Timothy C. Hain, MD • Page last modified: March 7, 2021


Mastoiditis is an inflammation or infection of the sinus behind the middle ear (Mastoid sinus). This can be often seen on imaging studies such as MRI (see below).

mastoid fluid mastoid CT
Right sided mastoiditis (white blotch on the left side of this image). On MRI films, the right side of the head is shown on the left side of the image. Mastoid fluid on MRI scan (coronal) -- Right side of image corresponding to L mastoid. On the more normal right side, the inner ear can be seen (loops just below temporal lobe of brain). Mastoid fluid on axial view of CT scan, again right side of image. This is the same patient as the image to the immediate left. On the left side, the more normal right mastoid is full of air (e.g. is black)

Mastoiditis means inflammation of the sinus which is behind the middle ear. This can be seen on imaging studies (see above).

Generally speaking, mastoiditis is ignored. However, this cannot be done 100% of the time. The position of the writer of this page (Dr. Hain), is that there should be both consideration of the MRI and the clinical picture.

Sayal et al (2019) reported that " Physical examination revealed that only 14 of 160 patients (8.8%) had clinical evidence of otologic disease." They took this to suggest that mastoid fluid is "incidental".

Wilkinson et al (2017) reported on 468 CT scans of the head, and noted that 13% of them had Mastoid and/or middle ear opacification. They called these "incidental temporal bone disease". They recommended: "Data from this study suggests that incidental findings in an asymptomatic individual do not necessitate referral or further intervention. Furthermore, it is the author's recommendation that radiological findings be closely correlated with clinical examination to reduce false diagnosis and inappropriate referral to ENT." So in other words, don't bother ENT with the 13% of CT scans that show mastoid fluid, as long as they are "incidental".

Meredith and Boyev (2008) wrote on mastoditis on MRI, and suggested that the term is most often applied to the observation of fluid in the mastoid, which may be clinically insignificant. Nevertheless, they note that the literature indicates that only 4/1000 temporal bones have fluid on MRI in the mastoid in asymptomatic volunteers, and in TMJ MRI, only 10 patients had fluid out of 2700 (thus about 1/270). This suggests that fluid in the mastoid is generally rare. Note that above, Wilkinson et al said that 13% of CT scans show mastoid fluid. Obviously, there is quite a big discrepency between 0.4% and 13%.

Abbas et al (2018) reported that 5.8% of individuals who underwent MRI for asymmetrical hearing loss or tinnitus had mastoiditis. Not here that they were scanning people with hearing symptoms, unlike the case of Meredith and Boyev who were reporting on "asymptomatic volunteers". It would seem to us that again, individuals with hearing symptoms seem to have more fluid in their mastoid sinus than normal people. Abbas et al. stated "An incidental finding of high signalling in the mastoid region on magnetic resonance imaging is highly unlikely to represent actual clinical disease. In patients who are scanned for other reasons and who do not complain of otological symptoms, such findings are unlikely to require otolaryngology input."

It has been our observation that in our dizziness and hearing practice in Chicago, at least 1/100 of our patients has mastoid fluid (i.e. about 1%). Still if you consider that there are now more sophisticated scanners that can "see" smaller amounts of fluid, and perhaps also that we here have higher sensitivity than many others, these numbers are not that different. This suggests to us that mastoiditis may be an underrecognized cause of dizziness or hearing symptoms. Alternatively, it may be much more common in Chicago than reported in general (seems unlikely to us).

There are several types of Mastoiditis

Severe mastoiditis is characterized by a swollen external auditory canal. Mild mastoiditis, may be silent, and only seen on imaging (as above).

If a mastoidectomy is needed for a severe bacterial mastoid infection, or to treat a cholesteatoma, there can be an opening left in the ear canal, that goes into the mastoid. These "mastoid cavities", left behind by "canal wall up" mastoid surgeries, typically need to be cleaned out periodically with a microscope and suction by an otology doctor.

Mimickers of mastoidtis

These are exceedingly rare.

There are several treatment approaches to mastoiditis --


Complications of Mastoiditis

Facial Paralysis associated with mastoiditis

An acute lower motor neuron facial palsy is rare even though dehiscence of the facial canal is very common. When this happens, there should be a myringotomy with PE tube placement, Infectious disease consultation, intravenous antibiotics, and consideration of mastoidectomy. Once the infection resolves, facial nerve function usually recovers over several months.

Lateral sinus thrombosis

A rare complication of mastoiditis is thrombosis of the lateral sinus. This is mainly reported in children, but adults are not entirely spared (Palma et al, 2014). According to Ghosh and others (2011), clinical features include headache, vomiting, fever, diplopia, papilledema, sixth nerve palsy, seventh nerve palsy, and unilateral cerebellar ataxia. Mastoiditis is often appreciated from postauricular swelling, redness or tenderness, protrusion of the auricle, and fever. Diagnosis is generally with imaging (contrast MRI or CT scan), showing lack of the usual flow in the venous sinuses of the brain. Of course, there should also be fluid in the mastoid. Treatment primarily includes antibiotics (Palma et al, 2014).

Labyrinthitis associated with mastoiditis

This comes in several stages.

  • Serious labyrinthitis - -bacterial toxins enter the inner ear and cause vertigo and mild hearing loss.
  • Purulent labyrinthitis occurs as bacteria enter the inner ear.
  • Labyrinthitis ossificans -- occurs when the inner ear fills with scar tissue

In patients believed to have labyrinthitis associated with AOM, one should image the brain, obtain a lumbar puncture, place a PE tube, administer IV antibioitics, and consider mastoidectomy.

Gradenigo's syndrome (Petrous apicitis)

The symptoms of this include severe frontal headache, eye pain, diplopia, dizziness, nausea, and 6th nerve palsy. There should be otitis media seen on otoscopy. MRI shows inflammation of the petrous apex and mastoids. CT may show bone erosion in the petrous apex.

Treatment is with myringotomy with PE tube, and culture-directed IV antibiotic therapy.