PMC8039292_01
Instrumental and radiological data of case one. (A) Audiometry showing mixed HL on the right side and profound HL on the left. (B) vHIT measurements. Blue lines represent head impulses exciting left SCs, orange lines correspond to impulses for right SCs, green lines represent eye movements induced by the activation of VOR following each impulse and red lines correspond to corrective saccades. Mean value of VOR-gain (eye velocity/head velocity) is reported for each SC. The hexagonal plot in the center of the figure summarizes mean VOR-gains for each SC; normal gains are shown in green and deficient gains are in red. A global canal hypofunction on the left and a slight reduction of the VOR-gain for contralateral PSC with overt saccades could be clearly observed. Axial (C) and coronal (D) images of temporal bones CT scans completed with axial T1-weighted (E) and coronal T2-weighted (F) gadolinium-enhanced brain MRI showing soft tissue density (yellow asterisks) within left external/middle-ear and mastoid cavity disrupting surrounding structures. Ossicular chain is not detectable. Bony erosion areas at the posterior fossa (white arrowheads) and middle fossa floor (yellow arrowheads) with dural infiltration are highlighted. Otic capsule erosion at the left HSC is indicated with red arrows. AC, air conduction; BC, bone conduction; CT, computed tomography; HL, hearing loss; HSC, horizontal semicircular canal; L, left; LA, left anterior; LL, left lateral; LP, left posterior; MRI, magnetic resonance imaging; PSC, posterior semicircular canal; R, right; RA, right anterior; RL, right lateral; RP, right posterior; SC, semicircular canal; vHIT, video-head impulse test; VOR, vestibulo-ocular reflex.
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F1
Pure tone audiometry detected ipsilateral profound HL and right-sided mixed HL (Figure 1A). Gains were considered normal if >0.8 for horizontal SCs and >0.7 for vertical canals. vHIT highlighted left global canal deficit and slight right-sided posterior SC (PSC) hypofunction (Figure 1B). Temporal bones CT scan showed soft tissue occupying the left EAC, mastoid, and tympanic cavities with bony erosion involving ossicular chain, HSC, fallopian canal, tympanic medial wall, and tegmen tympani (Figures 1C,D). Magnetic resonance imaging (MRI) of the brain showed contrast enhanced tissue invading the intracranial compartment through superior and posteromedial walls of the temporal bone (Figures 1E,F).
PMC8039292_02
Instrumental and radiological data of case two. (A) Audiometric test exhibiting mixed HL on the right with predominant ABG at lower frequencies and left high-frequency sensorineural HL consistent with patient's age. (B) vHIT showing reduced VOR-gain values for all right SCs with both overt and covert saccades and slight hypoactive VOR for contralateral PSC without corrective saccades. Axial (C,D) and coronal (E,F) images of temporal bone CT scans detecting signs of previous CWD mastoidectomy (white asterisks) with HSC fistula (white arrows). ABG, air-bone gap; AC, air conduction; BC, bone conduction; CWD, canal wall down; CT, computed tomography; HL, hearing loss; HSC, horizontal semicircular canal; L, left; LA, left anterior; LL, left lateral; LP, left posterior; PSC, posterior semicircular canal; R, right; RA, right anterior; RL, right lateral; RP, right posterior; SC, semicircular canal; vHIT, video head impulse test; VOR, vestibulo-ocular reflex.
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F2
Her audiogram showed right-sided mixed HL with widened air-bone gap at lower frequencies and contralateral age-related sensorineural HL (Figure 2A). Even though she denied positional vertigo, left-beating nystagmus could be observed on supine positioning and slightly persistent geotropic direction-changing nystagmus was elicited after head rolls, with stronger amplitude on right-sided positioning (Supplementary Video 2). vHIT measurements were taken on the same day, showing VOR-gain reduction for all SCs of the right side and mildly impaired function for left PSC (Figure 2B). High-resolution CT scan detected postoperative LF involving right HSC without inflammatory recurrences (Figures 2C-F).
PMC8039292_03
Instrumental and radiological data of case three. (A) Audiometric testing showing high-frequency sensorineural HL on the right side and left mixed HL with significant ABG widened for low frequencies and mild-to-moderate down-sloping sensorineural hearing impairment. (B) vHIT detecting reduced VOR-gain values for all left SCs with overt saccades and slight hypofunction for contralateral PSC with no corrective saccades. Axial (C-E) and coronal (F-H) temporal bones CT scans completed with axial (I) and coronal (J,K) T2-weighted gadolinium-enhanced brain MRI showing soft tissue density (yellow asterisks) within left middle-ear and mastoid cavity eroding ossicles and tegmen tympani (yellow arrowheads). Bony labyrinthine erosions of left SSC (red arrows), HSC (yellow arrows), and PSC (green arrows) are highlighted. ABG, air-bone gap; AC, air conduction; BC, bone conduction; CT, computed tomography; HL, hearing loss; HSC, horizontal semicircular canal; L, left; LA, left anterior; LL, left lateral; LP, left posterior; MRI, magnetic resonance imaging; PSC, posterior semicircular canal; R, right; RA, right anterior; RL, right lateral; RP, right posterior; SC, semicircular canal; SSC, superior semicircular canal; vHIT, video head impulse test; VOR, vestibulo-ocular reflex.
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F3
Audiometric testing showed down-sloping sensorineural HL on the right and left-sided mixed HL with predominant conductive loss for low frequencies (Figure 3A). The patient underwent vHIT measurements on the same day, showing left global hypofunction and slightly reduced VOR-gain for the right PSC (Figure 3B). Temporal bones CT scan revealed soft tissue consistent with cholesteatoma obliterating the right-sided tympano-mastoid cavity and eroding ossicular chain, all SCs, sigmoid sinus bony wall, and tegmen tympani (Figures 3C-H). Angio-MRI of the brain ruled out venous thrombosis and meningeal involvement (Figures 3I-K).