What Is a Tympanogram?

The tympanic cavity is the most important part of the middle ear. It is a flat cavity that is surrounded by the temporal bone, scales, drum, and tympanic membrane, and is nearly parallel to the sagittal plane. The eustachian tube is used to communicate with the nasopharynx, and the tympanic sinus is used to communicate with the tympanic sinus and mastoid air chamber. The inner side is adjacent to the inner ear by the headland, vestibular window and worm window, and the outer ear is separated from the external ear canal by the eardrum. The tympanum is divided into upper tympan, middle tympanum, lower tympanum, and rear tympanum. The upper and lower diameters of the tympanum are about 15 mm, and the front and rear diameters are similar to the upper and lower diameters. , Only 2mm at the umbilicus. The volume of the tympanic cavity is 1 to 2 ml. The inner surface of the tympanic cavity is lined with mucosa, and the cavity contains structures such as the ossicle, ligaments, mucosal folds, muscles and nerves.

The tympanic cavity is the most important part of the middle ear. It is a flat cavity that is surrounded by the temporal bone, scales, drum, and tympanic membrane, and is nearly parallel to the sagittal plane. The eustachian tube is used to communicate with the nasopharynx, and the tympanic sinus is used to communicate with the tympanic sinus and mastoid air chamber. The inner side is adjacent to the inner ear by the headland, vestibular window, and worm window. The tympanum is divided into upper tympan, middle tympanum, lower tympanum, and rear tympanum. The upper and lower diameters of the tympanum are about 15 mm, and the front and rear diameters are similar to the upper and lower diameters. , Only 2mm at the umbilicus. The volume of the tympanic cavity is 1 to 2 ml. The inner surface of the tympanic cavity is lined with mucosa, and the cavity contains structures such as the ossicle, ligaments, mucosal folds, muscles and nerves.

Chinese name

Tympanum

Nature

The upper hole is oval,

Attributes

Vestibular window

Features

Closed by a second tympanic membrane when living

Drum Chamber I. Overview:

The upper tympanum (attic), also known as the epicympanum and the epitympanic attic, is located above the plane of the upper edge of the tympanic tension. The hypotympanum is located below the plane of the lower edge of the tympanic tension. The middle tympanic chamber (mesotympanum) is located between the plane of the upper and lower edges of the tympanic membrane tension, and most of it corresponds to the tympanic membrane tension. The posterior tympanum is located behind the posterior edge of the tympanic tension and is one of the important parts of middle ear surgery.

Drum chamber two, walls of the drum chamber

The tympanic cavity is usually considered clinically as having a 6-wall cavity.

1. Outer side wall: two parts of the diaphragm part and the bone part of the outer wall of the tympanum. The membrane is the tympanic membrane, which is the main part of the side wall of the drum chamber. The bone is the bony outer wall around the tympanic membrane, which is mainly composed of a bony tympanic ring and a tympanic shield.

The tympanic membrane is a semi-transparent film with a shallow funnel shape with a concave surface facing outward. The adult tympanic membrane has an upper and lower diameter of 9 to 10 mm, an anterior-posterior diameter of 8 to 9 mm, and a thickness of about 0.1 mm. The tympanic membrane is located in the sulcus, and its plane is inclined forward and outward, forming an angle of 45-55 ° with the lower wall and anterior wall of the external ear canal, and an obtuse angle of approximately 140 ° with the upper wall of the external ear canal. The malleolus is embedded in the tympanic membrane and pulled inward, so the tympanic membrane is slightly depressed inward and has a shallow funnel shape. The tympanic membrane is divided into two parts, the tension part and the slack part. The tension part is the main part. The edges of the tympanum are thickened to form a fibrous cartilage ring attached to the sulcus. The slack part is also called the Shrapnell membrane. Ring attached to the lower edge of the drum notch tympanum shield. The umbilical cord is the most depressed part of the tympanic membrane at the end of the malleolus, and is located slightly rearward in the center of the tympanic membrane. The hammer pattern is a white stripe shadow formed by the hammer bone attached to the tympanic membrane. There is a small white protrusion at the upper end of the hammer pattern, which is formed by lifting the tympanic membrane outward for the short process of the hammer bone. The stripes running forward from the short process of the malleus on the tympanic membrane are anterior tympanic folds, and the stripes running backward from the short processes of the malleolus are posterior tympanic folds. Two folds are attached to the two ends of the drum notch. The tympanic membrane is divided into the above loose part and the tense part with the front and back wrinkles of the hammer as the boundary. The edges of the tense part are continuous with the two wrinkles at the front and back drum spines. When examining the eardrum with an otoscope, it can be seen that there is a narrow triangular reflective area at the front and lower part, which is caused by the incident light reflected by the concave surface of the eardrum, which is called a light cone. From the newborn to the 5-month-old infant, because the tympanic membrane is tilted almost horizontally, and the angle with the bottom of the external auditory meatus is about 35 °, no light cone can be seen on inspection.

2. Upper wall: The upper wall is the tympanum cover (tegmen tympani), or the tympanum cover. The tympanum is separated from the middle cranial fossa by this bone plate. There are rock scale cracks on the tympanic lid, which are usually closed after 2 years old, so the symptoms of meningeal irritation may occur in children with acute otitis media. Under normal circumstances, the tympanum cover is located 5-10 mm above the line connecting the lower edge of the orbital and the upper edge of the external auditory meatus, otherwise the tympanic cover is in a low position.

3. Lower wall: The lower wall is called the jugular wall, which is a narrow thin bone plate that separates the tympanum from the jugular bulb. The surface of the lower wall of the tympanum is irregular, there are many air cells, and there is a prominent protrusion near the posterior part, which is called styloid prominence, which corresponds to the root of the styloid process. Below the inferior wall is the jugular fossa, which houses the jugular bulb, and in front of it is the internal carotid artery tube, which is passed by the internal carotid artery, so the inferior wall is adjacent to the jugular bulb and internal carotid artery. There may be defects in the inferior wall bone. In middle ear surgery, care should be taken to avoid severe blood vessel damage and severe bleeding. There is a small hole in the lower wall, where the tympanic branch of the glossopharyngeal nerve passes. There is a jugular vein spheroid in the adventitia at the top of the jugular bulb, which is close to the jugular vein fossa and is the primary tissue of the jugular bulb tumour.

4. Anterior wall: The anterior wall has a carotid wall, which is wide upper and narrower. The upper part has a semicanal for tensor tympani muscle and an intratympanic tympanic muscle. The eustachian tube tympanum is located below it, and the tympanic chamber communicates with the nasopharynx. A thin bone piece is separated between the two tubes, and this bone piece extends rearward and outward to form a spoon-shaped process. The swelling of the bone wall under the mouth of the eustachian tube is caused by the internal carotid artery bulging. This bone wall is thin and may have defects. Pay attention to it during surgery. There are many small perforations on the surface of the bone wall, through which the cervical and tympanic nerves and blood vessels penetrate into the tympanic cavity.

5. Posterior wall: The posterior wall is also called the mastoid wall, with upper width and lower width. The vertical segment of the facial nerve passes through the inside of this wall. The upper section of the back wall is equivalent to a small hole in the back wall of the upper tympanic cavity, which is the entrance of the tympanic sinus. Inside the tympanic sinus entrance there is an external semicircular canal bulge. The bottom of the tympanic sinus entrance is suitable for the intersection of the horizontal and vertical sections of the facial canal. An important sign for middle ear surgery.

6. Inner wall: The inner wall, also known as labyrinthine wall, is the outer wall of the inner ear, and its structure is related to the labyrinth system of the inner ear. It has the following structure: The promonorium tympani is formed by the bulge of the cochlear basal turn from the beginning. It has a groove on the surface and the tympanic nerve (jacobson nerve) passes through it. The vestibular window niche is a depression inwardly above and behind the headland, also known as the fossula fenestrae vestibuli. There is a vestibule at the bottom of the iliac crest which is inwardly shaped into the inner ear. It is called a vestibular window or oval window. It covers an area of 3 to 3.2 mm ² and is closed by the sacrum floor and annulus ligament. The round window niche is a depression inward behind the headland of the drum, also known as the fossula fenestrae cochleae. At the bottom of the round window niche is a type of round window opening that leads to the beginning of the cochlear drum stage, called a round window or a cochlear window. The round window is closed by a membrane fibrous tissue structure covering the mucosa on the surface, called a round window membrane or a secondary tympanic membrane. It is also known as a second tympanic membrane, with an area of about 2 mm ² and a thickness of 0.5 1mm, facing backward and downward, its plane is almost at right angles to the vestibule window. The front upper edge of the round window ridge is prominently convex, and the trailing edge is flat. Due to the cover of the front upper edge of the round window ridge, some of the upper and front edges of the round window ridge must be abraded to observe the round window film.