Parafalcine meningioma is difficult to expose due to its deep location in the cerebral longitudinal fissure. Generally, the ipsilateral craniotomy is performed. Under the microscope, the cerebral hemisphere is retracted from the falx cerebri by a brain retractor. The tumor base is first devascularized and then dissected from the surrounding cerebral structures. After tumor is completely removed, the base on the falx cerebri is electrocauterized [4, 5]. However, this approach has its limitations: 1. The meningioma is deeply buried in the ipsilateral cerebral longitudinal fissure. It requires a use of brain retractor to retract hemisphere from the falx cerebri. This operation may lead to postoperative intracerebral hematoma and injury, retractor-induced edema, or ischemic injury due to retractor-induced decrease in cerebral blood perfusion resulting from a direct compression to the cortex and subcortical tissues . 2. The tumor has to be devascularized at its base. Debulking and devascularization has to be done at the same time due to the block from tumor itself, which easily lead to the excessive blood loss and is not conducive to postoperative recovery. In some cases, sometimes, it is even required to remove the brain tissues in frontal or occipital lobes to expose tumor .
Soumya Mukherjee reported the resection of a parafalcine meningioma from the contralateral longitudinal fissure approach under the microscope. It can avoid the retraction of cortex to expose tumor and reduce the retraction-induced brain injury and edema. At the same time, it can expose the falx first to facilitate the devascularization of meningioma . However, it is still required to retract the brain tissue using retractor to expose the lateral fissure for surgery, which cannot achieve a complete retractorless. Thus, it may still lead to retractor-induced edema, or a direct compression to the cortex and subcortical tissues.
The rapid development of neuroendoscopy in recent years has provided us a basis for exploring the resection of parafalcine meningioma without a retractor. The surgical position is rotated 15–20° to the opposite side, and the contralateral cerebral lobe is collapsed laterally by gravity, so that the natural cavity of the longitudinal fissure is exposed as wide as possible. The endoscope can be directly inserted into the longitudinal fissure and reach the lower boundary of the falx cerebri- the lower sagittal sinus -without any brain retractor to facilitate the exposure of the longitudinal fissure. When the operation begins to excise the falx cerebri, the endoscopic close observation and multi-angle observation are used to assist the tumor devascularization from any part of contralateral falx cerebri without any retractor. The falx cerebri can be more widely exposed and excised to achieve SIMPSON Grade I resection and reduce recurrence. When separate the arachnoid between the tumor and the surrounding normal brain tissues, the ipsilateral approach is vertical to the tumor boundary, while the contralateral approach enters at an oblique angle that reduces the retraction of brain tissues. Combining endoscopic close- and multi-angle observations, the contralateral approach can completely separate the arachnoid between tumor and surrounding normal brain tissues and reduce the retraction-induced brain edema and injury (Fig. 3). In addition, in this case, the ipsilateral brain surface has a thick drainage vein, which also increases the difficulty of ipsilateral approach. Once the drainage vein of the functional area is damaged, it is easy to cause severe postoperative dysfunction or even unrecoverable dysfunction. Moreover, in this case, arachnoid cysts were observed on the contralateral side and the cerebral cortex was significantly lower than the contralateral side, which also created conditions for the contralateral approach. In our another case, we observed the contralateral arachnoid cyst and the significantly lower cortex. Whether the contralateral arachnoid cysts are accidental events or patterns remains unknown and it needs further studies.