Inflammatory Diseases of the Middle Ear Workup

Updated: Jun 18, 2018
  • Author: Diego A Preciado, MD, PhD, FAAP; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Workup

Laboratory Studies

Culturing of the discharge after a spontaneous perforation in patients with acute suppurative otitis media is reliable in only the first few hours because external ear canal flora contaminates the otorrhea.

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Imaging Studies

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  • Cholesteatoma is usually treated surgically. Bearing this in mind, radiologic evaluation serves to demonstrate any underlying anatomical variation and to assist in diagnosing both the extent and the nature of pathological change. The extent of mastoid pneumatization influences the surgical approach taken.

    • CT scanning is generally the imaging modality of choice in the assessment of cholesteatoma.

      • High-resolution CT scans can demonstrate bony erosion of the tegmen, the lateral semicircular, and the bony covering of the facial nerve. Ossicular erosion of the malleus and the incus is often visible on CT scans, although stapes erosion is frequently not demonstrated.

      • MRIs are inferior to CT scans in demonstrating bony abnormalities associated with cholesteatoma. However, MRIs help distinguish between the different pathological processes that cause soft tissue accumulation in the mastoid and the middle ear spaces.

      • MRIs are particularly useful in distinguishing among cholesteatoma, cholesterol granuloma, and inflammatory granulation tissue.

    • Radiologic documentation of ears with chronic cholesteatoma, which usually require surgery, reveals underlying anatomical variations and assists in diagnosis of the extent and the nature of the disease.

    • Plain radiographs may depict the height of the middle fossa dura and the site of the sigmoid sinus, but they usually reveal little information on the extent of disease.

      • Both CT scans and MRIs can reveal the disease and its extent.

      • CT scans reveal a nonenhancing mass eroding the bone, including the ossicles, with sharply defined smooth margins, isodense with CSF; likewise, MRI depicts a mass with a low-intensity T1-weighted signal and a high T2 signal. In practice, distinguishing between cholesteatoma and pure mucosal disease is often difficult on imaging.

    • A high-definition CT scan of the petrous temporal bone depicts the extent of the mastoid disease, although it may not assist in distinguishing cholesteatoma from mucosal disease.

  • High-resolution CT scanning has allowed better detection of acute otomastoiditis. The mastoid air cells appear opacified because of mucosal swelling and the presence of mucus or mucopurulent secretions. With effective therapy, the inflammatory process can be arrested, and the mastoid air cells resume a normal radiographic appearance.

  • A gadolinium-enhanced magnetic resonance scan is currently the imaging modality of choice to aid in the diagnosis of intracranial venous thrombosis and intracranial abscess.

    • With intracranial venous thrombosis, simple thrombus shows an intermediate signal; vascularized thrombus, granulation tissue, and slow-flowing blood show a high signal; and fast-flowing blood shows no signal.

    • Intracranial abscess shows a center of low attenuation with an outer rim of a high signal.

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Other Tests

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  • Audiometry is not diagnostic, but it allows an examiner to assess the severity of the patient's condition.

    • Audiometry may also be used to monitor the progress of the patient's condition.

    • According to observations made in a prospective cohort study of 3-year-old children, dry ears have a mean hearing threshold of 17 dB, while ears with mild chronic secretory otitis media (SOM) and moderate chronic SOM have thresholds of 23 dB and 29 dB, respectively.

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Histologic Findings

The degree of inflammation in chronic suppurative otitis media (CSOM) without cholesteatoma is related to clinical activity, with the most intense changes seen in ears with continuous otorrhea. First, chronic inflammatory infiltrate (eg, lymphocytes, plasma cells, histiocytes) develops with increased capillary permeability of the lamina propria of the middle ear mucosa and resultant mucosal edema. The middle ear epithelium transforms as counts of goblet cells and ciliated cells increase, with the epithelium generally becoming more glandular and secretory.

Inflammatory granulation tissue develops during the early stages of healing after the destruction of the tissue. Sometimes, polyps covered with ciliated columnar epithelium form when the granulation tissue is florid. Later, the disease is characterized by decreased vascularity, fibrosis with sclerosis, and new bone formation in the mastoid air cells.

Ossicular changes are mainly due to osteoclastic bone resorption in granulation tissue or avascular necrosis. New bone formation may occur with fixation of the heads of the malleus and the incus in the attic. A foreign body granulomatous response to cholesterol crystals can result after hemorrhage into the middle ear, with crystals surrounded by foreign body giant cells and other chronic inflammatory cells. Tympanosclerosis is associated with CSOM with hyalinization of collagen and calcium deposition and may result from a specific autoimmune reaction.

Cholesteatomatous CSOM appears macroscopically as a crystallike structure with pale debris in the middle ear cleft. Light microscopy reveals a matrix of fully differentiated stratified squamous epithelium resting on connective tissue. The central core of cholesteatoma consists of anucleate keratin squames. Other inflammatory changes are similar to noncholesteatomatous CSOM, including aural polyps. Histologically, aural polyps that consist of granulation tissue with keratin as masses or flakes suggest that cholesteatoma is a likely diagnosis. Conversely, polyps without this feature but with lymphoid aggregates, a connective tissue core with glands, and a covering epithelium make cholesteatoma a much less likely diagnosis. Epidermal Langerhans cells are found in high numbers in cholesteatoma and are thought to be epidermal macrophages.

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