This webpage presents the anatomical structures found on skull base CT.
Image 1. CT anatomy of skull base.
1, Orbital cavity. 2, Superior orbital fissure. 3, Anterior clinoid process. 4, Mastoid air cells. 5, Internal occipital protuberance .
Image 2. CT anatomy of skull base.
1, Orbital cavity. 2, Superior orbital fissure. 3, Sphenoid sinus. 4, Optic canal. 5, Dorsum sellae. 6, Internal occipital protuberance .
Image 3. CT anatomy of skull base.
1, Superior orbital fissure. 2, Petrooccipital fissure. 3, Internal auditory canal.
Image 4. CT anatomy of skull base.
1, Internal auditory canal. 2, Sphenoid sinus. 3, External auditory canal.
Image 5. CT anatomy of skull base.
1, Sigmoid sinus. 2, Jugular bulb. 3, Foramen rotondum. 4, Carotid canal (pars horizontal).
Image 6. CT anatomy of skull base.
1, Jugular bulb. 2, Carotid canal (pars horizontal). 3, Sphenoid sinus. 4, Foramen ovale. 5, Foramen spinosum. 6, Jugular foramen.
Image 7. CT anatomy of skull base.
1, Jugular bulb. 2, Carotid canal (vertical portion). 3, Foramen spinosum. 4, Foramen ovale. 5, Sphenoid sinus. 6, Clivus. 7, Vidian canal. 8, Mandibular condyle.
Image 8 de 8. CT anatomy of skull base.
1, Mastoid process. 2, Mandibular condyle. 3, Hypoglossal canal.
Foramina of the Skull Base
The foramina of the skull refer to small openings that allow the passage of nerves and blood vessels(1).
The human skull has various foramina in which cranial nerves, veins, arteries, and other essential structures pass(2). Moreover, the frontal, ethmoid, sphenoid, maxilla, temporal, palatine, and occipital lobes are the skull bones that contain foramina.
The primary foramina in the skull include the optic foramen, supraorbital foramen, foramen magnum, foramina of cribriform plate, and foramen rotundum(3).
The optic foramen lies in the sphenoid and facilitates the passage of the ophthalmic artery and nerve from the optic canal into the orbit(4).
The supraorbital foramen occupies the frontal bone(5). This foramen allows the passage of the supraorbital vein, artery, and nerve into the orbit.
Meanwhile, the foramen magnum occupies the occipital bone(6). It enables the spinal and vertebral arteries and the spinal cord to pass from the skull into the vertebral column.
The foramina of the cribriform plate are found in the ethmoid bone, allowing the olfactory nerve’s passage(7).
The foramen rotundum primarily occupies the sphenoid bone(8). It permits the passage of the maxillary nerve.
Usually, there is enough room for the smooth passage of these structures without traction or pressure(9). However, the presence of a tumor at a foramen can damage the passing structures.
Skull Base Foramina CT
Computed tomography (CT) and magnetic resonance imaging (MRI) are used together to help detect diseases related to the skull base(10).
A CT scan involves a series of X-ray images from various angles around one’s body(11). It uses computer processing to generate cross-sectional images of the blood vessels, bones, and soft tissues in the body.
Meanwhile, MRI utilizes a magnetic field and computer-generated radio waves to provide detailed images of the body’s internal organs and tissues(12).
A CT scan is ideal in defining the bony anatomy of the skull base(13). It shows the thin cortical margins of skull base neurovascular foramina. The procedure is also more sensitive in detecting fibro–osseous skull base lesions, calcification, and sclerosis.
Moreover, a CT scan is the standard technique in assessing base skull fractures and detecting cerebrospinal fluid leak (CFL)(14). CFL occurs when there is a hole in the membranes surrounding the brain and spinal cord(15).
CT and MRI scans are often used together to plan for surgery.
What to Expect From Skull Base Foramina CT
Before the Exam
Patients undergoing a CT scan should wear comfortable and loose clothing. They may have to wear a hospital gown during the exam.
Moreover, they must remove jewelry, eyeglasses, dentures, hairpins, and other metal objects as these may affect the quality of the CT images.
They should not eat or drink anything several hours before their scheduled CT scan. Those who have allergies, take other medications, or experience illnesses must notify their doctor to avoid the risk of adverse effects.
Nursing or pregnant women should also inform their doctors. While the radiation from a CT scan is highly unlikely to harm their baby, the doctor may suggest a different examination, like MRI, to avoid exposing the baby to radiation(16).
During the Exam
A CT scan is like other regular X-ray examinations. This safe and painless procedure may last for around 30 minutes(17).
A CT scanner is a doughnut-shaped machine that stands on its side. The patient lies on a small table that slides through the opening into a tunnel.
Detectors and the X-ray tube rotate around the patient while the table moves them into the scanner. With each rotation, different images of the patient’s body are produced.
Using a speaker or microphone, the patient can communicate with the technologist who is in a separate room. At specific points, the patient may be asked to hold their breath to preserve the images’ quality.
Moreover, a contrast material (a special dye) may be needed to emphasize specific body areas(18). This contrast material blocks X-rays and appears white on images, highlighting blood vessels, intestines, or other structures.
Contrast material may be in the form of a drink, an injection, or insertion in the patient’s rectum.
After the Exam
The patients can return to their usual routine after taking the CT scan(19). However, those who had contrast material need to follow their doctor’s special instructions.
They should drink plenty of fluids to help the kidneys eliminate the contrast material from their body(20).
The doctor discusses the CT scan results with the patient once the radiologist sends a report of the assessment.
- Felten, D. L., MD, PhD., O’Banion, M. K., & Maida, MD, PhD. (2016). Netter’s Atlas of Neuroscience (3rd edition). Elsevier.
- LibreTexts. Foramina. Rertrieved from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/7%3A_Skeletal_System_-_Parts_of_the_Skeleton/7.1%3A_The_Skull/7.1E%3A_Foramina
- Felten, D. L. (2016). Op Cit.
- Raut, A. A., Naphade, P. S., & Chawla, A. (2012). Imaging of skull base: Pictorial essay. The Indian journal of radiology & imaging, 22(4), 305–316. doi.org/10.4103/0971-3026.111485. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3698894/
- Mayo Clinic. CT scan. Retrieved from https://www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675
- Mayo Clinic. MRI. Retrieved from https://www.mayoclinic.org/tests-procedures/mri/about/pac-20384768
- Raut, A. A. (2012). Op Cit.
- Cedars Sinai. Cerebrospinal Fluid Leak. Retrieved from https://www.cedars-sinai.org/health-library/diseases-and-conditions/c/cerebrospinal-fluid-leak.html
- Mayo Clinic. CT scan. Op Cit.