A 44-year-old man was referred to our interdisciplinary center for vertigo and balance disorders at the University Hospital Zurich (tertiary referral center) with recurrent spontaneous attacks of spinning vertigo, which started several months prior to his first visit. The attacks usually lasted for 3-12 h and were accompanied by fluctuating hearing loss and tinnitus in the right ear.
According to the patient's medical history, he had suffered a left-sided longitudinal TB fracture caused by a car accident at 10 years of age (the original neuroradiology report but not the CT images were available for this study). Pure-tone audiometry (PTA) 4 months after the accident showed a pronounced high-frequency shift in bone conduction thresholds at 6 kHz on the left side (PTA not shown here), consistent with acoustic trauma and probably caused by the impact noise in the car. No further accident-related injuries or audiovestibular symptoms occurred, according to the available clinical records from that time. A synopsis of relevant events in the patient's medical history is given in Figure 1A.
In the initial neurotological work-up at age 44, vestibular-evoked myogenic potentials (VEMPs) indicated left-sided saccular dysfunction (absent cervical VEMPs). Other vestibular test results (ocular VEMPs, subjective visual vertical, video-oculography with caloric stimulation, and video head impulse test) were within the normal range (data not shown). PTA showed that the left ear had mixed, predominantly sensorineural, downward-sloping hearing loss (HL) up to 100 dB HL at 6 kHz (Figure 1B), while the right ear had moderate to severe presbyacusis (Figure 1C). Speech discrimination scores were 35 % on the left side and 100 % on the right side, and stapedial reflex responses were normal on both sides (data not shown).
Two months later, the patient presented in our emergency department immediately after an acute, hours-long vertigo attack accompanied by nausea and emesis. The HL and tinnitus in the left ear temporally worsened. Clinical examination showed a spontaneous nystagmus to the right side, a positive head impulse test to the left, and a positive Romberg test with a tendency to fall to the left side. Finally, a diagnosis of left-sided Meniere's syndrome was made, and a possible traumatic etiology was considered based on the patient's history.
The patient subsequently received repeated intratympanic dexamethasone (6.6 mg)/hyaluronate (2 mg/ml) injections over the course of several days, and in the following years, he undertook sequential trials of different vestibular suppressants [cinnageron, 75 mg, two times daily for 8 weeks, betahistine, 24 mg, two times daily for 16 weeks; prior to publication of ]. Although the vertigo episodes continued with an average frequency of two attacks per month, the patient was coping well with the symptoms, and no vestibular ablative treatment was considered. In the 4 years following the onset of MD symptoms, hearing function in the left ear fluctuated in the low and middle frequencies and progressively declined to a level of 50-80 dB HL (Figure 1B). Finally, the patient was fitted with a contralateral routing of signals (CROS) hearing aid. He was then lost to further follow-up.
During initial neurotological evaluation (age 44), high-resolution CT (HRCT) imaging of the TBs was performed to rule out retrocochlear pathologies (e.g., vestibular schwannoma), posttraumatic inclusion cholesteatoma, and otosclerosis. HRCT imaging showed no evidence for the previously mentioned pathologies but demonstrated an old fracture sign in the posterior wall of the external ear canal. Four years later (age 48), gadolinium-enhanced MRI (Gd-MRI) of the inner ear fluid spaces with a 4-h delayed 3D inversion recovery (3D IR) sequence detected moderate [grade I, ] vestibular and moderate-to-severe [grade I-II, ] cochlear hydrops in the left inner ear, consistent with the previously assigned clinical diagnosis. No radiological (Gd-MRI) signs of endolymphatic hydrops were found in the right inner ear.
In the present study, we reassessed the available imaging data with regard to potential pathologies of the VA and ES on the clinically affected left side. On HRCT imaging, the left VA appeared to be almost completely obliterated by bone along its course between the isthmus and the operculum (Figure 2A). In contrast, the right VA exhibited a patent lumen throughout its entire course (Figure 2B). Correspondingly, on Gd-MRI (3D IR sequence), a segment of total T2 signal loss was observed in the partially obliterated left VA (Figure 2C) but not in the right VA (Figure 2D). In the left VA, a delineated T2 signal was seen distal (posterior) to the segment with total signal loss (Figure 2C, blue arrows). Fusion of HRCT and Gd-MRI (color-coded) data in the focal plane of the operculum clearly localized this T2 signal distal (posterior) to the operculum (Figures 2E-H). Therefore, the signal most likely originated from the eES, as proposed previously. In summary, the HRCT and Gd-MRI data indicated that the left eES was structurally preserved but anatomically separated from the labyrinth due to bony obliteration of the VA. Upon reassessment of the imaging data for the present study, no radiological signs for bony labyrinthine dehiscence, nor for cerebellopontine angle tumors were found that could account for the fluctuating otological symptoms.