Transorbital and supraorbital uniportal multicorridor approach to the orbit, anterior, middle and posterior cranial fossa: Anatomic study

Abstract

Introduction: The transorbital route has been proposed for addressing orbital and paramedian skull base lesions. It can be complemented by further marginotomies, as per "extended-transorbital approach" and combined with others ventro-basal approaches featuring the concept of "multiportal surgery". Nevertheless, it cannot address some anatomical regions like the clinoid, carotid bifurcation and the Sylvian fissure. Therefore, we propose a combined transorbital and a supraorbital approach, attainable by a single infra-brow incision, and we called it "Uniportal multicorridor" approach.

Research question: The aim of our study is to verify its feasibility and deep anatomical targets through a cadaveric study.

Materials and methods: Anatomic dissections were performed at the Laboratory of ICLO Teaching and Research Center (Verona, Italy) on four formalin-fixed cadaveric heads injected with colored neoprene latex (8 sides). A stepwise dissection of the supraorbital and transorbital approaches (with an infra-brow skin incision) to the anterior tentorial incisura, clinoid area, lateral wall of the cavernous sinus, middle temporal fossa, posterior fossa, and Sylvian fissure is described.

Results: We analyzed the anatomic areas reached by the transorbital corridor dividing them as follow: lateral wall of the cavernous sinus, middle temporal fossa, posterior fossa, and Sylvian fissure; while the anatomic areas addressed by the supraorbital craniotomy were the clinoid area and the anterior tentorial incisura.

Conclusions: The described uniportal multi-corridor approach combines a transorbital corridor and a supraorbital craniotomy, providing a unique intra and extradural control over the anterior, middle, and posterior fossa, tentorial incisura and the Sylvian fissure, via an infra-brow skin incision.

Keywords: Anatomy; Endoscopic transorbital approach; Endoscopy; Multicorridor approach; Skull base; Supraorbital approach; Transorbital approach.

Fig. 1

Left side: A) A curvilinear skin incision is planned immediately inferior to the eyebrow from the supraorbital groove to the lateral canthus; B) The incision is made through the orbital portion of the orbicularis oculi muscle along its fibers until the periosteum is identified (POst); C) After caudo-cranial subperiosteal dissection, the orbital ridge (OR) and the frontal bone (FB) are exposed; D) The temporalis fascia and muscle are dissected in an antero-posterior caudo-cranial fashion from the lateral aspect of the orbital rim and the temporal fossa; E) the MacCarty keyhole is exposed (red circle); F) The orbital rim (OR) and the frontozygomatic suture (FZs) are exposed and the periorbita (PO) is peeled off the lateral and superior orbital wall exposing the greater sphenoid wing (GSpW); G) The supraorbital groove along with the supraorbital artery (*) and nerves (**) are identified medially; H) The transorbital corridor and the bony area for the supraorbital craniotomy are exposed. (POst: periosteum; OR: orbital ridge; FB: frontal bone; FZs: frontozygomatic suture; GSpW: greater sphenoid wing; PO: periorbita). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

Left transorbital approach: A) The periorbita is detached from the lateral wall and lateral aspect of the roof of the orbit; B) The zygomaticotemporal artery and nerve (*) are identified at the superior aspect of the lateral orbital wall; C) The zygomaticotemporal bundle is cut; D) The Hyrtl foramen (**) is visualized superolaterally to the superior orbital fissure. (OR: orbital ridge; FZs: frontozygomatic suture; GSpW: greater sphenoid wing; PO: periorbita).

Fig. 3

Left side: A) The superior orbital fissures (SOF) is exposed; B) The lateral wall of the orbit is drilled until the deep temporalis fascia is exposed. The SOF medially, the deep temporal fascia (dTF) laterally, and the lesser sphenoid wing superiorly (LSpW), represents the limits of the “V shape” craniectomy; C) After the drilling of the greater sphenoid (GSpW), the dura mater of the temporal pole is exposed and the sagittal crest (SC) medially and the inner projection of the MacCarty keyhole (red circle) laterally can be identified; D) The inferior and inferolateral portion of the greater sphenoid wing should be drilled flush with the floor of the middle fossa in order to address the structure therein located. (SOF: superior orbital fissure; suture; GSpW: greater sphenoid wing; PO: periorbita; LSpW: lesser sphenoid wing; dTF: deep temporal fascia; TD: temporal dura; SC: Sagittal crest; V3: mandibular nerve). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

Left side: A) Exposure of the frontal dura (FD) after latero-supraorbital craniotomy; B) The double transorbital and supraorbital corridors are exposed. (FD: frontal dura; PO: periorbita; OR: orbital rim).

Fig. 5

Left transorbital approach to the cavernous sinus: A) The meningo-orbital band (MOB) tethers the temporal dura (TD) to the periorbita and the superior orbital fissure (SOF) hindering the access to the lateral wall of the cavernous sinus (lwCS); B) Exposure of the lateral wall of the cavernous sinus: the first structure that can be identified is V1; C) The third and the fourth cranial nerves come then into view supermoedially to V1; D) Visualization of the oculomotor and trochlear nerves may help to infer the anterior border of the supratrochlear (black dotted circle) and infratrochlear triangles (black circle). E) Through the infratrochlear triangle, the abducens nerve can be visualized; F) Infero-laterally to V1, the second division of the trigeminal nerve (V2) can be identified. The two neural structures are divided by a bone pillar known as maxillary strut (MS). Laterally, the mandibular nerve (V3) and the middle meningeal artery (MMA) can be seen. (MOB: meningo-orbital band; TD: temporal dura; SOF: superior orbital fissure; lwCS: lateral wall of the cavernous sinus; V1: ophthalmic nerve; V2: maxillary nerve; V3: mandibular nerve; MS: maxillary strut; III: oculomotor nerve; IV: trochlear nerve; VI: abducens nerve; MMA: middle meningeal artery).

Fig. 6

Left transorbital approach to the middle fossa: A) The anteromedial (Mullan triangle) is defined by V1, V2 and by a line from the superior orbital fissure to the foramen rotundum (FR) (black dotted angle). The bone thereby present is known as maxillary strut (MS). The anterolateral triangle is bordered by V2, V3, and the line from the FR to the foramen ovale (FO) (red dotted angle); B) The mid-subtemporal ridge (STR) came into view in the lateral aspect of the surgical field, hindering the access to the foramen spinosum and the middle meningeal artery (MMA). C) The posterolateral (Glasscock) (blue dotted angle) and posteromedial (Kawase) (green dotted angle) triangles are visualized. The Glasscock's triangle is bounded by the lateral surface of the mandibular nerve, and the greater superior petrosal nerve (GSPN). The Kawase triangle is featured by the GSPN laterally, the Gasserian Ganglion (GG) and V3 anteriorly, and the petrous ridge medially. (V1: ophthalmic nerve; V2: maxillary nerve; V3: mandibular nerve; FR: foramen rotundum; FO: foramen ovale; MS: maxillary strut; TD: temporal dura; STR: mid-subtemporal ridge; MMA: middle meningeal artery; GG: Gasserian Ganglion; GSPN: greater superior petrosal nerve; FS: foramen spinosum). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 7

Left transorbital approach to the posterior fossa: A) Wide overview of the lateral wall of the cavernous sinus and middle fossa. The Kawase triangle (*) is drilled exposing the posterior fossa dura. B) The cerebellopontine angle is exposed: the acoustic-facial boundle (AFb) is seen coursing laterally toward the internal acoustic canal. The facial nerve origin from the pons (P) can be inferred on the presence of the choroid plexus (CP) protruding from the Luschka foramen, also known as Bochdalek's flower basket. Anteriorly the anteroinferior cerebellar artery (AICA) follows its course around the brainstem. (V1: ophthalmic nerve; V2: maxillary nerve; V3: mandibular nerve; TD: temporal dura; MMA: middle meningeal artery; GG: Gasserian Ganglion; GSPN: greater superior petrosal nerve; III: oculomotor nerve; IV: trochlear nerve; AFb: acoustic-facial boundle; P: pons; CP: choroid plexus; AICA: anteroinferior cerebellar artery).

Fig. 8

Left transorbital approach to the Sylvian fissure: A) The inferior orbital gyrus (IOG) of the frontal lobe (FL) and the temporal lobe (TL) are exposed and the anterior aspect of sylvian fissure (SF) is opened via sharp dissection of its arachnoid membranes; B) The Sylvian fissure is opened until the main trunk of the middle cerebral artery (mMCA) is identified bifurcating into superior (ST) and inferior (IT) trunks distally to the Limen Insulae (LI). The lateral orbitofrontal artery (*) can be seen running over the frontal side of the Sylvian fissure while the early temporal branch (**) lies on its temporal aspect branching from the main trunk or bifurcation of MCA; C) inferiorly and dorsally to the main trunk of the mMCA the uncus (black arrow) can be seen (in the picture it is located behind the early temporal branch (**)). Beyond the LI the Sylvian or insular cistern can be identified covered by arachnoid membranes (black arrowhead). (IOG: inferior orbital gyrus; FL: frontal lobe; TL: temporal lobe; lwCS: lateral wall of the cavernous sinus; SF: Sylvian fissure; mMCA: main trunk of the middle cerebral artery; ST: superior trunk of the MCA; IT: inferior trunk of the MCA; LI: limen insulae).

Fig. 9

A) Supraorbital approach to the anterior incisural space: The optic nerves (ON) and chiasm (OC) along with the lamina terminalis (LT) are exposed. Laterally to the optic nerves the supraclinoid segment of both internal carotid arteries (ICA) can be identified. The anterior communicating artery (AcoA) complex is detected, and the A1 segment of the anterior cerebral artery is followed toward the carotid bifurcation. The A2 segment is visualized into the cistern of the LT. The interoptic triangle is labelled by the *; B) Endoscopic exploration of the subchiasmatic area: the pituitary stalk (PS) piercing the diaphragm sellae (DS) is unveiled followed laterally by the superior hypophyseal arteries (black arrow); C) Endoscope exploration of the infrachiasmatic area and interpeduncular cistern: the basilar artery (BA) and its bifurcation, the right oculomotor nerve (III), the P1 segment of both posterior cerebral arteries, and the superior cerebellar artery (SCA) (Fig. 9C) can be identified. It should be noted the fetal conformation of the left posterior communicating artery (PcoA). The tuber cinereum (TC) and the mammillary bodies (MB) lie above the interpeduncular cistern. (TS: tuberculum sellae; rACP: right anterior clinoid process; lACP: left clinoid process; rON: right optic nerve; lON: left optic nerve; rICA: right internal carotid artery; ICA: left internal carotid artery; OC: optic chiasm; LT: lamina terminalis; AcoA: anterior communicating artery; A1: A1 segment of the anterior cerebral artery; A2: A2 segment of the anterior cerebral artery inferior orbital gyrus; FL: frontal lobe; DS: diaphragm sellae; PS: pituitary stalk; BA: basilar artery; P1: P1 segment of the posterior cerebral artery; P2: P2 segment of the posterior cerebral artery; PcoA: posterior communicating artery; SCA: superior cerebellar artery; TC: tuber cinereum; MB: mammillary bodies; PS: pituitary stalk; III: oculomotor nerve).

Fig. 10

Left supraorbital approach to the clinoid area: A) close up view of the oculomotor nerve (III) piercing the roof of the cavernous sinus inside the oculomotor triangle (black angle); B) the cisternal portion of the III and the trochlear nerve entering the posterolateral portion of the oculomotor triangle (Hakuba) can be used for inferring the supratrochlear (red dotted angle) and the superior portion of the infratrochlear triangle (blue circle). (III: oculomotor nerve; IV: trochlear nerve; APCF: anterior petroclinoid fold). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 11

Anterior (A) and lateral (B) views of the three trajectories attainable through the combined lateral-supraorbital and transorbital corridor: the anterior trajectory inferior to the sphenoid ridge (red arrow); the anterior trajectory superior to the sphenoid ridge (blu arrow) and the antero-lateral trajectory (green arrow). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)