Anatomy of the superior border of the lateral orbital wall: Surgical implications in deep lateral orbital wall decompression surgery

Purpose: To present the anatomical characteristics of the superior border of the lateral orbital wall and thereby reduce the risk of inadvertent dural damage during deep lateral orbital wall decompression. Methods: Twenty-five orbits (13 right and 12 left) of 13 Asian cadavers (6 men and 7 women) aged 61 to 93 years at death (average, 79.5 years) were used. After removing the orbital content, the lateral orbital wall, and the skull and brain, the superior border of the lateral orbital wall was exposed, which was analyzed from an orbital cavity view and an intracranial cavity view. Results: The anterior part of the superior border of the lateral orbital wall is parallel with the orbital roof; however, more posteriorly, as the orbital roof curves inferiorly, they become perpendicular. The cortical bone conspicuously separates the thin superior border from the orbital roof. In the junction between the superior and the posterior borders, a thick bone marrow exists. Complete removal of this bone marrow resulted in penetration in the junction of the anterior and middle cranial fossae. Conclusion: The authors documented the anatomy of the superior border of the lateral orbital wall, including the different relative positions between the superior border and the orbital roof in the anterior and posterior parts of the orbit. To avoid dural exposure, the cortical bone should not be exposed at the junction between the superior and posterior borders of the lateral orbital wall, which corresponds to the junction of the anterior and middle cranial fossae.Hirohiko Kakizaki, Yasuhiro Takahashi, Ken Asamoto, Takashi Nakano, Dinesh Selva, and Igal Leibovitc

The ethmoidal sinus roof: Anatomical relationships with the intracranial cavity

A detailed understanding of the relationship between the ethmoidal sinus and the intracranial cavity is essential to prevent intracranial penetration during orbital surgery. The authors analyzed 10 postmortem orbits with their adjacent skull bases of 5 Asian cadavers (3 males and 2 females; mean age of 80 years at death). After removing all orbital contents, skull and brain, the medial orbital wall, ethmoidal cells, and ethmoidal roof were also removed. From the intracranial cavity view, the ethmoidal roof was situated just lateral to the cribriform plate. From the orbital view, the location of the roof was close to the superior border of the medial orbital wall. These anatomical observations may be useful to prevent intracranial penetration and cerebrospinal fluid leakage during medial orbital wall decompression.Yasuhiro Takahashi, Hirohiko Kakizaki, Takashi Nakano, Ken Asamoto, Dinesh Selva and Igal Leibovitc

The narrowest part of the bony nasolacrimal canal: an anatomical study

PurposeTo determine the narrowest diameter of the bony nasolacrimal canal.MethodsFifty-eight bony nasolacrimal canals from 29 Japanese cadavers (12 men and 17 women; average age at death, 83.4 years; range, 70-99 years) had been fixed in 10% buffered formalin before use. After exposing the medial (44 canals) or posterior half (14 canals) of the bony nasolacrimal canal, the part with the shortest anteroposterior or transverse diameter was determined on inspection. These positions from the canal entrance were measured, and the distance ratio, indicating where the shortest diameter was located in relation to the total length of the canal, was calculated.ResultsThe shortest anteroposterior and transverse diameters were at the entrance to the canal in 32 of 44 canals (72.7%) and in 9 of 14 canals (64.3%), respectively. In the other canals, the shortest anteroposterior and transverse diameters were located at an average of 3.6 and 5.6 mm from the entrance, and the distance ratios were 29.0% and 46.7%, respectively. The mean shortest anteroposterior and transverse diameters were 5.6 and 5.6 mm, respectively.ConclusionsThe shortest anteroposterior and transverse diameters were at the entrance of the canal in most of the bony nasolacrimal canals. These results are comparable with the rate of obstruction at the canal entrance in primary acquired nasolacrimal duct obstruction.Yasuhiro Takahashi, Yasuhisa Nakamura, Takashi Nakano, Ken Asamoto, Masayoshi Iwaki, Dinesh Selva, Igal Leibovitch and Hirohiko Kakizak

Muller's muscle: A component of the peribulbar smooth muscle network

Purpose To examine Müller's muscle's horizontal extensions in relation to the peribulbar smooth muscle network. Design Observational anatomic study. Participants Twenty postmortem orbits (10 right, 10 left) of 15 Asians (8 males, 7 females; age range at death, 61–93 years; mean age, 78.4 years) fixed in 10% buffered formalin. Methods After performing a full-thickness 360° incision of the periosteum around the circumference of the orbit, the periosteum was elevated and finally detached near to the orbital apex. Nerves, blood vessels, and the nasolacrimal duct arising from the orbital wall were cut. The lateral orbital wall then was removed at approximately 3 cm posterior to the orbital rim and the retrobulbar content was incised with a sharp scalpel in a coronal plane. The removed orbital content was incised at a plane passing from a point located 15 mm superior to the upper eyelid margin and the globe equator at 3- and 9-o'clock areas. The sliced specimens were dehydrated and embedded in paraffin, cut into 7-μm thickness sections, and then stained with Masson trichrome. Main Outcome Measures The medial and lateral extensions of Müller's muscle in relation to the peribulbar smooth muscle network. Results In all specimens, Müller's muscle extended medially and laterally. The medial extension reached the medial rectus muscle pulley, which is rich in smooth muscle fibers. The lateral extension reached the lateral rectus muscle pulley by passing through the lacrimal gland fascia of the palpebral lobe, in which 12 specimens also showed a direct extension to the lateral rectus muscle pulley in the posterior part. Conclusions Müller's muscle has a medial and a lateral extension to the peribulbar smooth muscle network. These new findings indicated that Müller's muscle is not an independent structure in the upper eyelid, but rather a component of the peribulbar smooth muscle network.Hirohiko Kakizaki, Yasuhiro Takahashi, Takashi Nakano, Ken Asamoto, Hiroshi Ikeda, Dinesh Selva and Igal Leibovitc