCVs (right side). Red arrow shows the dissecting line of the SMCV to provide mobility to the frontal and temporal lobes while preserving venous structures as much as possible. III N: oculomotor nerve, Acho A: anterior choroidal artery, AN: aneurysm, FBBV: fronto-basal bridging vein, FST: frontosylvian trunk, FSV: frontosylvian veins, IC: internal carotid, ICA: internal carotid artery, P-com A: posterior communicating artery, SMCCT: superficial middle cerebral common trunk, SMCV: superficial middle cerebral vein, TST: temporosylvian trunk, URAN: unruptured aneurysm.

Fig. 3

(A) Photograph of Type A with multiple SMCVs. (B) Photograph of Type C with multiple SMCVs. (C) The schema of dissection of the sylvian veins in cases in which the DMCV impede a wide opening of the Sylvian fissure. DMCV: deep middle cerebral vein, FBBV: fronto-basal bridging vein, FST: frontosylvian trunk, SMCCT: superficial middle cerebral common trunk, SMCV: superficial middle cerebral vein, TST: temporosylvian trunk, TSV: temporosylvian veins.