Invisible Culprit: Intralabyrinthine Schwannomas That do not Appear on Enhanced Magnetic Resonance Imaging

Intralabyrinthine schwannoma (ILS) is an infrequent tumor that arises in isolation within the periphery of the temporal bone. Only 32 cases have been reported to date in the literature, of which 12 were discovered at autopsy. Prior to the advent of gadolinium-enhanced magnetic resonance imaging (Gd-MRI), only 1 ILS had been diagnosed preoperatively. However, after Gd-MRI became a common modality, 5 ILSs were imaged. Two additional cases are reported that were discovered during labyrinth-destructive surgery despite normal Gd-MRI findings. Possible explanations for and potential ramifications of nonenhancing ILS are discussed.