PMC7840843_01
Audiological assessment: auditory brainstem responses (ABR) were recorded using TDH-39 headphones and monaurally presented alternating polarity click stimuli of 100 mus duration, 11.33 Hz repetition rate and intensity of 90 dB nHL (normalized hearing level). The electrodes were mounted on center forehead (common); A1 left mastoid (active), A2 right mastoid (active) and high center forehead (reference). The responses were compared with our institutional normative values (provided) and demonstrated reproducible right waves I-V of degraded morphology, yet normal amplitude and latency and absent left responses at baseline (A) and at a 6-month interval (B), with additional findings of poorly reproducible right waves I-V and poor wave I morphology at a 6-month interval (B). Due to retrospective nature of the case report, it was impossible to separate the recordings into condensation and rarefaction buffers and to comment on the cochlear microphonic potentials.
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F1
Pure-tone audiometry, speech recognition tests, transient evoked otoacoustic emissions, and auditory brainstem responses were performed to assess auditory function up to the brainstem (Figure 1 and Table 1).
Peripheral vestibular assessment: (A) video head impulse Test (vHIT), demonstrated reduced gain in all six canals, more marked in the right anterior (asymmetry 17%) and both posterior canals; (B) ocular vestibular evoked myogenic potentials (oVEMP) were not detected on the left; (C) cervical vestibular evoked myogenic potentials (cVEMP) were compared to our normative values and were within normal limits. Tone burst stimuli of 500 Hz was used for both oVEMP and cVEMP, of alternating polarity (specific to the unit's equipment) and 2:1:2 cycle. The scale was 5 ms per division (oVEMP) and 3 ms per division (cVEMP). For oVEMP, the electrodes were placed on forehead (common), A1 centrally below the eye; REF (reference) electrode on the cheek 1 cm below (but not touching) A1. For cVEMP, the electrodes were placed on forehead (common), sternoclavicular joint (inverting/negative), sternocleidomastoid muscle belly (non-inverting/positive).
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F2
Peripheral vestibular tests included cervical and ocular vestibular evoked myogenic potentials and video head impulse test, whereas videonystagmography was performed to distinguish between the peripheral and central vestibular involvement and to assess severity of the dysfunction (Figure 2). Video head impulse testing identified reduced mean vestibulo-ocular reflex gains for all six canals (Figure 2A). Left ocular vestibular evoked myogenic potentials were not detected (Figure 2B). Cervical vestibular evoked myogenic potentials were within normal limits (Figure 2C).
Axial susceptibility-weighted magnetic resonance images (SW-MRI) at the level of (A) brainstem/internal auditory canals, demonstrating haemosiderin deposition over the pons and vestibulocochlear nerves bilaterally with slightly thicker hypointense rim of hemosiderin on the left (arrows); (B) superior temporal gyri, demonstrating supratentorial haemosiderin deposition along the surfaces of the temporal lobes, involving insular areas and particularly Sylvian fissures and Heschl's gyri (arrowheads); and (C) asymmetry in the supratentorial appearance of haemosiderin deposition on the left (asterisks).
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F3
There was additional involvement of supratentorial structures, with severe and widespread siderosis affecting the surfaces of temporal lobes, including Sylvian fissures and insular areas, frontal and occipital lobes, but sparing the vertex (Figure 3).