A 69-year-old man presented for cochlear implant consultation for imbalance and single-sided deafness. Per the patient, his imbalance and hearing loss started after a reported retrosigmoid resection of an “acoustic neuroma.” In addition, he was suffering from hoarseness. He reported that the imbalance is constant. The patient has participated in regular physical therapy with no dizziness improvement. His vocal cord paralysis is being addressed with a thyroplasty. The patient denies vertigo, falls, headaches, vision changes, cognitive changes, facial paralysis, aural fullness, and vomiting. Audiometry shows right moderate high-frequency hearing loss and left profound hearing loss (Figure 1).
Diagnosis: Vagal Schwannoma Resection and Resultant Cochlear Fibrosis
The symptoms of imbalance and dizziness can be very frustrating for a patient, and a diagnosis may be difficult to determine. Narrowing the differential diagnosis is dependent on a detailed history and thorough exam and can be aided with imaging. For this patient with a history of skull base surgery prior to the onset of symptoms (Figures 2, 3, 4), possible etiologies include semicircular canal dehiscence, perilymphatic fistula, Parkinson’s disease, normal pressure hydrocephalus, postoperative vertigo, and vestibular migraine.
Semicircular canal dehiscence is defined by the absence of bone overlying the semicircular canal. The most common symptoms are pressure- or sound-induced vertigo and dizziness. These symptoms are typically triggered by activity that alters inner ear pressure and can also be sound-induced vertigo known as Tullio phenomenon. Patients may also experience autophony of fluctuating hearing loss or may be asymptomatic. High-resolution CT can be used for diagnosis. Additionally, surgical repair can be done for symptomatic patients to resurface, plug, or cap the bony dehiscence via a transmastoid approach or middle fossa craniotomy. Some patients may benefit from a round window plugging procedure.
Perilymphatic fistulas are defined as abnormal communications from the inner ear allowing perilymph to leak from the cochlea or vestibule. Patients present with acute onset of episodic vertigo with or without hearing loss. Symptoms are provoked by loud sounds (Tullio phenomenon), sneezing, lifting, coughing, and straining. The etiology of perilymphatic fistulas may be due to barotrauma, penetrating ear trauma, iatrogenic injury, or head trauma. Imaging consisting of CT of the temporal bone and MRI of the internal auditory canal is used to rule out other diagnoses. Conservative treatment can include avoidance of increased intracranial or inner ear pressure. Surgical treatment can be done to seal the fistula if an intratympanic blood patch procedure is not successful (i.e., intratympanic injection of autologous blood for traumatic perilymphatic fistulas). 1
Parkinson’s disease is a progressive and chronic disorder resulting from degeneration of dopaminergic neurons. Parkinson’s disease is diagnosed clinically. Features of this disease include resting tremor, bradykinesia, cogwheel rigidity, change in handwriting, and postural instability resulting in imbalance and falls. Postural instability typically does not appear until late in the disease course and subsequent falls can cause severe disability. Less common and more severe Parkinsonian syndromes such as a progressive supranuclear palsy or multiple system atrophy may present earlier with postural instability. Imbalance in Parkinson’s disease can be attributed to changes in vestibular function. A prolonged latency in P13, N23, and reduced amplitude in vestibular-evoked myogenic potential testing has been found in patients with Parkinson’s disease. 2 Parkinsonism syndromes are initially treated with levodopa. Unfortunately, imbalance has poor response to dopaminergic therapy.
Elevated intracranial pressure can be a complication of craniotomy. Intracranial hypertension is characterized by a headache that is worse in the morning and improved when sitting or standing. Additional symptoms can include vomiting, vision changes, irritation, and pulsating tinnitus exacerbated by movement or Valsalva maneuver. Fundoscopic exam may find papilledema, which supports this diagnosis. CT or MRI may reveal enlarged ventricles an empty sella or mass effect. Intracranial hypertension can be relieved by the carbonic anhydrase inhibitors acetazolamide or topiramate. If symptoms are refractory or vision is deteriorating, surgical interventions can be utilized including cerebral spinal fluid diversion or optic nerve sheath fenestration.
Postoperative vertigo and disequilibrium can be experienced after skull base microsurgery. Mechanisms resulting in disequilibrium include cerebellar damage, brainstem injury, and injury to anterior inferior cerebellar artery vessels. One study of postoperative outcomes in patients with vestibular schwannoma reported hearing loss in 24.6% and disequilibrium in 6.3%. Immediately after surgery, 10.2% of patients reported unsteadiness and 62% of these had improvement at follow-up. 3 Preoperative vestibular training programs and visual feedback-based balance training may improve resolution of postoperative vertigo. One final etiology of postoperative dizziness and imbalance is vestibular migraine. 4
Regarding this patient, the questions remain: what is the source of the current imbalance, and can a cochlear implant be performed? Examination of the imaging shows that the patient currently has a tumor in the jugular foramen (Figure 2), which extends into the neck along the jugular bulb (Figure 3). This indicates that the patient’s primary tumor was not a vestibular schwannoma as the outside neurosurgeon had thought but rather a jugular foramen schwannoma. The three cranial nerves IX through XI traverse the jugular foramen and could have schwannomas. The presence of hoarseness indicates that the patient’s schwannoma was most likely vagal in origin. Then, the question is how would the patient suffer from a vagal schwannoma and suffer from hearing loss and imbalance postoperatively. The preoperative imaging shows that the tumor started in the jugular foramen but extended to the cerebellopontine angle (Figures 4A). The internal auditory canal appeared clear (Figure 4B) of tumor, and therefore, the cochlear and vestibular nerves should not have been disturbed in surgery. However, a closer examination of the CISS sequence (Figure 5) on the MRI shows that the left vestibule and semicircular canals are entirely filled with scars (fibrosis) and do not contain the normal fluid seen on MRI. Other levels of the CISS images showed that the cochlea was also filled with fibrosis. Finally, if the CT of the head postoperatively is examined (Figure 6), one can see that the cochlear aqueduct that opens into the posterior fossa was violated during the surgery, which allowed blood to enter the cochlea and vestibule in the perilymphatic space and lead to cochleovestibular fibrosis (scarring). A cochlear implant would probably not benefit the patient as much as desired for single-sided deafness given the fibrosis and likely partial ossification in the cochlea would limit the function of the device. In a patient with normal hearing on the other side, an implant in a fibrotic/partially ossified cochlea would not provide good speech perception that would leave the patient satisfied.
The patient was treated with vestibular rehabilitation, but, if not successful, we would consider gentamicin injection if a videonystagmography shows some caloric function in the left ear.
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) T1 fat saturated MRI (2022) showing the tumor in the jugular foramen.
Video 2. Coronal (parallel to the face) T1 fat saturated MRI (2022) showing the tumor in the jugular foramen extending into the neck.
Video 3. Axial T2 (horizontal) MRI (2021) before surgery showing the tumor in the jugular foramen extending into the CPA.
Video 4. Coronal (parallel to the face) CISS MRI (2022) after surgery showing the vestibule filled with scar on left ear (right side of images).
Video 5. Axial (horizontal) CISS MRI (2022) after surgery showing the cochlea filled with scar on left ear (right side of image) with loss of normal fluid signal (white) inside the cochlea.
Video 6. Axial (horizontal) CT showing post-craniotomy changes and that the cochlear aqueduct has been drilled open.
Watch the patient videos online at thehearingjournal.com.
1. Garg R, Djalilian HR 2009 Intratympanic injection of autologous blood for traumatic perilymphatic fistulas Otolaryngology-Head and Neck Surgery 141 294 295 https://doi.org/10.1016/j.otohns.2009.05.024
2. Gaur A, Rajamanickam R, Chinnathambi C, Selvaraju D, Sakthivadivel V 2022 Association of cervical vestibular-evoked myogenic potentials (VEMP) and postural instability in patients with parkinson’s disease: a cross-sectional study Annals of Neurosciences 29 137 143 https://doi.org/10.1177/09727531221106664
3. Nonaka Y, Fukushima T, Wtanabe K, et al. 2013 Contemporary surgical management of vestibular schwannomas: analysis of complications and lessons learned over the past decade Neurosurgery 72 ons103 ons115 discussion ons115. https://doi.org/10.1227/neu.0b013e3182752b05
4. Abouzari M, Goshtasbi K, Moshtaghi O, Tan D, Lin HW, Djalilian HR 2020 Association between vestibular migraine and migraine headache: yet to explore Otology & Neurotology 41 392 396 https://doi.org/10.1097/mao.0000000000002528