Transorbital Microsurgery: An Anatomical Description of a Minimally Invasive Corridor to the Anterior Cranial Fossa and Paramedian Structures.

 Transorbital neuroendoscopic surgery (TONES) has ignited interest in the transorbital access corridor, increasing its use for single and multi-portal skull base interventions. However, the crowding of a small corridor and two-dimensional viewing restrict this access portal.  Cadaveric qualitative study to assess the feasibility of transorbital microsurgery (TMS).  Anatomical dissection steps and instrumentation were recorded for homogeneous methodology.  Six cadaveric specimens were systematically dissected using TMS to the anterior cranial fossa and paramedian structures.  Anatomical parameters of the TMS craniectomy were established, and the visible and accessible neuroanatomy was highlighted.  A superior lid crease incision achieved essential orbital rim exposure and preseptal dissection. The orbital roof craniectomy is defined by three boundaries: (1) frontozygomatic suture to the frontosphenoid suture, (2) frontal sinus and cribriform plate, and (3) frontal sinus and orbital rim. The mean (standard deviation) craniectomy was 440 mm (78 mm ). Exposing the ipsilateral optic nerve and internal carotid artery obviated the need for frontal lobe retraction to identify the A1-M1 bifurcation as well as near-complete visualization of the M1 artery.  TMS is a feasible corridor for intracranial access. Mobilization of orbital contents is imperative for maximal intracranial access and protection of the globe. TMS enables access to the frontal lobe base, ipsilateral optic nerve, and most of the ipsilateral anterior circulation. This cosmetically satisfactory approach causes minimal destruction of the anterior skull base with satisfactory exposure of the anterior cranial fossa floor without sinus invasion.