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Clinical Problem Solving: Radiology
Jan 2012

Radiology Quiz Case 3: Diagnosis

Arch Otolaryngol Head Neck Surg. 2012;138(1):94. doi:10.1001/archoto.2011.222-b

Diagnosis: Meningioma of the geniculate ganglion

Primary facial nerve tumors are rare. Although meningioma is a common cause of intracranial tumor, it is not frequently located extracranially.1,2 Isolated intratemporal meningioma is extremely rare, and only a few cases of geniculate ganglion meningioma have been described in the literature.1-5 Intratemporal meningioma can arise from direct extension of an intracranial meningioma or from ectopic arachnoid cells within the temporal bone. It can be localized to the internal acoustic meatus, jugular foramen, geniculate ganglion, and major or minor superficial petrosal nerve.4 Ectopic arachnoid cells along the facial nerve do not have continuity with the intracranial meninges. It has been hypothesized that arachnoid villi at the geniculate ganglion may represent tissues that have migrated from the middle fossa meninges through the thin cranial floor during embryogenesis.2 Therefore, in this case, as well as in others described in the literature,2-5 the lesion did not infiltrate the dura of the middle cranial fossa, which was easily elevated during the surgical approach, suggesting that the lesion originated from arachnoid cells that were displaced during embryogenesis and lying within the sheath of the facial nerve.