Lessons from the past: cribra orbitalia, an orbital roof pathology.

AIMS: To define a computed tomography protocol that may be used in future clinical practice for the reliable detection and analysis of cribra orbitalia. MATERIALS AND METHODS: Two osteological assemblages from the Museum of London were used to select 13 cribratous skulls and 5 non-cribratous skulls. Area of cribra orbitalia was measured using image analysis. Morphology of cribra orbitalia, orbital roof density and the associated optic canal diameter was analysed using computed tomography reconstructions. RESULTS: The presence of cribra orbitalia was associated with changes in the internal diploë layer as well as the cortical bone table. A novel radiological grading system and protocol was developed to identify the pathology. A decrease in the orbital roof density by 210 Hounsfield units and a reduction in the optic canal diameter, up to 1 mm, were found to be associated with the presence of cribra orbitalia. CONCLUSIONS: The occurrence of cribra orbitalia is found to be associated with stenosis of the optic canal, and could explain a proportion of cases ofoptic nerve entrapment. This study provides a guideline for radiologists and oculoplastic surgeons to help detect the presence of cribra orbitalia in suspected patients.

A cadaveric study of the morphometric relationships and bony composition of the caucasian nasolacrimal fossa.

AIMS: To describe the morphometric relationships and bony composition of the nasolacrimal fossa in a Caucasian population with particular reference to the lacrimo-maxillary suture (LMS). METHODS: Forty-seven orbits from 24 formalin fixed cadavers were exenterated. Morphometric measurements were taken between anatomical landmarks forming the lacrimal fossa on the medial orbital wall. RESULTS: The mean recorded distance from the anterior lacrimal crest (ALC) to the posterior lacrimal crest (PLC) and the LMS were 8.8 mm (± 1.6) and 4.3 mm (± 1.1), respectively. In 25.5% of the orbits the LMS was at the mid-vertical line (MVL), defined as a line equidistant from the ALC and PLC. In 42.5% the LMS was located anterior to the MVL toward the ALC. In 66% of the orbits the LMS was at or within one standard deviation (SD) of the MVL. The LMS was >1 SD away from the MVL toward the ALC and PLC in 19% and 15% of orbits, respectively. CONCLUSIONS: In a quarter of the orbits in our Caucasian population the nasolacrimal fossa was formed equally by the maxillary and lacrimal bones. However, in nearly a third of the cases the LMS was located closer to the PLC, indicating predominance of the thicker maxillary bone. This may result in greater difficulty in initiating the surgical osteotomy when performing a dacryocystorhinostomy. These data contribute to our understanding of the variation in lacrimal fossa anatomy and encourage further studies in different racial groups.

A cadaveric study of the cranio-orbital foramen and its significance in orbital surgery.

BACKGROUND: The cranio-orbital foramen is an osseous anatomical landmark located adjacent to the superior orbital fissure. It is a potential source of hemorrhage during deep orbital dissection because it is the location of an anastomosis between the lacrimal artery and the middle meningeal artery. The purpose of this study was to determine the incidence, location, and number of cranio-orbital foramina within a Caucasian population. METHODS: Forty-seven orbits from 24 formalin-fixed Caucasian cadavers were exenterated. If the cranio-orbital foramen was present within an orbit, its distance from the frontozygomatic suture, supraorbital notch, and Whitnall's tubercle was measured. The gender variations and asymmetric presentations of foramina were studied. RESULTS: The cranio-orbital foramen was present in 26 orbits (55 percent). The average distance from the frontozygomatic suture, supraorbital notch, and Whitnall's tubercle was 30.92 mm (±4.37 mm), 37.77 mm (±3.55 ±), and 29.69 mm (±3.89 mm), respectively. In nine orbits (19 percent), an additional accessory cranio-orbital foramen was identified. The average distance from the frontozygomatic suture, supraorbital notch, and Whitnall's tubercle was 28.56 mm (±5.00 mm), 32.64 mm (±3.20 mm), and 27.78 mm (±5.24 mm), respectively. CONCLUSION: The presence of the cranio-orbital foramen and other accessory foramina represents a source of hemorrhage that surgeons should be aware of when operating along the lateral orbital wall.

A cadaveric study of ethmoidal foramina variation and its surgical significance in Caucasians.

AIMS: To describe the morphometric and geometric relationships of the medial orbital wall ethmoidal foramina and the orbital apex in a Caucasian population. METHODS: 47 orbits from 24 formalin-fixed cadavers were exenterated. Morphometric measurements were taken between anatomical landmarks located on the medial orbital wall and geometric values were calculated. RESULTS: The average distances from the anterior lacrimal crest to the anterior ethmoidal foramen, posterior ethmoidal foramen and optic canal were 25.61 mm (± 2.25), 36.09 mm (± 3.86) and 43.77 mm (± 2.52), respectively. The average distances from the anterior ethmoidal foramen to the first posterior ethmoidal foramen, last posterior ethmoidal foramen and optic canal were 13.88 mm (± 3.51), 16.60 mm (± 2.19) and 21.65 mm (± 2.59), respectively. The average distances from the first and last posterior ethmoidal foramen to the optic canal were 11.63 mm (± 3.79) and 7.25 mm (± 2.59), respectively. CONCLUSION: The distance between the posterior ethmoidal foramen and optic canal is more than double the distance quoted in the surgical literature. This is due to a high incidence of ethmoidal foramina variation. Surgeons operating on the medial orbital wall of a Caucasian population must be aware of these variations as they are a source of haemorrhage and act as landmarks of proximity to the optic canal.

Morphometric and geometric anatomy of the caucasian orbital floor.

INTRODUCTION: To describe the morphometric and geometric relationships of the orbital floor in a Caucasian population. MATERIALS AND METHODS: Exenterations of 47 orbits from 24 formalin fixed cadavers were performed. Morphometric measurements were taken between anatomical landmarks located along the orbital floor and the orbital apex. The mean measurements were used to calculate geometric data. These results were analysed according to sex and side and compared to results from other ethnic populations. RESULTS: The average distances from the infraorbital foramen to the nasolacrimal fossa, inferior orbital fissure, optic canal and inferior orbital rim were 20.67 mm (± 2.42), 25.40 mm (±2.70), 43.23 mm (±3.35) and 8.95 mm (± 1.53), respectively. The average distances from the tip of the infraorbital groove to the tip of the inferior orbital fissure, lateral aspect of the inferomedial strut, optic canal and the intersection with the inferior orbital fissure were 14.08 mm (±2.41), 12.12 mm (±2.42), 35.02 mm (±3.17) and 20.05 mm (± 2.87), respectively. The distances from the tip of the inferior orbital fissure to the optic canal and the intersection with the inferior orbital groove were 29.56 mm (±2.73) and 13.37 mm (±2.76), respectively. DISCUSSION: Orbital surgeons should be aware of the morphometric relationships of the orbital floor due to the degree of variation that exists between different ethnic groups. Geometric data may be used to provide orbital surgeons with a navigational template that can be used to plan surgery and as a guide intraoperatively.

A cadaveric study of the morphometric and geometric relationships of the orbital apex.

INTRODUCTION: To define the morphometric and geometric relationships which exist at the orbital apex. MATERIALS AND METHODS: Forty-seven orbits from twenty-four formalin-fixed Caucasian cadavers were exenterated and the relevant sutures, fissures and foramina identified. Measurements were taken from the optic canal to anatomical landmarks located along the medial wall, inferior wall and lateral wall of each orbit. Based on the mean results the geometric angles between the different anatomical structures were calculated and used to create three-dimensional models. RESULTS: The mean distances from the midpoint of the optic canal to the superior orbital fissure, inferior orbital fissure and anterior ethmoidal foramen were 10.22 mm, 29.56 mm and 21.65 mm, respectively. The mean distances from the anterior ethmoidal foramen to the superior and inferior orbital fissures were 24.27 mm and 31.93 mm, respectively. The mean distance between the tips of the superior and inferior orbital fissures was 27.70 mm. The mean distances directly from the tips of the superior and inferior orbital fissures and the anterior ethmoidal foramen to the orbital rim were 39.23 mm, 17.11 mm and 18.94 mm, respectively. These values were used to calculate geometric values and create three-dimensional models. DISCUSSION: The orbital apex is a congested structure and the practicing orbital surgeon must have an intimate knowledge of its contents. We have presented novel data, which in conjunction with radiology may be used as both a navigational aid to plan orbital surgery and to guide the surgeon intraoperatively to assess proximity to key anatomical structures.