Function of the Mastoid Bone - Anatomy and Related Conditions

What Is the Mastoid Bone?

If you touch behind your ear, you'll feel a hard, bony bump; that's the mastoid bone. The mastoid bone behind the ear might seem like nothing more than a small lump, but it actually plays some pretty important roles, from protecting your ear to supporting movement in your head and neck.

1. Definition:

The mastoid bone is the bony area just behind your ear. Filled with tiny honeycomb-like air spaces, it works closely with the parts of your ear that handle hearing and balance.

2. Is the Mastoid Bone a Separate Bone?

Not exactly. Even though we call it the "mastoid bone," it isn't actually a separate bone. It's part of a larger bone in your skull called the temporal bone. So really, it's a section of that bigger bone rather than a standalone one.

3. Difference Between Mastoid Bone and Mastoid Process

These two terms are often mixed up. The mastoid bone refers to the whole bony region behind the ear, while the mastoid process is the specific cone-shaped bump you can actually feel with your fingers. In other words, the mastoid process is just one part of the mastoid bone.

Where Is the Mastoid Bone Located?

The mastoid bone location is explained below:

1. Position Behind the Ear: The mastoid bone sits directly behind your outer ear, at the side and slightly toward the back of your head. That firm bump you can feel behind your earlobe is the mastoid process poking out.

2. Relation to the Temporal Bone: As mentioned, the mastoid bone is part of the temporal bone, one of the bones that make up the sides and base of your skull. The temporal bone also surrounds and protects the inner workings of your ear.

3. Nearby Structures: The mastoid bone sits very close to several important and delicate structures, which is part of why problems in this area need to be taken seriously.

• Middle Ear: The mastoid connects to the middle ear through a small opening, which is why ear infections can sometimes spread into the mastoid.

• Inner Ear: This houses the organs responsible for hearing and balance, sitting just deep to the mastoid.

• Facial Nerve: The nerve that controls the muscles of your face runs right through this area, so any issues here can sometimes affect facial movement.

• Skull Base: The mastoid sits close to the base of the skull, near the brain, which is why untreated infections here can occasionally become serious.

Anatomy of the Mastoid Bone

The mastoid bone anatomy might look simple from the outside, but it has several distinct parts that each play a role.

• Mastoid Process: The cone-shaped bump you can feel behind your ear. It serves as an attachment point for several muscles.

• Mastoid Air Cells: The honeycomb-like network of air pockets inside the bone. These help lighten the skull and help regulate air pressure around the ear.

• Mastoid Antrum: A larger air-filled space that connects the air cells of the mastoid to the middle ear.

• Mastoid Notch: A groove on the underside of the mastoid where a muscle attaches.

• Mastoid Foramen: The mastoid receives its blood supply from nearby arteries that branch off the main vessels of the head.

• Blood Supply: The mastoid receives its blood supply from nearby arteries that branch off the main vessels of the head.

• Nerve Supply: Small nerves in the area innervate the mastoid and surrounding tissues.

Mastoid Bone at a Glance

Feature	Description
Location	Behind the ear in the temporal bone
Bone Type	Part of the temporal bone
Main Function	Muscle attachment and protection of ear structures
Contains	Mastoid air cells
Important Landmark	Mastoid process
Common Diseases	Mastoiditis, fractures, cholesteatoma
Imaging	CT scan, MRI

Function of the Mastoid Bone

So what does this little bump behind your ear actually do? Quite a lot, as it turns out. The mastoid bone function is explained below.

• Muscle Attachment: The mastoid process serves as an attachment point for several neck and head muscles.

• Supports Head and Neck Movement: Because these muscles attach here, the mastoid helps you turn, tilt, and steady your head.

• Protects Delicate Ear Structures: The bone helps shield the sensitive parts of your ear involved in hearing and balance.

• Helps Regulate Middle Ear Air Pressure: The air cells within the mastoid help regulate the air pressure in the middle ear, which is important for healthy hearing.

• Reduces Skull Weight: Those air-filled spaces make the bone lighter than it would be if it were solid, reducing the overall weight of the skull.

Muscles Attached to the Mastoid Process

The main function of the mastoid process is to serve as an anchor point for several muscles in your head and neck, giving them something solid to attach to and helping you turn, tilt, and steady your head throughout the day.

• Sternocleidomastoid: It helps turn and tilt the head.

• Splenius Capitis: It helps extend and rotate the neck.

• Longissimus Capitis: Supporting and straightening the head.

• Posterior Belly of Digastric: Helps with swallowing and jaw movement.

• Occipitalis: Helps with moving the scalp.

• Auricularis Posterior: Helps with small ear movements.

Development of the Mastoid Bone

• Development After Birth: Interestingly, the mastoid bone isn't fully formed at birth. At birth, the air cells inside it haven't developed yet.

• Growth of Mastoid Air Cells: The honeycomb-like air cells gradually develop during the first few years of life, slowly filling out the bone.

• Changes During Childhood: As a child grows, the mastoid process becomes larger and more defined, which is why it's much more noticeable in adults than in babies.

• Adult Anatomy: By adulthood, the mastoid is fully developed, with its complete network of air cells and its prominent bony bump.

Common Conditions Affecting the Mastoid Bone

Because the mastoid sits so close to the ear, it can be affected by several conditions, many of which are linked to ear infections.

• Mastoiditis: An infection of the mastoid bone, usually caused by a middle ear infection that spreads. It needs prompt treatment.

• Mastoid Bone Fracture: A break in the mastoid bone, typically resulting from a significant head injury.

• Mastoid Bone Pain: Discomfort in the area behind the ear that can have several causes, including infection and injury.

• Mastoid Tumors: Growths in the mastoid area are rare but can occur and require proper evaluation.

• Cholesteatoma Affecting the Mastoid: An abnormal skin growth in the middle ear that can spread into the mastoid and cause damage over time.

• Chronic Ear Infections: Repeated or long-lasting ear infections can affect the mastoid and increase the risk of complications.

Symptoms of Mastoid Bone Problems

Problems with the mastoid bone often come with noticeable symptoms, including:

• Pain behind the ear.

• Swelling behind the ear.

• Fever.

• Discharge or fluid draining from the ear.

• Hearing loss.

• Headache.

• Redness behind or around the ear.

• Balance problems.

How Are Mastoid Bone Disorders Diagnosed?

Doctors use a combination of methods to figure out what's going on:

• Physical Examination: The doctor will start by looking at and gently feeling the area behind the ear for swelling, redness, or tenderness.

• Otoscopy: A small, lighted instrument called an otoscope is used to examine the eardrum and the inner ear.

• Hearing Tests: These check whether the condition has affected your hearing.

• CT scan (Computed & Tomography): This gives a detailed picture of the bone and can clearly show infection, fluid, or damage in the mastoid.

• MRI (Magnetic Resonance Imaging): Sometimes used to get a closer look at the soft tissues and nearby structures.

• Blood Tests: These can help confirm whether there's an infection in the body.

• Culture of Ear Discharge: If there's fluid draining from the ear, a sample may be tested to identify the exact cause and guide treatment.

Treatment for Mastoid Bone Conditions

Treatment depends on the specific condition and its severity.

• Antibiotics: For infections like mastoiditis (mastoid infection), antibiotics are usually the first step, and in more serious cases, they may be given directly through a drip.

• Pain Relief: Over-the-counter or prescribed pain medication helps manage discomfort and mastoid bone pain.

• Ear Drainage: If fluid has built up, a doctor may need to drain it to relieve pressure and clear the infection.

• Mastoidectomy: In more severe or persistent cases, surgery to remove the infected air cells may be needed. This procedure is called a mastoidectomy.

• Follow-up Care: After treatment, regular check-ups help make sure the infection has fully cleared and hasn't caused any lasting damage.

Our patient has asked, ‘Can mastoidectomy cause hearing loss?’ Our doctor has responded that hearing does not get worse after a mastoidectomy.

When Should You See a Doctor?

Some symptoms shouldn't be ignored. See a doctor if you experience:

• Persistent pain behind the ear.

• A fever alongside an ear infection.

• Swelling behind the ear.

• Hearing loss.

• Weakness or drooping on one side of the face.

• A severe headache.

These can be signs of a more serious problem that needs prompt attention.

How Can You Keep Your Mastoid Bone Healthy?

The best way to protect your mastoid bone is to look after your ears in general:

• Treat Ear Infections Early: Don't let ear infections linger, as they can spread to the mastoid if left untreated.

• Avoid Inserting Objects Into the Ear: Cotton buds and other objects can cause damage or push wax deeper.

• Attend Follow-up Appointments: Especially after an ear infection to make sure everything has healed properly.

• Maintain Ear Hygiene: Keep your ears clean, but always gently and safely, without pushing anything deep inside.

• Protect Your Ears During Sports: Wear proper head protection during activities where knocks or injuries are a real possibility.

Conclusion

The mastoid bone may be small, but it plays many important functions, protecting the delicate parts behind your hearing, holding key muscles in place, and keeping the air pressure around your ear balanced. But because it sits so close to the ear and other sensitive areas, problems here shouldn't be ignored. Treating ear infections early and taking good care of your ears goes a long way toward keeping this hardworking little bone in good shape. And if you ever notice lasting pain, swelling, or a fever behind your ear, don't put off getting it checked by an ear specialist.

Key Takeaways:

• The mastoid bone sits just behind the ear and is actually part of the larger temporal bone, rather than a separate bone.

• It protects the delicate structures behind your hearing and balance, anchors several muscles in the head and neck, and helps maintain pressure in your ear.

• The bone is filled with honeycomb-like air cells that lighten the skull and develop gradually after birth.

• Common problems include mastoiditis, cholesteatoma, and complications of chronic ear infections.

• Ongoing pain, swelling, or fever behind the ear needs prompt medical attention to prevent serious complications.