Contralateral hearing loss after vestibular schwannoma excision: A rare complication of neurotologic surgery | Ear, Nose & Throat Journal Skip to content Skip to navigation

Contralateral hearing loss after vestibular schwannoma excision: A rare complication of neurotologic surgery

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January 19, 2015
by Robert H. Deeb, MD; Jack P. Rock, MD; Michael D. Seidman, MD, FACS

Abstract

We report a rare case of contralateral hearing loss after vestibular schwannoma excision in a 48-year-old man who underwent surgery via a suboccipital approach for removal of a nearly 2-cm lesion involving the right cerebellopontine angle. Postoperatively, the patient awoke with bilateral deafness, confirmed by both audiometry and spontaneous otoacoustic emissions. The patient was treated aggressively with high-dose intravenous steroids, vitamins E and C, and oxygen. Over the next several months he had gradual recovery of most of the hearing in his left (unoperated) ear. Contralateral hearing loss may develop after vestibular schwannoma excision; multiple pathophysiologic mechanisms for this occurrence have been proposed.

Introduction

Contralateral hearing loss after vestibular schwannoma surgery is extremely uncommon. Although there are sporadic reports, a literature review reveals this occurrence to be quite rare. Possible explanations include compensatory endolymphatic hydrops, occlusion or vasospasm of the internal auditory artery, sympathetic cochleolabyrinthitis, acoustic trauma due to drill noise, and labyrinthine rupture from elevated intratympanic pressure.

We present such a case and show that recovery of hearing is indeed possible with aggressive medical measures. Documentation of this case of contralateral hearing loss after vestibular schwannoma excision is intended to remind neurotologic surgeons of the possibility for this potentially devastating complication.


Case report

A 48-year-old man initially presented with new-onset atrial fibrillation with associated headaches in the fall of 2008. A magnetic resonance imaging (MRI) scan obtained at that time revealed a 17.2 x 12.8 x 1.8-mm enhancing lesion involving the right cerebellopontine angle with extension into the right internal auditory canal and widening of the canal (figure 1). Interestingly, the patient was asymptomatic from an otologic standpoint. Preoperative audiometry demonstrated a mild to moderate high-frequency sensorineural hearing loss on the right side (figure 2). A presumptive diagnosis of a vestibular schwannoma was made, and the patient underwent a suboccipital craniotomy for excision of the tumor in March 2009.


Figure 1. Preoperative MRI scan with gadolinium shows a 17.2 x 12.8 x 1.8-mm enhancing lesion involving the right cerebellopontine angle with extension into the right internal auditory canal.


Figure 2. Preoperative audiogram reveals a mild to moderate high-frequency sensorineural hearing loss on the right side.

Intraoperatively, cranial nerves VII and VIII were positively identified and preserved throughout their entire course from the brainstem to the porus acousticus. The tumor was removed from the internal auditory canal with preservation of the VIIth and VIIIth nerves. The auditory waveforms were significantly diminished bilaterally, and wave V was reduced within minutes of placement of the cerebellar retractor, suggesting vascular compression. Retractors were released, but there was little improvement. Waves I and III remained robust throughout most of the procedure.

Once the majority of the tumor was removed, monitoring could no longer record activity on either side. The primary surgeons (MDS and JPR) were notified that tracings were no longer present from the contralateral (unoperated) side; initially this was felt to be spurious information.

In the recovery room, the patient was unable to hear from either ear. Bedside auditory brainstem response testing in the recovery room revealed the absence of waves bilaterally. The patient was immediately started on dexamethasone 10 mg every 6 hours, vitamins C 500 mg daily, vitamin E 400 units daily, and oxygen.

A formal audiogram on postoperative day 1 confirmed no response on the right side and severe sensorineural hearing loss on the left side (figure 3). MRI performed on postoperative day 1 showed no evidence of an enlarged vestibular or cochlear aqueduct on either side. Subsequent audiograms over the next several weeks showed a gradual recovery of hearing in the left ear (figure 4). The most recent audiogram, performed more than 1 year after surgery, reveals near-normal hearing up to 3,000 Hz, sloping to a moderate loss in the high frequencies.


Figure 3. Postoperative day 1 audiogram shows no response on the right side (operated ear) and severe sensorineural hearing loss on the left side (unoperated ear).


Figure 4. Composite audiogram shows the progression of the patient's recovery.


Discussion

Contralateral hearing loss after neurotologic surgery is an extremely rare phenomenon. Although the exact incidence is not known, sporadic case reports exist in the literature. A 1988 study by Barratt and Prasher showed this phenomenon to take place in a subclinical fashion relatively often.1 Twenty-two patients undergoing excision of a unilateral vestibular schwannoma were assessed pre- and postoperatively, and 36% were found to have a hearing loss of 10 dB or more in the contralateral ear in the postoperative period. Given the high incidence yet mild degree of hearing loss, combined with the brief time course of recovery, the authors hypothesized the mechanism to be biochemical in nature, acting through the vascular system, or neural, acting through the acoustic efferent system on the contralateral cochlea.1

Additional etiologic theories exist. In 1982, Clemis et al reviewed 3 case reports of sudden hearing loss in the contralateral ear after vestibular schwannoma excision.2 Allergic factors were implicated in 2 cases. Similarly, in 1985, Harris et al postulated that exposure of the ipsilateral inner ear during tumor excision may result in a systemic immunologic response, causing damage to the opposite membranous labyrinth.3 This entity is referred to as sympathetic cochleolabyrinthitis. This disease process seems akin to sympathetic ophthalmia. It is thought that the marked disruption in the inner ear membranes that takes place during acoustic neuroma surgery acts to release tissue antigens into the systemic circulation. These antigens then stimulate the immunologic response.3

A proposed mechanism by Lustig et al states that low cerebrospinal fluid (CSF) pressure can be transmitted to the cochlea through the cochlear aqueduct.4 Low CSF pressure may induce low perilymphatic pressure and, in theory, low perilymphatic pressure may trigger a pressure imbalance, leading to compensatory endolymphatic compartment swelling. This process may explain the fact that hearing loss is rarely seen after lumbar puncture. A case report of contralateral deafness after unilateral suboccipital brain tumor excision in a patient with a large vestibular aqueduct by Nishioka et al suggests a similar mechanism.5 Although this loss is often transitory, cochlear damage after abrupt pressure changes can lead to a permanent loss.

Another plausible explanation is ototoxicity due to operative exposure to antibiotics (systemic or topical) or diuretics.4 Also, meningitis is a well known cause of sensorineural hearing loss and is known to be a possible sequela of any intracranial procedure.

Vascular events associated with the blood supply to the internal auditory canal have also been implicated. De Keyser et al suggest that a thrombosis of the contralateral internal auditory artery may occur secondary to a postoperative brainstem shift to the ipsilateral side.6 Similarly, vertebrobasilar arterial ischemia, either due to perfusion insufficiency or embolic disease, is an attractive theory, as well. This is supported by the known complication of sensorineural hearing loss after cardiopulmonary bypass surgery.

Although our patient recovered hearing in the contralateral ear to near preoperative levels, there was a great amount of uncertainty regarding this outcome, as well as patient anxiety. We have no clear explanation for our patient's bilateral hearing loss. Given his return to normal hearing, the most plausible explanation for this phenomenon is either perilymphatic fluid shifts or the poorly understood acoustic efferent system's acting on the contralateral cochlea.

A frank preoperative discussion of this entity should be included during the evaluation of all potential treatment options. As a result of the present case, the primary surgeon now discusses this as a potential complication from such surgery.

 


References

  1. Barratt HJ, Prasher DK. The effect of acoustic neuroma removal on hearing in the contralateral ear. Scand Audiol 1988; 17 (3): 137-42.
  2. Clemis JD, Mastricola PG, Schuler-Vogler M. Sudden hearing loss in the contralateral ear in postoperative acoustic tumor: Three case reports. Laryngoscope 1982; 92 (1): 76-9.
  3. Harris JP, Low NC, House WF. Contralateral hearing loss following inner ear injury: Sympathetic cochleolabyrinthitis? Am J Otol 1985; 6 (5): 371-7.
  4. Lustig LR, Jackler RK, Chen DA. Contralateral hearing loss after neurotologic surgery. Otolaryngol Head Neck Surg 1995; 113 (3): 276-82.
  5. Nishioka T, Ishikawa M, Kondo A, Fukushima H. Contralateral deafness following unilateral suboccipital brain tumor surgery in a patient with large vestibular aqueduct-case report. Neurol Med Chir (Tokyo) 1998; 38 (12): 871-4.
  6. de Keyser J, Bruyland M, Demol P ,et al. Sudden hearing loss and facial palsy at the contralateral side following acoustic tumour removal. J Neurol Neurosurg Psychiatry 1983; 46 (7): 687.
From the Department of Otolaryngology-Head and Neck Surgery (Dr. Deeb and Dr. Seidman) and the Department of Neurosurgery (Dr. Rock), Henry Ford Hospital, Detroit.
Corresponding author: Robert Deeb, MD, Department of Otolaryngology-Head and Neck Surgery, Henry Ford Health System, 2799 West Grand Blvd., Detroit, MI 48202. Email: rdeeb1@hfhs.org
 
Ear Nose Throat J. 2015 January;94(1):28-31