Sylvian and Insular Exposure in the Extended Minipterional Approach: Landmarks, Benefits, and Quantitative Analysis Using a Cadaveric Study

Abstract

The minipterional approach (MPTa) has been widely accepted as a minimally invasive technique in the treatment of anterior and middle cranial fossa lesions. However, this craniotomy does not facilitate exposure of the distal sylvian fissure or wide sylvian dissection. We have described a modification of the MPTa, the extended minipterional approach (eMPTa), which results in improved access to the distal sylvian fissure with minimal additional bony removal. We have defined the ideal posterior landmark for this craniotomy, the preauricular line, using an anatomic cadaveric study. The insular and sylvian exposure offered by the MPTa and eMPTa were compared in 5 cadaveric heads. Anatomic exposure of the eMPTa and its anatomic relation to different landmarks were also evaluated. The eMPTA, extending posteriorly to the preauricular line, offers improved surgical exposure of the sylvian fissure (30.5 vs. 13 mm; P < 0.001) and insula (31 vs. 10 mm; P < 0.001) compared with the MPTa. The frontal precentral artery, an important landmark for performing distal-to-proximal sylvian dissection, is 17 ± 5.2 mm anterior to the preauricular line, the posterior limit of the eMPTa. In contrast, it is 6.5 ± 3.6 mm posterior to the traditional posterior limit of the MPTa. The eMPTA offers improved access to the sylvian fissure, allowing for wider fissure splitting and only requiring extension of the posterior limit of the MPT craniotomy up to the preauricular line. This could allow for improved freedom of movement deep in the sylvian cistern and potentially expand the indications of the MPTa.