PMC5966533_01
Caloric exam. (A) Top, the standard bithermal caloric test showed no response to either temperature irrigation from either ear. (B) Bottom, ice water irrigation (20 C) shows only a minor residual response (total response = 4 /s).
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F1
However, bithermal caloric testing with water irrigation revealed a bilateral vestibular areflexia, with very weak, though residual responses to ice water irrigation (Figure 1).
Video head impulse test (vHIT). The vHIT shows severe and reduced vestibulo-ocular reflex (VOR) gain in the horizontal and superior semicircular canals with corrective compensatory saccades. Both posterior semicircular canals (RP, right posterior; LP, left posterior) show normal VOR gain (parenthesis) without compensatory saccades.
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F2
Video head impulse test (vHIT) (EyeSeeCam:Interacoustics, Middelfart, Denmark) showed a severe reduction in each horizontal and superior semicircular canal gains but a normal response in both posterior semicircular canal gains (Figure 2).
Air-conducted VEMP traces. (A) Acute cervical (top) and ocular (bottom) VEMP responses recorded 2 weeks from the onset of symptoms. (B) Chronic cervical (top) and ocular (bottom) VEMP recorded again at 12 months. The cVEMP responses were reproduced bilaterally at the acute and chronic stages with latency, amplitude and asymmetry within the normal range. The cVEMP amplitudes [normalized to background electromyography (EMG) activation (EMG scaling)], showed <20% asymmetry, suggesting bilaterally spared inferior vestibular nerves. In contrast, the acute oVEMP showed no reproducible responses bilaterally. At 1 year, a reproducible oVEMP was observed only on the left side. Two trials were conducted in order to confirm results (two traces). Cervical and ocular VEMP waves of respective potentials (positive and negative deflections:P1/N1) were analyzed. Stimuli was a 100 db air-conducted 500 Hz tone burst.
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F3
In a follow-up consultation 2 weeks later, air-conducted cervical and ocular vestibular evoked myogenic potential (cVEMP and oVEMP) (Eclipse-Interacoustics, Middelfart, Denmark) showed an absence of both oVEMP responses but normal cVEMP responses (Figure 3). An improvement in the left oVEMP was documented (Figure 3).
Brain MRI. (A) Normal internal auditory canals as visualized via axial FIESTA (upper) and coronal T1 with contrast (lower). (B) Normal inferior and medial vestibular nuclei at the level of the medulla (axial diffusion:upper) and FLAIR (lower).
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F4
A second MRI 3 tesla (3 T Discovery 750, General Electrics, Milwaukee, WI, USA) did not show any changes within the auditory canal or of the brain structures (Figure 4).