Keywords
foramen ovale - greater wing of sphenoid - middle cranial fossa - mandibular nerve
Introduction
The foramen ovale is one of the important foramina in the greater wing of the sphenoid
bone, through which the infratemporal fossa communicates with the middle cranial fossa.
It is located lateral to the foramen lacerum and medial to the foramen spinosum. It
transmits the mandibular division of the trigeminal nerve, of the lesser petrosal
nerve, of the accessory meningeal artery, and of the emissary vein connecting the
pterygoid venous plexus with the cavernous sinus.[1]
The foramen ovale is used for various invasive surgical and diagnostic procedures.[2] The foramen ovale is one of the important routes for the spreading of nasopharyngeal
carcinomas into the cranial cavity.[3]
Like other foramina of the skull, the foramen ovale also differs in shape, size and
other morphological features. Sometimes, it is covered by an osseous ligament extending
from the lateral pterygoid plate to the spine of the sphenoid bone.[4] Ossified pterygospinous and pterygoalar ligaments divide the foramen ovale into
compartments.[5] They can compress the structures passing through it or block the passage of the
needle through the foramen ovale.[6]
[7] A bony spur on the anteromedial side divides the foramen ovale in two.[8]
The right side (RS) foramen ovale is smaller than the left side (LS) foramen ovale.[9] The available literature reveals that the foramen ovale shows a wide range of variations.
The present study aims to measure the length and the width of the foramen ovale, the
knowledge of which helps in reducing complications during surgeries for neurological
diseases.
Materials and Methods
The present study was conducted on 40 dried adult skulls of unknown gender and age
obtained from the Department of Anatomy of the JSS Medical College, Mysuru, Kamakata,
India. Ethical clearance was obtained from the institutional ethical committee to
conduct this study. The measurement of the length (Anteroposterior diameter) and width
(transverse diameter) of the foramen ovale was taken using sliding digital calipers
(Kristeel-Shimwa industries, Bombay, India) and then analyzed ([Fig. 1] and [Fig. 2]).
Observations
Table 1
The following observations were made
|
Parameters
|
Mean and SD
|
|
Right side length
|
0.745 ± 0.31 cm
|
|
Left side length
|
0.68 ± 0.15 cm
|
|
P-value
|
0.26
|
|
Right side width
|
0.6 ± 0.71 cm
|
|
Left side width
|
0.56 ± 0.14 cm
|
|
P-value
|
0.29
|
Abbreviations: SD, standard deviation.
The present study was conducted on a total of 80 sides of 40 dry adult skulls. The
mean length of the foramen ovale was 0.745 ± 0.31 cm on the RS, and 0.68 ± 0.15 cm
on the LS. The mean width was 0.6 ± 0.17cm on the RS, and 0.56 ± 0.14 cm on the LS
([Table 1]).
The length and the width were longer on the RS when compared with the LS. The difference
between the length of the RS and of the LS was not statistically significant (p > 0.05). Similarly, the difference between the width of the RS and of the LS was
not statistically significant ([Graph 1]).
Graph 1 Bar chart showing mean ± standard deviation of the length and of the width of the
foramen ovale. Abbreviations: LL, left length; LW, left width; RL, right length; RW,
right width; SD, standard deviation.
Fig. 1 Base of the skull showing the foramen ovale.
Fig. 2 Showing the measurement of the foramen ovale using digital sliding calipers.
Discussion
In the present study, the mean length of the foramen ovale was 0.745 ± 0.31 cm on
the RS, and 0.68 ± 0.15 cm on the LS. The mean width was 0.6 ± 0.17 cm on the RS,
and 0.56 ± 0.14 cm on the LS. Therefore, both the length and the width are longer
on the RS when compared with previous studies.
In his developmental study, Yanagi[10] reported that the length of the foramen ovale in newborns is ∼ 3.85 mm, and ∼ 7.2 mm
in adults. The earliest appearance of the foramen ovale as a ring-shaped area is seen
in the 7th month of intrauterine life and lasts for 3 years after birth.[8]
Lang et al[11] reported that the average maximum length of the foramen ovale is ∼ 7.48 mm, and
that the average minimum length is ∼ 4.17 mm in adults. The width ranges from 1.81 mm
in newborns to 3.7 mm in adults.[12]
A study by Chandra Philips et al[13] conducted on 50 dry skulls showed that the mean length of the foramen ovale was
7.27 ± 1.41 mm on the RS, and 7.46 ± 1.41 mm on the LS.[14]
A study by Patel et al[12] conducted on 100 dry skulls showed that the mean length of the foramen ovale was
6.6 mm on the RS, and 6.5mm on the LS. The RS foramen ovale was longer than the LS.
The mean width was 3.6 mm on the RS, and 3.5 mm on the LS.[7]
Ray et al[2] conducted a study on 35 dry skulls that showed that the mean length of the foramen
ovale was 7.46 ± 1.41 mm on the RS, and 7.01 ± 1.41 mm on the LS. The mean width was
3.21 ± 1.02 mm on the RS, and 3.29 ± 0.85 mm on the LS.
In the present study, the length and the width are longer on the RS when compared
with the LS, which is in line with the studies conducted by Daimi et al[6] and by Patel et al.[12]
It is through the foramen ovale that many invasive surgeries and diagnostic procedures
are performed.[2] Percutaneous trigeminal rhizotomy in trigeminal neuralgia is also performed through
the foramen ovale.[15] Percutaneous biopsy of cavernous sinus tumors and biopsy of deep lesions of the
brain, such as Meckel cave lesions, are performed through the foramen ovale, which
decreases patient morbidity and is cost-efficient.[14]
[16] The foramen ovale is also used to diagnose squamous cell carcinomas and meningiomas
via computed tomography (CT) guided transfacial fine needle aspiration.[17]
It is through the foramen ovale that the trigeminal nerve is accessed. Therefore,
the variations in the length and in the width of the foramen ovale are of utmost importance
during the anesthesia of the trigeminal nerve.
Conclusions
The present study demonstrates the anthropometric significance of the foramen ovale,
which may help radiologists and neurosurgeons. These variations in measurements of
foramen ovale found in the present study may be useful for treating trigeminal neuralgia,
abnormal tumors, and to perform biopsies from deeper parts of the brain.
