A 62-year-old woman presented with four months of progressive bilateral hearing loss. Her history is notable for breast cancer treated with chemotherapy over the past year, and she has no history of previous ear problems. Initially, she did not seek treatment for her hearing issue as it was considered to be a side effect of her ongoing chemotherapy treatment. Recently, however, she developed a severe headache with rapidly worsening bilateral hearing loss, imbalance, and left-sided facial droop. She reported intermittent bilateral aural pressure since the onset of her hearing loss but denied otalgia, dizziness, vertigo, or tinnitus. Microscopic ear exam and complete head and neck exam were normal at the time of presentation. Her audiogram at presentation is shown in Figure 1.
DIAGNOSIS: METASTATIC BREAST CANCER
Sudden bilateral hearing loss is commonly due to a systemic process such as a metabolic or an auto-immune disorder. It is necessary to perform a metabolic workup and to obtain imaging in any patient presenting with sudden bilateral hearing loss, particularly in the context of known malignancy. The metabolic workup includes looking at blood sugar, cholesterol, red blood cells, platelets, and markers of autoimmunity (e.g., sedimentation rate, CRP, ANCA, etc.). In addition, infectious etiologies need to be evaluated such as HIV, Lyme, syphilis, meningitis, etc. Clinical history should also be assessed for ototoxic pharmacologic substances such as aminoglycoside antibiotics and chemotherapy agents such as cisplatin. For this patient, we obtained an MRI of the internal auditory canals (IACs) (Fig. 2), which showed bilateral lesions of contrast enhancement in the IACs. By comparison, only a small amount of contrast enhancement was evident on her MRI five months prior to presentation (Figs. 3, 4, 5).
The type of MRI ordered in these clinical scenarios has important implications for the resolution of anatomic detail that will be visible. With a standard MRI of the brain, 5-mm tissue slices are used in various sequences to produce a single image. In these relatively large slices, small abnormalities in the IACs, cochlea, and vestibule may be missed, and a standard brain MRI may even fail to visualize the IACs altogether. If a non-contrast brain MRI is all that is available, then the T2 sequence is the best set of images to evaluate the IACs for a tumor. Normally, the IACs are mostly filled with cerebrospinal fluid (CSF). In the T2 sequence, an IAC tumor will appear dark, while CSF appears white. With contrast, the mass lesion will appear white due to its high vascularity and uptake of the contrast material (gadolinium). On IAC screening MRI protocol, the T1 post-contrast MRI is performed with 3-mm slices, which provide more details than a brain MRI. While newer brain MRI protocols utilize even thinner imaging slices (e.g., 1-mm with multiplanar reformation sequence [MPR]) to reveal more structural detail, the temporal bone region can sometimes appear indistinctly. For these reasons, another option for evaluating tumors of the inner ear is through an MRI of the IAC using the T2-weighted fast spin-echo (FSE) protocol. The T2-weighted FSE MRI, also referred to as three-dimensional constructive interference in steady-state (CISS) MRI or 3D MPR/FIESTA, has the ability to show high-resolution details of cranial nerves and spaces involving or adjacent to the inner ear structures. On CISS MRI, potential tumors appear dark, and CSF and inner ear fluids appear bright.
The majority of IAC and cerebellopontine angle (CPA) lesions are benign tumors, such as meningioma and vestibular schwannoma. Less than one percent of CPA lesions involve metastases to the IAC, with the most common sources being breast cancer, lung cancer, gastric cancer, and melanoma. The possible routes of temporal bone metastasis are hematogenous dissemination, direct extension from local preexisting lesions, and leptomeningeal carcinomatosis through CSF spread. Although leptomeningeal carcinomatosis occurs in only five percent of cancer patients, it is being diagnosed with increasing frequency as both patient life expectancy and quality of neuroimaging studies have improved over the years. For metastases involving the IAC, neoplastic spread into the meninges and CSF is generally considered the primary mechanism of bilateral tumor deposits.
Patients with IAC metastases most commonly present with bilateral and rapidly progressing sudden sensorineural hearing loss (SSNHL), facial nerve palsy, and tinnitus. This etiology of SSNHL at presentation is unknown but recent studies have shown some correlation with migraine (Arch Otolaryngol Head Neck Surg. 2002 Oct;128:1213, 1215). The mechanism is likely due to a change in hearing from vascular changes to the cochlea from trigeminal nerve activation. Neoplasms cause two percent of cases of sudden hearing loss. Although malignancy is implicated in only a minority of cases, the presence of bilateral SSNHL should raise strong suspicion and prompt further investigation into a neoplastic process. Metastasis from multiple myeloma, breast (Laryngoscope. 2021 Jan;131:E283-E288), gastric, lymphoma, and pancreatic cancer have all been reported to manifest with central nervous system dysfunction, including SSNHL. In rare cases, hearing loss, tinnitus, vertigo, and facial paralysis may be the only presenting symptoms, and clinicians should always consider occult disease in the differential diagnosis.
Given her history and imaging findings, our patient was diagnosed with metastatic breast cancer in her bilateral IACs. It is often difficult to differentiate between IAC metastasis and primary benign tumors such as vestibular schwannoma. However, combined with the clinical history, certain radiographic features may help aid in the diagnosis. On both T1- and T2-weighted MRI, vestibular schwannoma generally shows a homogenous and isointense signal compared to gray matter with strong post-contrast enhancement. MRI findings suggestive of IAC metastasis include the presence of thick linear or nodular leptomeningeal contrast enhancement. Further favoring leptomeningeal carcinomatosis, as in our patient, are MRI findings of irregular nodular enhancement around the IAC in the dura. The contrast enhancement in Figure 2A is due to the tumor involving the dura of the IAC, since Figure 2B shows that the tumor is not within the IAC and the IAC is filled with CSF (white on the image). It is important to note that these distinctive features may not always be observed on MRI, making it imperative for clinicians to perform a thorough history and physical examination with special attention given to patients with a history of primary malignancy. The MRI from five months prior at the onset of hearing loss showed some faint enhancement, which was probably an early tumor involving the IAC dura (Figs. 3, 4, 5).
Prompt diagnosis of leptomeningeal carcinomatosis with lumbar puncture and morphologic examination of CSF is critical to preventing the irreversible neurologic dysfunction that can result from further spread. Unfortunately, the prognosis of leptomeningeal carcinomatosis from breast cancer is very poor, with median survival ranging from four to six weeks without treatment. Several treatment options exist, including intrathecal chemotherapy and radiation; however, these options are largely palliative and have little effect on survival. Additional treatments such as corticosteroids may be considered to improve functional status and symptoms such as hearing loss, as in our patient.
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) post-gadolinium MRI five months prior to presentation showing a possible early tumor.
- Video 2. Coronal (vertical) post-gadolinium MRI five months prior to presentation showing a possible early tumor.
- Video 3. Axial (horizontal) T2 MRI five months prior to presentation showing no obvious tumor.
- Video 4. Axial (horizontal) post-gadolinium MRI at the time of presentation showing a bilateral tumor.
- Video 5. Coronal (vertical) post-gadolinium MRI at time of presentation showing a bilateral tumor.
- Video 6. Axial (horizontal) T2 MRI at presentation showing a bilateral tumor.
Watch the patient videos online at thehearingjournal.com