PMC7838557_01
(A-C) Brain MRI performed 4 years prior to left-sided labyrinthine ischemia exhibiting (A) Slight signs of periventricular leukoaraiosis on axial T2-weighted FLAIR (fluid-attenuated inversion recovery) images. (B) Axial and (C) sagittal MRI with 3D-FIESTA (fast imaging employing steady-state acquisition) sequences showing normally fluid filled semicircular canals on both sides (red arrows indicate left posterior semicircular canal). (D-F) Brain MRI performed 14 days after left-sided labyrinthine ischemia showing (D) Increased areas of periventricular leukoaraiosis and widened cerebrospinal fluid spaces on atrophic basis on axial T2-weighted FLAIR images. (E) Axial and (F) sagittal MRI with 3D-FIESTA sequences showing filling defect within the left posterior semicircular canal (black arrows). A, anterior; L, left; P, posterior; R, right.
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Corresponding brain MRI images were reviewed, showing signs of periventricular leukoaraiosis and normal posterior fossa structures, including normally fluid-filled SCs on FIESTA sequences (Figures 1A-C). Acute brainstem infarction in diffusion-weighted and T2-weighted fluid-attenuated inversion recovery (FLAIR) images were excluded, whereas widened cerebrospinal-fluid spaces on atrophic basis and increased areas of leukoaraiosis compared with previous neuroimaging were detected (Figure 1D). 3D-FIESTA sequences detected signal loss within left-sided PSC consistent with fibrous tissue deposits (Figures 1E,F).
(A,B) Presenting scenario including (A) Pure-tone audiometry exhibiting right-sided high-frequency sensorineural hearing impairment and profound left-sided hearing loss. (B) vHIT. Blue lines represent head impulses exciting left canals, orange lines correspond to impulses for right canals, 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 canal. The hexagonal plot in the center of the figure summarizes mean VOR-gains for each canal; normal gains are shown in green and deficient gains are in red. A selective deficient VOR-gain for the left posterior semicircular canal (0.59) with overt saccades can be observed. Cervical VEMPs (C) and ocular VEMPs (D) for air-conducted sounds. For cervical VEMPs, right and left lines correspond to myogenic responses (p1-n1) recorded on the right and left SCM muscle (i.e., right and left saccular responses), respectively. For ocular VEMPs, being crossed responses, right and left lines represent potentials (n-p) recorded under the left and right eye (i.e., right and left utricular responses), respectively. VEMPs testing revealed normal responses on the right side (83 muV at 100 dB HL stimuli) and absent potentials on the left, whereas symmetrical amplitudes for ocular VEMPs (R: 6 muV and L: 5 muV at 100 dB HL stimuli) could be detected. L, left; LA, left anterior; LL, left lateral; LP, left posterior; R, right; RA, right anterior; RL, right lateral; RP, right posterior; SCM, sternocleidomastoid; vHIT, video head impulse test; VEMPs, vestibular evoked myogenic potentials; VOR, vestibulo-ocular reflex.
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Pure-tone audiometry showed right-sided high-frequency sensorineural HL consistent with the patient's age and profound left-sided hearing impairment (Figure 2A). Selective mild reduction of left posterior SC (PSC) activity was detected on vHIT (Figure 2B). Although no cervical responses could be detected on the pathologic side consistent with left-sided isolated saccular loss, symmetrical potentials were evoked for ocular testing (Figures 2C,D).
(A-C) Instrumental picture following steroids and hyperbaric oxygen therapy. (A) Pure-tone audiometry exhibiting partial recovery for right-side hearing function with a pure-tone average (500 Hz-4 kHz) of 77.5 dB. (B) Standard speech audiometry in silent setting showing optimal (100%) and poor (20%) speech discrimination score on the right and left sides, respectively. (C) vHIT showing persistent selective loss for left posterior canal VOR-gain (0.46) with both overt and covert saccades. Affected canal VOR-gain is further impaired compared to presenting values. (D,E) Temporal bones HRCT scans with axial (D) and parasagittal reconstructed image along the Stenver plane (E) excluding signs of posterior semicircular canal ossification on the left side (yellow arrows). HRCT, high-resolution computed tomography; L, left; LA, left anterior; LL, left lateral; LP, left posterior; R, right; RA, right anterior; RL, right lateral; RP, right posterior; vHIT, video head impulse test; VOR, vestibulo-ocular reflex.
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Hearing evaluation with pure-tone audiometry showed a moderate to severe down-sloping sensorineural HL on the left side, consistent with mild recovery of cochlear function (Figure 3A). Nevertheless, word recognition on the left side was poor on speech audiometry, while the speech discrimination score was optimal on the healthy side (Figure 3B). Although vHIT showed further reduction in left-sided PSC activity (Figure 3C), the patient reported that his vestibular symptoms were substantially relieved. Temporal bone HRCT performed 2 weeks later finally excluded signs of labyrinthine ossifications (Figures 3D,E).