Intracranial meningioma extending into the middle ear: A report of two cases

Abstract

We report two cases of an intracranial meningioma extending into the middle ear.

Case 1: A 74-year-old woman presented with left-sided hearing loss. Evaluation revealed a mass that was visible through the left tympanic membrane. Computed tomography (CT) showed bone thickening of the left tegmen tympani and a soft tissue density in the left middle ear cavity. T2-weighted magnetic resonance imaging (MRI) showed slight hyperintensity in the left tympanic cavity; however, no intracranial lesion was observed. The left middle ear mass was surgically resected and histopathologically diagnosed as a meningothelial meningioma. Postoperative contrast-enhanced T1-weighted MRI revealed dural enhancement along the floor of the left middle cranial fossa. Therefore, we finally diagnosed the patient with an en plaque meningioma originating from the middle cranial fossa dura with spread through the tegmen tympani to the middle ear cavity.

Case 2: A 50-year-old woman presented with right-sided hearing loss and tinnitus. Evaluation revealed a mass that was visible through the right tympanic membrane. CT showed a soft tissue mass in the right mesotympanum. Contrast-enhanced T1-weighted MRI revealed a homogeneously enhancing mass extending from the cerebellopontine angle to the area surrounding the jugular foramen. Biopsy of the right middle ear mass confirmed diagnosis of a right cerebellopontine angle meningothelial meningioma that infiltrated into the middle ear cavity with extension into the jugular foramen.

Previous studies categorize temporal bone meningiomas into the following types based on the site of origin, vector of spread, and imaging findings: (1) tegmen tympani meningioma with inferomedial spread through the tegmen tympani into the middle ear cavity (Case 1), (2) jugular foramen meningiomas that spread superolaterally into the middle ear cavity (Case 2), and (3) internal auditory canal meningiomas that spread laterally to involve the cochlea and vestibular apparatus. All types are characterized by an intracranial contrast-enhanced dural component and preserved internal trabecular architecture of the involved bone.

Extension of intracranial meningiomas to the temporal bone is rare. However, it is important to not miss the characteristic CT findings of meningiomas in patients with a high likelihood of a middle ear tumor. Accurate identification of en plaque meningiomas using CT or plain MRI alone is challenging; therefore, contrast-enhanced MRI is necessary in such cases.