Symptoms: Dizziness and Sudden Hearing Loss

Abstract

A 54-year-old man with a history of Ménière's disease and migraine presented with left-sided sudden hearing loss with associated vertigo, left-sided tinnitus, and left-sided aural fullness that had been going on for two weeks. The episodes of vertigo lasted about one minute and were provoked by position changes. He had a history of vertigo that was resolved with Epley maneuvers. His physical exam results were normal. He had a Dix-Hallpike test, which turned out to be negative. His audiogram showed normal hearing in his right ear and profound hearing loss in his left ear (Fig. 1A). His audiogram from six months ago is also shown below (Fig. 1B).Figure 1: (A) The patient's audiogram at presentation and (B) from six months before presentation. Hearing loss, tumor, Ménière's disease.Figure 2: Axial (horizontal) T2 MRI of the brain (5 mm slice) from six months before showing the IACs and a possible space-occupying lesion in the anterior limb of the horizontal canal on the left (in retrospect), which couldn't be ascertained due to slice thickness. Hearing loss, tumor, Ménière's disease.Figure 3: Axial (horizontal) T1 MPR MRI of the brain (1 mm slice) from six months prior to presentation showing the internal auditory canals, but the mass cannot be seen clearly due to a lack of contrast. Hearing loss, tumor, Ménière's disease.Figure 4: Axial (horizontal) CISS sequence MRI of the internal auditory canals showing a small mass displacing the intravestibular fluid. The mass appears dark. Hearing loss, tumor, Ménière's disease.Figure 5: Axial (horizontal) T1 post-contrast MRI of the internal auditory canals showing a small mass (white) in the vestibule extending into the anterior limb of the horizontal canal. Hearing loss, tumor, Ménière's disease.Figure 6: Coronal (parallel to the face) T1 post-contrast MRI showing a hyperintense (white) mass extending into the superior and horizontal canals. Hearing loss, tumor, Ménière's disease.Diagnosis: Intravestibular Schwannoma The patient's presentation was initially suspicious for an exacerbation of Ménière's disease, which can involve fluctuations in hearing, vertigo, tinnitus, and aural fullness. However, typical episodes of Ménière's disease usually resolve within a few hours and only last about a day at most. Regardless, this patient should have radiographic imaging done due to his sudden unilateral hearing loss. Approximately three percent of patients with sudden hearing loss can have a retrocochlear lesion, and about 10 percent of patients with vestibular schwannoma (acoustic neuroma) present with sudden hearing loss. Concerning imaging of the temporal bone and the inner ear, the type of magnetic resonance image (MRI) ordered has important implications for the amount of detail and types of structures that will be visible. A standard MRI of the brain uses 5 mm tissue slices in various sequences, which means that each slice produces one image. Tissues within that 5 mm space will need to be averaged into one image, resulting in an artifact known as a partial volume effect. When taking a relatively large slice, small abnormalities in the internal auditory canal (IAC), cochlea, and vestibule may be easily missed. MRI of the brain may sometimes not get a proper image of the IAC. When evaluating for vestibular schwannoma, the T2 sequence produces the best MRI of the brain without contrast. In this sequence, the cerebrospinal fluid (CSF) appears white while a tumor will appear dark, and the nerves in the IAC are visible. With contrast, the tumor will appear white since it has more vascularity and will have a higher concentration of the contrast material (usually gadolinium). Some newer MRI of the brain protocols includes imaging slices of the brain as thin as 1 mm (called multiplanar reformation [MPR] sequence). While this sequence may help reveal more structural details, it tends to produce blurry images of the temporal bone region. The use of a contrast medium can aid in the identification of small IAC or temporal bone lesions, but in general, brain MRIs have limited use in detecting IAC lesions measuring 2 mm or smaller due to the slice thickness. A better option for evaluating the inner ear is an MRI of the IACs. In a study of more than 1,000 patients with sudden hearing loss, Daniels, et al., found MRIs of the IACs without contrast, using the T2-weighted fast spin-echo (FSE) protocol, to be just as sensitive in detecting vestibular schwannomas as typical MRIs with contrast (Am J Otol. 2000;21[2]:173-80). This protocol was able to detect other lesions in different locations as well, including those in patients with multiple sclerosis, infarction, and colloid cysts. By avoiding the use of contrast, T2-weighted FSE MRIs of the IACs also help reduce imaging cost, the time needed to obtain the scan, and possible adverse effects from the contrast itself. The T2-weighted FSE sequence is also referred to as three-dimensional constructive interference in steady-state (CISS) MRI, 3D MPR, or 3D FIESTA, depending on the imaging device being used. This T2-based sequence can show high-resolution details of cranial nerves, cisternal spaces, and spaces involving or adjacent to the CSF as well as the inner ear. On CISS imaging, fluids such as the CSF and perilymph/endolymph appear bright, and potential tumors and masses appear dark. Post-contrast images of the IAC can be obtained in 1 or 3 mm slices by convention in the IAC screening MRI protocol. Upon initial presentation, the patient was started on prednisone and given an injection of intratympanic steroids. A prior MRI of his brain revealed no abnormalities (Figs. 2 and 3); however, due to the patient's sudden hearing loss and concern for a possible neoplastic cause (the patient had a history of breast cancer), a high-resolution MRI of the left IAC, which showed a small intravestibular schwannoma in the vestibule and the anterior limb of the horizontal canal on the left (Figs. 4-6). In this case, if we had only obtained an MRI of the brain, we would have missed this lesion. However, discovering the intravestibular schwannoma earlier would have unlikely changed the outcome since small intravestibular schwannomas are often only observed. Surgical treatment of these schwannomas results in total loss of hearing, so it is used only a as last resort in cases wherein the patient has non-serviceable hearing, the intravestibular schwannomas are growing into the IAC, or the patient is unable to perform daily functions due to dizziness. Stereotactic radiosurgery is an option, but it may not be as effective in patients with persistent dizziness. It could help stop the growth of the tumor if it is extending into the IAC and the patient has poor hearing. Though it is tempting to attribute all of this patient's symptoms to the schwannoma, his vertigo can have other causes that should not be overlooked, particularly when it is preferable to observe the mass rather than remove it. A fixed lesion in the inner ear would be unlikely to cause intermittent vertigo episodes, and is more likely going to cause constant dizziness. With a prior history of benign positional vertigo, migraine, and Ménière's disease, this patient's vertigo and associated symptoms may be due to exacerbations of these conditions rather than, or in addition to, the schwannoma. They may also be caused by vestibular migraine or benign positional vertigo, both of which can occur with a mass (Otol Neurotol. 2017;38[10]:e457-e9ref 2). By identifying other causes of vertigo, tinnitus, and aural fullness, surgery and radiotherapy, and their associated comorbidities can be avoided, leading to better patient outcomes. BONUS ONLINE VIDEOS: VISUAL DIAGNOSIS Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself. Video 1. Axial (horizontal) T2 MRI of the brain (5 mm slices) taken six months prior to presentation showing that the mass was not visible on the previous MRI. Video 2. Axial (horizontal) T1 MPR MRI of the brain (1 mm slices) taken six months prior to presentation showing an unclear image in the area of the tumor. Video 3. Axial (horizontal) T1 post-gadolinium MRI images (3 mm slices) showing the mass in the left (right side of the image) vestibule. Video 4. Coronal (parallel to the face) T1 post-contrast MRI images (3 mm slices) showing the mass in the coronal direction. Video 5. Sagittal (parallel to the ear) T1 MPR (1 mm slices) post-contrast MRI showing the mass and its extension in the sagittal direction. Video 6. Axial (horizontal) CISS sequence (1 mm slices) showing the mass in the left vestibule. Watch the patient videos online at thehearingjournal.com.