Fig. 1

Examples of grading and comparisons of signal intensity of the perilymph: The first row represents PPI for grades 0 (a), 1 (b), and 2 (c). The second and third rows are the corresponding MRC (d–f) and HYDROPS (g–i) images, respectively. a PPI for grade 0: The signal intensity of the perilymph, including the entire cochlea (arrow), vestibule (small arrow), and lateral as well as posterior semicircular canals (arrowheads), was similar to that of CSF in the cerebellopontine angle cistern (asterisk). b PPI for grade 1: The signal intensity of the perilymph, including the cochlear basal and middle/apical turns (arrows), and vestibule (small arrow), was higher than that of CSF (asterisk) without sharply delineated borders. c PPI for grade 2: The signal intensity of the perilymph, including the entire cochlea (arrows), vestibule (small arrow), and lateral as well as posterior semicircular canals (arrowheads), was markedly higher than that of CSF with sharply delineated borders. The higher the grade on PPI, the higher the signal intensity of the perilymph was on corresponding HYDROPS images. d–f The corresponding MRC: Each arrow showed a vestibular schwannoma. g–i The corresponding HYDROPS: Of note, HYDROPS (i) more easily detected the vestibular endolymphatic space as hypointensity (dotted arrow) than the corresponding PPI for grade 2 (c). j Comparison of perilymph signal intensity between the affected and unaffected sides on PPI: The signal of the perilymph on the affected side (arrows) was higher than that on the unaffected side (arrowheads)