CT scan of the middle ear (anatomy)

Gallery #1: level 1 to 6

Gallery #2: Serie of successive coronal reconstructions

Gallery #3: Series of successive sagittal reconstructions

This page presents the anatomy of middle ear by means of CT-scan.

You have three different galleries of images depicting the anatomy of the middle ear: • level 1 to 6 (axial, coronal, sagittal reconstruction for the same level . A set of 3 images correspond to a given level and the green cross indicates the reference planes for each image of this level .) • Serie of successive coronal reconstructions • Serie of successive sagittal reconstructions

Computed tomography (CT) scans are medical imaging tools that may effectively diagnose medical conditions or diseases and detect internal abnormalities(1).

CT scans take several pictures of the internal organs from different angles, with the final image eliminating any overlapping structures to provide an unobstructed view of the target organ(2).

CT scans are seldom used during the preliminary or initial diagnosis of middle ear diseases. Instead, CT imaging is more often performed after ineffective treatments or upon suspicion of further medical complications(3).

Anatomy of the Middle Ear

The area of the middle ear is found immediately after the outer ear’s ear canal. The eardrum or the tympanic membrane serves as a wall that separates the inner ear and outer ear.

The middle ear’s location directly behind the eardrum or tympanic membrane makes direct non-invasive assessments challenging and limited(4).

CT scans and other diagnostic imaging modalities may greatly help in evaluating middle ear complications and diseases.

Air Cavity of the Middle Ear

A large area of the middle ear is a pneumatized or air-filled chamber within the petrous part of the temporal bone(5). This chamber is called the tympanic cavity or the tympanum.

The temporal bones make up the lateral (side) skull base and form parts of the middle and posterior cranial fossae (depressions in the skull)(6).

The tegmen tympani, a projection of the petrous portion of the temporal bone, serves as the roof of the tympanic cavity(7).

Meanwhile, the tympanic membrane serves as the cavity’s wall or physical barrier to the outer ear.

Bones of the Middle Ear

Within the tympanic cavity are the three smallest bones in the human body(8):

  • The malleus or hammer, which has a long handle attached to the center of the eardrum
  • The incus or anvil, which connects the malleus and the stapes
  • The stapes or stirrup, which features a footplate connected to the inner ear’s oval window or fenestra vestibuli

Together, the three bones are collectively known as the ossicles(9). The ossicles are named based on the shapes they most resemble.

Together with the tympanic membrane, the bones of the middle ear transmit sound vibrations to the inner ear(10).

Common Middle Ear Problems

Ear infections are a predominant problem among children and usually affects the middle ear.

Ear infections, also called acute otitis media, is the second-most common reason for a visit to the family doctor(11). Findings show that almost 60% to 85% of children develop ear infections during their first year.

Adults may also develop ear infections, though the incidences are less common(12).

Symptoms of acute otitis media may include earache, fluid discharge, hearing problems or hearing loss, and balance issues(13).

Middle ear disorders that may require or benefit from a CT examination are:

  • Eustachian tube dysfunction (persistent accumulation of mucus in the middle ear)
  • Acute otomastoiditis (characterized by a red and swollen eardrum)
  • Chronic inflammation and infections

The CT Scanning Procedure

A study indicated that CT imaging is a safe and non-invasive method for diagnosing and evaluating chronic inflammatory middle ear diseases(14).

CT scans are fast and painless diagnostic procedures, usually lasting no more than 30 minutes(15).

Before a CT Scan

Patients undergoing CT scans are often asked to take off any personal belongings that may affect the quality of the CT image results. These include:

  • Pieces of jewelry
  • Metal accessories, such as belts
  • Hairpins and hair ties with metal parts
  • Eyeglasses
  • Dentures
  • Clothes with metal fastenings or designs

Patients may have to wear a hospital gown during the exam, depending on the body part being scanned.

Fasting is generally not a requirement before undergoing CT scans. However, doctors usually request a food and drink fast for CT scans that require intravenous (IV) contrast material(16).

Contrast materials are sometimes used to help highlight specific areas of the body in the CT images.

During a CT Scan

Patients lie face up on a small, motorized table. Straps and pillows may be used to help maintain the patient’s position comfortably. Patients are asked to lie still to prevent blurry images.

Once the procedure starts, the table slowly passes through a short tunnel in the middle of the CT scan machine.

The detectors and X-ray tube on the tunnel rotate around the patient, with each rotation taking several images of the body.

Patients are left alone in the room during the procedure. The physician or CT technician stays inside the control room and communicates with the patients via an intercom system.

After a CT Scan

Once a CT scan is finished, the images are forwarded to a radiologist for interpretation. A follow-up doctor’s visit is scheduled to explain the results and diagnosis to the patient.

Patients are allowed to leave right away and return to their daily routine after a CT scan(17). However, if a contrast material was administered, the patients may be asked to rest for a while before leaving.

Additionally, patients are reminded to drink large quantities of fluids to help flush the contrast material out of the body(18).

Reference

• Harnsberger HR, Osborn AG, Ross JS, Moore KR, Salzman KL, Carrasco CR, Halmiton BE, Davidson HC, Wiggins RH. Diagnostic and Surgical Imaging Anatomy: Brain, Head and Neck, Spine. 3rd ed. Salt Lake City, Utah. Amirsys. 2007. • Bourjat P, Veillon F. Imagerie radiologique tête et cou. Paris, Vigot. 1995. • Gouazé A, Baumann JA, Dhem A. Sobota. Atlas d’Anatomie humaine. Tome 3. Système nerveux central, système nerveux autonome, organe des sens et peau, vaisseaux et nerfs périphériques. 1er éd. Paris, Maloine. 1977. • Kahle W, Cabrol C. Anatomie. Tome 3: Système nerveux et organe des sens. 1er éd. Paris, Flammarion. 1979.


References

  1. Radiological Society of North America. (2020, May 15). What are the benefits of CT scans?. Radiology Info. Retrieved from https://www.radiologyinfo.org/en/info.cfm?pg=safety-hiw_04
  2. Ibid.
  3. Trojanowska, A., Drop, A., Trojanowski, P., Rosińska-Bogusiewicz, K., Klatka, J., & Bobek-Billewicz, B. (2012). External and middle ear diseases: radiological diagnosis based on clinical signs and symptoms. Insights into imaging, 3(1), 33–48. https://doi.org/10.1007/s13244-011-0126-z
  4. Ibid.
  5. Crumbie, L. (2020, Nov. 13). Middle ear. Kenhub. Retrieved from https://www.kenhub.com/en/library/anatomy/middle-ear
  6. Juliano, A. F., Ginat, D. T., & Moonis, G. (2013). Imaging review of the temporal bone: part I. Anatomy and inflammatory and neoplastic processes. Radiology, 269(1), 17–33. https://doi.org/10.1148/radiol.13120733
  7. Crumbie, L. (2020, Nov. 13). Op. cit.
  8. Ibid.
  9. Ibid.
  10. Ibid.
  11. Worrall G. (2007). Acute otitis media. Canadian family physician Medecin de famille canadien, 53(12), 2147–2148. https://doi.org/10.1016/j.ejrnm.2015.05.005
  12. Medline Plus. (n.d.). Ear Infections. Retrieved from https://medlineplus.gov/earinfections.html
  13. Ibid.
  14. Khater, N. H., Fahmy, H. S., El Shahat, H. M., & Khater, A. M. (2015). Chronic inflammatory middle ear disease: Postoperative CT and MRI findings. The Egyptian Journal of Radiology and Nuclear Medicine, 46(3), 629-638. https://doi.org/10.1016/j.ejrnm.2015.05.005.
  15. Mayo Clinic. (2020, Feb. 28). CT scan. Retrieved from https://www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675
  16. Lee, B. Y., Ok, J. J., Abdelaziz Elsayed, A. A., Kim, Y., & Han, D. H. (2012). Preparative fasting for contrast-enhanced CT: reconsideration. Radiology, 263(2), 444–450. https://doi.org/10.1148/radiol.12111605
  17. Mayo Clinic. (2020, Feb. 28). Op. cit.
  18. Mayo Clinic. (2020, Feb. 28). Op. cit.
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