Anatomical and Morphometric Study of Optic Foramen in North Indian Population

Published online: 26.06.2019 THIEME Original Article 53

Ajay Kumar1 Alok Tripathi1 Shilpi Jain1 Satyam Khare1 Ram Kumar Kaushik1 Hina Kausar1 Saurabh Arora1

1Department of Anatomy, Subharti Medical College, Swami Address for correspondence Alok Tripathi, MS, Department of Vivekanand Subharti, University, Meerut, Uttar Pradesh, India Anatomy, Subharti Medical College, Swami Vivekanand Subharti University, Meerut 250005, Uttar Pradesh, India (e-mail: [email protected]).

Natl J Clin Anat 2019;8:53–56

Abstract Introduction Optic canal connects orbit to middle cranial fossa. Optic nerve and ophthalmic artery pass through this canal. The aim of the present study is to make morphometric and anatomical observations of endocranial opening of optic canal. Materials and Methods The observations were conducted on 30 dry adult human skulls. The observations were made on shape, margins, confluence, septations, dimensions, and distance of optic foramen from apex of petrous temporal bone. Result and Statistical Analysis On morphometric observation, transverse diameter (TD) was 6.00 mm and 6.15 mm on the left and the right side, respectively. The vertical diameter (VD) was 5.14 mm on the left side and 4.82 mm on the right side. The distance of optic foramen to apex of petrous temporal bone was 21.84 mm on the Keywords left side and 21.90 mm on the right side. The mean, standard deviation, range, and

►►optic foramen p value were measured by using SPSS software version 19.00. ►►dry skull Conclusion In the present study we attempt to provide a comprehensive anatomical ►►morphometry and morphometric data of optic foramen that may help ophthalmologists and ►►dimensions neurosurgeons during surgery.

Introduction Materials and Methods

Optic canal connects orbit to middle cranial fossa. It is The study was carried out in the Department of Anatomy, present in the lesser wing of sphenoid bone and bounded Subharti Medical College, Meerut. The present study was by two roots of lesser wing and body of sphenoid bone. carried out on 30 dry adult human skulls. The structures passing through optic canal are optic nerve, Inclusion criteria: dura and arachnoid matter, ophthalmic artery, and sym- pathetic nerve.1–5 As optic nerve passes from the optic •• Bones with normal gross morphology. canal, injury in this region can lead to visual defect, so it •• Adult human skulls. becomes imperative for ophthalmologists to have compre- Exclusion criteria: hensive knowledge of optic foramen morphometry and •• Skulls showing gross deformity or defects its related structures.6 In the present study we tried to obtain comprehensive anatomical and morphometric data The observations on the foramina were recorded using of optic foramen. The present study is also an attempt to following parameters: find out the frequency of anomaly in optic canal. Duplica- 1. Dimensions (transverse diameter and vertical diameter). tion of optic canal is a rare anomaly, which may present 2. Shape. unilaterally2,7,8 or bilaterally.5,9,10 3. Margins (presence of tubercles, spine, notch, etc.).

4. Septation (presence of osseous spur/bridges dividing the 3.50–7.20 mm) on right side. The mean distance of optic fora- foramina). men to apex of petrous temporal bone was 21.84 ± 1.41 mm 5. Distance from optic foramina to apex of petrous temporal (range 19.20–25.40 mm) on left side and 21.90 ± 1.15 mm bone. (range 19.80–24.20 mm) on right side. The TD observed in dry skulls were ranged from 4.00 mm All these measurements were noted endocranially. These to 8.00 mm (►Table 1) but majority of the values were in measurements in the dry human skulls were recorded by the range between 6.00 mm and 6.9 mm on both sides using digital Vernier caliper with sensitivity 0.1 mm. The (►Table 2). Similarly, the values of vertical diameter were observations were carefully recorded and discussed in the in the range between 3.5 mm and 7.2 mm (►Table 1) but light of previous literature. majority of the values fall in the range between 4.5 mm and 5.4 mm on both the sides (►Table 3). Statistical Evaluation The data obtained from the present study were ana- Discussion lyzed as per standardized methods. The analysis was performed by applying paired t test using SPSS soft- Optic canal is present in the lesser wing of sphenoid bone ware (IBM SPSS V19.0; IBM Inc. Ltd. United States), for and formation of lesser wing occurs by the ossification of comparison of morphometric parameters of right and ala orbitalis cartilage at 12th to 16th week of gestation. So left sides and p ≤ 0.05 was considered statistically signif- the formation of optic canal is completed at the 16th week of 11 icant. Mean values, standard deviation and the range gestation. were taken into consideration in the statistical analysis. Optic nerve and ophthalmic artery are susceptible to various diseases and injuries; therefore, knowledge Results of optic canal morphometry is important for the proper diagnosis and intracanalicular procedure.12 Optic foramen was present bilaterally in all the dry skulls Some tumors like meningioma grown through the bone examined. The shape of the foramen was round with to compress the structures present within the canal. In order regular margins in all the specimens. No skull displayed to relieve compression bony border of canal is removed. septation of optic foramen or any other unusual morpho- Sometimes these tumors (meningioma and Schwannoma) logical features. grow along with optic nerve, requiring various parts of optic

The morphometric observations of optic foramen are canal to be opened. So removal of bones of optic canal is depicted in ►Table 1. The mean TD of optic foramen in dry a frequent procedure in these conditions.6 This makes the skulls was 6.00 ± 0.86 mm (range 4.00–8.00 mm) on left present study very important for the reference of compre- side and 6.15 ± 0.81 mm (range 4.00–7.60 mm) on right hensive data of optic foramen and related structures. side. The mean vertical diameter (VD) was 5.14 ± 0.73 mm The present study makes an attempt eliminate the lacunae (range 4.00–7.00 mm) on left side and 4.82 ± 0.77 mm (range present on existing knowledge. The most important lacuna

Table 1 Morphometric observations of optic foramen in dry skulls Parameters Mean ± SD (mm) p value Range = Max–Min (mm) Left (n = 30) Right (n = 30) Transverse diameter 6.00 ± 0.86 6.15 ± 0.81 0.346 (8.00–4.00) (7.60–4.00) Vertical diameter 5.14 ± 0.73 4.82 ± 0.77 0.013* (7.00–4.00) (7.20–3.50) Distance of optic foramen to apex of petrous 21.84 ± 1.41 21.90 ± 1.15 0.769 temporal bone (25.40–19.20) (24.20–19.80) * Significant.

Table 2 Correlation between transverse diameter and number Table 3 Correlation between vertical diameter and number of cases of cases Range (mm) Number of cases Range (mm) Number of cases Left side Right side Left side Right side 4.0–4.9 1 1 3.5–4.4 4 10 5.0–5.9 11 10 4.5–5.4 18 15 6.0–6.9 12 12 5.5–6.4 5 4 7.0–8.0 6 7 6.5–7.5 3 1

National Journal of Clinical Anatomy Vol. 8 No. 2/2019 Optic Foramen Anatomy Kumar et al. 55 present in existing knowledge is the lack of comprehensive in the present study (5.14 mm on left side and 4.82 mm data of optic foramen in north Indian population. Another on right side) is higher than the value of most of previous important lacuna that has never been addressed by previ- researchers1,3,6,10 except one researcher,12 where values are ous studies is the usage of osseous landmarks as reference comparable. points for describing topography of optic foramina. In the present study value of TD is larger on right side Conclusion but difference was not significant. Similarly, value of VD on left side is larger than right side but difference was The present study was an attempt to provide comprehen- statistically significant as p value was ≤ 0.05 (►Fig. 1). The sive data of anatomic and morphometric details of optic value of the distance of optic foramen to apex of petrous foramen and we expect it will help neurosurgeons while temporal bone was slightly higher on right side but operating meningioma. In the present study we found that difference was not significant. there is a significant difference in the value of VD between Morphometric dimensions in the present study in two sides and left being larger than right side. Our study dry skulls were compared with the dimensions observed may also help ophthalmologists during posterior compart- in previous studies. The mean values of TD in present ment surgeries. (6.00 mm on left side and 6.15 mm on right side) was ►Figs. 2 to 4 show how the measurements were taken higher than the values observed by Govsa et al6 and Kalthur and can be used as evidence. et al12 but it is comparable to the observations made by other researchers1,3,10 (►Table 4). The mean value of VD

Fig. 1 Bar diagram.

Table 4 Mean dimension of optic foramen in various studies in dry skulls Studies Transverse Vertical diameter diameter (mm) (mm) Lange et al3 6.25 3.7 Berlis et al1 6.25 (4.21–8.49) 3.70 (2.60–5.53) Magden et al10 6.48 4.35 Govsa et al6 4.60 4.62 Fig. 2 Vertical diameter of optic foramen in dry skull. Kalthur et al12 5.48 5.17 Present study 6.00 (left), 6.15 5.14 (left), 4.82 (right) (right)

National Journal of Clinical Anatomy Vol. 8 No. 2/2019 56 Optic Foramen Anatomy Kumar et al.

Funding None.

Conflict of Interest None.

References

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Fig. 4 Depicting distance from optic foramen to apex of petrous temporal bone.

National Journal of Clinical Anatomy Vol. 8 No. 2/2019