Anatomy of the medial orbit and various approaches to access it Osamu Akiyama, MD 1,2 ; Akihide Kondo, MD 1 ; Hajime Arai, MD 1 ; Albert L. Rhoton, Jr., MD 2† 1 Juntendo university, Department of Neurosurgery, Japan 2 Department of Neurological Surgery, University of Florida Osamu Akiyama MD, PhD. Juntendo University, Department of Neurosurgery Email:[email protected] Contact 1. Düz, B., Secer, H. I., & Gonul, E. (2009). Endoscopic approaches to the orbit: a cadaveric study. min-Minimally Invasive Neurosurgery, 52(03), 107-113. 2. Wu, W., Selva, D., Jiang, F., Jing, W., Tu, Y., Chen, B., ... & Qu, J. (2013). Endoscopic transethmoidal approach with or without medial rectus detachment for orbital apical cavernous hemangiomas. American journal of ophthalmology, 156(3), 593-599. 3. Gönül, E., Erdogan, E., Düz, B., & Timurkaynak, E. (2003). Transmaxillary approach to the orbit: an anatomic study. Neurosurgery, 53(4), 935- 942. 4. Moe, K. S. (2003). The precaruncular approach to the medial orbit. Archives of facial plastic surgery, 5(6), 483-487. 5. Rhoton Jr, A. L. (2003) Cranial anatomy and surgical approaches. Neurosurgery, 53(2)331-362. 6. Natori, Y., & Rhoton Jr, A. L. (1994). Transcranial approach to the orbit: microsurgical anatomy. Journal of neurosurgery, 81(1), 78-86. References The medial orbit can be the site of several pathological lesions such as cavernomas, neurinomas, and lymphomas. However, approaching the medial orbit remains a challenging task because of the narrow surgical corridors, surrounding critical neural structures, and complicated vascular relationships. Background The surgical approaches to the medial orbit can be classified into three categories: (1) transcranial approach, (2) trans-sinus approaches: transethmoidal and transmaxillary approaches, and (3) transorbital approaches: precaruncular and medial orbital approaches. The transcranial approach exposes the superior and medial surfaces of the orbit and the optic apex widely. The trans-sinus approach exposes the medial and inferior surfaces of the orbit and optic nerve. The transorbital approach exposes the anterior and medial surfaces of the orbit, but the surgical corridor to the optic canal and apex in this approach is relatively narrower and deeper compared to that in the previous two approaches. Ten adult cadaveric specimens were examined using magnifications ranging from 3X to 40X after perfusion of the arteries and veins with colored silicone. The microsurgical anatomy of the medial orbit and surgical approaches to it were examined. All approaches were performed using 0° rigid endoscopes or the surgical microscope. Methods and Materials The knowledge of the microsurgical anatomy of the medial orbit and surrounding critical structures and the selection of an appropriate surgical approach will make surgical procedures safe and precise. Conclusions Objective To examine the microsurgical anatomy of the medial orbit and compare the various surgical approaches 1-6 to access it. Results Microsurgical anatomy of the medial orbit Transcranial approach Trans-sinus approach Illustrative case –Orbitofrontal approach- A Illustrative Case. A 37-year-old woman presented with right exophthalmos. The orbitofrontal approach was performed. The pathological finding was schwannoma. A: Oblique anterior view B: Anterior view of the combined medial orbital and maxillary exposures. C: Inferior view of the anterior and middle cranial base. D: Enlarged inferior view of the orbit. E: Anterior view. F: Enlarged lateral view of the orbit. G: Medial view of the orbit. Illustrative case –Medial approach- 7-year-old girl presented with exophthalmos. MR imaging demonstrated a anteromedial tumor of the orbit. The medial approach was performed. The pathological finding was a lymphangioma. Transmaxillary approach A: Anterior view. B: Medial view. C: Anterior view D: Inferior view. Transorbital approach Orbitofrontal approach Medial approach Precaruncular approach V2 CN I Front. Sinus Eth. Sinus Ant. Eth. A. Sphen. Sinus Sup. Troch. N. Supraorb. N. Lac. Gland Lev. M. Sup. Rec. M. Front. N. CN II Lac. N. Post. Eth. A. Trochlea Sup. Obl. M. Infra. Temp. Fossa Sup. Rec. M.(Reflected) Lev. M. Reflected) V1 Ophth. A. Nasocil. N. Car. A. Bifr ontal approach Sphen.Sinus Car. A. Max. A. Med. Obl. M. Temp. M. Inf. Rec. M. Inf. Orb. N. & A. Pterygopal. A. CN I Clivus Max. Sinus CN II Inf. Rec. M. Lat. Rec. M. CN IV CN III to Inf. Rec. M. Med. Rec. M. Sphen. Sinus Car. A. Pit. Gland Ophth. A. Chiasm Sup. Hyp. A. V2 Infraorb. N. & A. Max. A. Pterygopal. A. Zygo. N. Ophth. V. CN II CN III Sup. Div. to Lev. M. CN III Inf. Div. to Inf. Obl. M. Sup. Rec. M. Front. N. V 1 V 2 CN III Cil. Gang. Ophth. A CN III Sup. Div. To Sup. Rec. M. Periorbita (reflected) Inf. Obl. M. Short Cil. N. Long. Cil. N. Nasocil. N. CN III Motor Root Inf. Rec. M. CN III Inf. Div. to Inf. Rec. M. CN III Inf. Div. Med. Rec. M. Inf. Obl. M. Lat. Rec. M. CN III Inf. Div. To Inf. Obl. M. Inf. Ophth. V. Short. Cil. N. Cent. Ret. A. Nasolac. Duct Eth. Sinus Nasal Septum Ant. Eth. A. Med. Canth. Lig. Inf. Concha Max. Sinus Mid. Concha Sup. Concha Nasal Septum Max. Sinus Font. Sinus Eth. Sinus Zygoma Nasolac. Duct Nasal Cavity Oral Cavity Inf. Orb. N. Short. Cil. N. Inf. Orb. N. & A. Lat. Rec. M. Nasal Cavity Med. Rec. M. Inf. Rec. M. Inf. Orb. N. & A. Max. A. Cav. Sinus v Müllers’s M. V2 Optic Canal Inf. Rec. M. Lat. Rec. M. Med. Rec. M. Sup. obl. M. Sup. Ophth. V. Ophth. A. Max. A. Orbit Floor Inf. Orb. N. Nasal Cavity Max. Sinus Nasal Septum Cav. Sinus Car. A. Optic Canal Eth. Sinus Max. A. CN II Med. Rec. M. Inf. Rec. M. Sup. Rec. M. Ophth. A CN II Pit. Gland Sphen. Sinus Inf. Rec. M. CN III Sup. Div. to Lev. M. Pterygopal. A. Max. A. Inf. Orb. N. & A. V2 Cav. Sinus Front. Sinus Sup. Opthal. V. Trochlea Lev. M. Lac. Gland Ant. Eth. A. Sup. Troch. N. Supraorb. N. Sup. Obl. M. Front. N. Lac. N. & A. Optic. Canal Lat. Rec. M. Eth. Sinus Sphen. Sinus Post. Eth. A. Long Cil. N. Ophth. A. Ant. Eth. N. & A. Front. N. (reflected) Lat. Rec. M. Nasocil. N. Sup. Rec. M. (Reflected) CN VI Short Cil. N. Med. Rec. M. Sphen. Sinus Front. N. Periorbita Eth. Sinus Front. Lobe CN II Front. Lobe Orbit Temp. M. Front. Sinus Front. Bone Transethmoidal approach Front. Bone Orbit Orbit Nasal Bone Temp. M. Orbit Front. Lobe Ant. Eth. Sinus Post. Eth. Sinus Nasal Cavity Nasal Septum Ant. Eth. A. Optic Canal Post. Eth. A. Periorbita Med. Canth. Lig. Med. Canth. Lig. Med. Rec. M. Ant. Eth. A. Periorbita CN II Ophth. A Inf. Obl. M. Inf. Rec. M. Sup. Ophth. V. Periorbita Med. Wall Caruncle Caruncle Med. Canth. Lig. Preoperative MRI (T1 High Resolution Isotropic Volume Excitation: THRIVE) Postoperative MRI (THRIVE) Periorbita Tumor Tumor Orb. Oculi M. Tumor Preoperative MRI (T1WI) Postoperative MRI (T1WI) Tumor Sup. Orb. N. Sup. Rec. M. Intraoperative photograph Intraoperative photograph Globe Globe Medial Lateral Medial Lateral