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Clinical Note
April 18, 2011

Arachnoid Cyst: Middle Ear Mass Diagnosis to Consider

Author Affiliations

Author Affiliations: Department of Otolaryngology–Head and Neck Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania (Drs Clary, Walker, Nicholas, and Artz); and Division of Otolaryngology–Head and Neck Surgery (Dr Goodman), Department of Radiology (Dr Kori), The George Washington University, Washington, DC.

Arch Otolaryngol Head Neck Surg. 2011;137(4):398-400. doi:10.1001/archoto.2011.31

The differential diagnosis of middle ear masses includes a wide array of typically benign diseases, with cholesteatoma as the leading entity. Other lesions frequently considered include glomus tumors, schwannomas, choristomas, and other vascular variants. Arachnoid cysts, despite being present in 4% of the population, are seldom considered.1

Arachnoid cysts are cerebrospinal fluid (CSF) filled spaces that usually form within the arachnoid membrane covering the brain and spinal cord. Most commonly, arachnoid cysts present in the middle cranial fossa.1 Their presentation in the middle ear space has been described as typically due to erosion through the tegmen tympani. We present the case of a patient with a middle ear mass that ultimately was found to be an arachnoid cyst isolated to the tympanic segment of the fallopian canal. We use this previously undescribed (to our knowledge) presentation to discuss the clinical and radiologic characteristics of this entity, as well as its treatment. Institutional review board approval was not required for this report.

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