The skull is made up of numerous small bones attached by fibrous joints. Several projections are present on the interior surface, which are responsible for attaching many structures of the neck and face. The temporal bone is one of the bones of the skull. The mastoid bone is a complex bone that, among other reasons, features a prominent bulge called the mastoid process.
Just behind the ear, the mastoid process is easily palpable. This is where many muscles of the head are attached. In addition, it has air-filled spaces known as mastoid air cells. Anatomy, functional anatomy, and the clinical relevance of one of the projections, the mastoid process will be discussed below.
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Mastoid Antrum
An air space situated in the petrous portion of the temporal bone that is connected posteriorly with the mastoid cells and anteriorly with the middle ear recess is known as the mastoid antrum (aditus to mastoid antrum).
Quick facts about mastoid antrum:
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It is located in the upper part of the mastoid, this air-filled space measures 9mm high, 14mm wide, and 7mm deep. It measures 1ml in volume.
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Pneumatic bones are not found in the mastoid.
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A mastoid antrum is located in the temporal bone’s petrous part.
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Mastoid air cells do not develop until after birth, with about 90% of them being formed by the age of 6 and the remaining 10% occurring up until age 18.
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Bimastoid skulls have the smallest diameter.
Mastoid Air Cells
Cellular mastoidal (mastoid air cells) are pneumatized portions of the mastoids that range in size and extent. Among the air cells, the larger and irregular ones at the superior and anterior parts contain air, whereas those at the inferior part shrink in size, whereas the smaller ones near the apex contain marrow. These cells can occasionally be completely absent.
Aditus ad antrum and mastoid antrum provide communication between the middle ear and mastoid air cells. The Koerner septum is a thin bony structure formed by the petro-squamous suture between the epitympanum and the mastoid air cells, separating the two compartments of the mastoid air cells.
Mastoid Foramen
The mastoid foramen’s location, size, and number are all variable and vary in their presence. Within the temporo-occipital suture, it is usually found near the posterior margin of the mastoid process. As well as connecting to the sigmoid sinus, the occipital artery also receives a small branch from the emissary’s vein of the mastoid foramen.
Mastoid Retractor
In mastoid surgery, a mastoid retractor is commonly used. There are four teeth on each prong. Besides helping hold the tissue apart, the teeth firmly anchor the retractor to the bone. Occasionally used in head & neck surgeries such as tracheostomies and thyroidectomies.
Advanced Features:
Mastoid Region
Many of the bones in your skull help to protect your brain. The mastoid process is located behind the ear on either side of the head, according to the Encyclopaedia Britannica. The mastoid process is easily located behind your ear by feeling the protruding bone in the mastoid tip.
Muscles attached to Mastoid Process
Following are the muscles attached to the mastoid process.
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The facial nerve innervates the posterior belly of the Digastric muscle (CN VII)
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Nerve innervating the sternocleidomastoid (CN XI) Spinal accessory
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The Longissimus Capitis is innervated by the dorsal ramifications of the C3-C8 spinal nerves.
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The dorsal rami of the middle cervical spinal nerves innervate the Splenius Capitis.
Mastoid Tenderness
Mastoiditis is often caused by a middle ear infection. Air cells in the mastoid bone can become infected with bacteria from the middle ear. More rarely, a growth of skin cells called a cholesteatoma may obstruct the drainage of the ear, causing mastoiditis.
Mastoid Anatomy
The neck is divided into an anterior and a posterior triangle by the sternocleidomastoid muscle (SCM). We find the suprahyoid and infrahyoid muscles in the anterior triangle, which is delimited by the posterior border of the SCM, the inferior edge of the mandible, and the inner border of the labrum. SCM anteriorly, clavicle inferiorly, and trapezius posteriorly define the posterior triangle. It contains the scalene muscles. The SCM is a large muscle that is easily recognizable and palpable.
SCM consists of Four Parts:
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Sterno-mastoid
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Sterno-occipital
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Cleido-mastoid
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Cleido-occipital
Located at the middle of the clavicle, the side of the muscle originates at the upper edge of the sternal manubrium, blending into a single muscle belly that is directed upwards and laterally. Insertions enter the mastoid process of the temporal bone and the inferior nuchal line. The SCM is parallel.
SCM does not have a pennate structure, it has greater strength and thickness in men than in women. Its sternomastoid region develops a greater degree of contractile strength than the rest of the muscles. There is less force in the cleido-occipital portion of the brain.
Diagnosis of Mastoiditis
During an examination of your ears and head for the presence of an ear infection, your doctor will check for evidence of infection spreading to your mastoid bone.
You may not be able to see your mastoid bone due to an infection in your inner ear. Your doctor may conduct other tests to confirm the diagnosis. Infection is confirmed by a white blood cell count.
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Your ears and head can be scanned with a CT scan
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A head and ear MRI scan
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A skull X-ray
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The doctor may perform a spinal tap, or lumbar puncture if a diagnosis of mastoiditis is confirmed. The spinal column infection can be detected using this test.