What's Your Diagnosis? Symptoms: Middle Ear Mass and Unilateral Hearing Loss

Abstract

A 64-year-old male presented with right-sided hearing loss that has been going on for a year. He reported occasionally feeling as if he was underwater. He denied any history of tinnitus, vertigo, ear infections, facial nerve weakness, or ear surgery. He did not use hearing aids. His audiogram from three months before presentation showed a mixed hearing loss on the right side with large air-bone gaps and normal hearing on the left. Figure 1 shows his microscopic ear exam. The remainder of his head and neck exam results were normal.Figure 1: Microscopic examination of the right tympanic membrane showing a mass in the posterior superior quadrant. Audiology, otolaryngology, hearing loss.Figure 2: Axial (horizontal) T1-weighted post-contrast MRI at the level of the middle ear showing the mass (white) in the right (left side of the image) posterior middle ear. Audiology, otolaryngology, hearing loss.Figure 3: Three mm higher than Fig. 2 at the level of the internal auditory canal (IAC) showing the mass in the right middle ear. Audiology, otolaryngology, hearing loss.Figure 4: Coronal (parallel to the face) T1-weighted post-contrast MRI at the level of the internal auditory canal showing the right middle ear mass just medial to and below the IAC. Audiology, otolaryngology, hearing loss.Figure 5: Axial (horizontal) CT of the right temporal bone at the level of the attic showing the mass in the middle ear cavity adjacent to the ossicles. Audiology, otolaryngology, hearing loss.Figure 6: Coronal (vertical parallel to the face) CT of the right temporal bone at the level of the vestibule showing the facial nerve mass adjacent to the oval window. Audiology, otolaryngology, hearing loss.Diagnosis: Facial Schwannoma Figure 1, which shows a pink area in the posterior superior quadrant of the tympanic membrane, can be misinterpreted as an ear infection in a primary care setting. But as the astute clinician will note, all that is pink in the middle ear is not an infection. Also, if an infection were present in the middle ear, it would not be limited to just one quadrant of the tympanic membrane. In the case of this patient, a mass was present and caused some bulging in the posterior superior quadrant of the tympanic membrane. Whenever a patient presents with a middle ear mass and hearing loss, the initial question a clinician must ask themselves is: What kind of tumor does this represent? Although this patient's symptoms were limited to his unilateral hearing loss, it is important to rule out malignancy, particularly squamous cell carcinoma of the middle ear. After performing a complete history and physical exam, imaging with MRI of the internal auditory canals is warranted as the next step in the workup, with high-resolution CT of the temporal bone as a complementary imaging modality. Often, a single cause can explain all of the patient's signs and symptoms, and it is usually best to start by looking for one unifying diagnosis. For this patient, we obtained an MRI of the internal auditory canal (Figs. 2-4), which showed an enhancing mass involving the efferent limb of the right facial nerve from the geniculate ganglion to the proximal mastoid segment. A temporal bone CT scan (Figs. 5-6) was also obtained, which further revealed the mass abutting the middle ear ossicles and tympanic membrane as well as an expansion of the facial nerve canal without evidence of erosion. The differential diagnosis of the mass included middle ear adenoma, meningioma, facial nerve tumor (most commonly facial schwannoma), and paraganglioma (glomus tumor). Facial nerve schwannomas are rare, benign peripheral nerve sheath tumors composed of Schwann cells that wrap the nerve fibers within the facial nerve trunk. Facial schwannomas most commonly originate in the geniculate ganglion area and spread along the nerve. In some cases, these tumors can traverse the entire length of the facial nerve from the cerebellopontine angle to the parotid gland. Although the most common symptom of facial schwannoma is facial paresis, hearing and balance are also frequently affected due to proximity to middle and inner ear structures, as in our patient. Facial nerve dysfunction is most severe with intracranial tumors, while extratemporal facial nerve schwannomas are associated with better facial nerve function. Though rare, these tumors most commonly present in the fifth decade of life, and appear to have an equal gender distribution.1,2 Management of facial schwannoma depends on both the presence of symptoms and the rapidity of tumor growth. For patients with intact nerve function, as in the case of this patient, observation with serial imaging is recommended since tumor resection is likely to impair facial nerve function. Treatment is typically only undertaken once the patient exhibits signs of facial paresis or brainstem compression. The treatment of facial schwannomas traditionally involved either total or subtotal resection of the affected nerve segment with possible nerve reconstruction. Facial nerve decompression has also been described for tumors within the bony confines of the temporal boe.1,3 More recently, however, stereotactic radiosurgery (focused radiation therapy, such as CyberKnife or GammaKnife) has become widely used in patients with progressively worsening facial paresis and expanding tumors, having demonstrated success in long term tumor control. This treatment has gained popularity due to its less invasive nature and favorable results; facial nerve and hearing outcomes with stereotactic radiosurgery have been found to be comparable or better than surgical resection.4 If surgical resection of the tumor is performed, facial nerve reconstruction at the time of surgical resection is generally the rule. If distal portions of the facial nerve are intact, this can be done with nerve grafting, most commonly using the greater auricular (for shorter segment resections) or sural (for long gaps in the facial nerve) nerves. If the patient presents with a prolonged duration of complete paralysis, the neuromuscular junction (the connection between the nerve and muscle) may have been lost. If the neuromuscular junction (NMJ) has been lost, nerve grafting would not restore muscular function. The best method of assessing the integrity of the NMJ is obtaining an electromyogram (EMG). Electrical silence on the EMG indicates a loss of the NMJ. Fibrillation potential indicates that the NMJ is intact. Polyphasic potentials indicate nerve regeneration. After determining via electromyogram (EMG) that the NMJ has been lost, other forms of reconstruction must be explored based on which portions of the facial nerve are functioning and to what degree. Alternative options to nerve grafting include both dynamic and static reanimation procedures. Dynamic procedures such as masseteric or temporalis muscle transfer enable a patient to “smile” by clenching their teeth or tensing their temporalis muscle, respectively. Common static reanimation procedures include upper eyelid gold weight placement to allow full eye closure or brow lift to prevent brow ptosis. Botox (botulinum toxin A) has also been used on the contralateral side to improve facial symmetry. While these interventions aim to restore basic facial function and improve appearance, patients are often still left with residual deficits, and research is ongoing to develop better methods for facial reanimation. Recent experiments have even demonstrated the potential of an implantable medical device capable of facilitating the transfer of facial nerve function from the normal to weak side in the animal model.5,6 This patient was determined to have a right-sided intratympanic facial nerve schwannoma based on imaging. Given the patient's intact facial function, he was managed with observation and scheduled for follow-up imaging at six-month intervals to assess for tumor growth. In the event of new-onset facial weakness, decompression of the nerve and possible radiosurgery may be considered. The resection approach of facial schwannomas depends on the areas of involvement. A middle ear/mastoid tumor can be resected with a transtemporal (tympanomastoid) approach, whereas tumor involvement of the geniculate or internal auditory canal would require the additional middle fossa approach. In cases where all hearing has been lost, a translabyrinthine approach may be undertaken. 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) CT of the right temporal bone showing the facial nerve tumor in an axial direction. Video 2. Coronal (vertical parallel to face) CT of the right temporal bone showing tumor involvement in the coronal direction and its relationship with the horizontal canal. Video 3. Sagittal (vertical parallel to ear) CT of temporal bone showing the facial nerve tumor from the side view and its relationship with the ear canal. Video 4. Axial (horizontal) T1 post-contrast MRI of the temporal bone showing the facial nerve tumor in the axial direction. Video 5. Coronal (parallel to face) T1 post-contrast MRI of the temporal bone showing the facial nerve tumor in a coronal direction. Video 6. Axial (horizontal) T2 MRI of the temporal bone showing that the tumor is not a fluid-filled cyst. Watch the patient videos online at thehearingjournal.com