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Clinical Problem Solving: Radiology
September 2002

Diagnosis Radiology Quiz 1

Author Affiliations
 

R. NICKBRYANMDS. JAMESZINREICHMD

Arch Otolaryngol Head Neck Surg. 2002;128(9):1105-1106. doi:
Diagnosis: Cervical extension of an EAC cholesteatoma

The term cholesteatoma is used to describe a cavity lined with squamous epithelium and filled with desquamated keratin. Histopathologically, it resembles an epidermal cyst or a keratoma. By definition, an aural cholesteatoma originates in the middle ear or other pneumatized areas of the temporal bone.1 Typically, it enlarges over time owing to the continuing desquamation and entrapment of epithelial debris within the cholesteatoma sac.

Aural cholesteatomas may be classified as either congenital or acquired. Congenital aural cholesteatoma, also called primary cholesteatoma, is rare and is believed to arise from epithelial rests in the temporal bone.2 It usually presents behind an intact tympanic membrane and causes no inflammation of the mucosa of the promontory until it ruptures. It has a sharply marginated expansile configuration, and usually arises in the anterosuperior portion of the middle ear. On the other hand, an acquired or secondary aural cholesteatoma can originate from an attic retraction or an existing posterior marginal tympanic membrane perforation.1 It frequently expands through bone and other anatomical structures by a combination of erosive pressure and localized destruction of bone due to pyogenic osteitis, enzymatic collagenolysis, or osteoclastic bone resorption.1 It can expand and erode from the middle ear into the internal ear and intracranial structures. It is usually located posterosuperiorly and has a more erosive pattern of growth than the congenital cholesteatoma. An acquired aural cholesteatoma can also be iatrogenic as a result of trapped squamous epithelial debris after otologic surgery. In these cases, the cyst can sometimes be localized solely on the tympanic membrane.

In the present case, the magnetic resonance imaging and computed tomographic scans showed a sharp lesion in the mastoid bone, eroding the mastoid tip, and 2 lobulated masses in the neck. Although it was a sharp lesion, it eroded through a bony structure (the mastoid tip), which is a feature that is more common to an acquired cholesteatoma than to a congenital cholesteatoma.

A cholesteatoma of the EAC may be idiopathic or due to infection, trauma, or surgery.3 When it is due to surgery, it is most commonly because of squamous debris left under the tympanomeatal flap. It can erode into the mastoid, but seldom affects the middle ear.4

Cholesteatomas arising from structures other than the ear are extremely rare. There are some cases in the literature of cholesteatomas of the paranasal sinuses.5 Cholesteatomas in these locations are thought to be the result of an inciting factor or a congenital rest. Although these lesions are generally called cholesteatomas of the paranasal sinuses, some authors consider this a misnomer. The term keratoma or epidermal cyst is thought to be more accurate.

To our knowledge, there are only 7 cases of cholesteatomas with extension to the neck reported in the literature.6-9 All the patients described had undergone a radical mastoidectomy for their aural cholesteatoma at least 5 years before the neck mass developed. One explanation for the extension of the cholesteatoma into the neck is that epithelial particles spread throughout the fascial cervical planes during the radical mastoidectomy, inducing the formation of epidermal cysts.9 This theory is supported by the fact that in all 7 reported cases no dehiscence of the mastoid tip was observed at the time of surgery. The neck cholesteatoma was attached to the mastoid tip by a fibrous stalk, and the mastoid tip was intact in all cases. Another possible theory is that the cholesteatoma eroded through the mastoid tip and extended into the neck in the same manner as the propagation of pus in a Bezold abscess.6

In the present case, the patient initially underwent a right intact canal wall mastoidectomy and a superficial parotidectomy with neck exploration. A large cholesteatoma was noted in the right mastoid, with erosion of a small portion of the EAC. The remainder of the bony EAC was extremely thin. The EAC skin was intact and adjacent to the cholesteatoma at the eroded area. The cholesteatoma had eroded through the mastoid tip and was connected to 2 large lobulated masses just anterior to the sternocleidomastoid muscle at level II in the neck. The right parotid gland was largely obliterated by the cholesteatoma. The mastoid portion of the cholesteatoma and its cervical extensions were all removed en bloc. The middle ear and ossicular chain were found to be intact and without any disease. To improve aeration, a tympanoplasty was not performed at that time but was planned to be carried out at the "second-look" operation. The patient did well after surgery except for some progressive retraction of posterior EAC skin into the mastoid. There was no squamous debris. Nine months later, he underwent a right tympanoplasty with mastoid exploration and reconstruction of the EAC. The lateral two thirds of the posterior bony EAC was found to be eroded. The EAC skin was intact but retracted into the mastoid. A remnant of cholesteatoma was found at the tip of the mastoid, almost entering the sternocleidomastoid muscle. It was not connected to the skin of the EAC. After the remnant was removed, the tympanic membrane was repaired with temporalis muscle fascia and the EAC defect was reconstructed with conchal cartilage. The patient is doing well, with a well-healed tympanic membrane and an intact EAC. There are no signs of recurrence.

The most likely explanation of our patient's disease is that he developed an iatrogenic EAC cholesteatoma after his tympanoplasties, with extension to the neck through an erosion of the mastoid tip, following the same pathway as the propagation of pus in a Bezold abscess. Dissemination of epithelial particles into the cervical tissues is an unlikely explanation in this case, since the patient had not previously undergone a mastoidectomy.

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