|Year : 2022 | Volume
| Issue : 1 | Page : 74-76
Atypical manifestation in vestibular schwannoma
Addina Mohd Baki1, Wan Nur Anis Wan Draman1, Zulkiflee Salahuddin2, Nik Adilah Nik Othman3
1 Department of Otorhinolaryngology-Head and Neck Surgery, School of Medical Sciences, Universiti Sains Malaysia; Department of Otorhinolaryngology-Head and Neck Surgery, Hospital Raja Perempuan Zainab, Kota Bharu, Kelantan, Malaysia
2 Department of Otorhinolaryngology-Head and Neck Surgery, Hospital Raja Perempuan Zainab, Kota Bharu, Kelantan, Malaysia
3 Department of Otorhinolaryngology-Head and Neck Surgery, School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Kelantan, Malaysia
|Date of Submission||09-Jul-2021|
|Date of Decision||28-Oct-2021|
|Date of Acceptance||03-Dec-2021|
|Date of Web Publication||25-Apr-2022|
Dr. Nik Adilah Nik Othman
Department of Otorhinolaryngology-Head and Neck Surgery, School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Kelantan
Source of Support: None, Conflict of Interest: None
The cerebellopontine angle (CPA) is a cerebrospinal fluid-filled space, found at the junction between the cerebellum and pons. Vestibular schwannoma (VS) is the most common CPA tumor. Typical initial symptoms are unilateral or asymmetrical hearing impairment, tinnitus in the affected ear, or imbalance or vertigo. We report an unusual case of the patient who presented with right sensorineural hearing loss but was found to have left VS in the normal hearing ear.
Keywords: Cerebellopontine angle tumor, contralateral hearing loss, unilateral, vestibular schwannomas
|How to cite this article:|
Baki AM, Draman WN, Salahuddin Z, Nik Othman NA. Atypical manifestation in vestibular schwannoma. Indian J Otol 2022;28:74-6
| Introduction|| |
Vestibular schwannoma (VS) is a benign tumor arising from abnormal proliferation of Schwann cells, most commonly arising from the superior vestibular division of cranial nerve (CN) VIII (vestibulocochlear)., It accounts for 8%–10% of all intracranial tumors and more than 90% of the cerebellopontine angle (CPA) tumors. Most VSs are unilateral and sporadic with unknown etiology., The most common presenting symptom is unilateral hearing loss, followed by tinnitus and unsteadiness.
Magnetic resonance imaging (MRI) with gadolinium is the gold standard investigation to achieve diagnosis. Other investigations are pure-tone audiometry (PTA) which will show unilateral or asymmetrical sensorineural hearing loss (SNHL) and auditory brainstem response (ABR) which demonstrates retrocochlear lesion., The main treatment option is surgical excision of tumor, and the other options are careful observation in selected patients, or stereotactic radiosurgery, considering the patient and surgical factors.
| Case Report|| |
A 43-year-old woman with no known medical illness presented with progressive hearing loss in the right ear for 6 years. Despite the loss, she did not seek any treatment initially as the symptom did not cause any problem. Only in the last 3 years, she noticed that she had difficulty to hear in the presence of background noise and often she needs to ask people to repeat the conversation. She did not complain of any other ear symptoms, imbalance, facial numbness, or facial asymmetry. There was no history of childhood ear infection, use of ototoxic drugs, head trauma, exposure to loud noise, or any family history of deafness.
Otoscopic examination was unremarkable. There was no facial asymmetry or spontaneous nystagmus. A tuning fork test revealed false-negative Rinne in the right ear (suggestive of right severe to profound SNHL).
A masked PTA showed right mild to profound SNHL with down-sloping configuration and normal hearing in the left ear [Figure 1]. We proceeded with MRI of the internal auditory meatus (IAM) and CPA, in view of the provisional diagnosis of right CPA tumor. It demonstrated an extra axial lesion at the left CPA measuring 9.52 mm × 8.60 mm in size [Figure 2]a. The lesion was hypointense in T1-weighted, hyperintense in T2-weighted, and showed an enhancement on postgadolinium contrast. The left IAM was widened due to the extension of the lesion into it. No enhancing lesion was seen at the right CPA region.
|Figure 1: Masked PTA showed right side mild to profound SNHL with ski sloping configuration, whereas left sided hearing was normal (a) During the first visit (b) The latest PTA result|
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|Figure 2: (a) Axial cut MRI T1W1 with gadolinium showing an enhancement lesion at the left CPA measures 9.52 x 8.60 mm in size during the diagnosis. (b) The latest MRI T1W1 with gadolinium which was repeated after 2 years of diagnosis, an enhancement lesion measuring 9.65 x 9.08 mm|
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The options of treatment were discussed with the patient, and she opted for observation in view of the only serviceable left hearing with a small tumor size <15 mm, nonprogressive, and the absence of compression symptoms. Yearly MRI was performed, and the latest size of the tumor was 9.65 mm × 9.08 mm [Figure 2]b. Her hearing remained the same with no other complaints for the last 5 years.
| Discussion|| |
In more than 95% of VS patients, the most common presenting symptom is a unilateral progressive hearing loss. It is characterized by gradual worsening of the hearing loss, but atypical presentations such as sudden hearing loss, symmetrical hearing loss, and normal hearing may also occur. In this case, although the tumor was on the left side, the patient did not complain of hearing loss in the left ear which was confirmed with the PTA. According to Shaan et al., 6 out of 100 patients with VS showed normal PTA at the side of tumor. From those six patients, four patients did complain of subjective hearing loss and one did not complain of any hearing loss. The sixth patient presented with left hearing loss with episodic vertigo and pulsatile tinnitus. Computed tomography (CT scan) showed glomus tumor on the left and 20-mm VS on the right side. There was no auditory response over the left ear with normal hearing in the right ear.
ABR is the most sensitive test in diagnosing VS, with an overall showed sensitivity of up to 93.4%. However, ABR is a size-dependent test and has limitation in detecting a small tumor. The sensitivity for tumour size < 10mm is 85.8% and for tumour size >10mm, the sensitivity increase to 95.6%. It is also higher for extracanalicular tumour than intracanalicular tumour. In a study in Italy, from 3768 patients with VS, there were 162 patients came with subjectively normal hearing. Only 133 ABR's data were available, and from that data, 35 (26.3%) patients reported normal ABR. As reported by Selesnick and Jackler, 2 cases out of 126 patients showed false negative in ABR result, and MRI demonstrated that the size of the tumor was <10 mm.
MRI with intravenous gadolinium is the imaging of choice for patient who presented with unilateral or asymmetrical hearing loss in demonstrating VS in the earlier stage. The result finding will be enhanced in postcontrast T1. MRI showed a more precise outline of the lesion compared to CT scan. About 0.02% of cases of VS were incidentals finding in California; three cases were investigated with MRI for other reasons (chronic seizure, epistaxis, and breast cancer metastasizes) but subsequently found lesions with VS features between 10 mm and 28 mm in size. All revealed normal PTA results. The size of the tumour in our patient was 9.52 mm x 8.60 mm.
Our patient was treated conservatively as the affected ear is the only hearing ear with small size tumor (<10 mm) and no compressive symptoms were observed. The aim is to preserve and monitor the left ear hearing while measuring the tumor growth. Elderly patients and those who experienced minimal symptoms or with a small-to-middle-sized tumor in the only hearing ear are indicated for observation and monitoring., Criteria for conservative management are small tumor, poor health, patient age or preference, hearing status, and anesthetic reaction.
Conservative management means that the progression of the disease is monitored by repeating the pure-tone and speech audiometry every 6 months and MRI every 1 or 2 years of the diagnosis. In this case, serial PTA was done; the results were similar to the initial assessment. MRI was repeated 1 year after with no significant increase in size noted. Growth was defined as an increase of 1 mm per year. Shin et al. in their study at France found that the mean annual tumor growth rate was 1.52 mm/year. In their study, from 20 intracanalicular neuromas, 14 exhibited no growth and the remaining 6 showed significantly increased in size.
Surgery with hearing preservation should be offered if there is a significant increase in size or extension. In this case, middle fossa (MF) approach is the best option in view of intracanalicular lesions with <15 mm and with good hearing on the affected ear. MF approach will be selected for small intracanalicular tumors because this approach is better in exposing the fundus of the internal auditory canal. A study in Carolina in 2010 noted that 76.7% of the patients in the MF group achieved class B or better hearing (PTA threshold >30 dB–50 dB) based on the American Academy of Otolaryngology-Head and Neck Surgery Hearing Classification System compared with 73.2% of those in the retrosigmoid (RS) group. However, facial nerve injury is easier to get compared to RS approach because of lesser anatomical landmarks that can be identified. RS approach provided easier operative technique, shorter operating time, and less blood loss compared to MF approach.
| Conclusion|| |
Patients who presented with asymmetrical or unilateral SNHL should raise the suspicion for retrocochlear disease and need to do ABR and MRI. However, atypical manifestations of VS might occur and therefore are prone to delay in diagnosis. VS patients could experience normal hearing with contralateral hearing loss. It is important to take thorough history and do physical examination. Furthermore, VS could be missed if we consider normal audiogram as exclusion criteria for retrocochlear pathology. A low threshold of suspicious and MRI are important to those who present with unusual neurological and otology symptoms even with normal audiology tests.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
I want to thank all involved in managing this case.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]