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Medial migration of intracanalicular vestibular schwannoma (VS) with associated widening of the fundal cap is a rare phenomenon that, to our knowledge, has only been described in a patient following stereotactic radiation treatment. Herein, we present a case of a woman in her 60s with an untreated intracanalicular VS that demonstrated medial migration on serial magnetic resonance imaging (MRI) scans over the course of 30 months.
A woman in her 60s with a history of right sensorineural hearing loss presented with worsening symptoms of vertigo. Axial, high-resolution T2-sampling perfection with application optimized contrasts using different flip angle evolution (SPACE) sequence MRI of the internal auditory canal (IAC) showed a right-sided spherical intracanalicular VS (Figure 1A) measuring 6 mm in diameter and situated 1.2 mm from the AIC of the fundus. Serial surveillance MRI demonstrated growth and progressive medial migration of the VS (Figure 1). At 6 months, the VS demonstrated 1 mm of growth and 1.5 mm medial migration. At 18 months, the VS showed a further 1.2 mm of growth and 1.3 mm medial migration. At 30 months, the VS demonstrated a further 2.8 mm of growth and 1 mm of medial migration. The VS reached a final axial dimension of 11 mm with a slightly flattened morphology along with protrusion into the cerebellopontine angle cistern. Relative to the baseline MRI, the VS had migrated medially over a distance of 3.8 mm. Accompanying the medial migration of the VS was progressive buckling of the cisternal segment of the facial and vestibulocochlear nerves (Figure 2). Subsequently, the patient underwent gamma knife treatment to the VS with a prescribed dose of 12.5 Gy delivered to the 50% isodose. The patient tolerated treatment well without adverse events. The patient is yet to attend post-therapy clinical and MRI surveillance follow-up.
Hsu CC, Watkins TW, Sommerville J. Medial Migration of an Untreated Intracanalicular Vestibular Schwannoma. JAMA Otolaryngol Head Neck Surg. 2016;142(10):1025-1026. doi:10.1001/jamaoto.2016.1769