Prevalence of Spontaneous Asymptomatic Facial Nerve Canal Meningoceles: A Retrospective Review

J.C. Benson; K. Krecke; J.R. Geske; J. Dey; M.L. Carlson; J. Van Gompel; J.I. Lane

doi:10.3174/ajnr.A6133

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Fig 1.
A 55-year-old woman who presented with persistent dizziness. From inferior to superior, axial T2 SPACE images demonstrate fluid-filled remodeling/expansion of the right geniculate ganglion fossa (straight arrows), compatible with a meningocele (A–C). The labyrinthine segment of the facial nerve canal (curved arrow) is 0.9 mm in diameter, which is at the upper limit of normal but does not meet the defined size criteria for a meningocele. The normal left side is shown for comparison (D).
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Fig 2.
A 45-year-old woman who underwent imaging to follow up a known right vestibular schwannoma. Axial T2 SPACE images demonstrate fluid within the geniculate ganglion of the left facial nerve canal, with dilation measuring up to 2.7 mm, compatible with a meningocele (long arrows, A and B). Fluid is also seen tracking along the expected course of the proximal left greater superficial petrosal nerve (short arrow, B). The known vestibular schwannoma is seen in the contralateral right internal auditory canal, extending through the porus acusticus (curved arrow, C).
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Fig 3.
A 64-year-old woman who presented with bilateral sensorineural hearing loss. Axial T2 SPACE imaging demonstrates fluid-filled dilation of the right geniculate ganglion fossa, compatible with a meningocele (solid straight arrow, A and B). Fluid is seen in the left labyrinthine (curved arrow, C) and geniculate (dashed straight arrow, C and D) segments of the left facial nerve canal without remodeling/dilation of the osseous canal.

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Incidence of facial nerve canal fluid/meningocele^{^a}

	None (No.)	Unilateral (No.)	Bilateral (No.)
Labyrinthine segment fluid	168 (82.4%)	22 (10.8%)	14 (6.9%)
Geniculate ganglion fossa fluid	164 (80.4%)	21 (10.3%)	19 (9.3%)
Geniculate ganglion fossa meningocele	199 (97.5%)	5 (2.5%)	0 (0.0%)

↵a Incidence of fluid signal in the facial nerve canal on 3D fast spin-echo T2 sequences in 204 patients. Meningoceles were defined on the basis of size criteria: ≥1.0-mm diameter of the labyrinthine segment of the facial nerve canal, and ≥2.0-mm diameter of the geniculate ganglion fossa. No meningoceles were observed within the labyrinthine segment.