|Year : 2016 | Volume
| Issue : 1 | Page : 44-47
Manoj Manikoth Puthiyaparambil, Sandeep Puthiya Koiloorveetil
MESIARC ENT Hospitals Private Limited, Calicut, Kerala, India
|Date of Web Publication||16-Feb-2016|
Manoj Manikoth Puthiyaparambil
Mesiarc, 2/44A, East Hill Junction, West Hill Post, Kozhikode - 673 005, Kerala
Source of Support: None, Conflict of Interest: None
Intracochlear schwannoma is rarely diagnosed. We report the case of a 27-year-old woman with intracochlear schwannoma who presented with 7 years history of hearing impairment. Audiological tests and imaging studies revealed a possibility of intracochlear schwannoma. Excision of the tumor was done by transcochlear approach. The histologic diagnosis was schwannoma. Her postoperative course was uneventful. We present this rare case and discuss the presentation, diagnosis, and management options in such cases.
Keywords: Auditory brain stem response, Schwannoma, Transcochlear approach
|How to cite this article:|
Puthiyaparambil MM, Koiloorveetil SP. Intracochlear schwannoma. Indian J Otol 2016;22:44-7
| Introduction|| |
Tumors of the eighth cranial nerve have often been erroneously called acoustic neuromas. Most of them actually are schwannomas, which arise from the Schwann cells of the nerve. These are more commonly located at the cerebellopontine angle or the internal auditory canal. Sometimes, these tumors can arise from neural elements within the labyrinth where they are called labyrinthine schwannomas. Among labyrinthine schwannomas, intracochlear ones are very rare. Here, we report a case of schwannoma, which was intracochlear in location.
| Case Report|| |
A 27-year-old female reported to us with a nonfluctuating left sided hearing impairment of 7 years duration, which was gradually progressive. It was associated with tinnitus and aural fullness and blockade sensation. There was no history of dizziness or ear discharge. Her past medical history was normal.
Her otologic examination was normal. Her facial nerve function was normal and symmetric bilaterally. A pure tone audiogram revealed pure tone averages of 8 dB and 80 dB on the right and left side, respectively [Figure 1]. Speech reception threshold and word discrimination could not be established on the left ear. Auditory brain stem response (ABR) did not reveal any retrocochlear pathology [Figure 2]. Since the speech discrimination was poor, imaging was resorted to rule out a labrythine schwannoma. Magnetic resonance imaging (MRI) of brain with gadolinium contrast showed a small enhancing mass seen in the left cochlea, involving the middle and apical turns, size 3 mm. Basal turn was free. The mass appeared to be close to the osseous spiral lamina. T1 images showed contrast enhancement [Figure 3] and [Figure 4]. Therefore, a radiological diagnosis of intracochlear schwannoma was made.
|Figure 2: Brainstem evoked response audiometry tracing showing poor waverform, indicative of a retrocochlear pathology left side|
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|Figure 4: Magnetic resonance imaging showing intracochlear filling defect|
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Taking into consideration the hearing status and extent of the tumor, treatment options were discussed with the patient and we went ahead with the excision of the lesion via transcochlear approach. Tumor involved the second turn and apical turn of cochlea [Figure 5].
Complete excision of tumor was done [Figure 6]. As expected cerebrospinal fluid (CSF) leak from osseous spiral lamina was sealed and cavity obliterated with fat, bone pâté, and bone chips. A blind sac closure of external auditory canal was also completed. Histopathological examination confirmed the diagnosis of schwannoma [Figure 7]. Postoperative period was smooth with the patient having very minimal unsteadiness, which recovered in a couple of days. There was no CSF leak after the procedure. The patient is under regular follow-up and [Figure 8] and [Figure 9] are the MRI 6 months after the surgery, showing no residual tumor.
|Figure 8: Six months postoperative magnetic resonance imaging showing no residual tumor|
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| Discussion|| |
Intracochlear schwannomas are rare tumors among the intralabyrinthine group of schwannomas, intravestibular ones being more common. The largest series of intracochlear schwannomas published was by Jiang et al. the number of cases reported being 10. [Table 1] shows few case reports and their management modalities.
Kennedy et al. had proposed a classification system for labyrinthine schwannomas based on the site of the lesion. Our patient's tumor belongs to the intracochlear variety. The most common presenting symptom in intracochlear schwannomas is unilateral progressive hearing loss., The hearing impairment is mostly sensorineural with low word recognition scores. Vertiginous symptoms usually present in the later stages of the disease.
MRI with contrast is considered the gold standard investigation to diagnose intracochlear lesions. ABR is done in our center as a protocol for the management of unilateral sensorineural hearing loss to rule out any retrocochlear pathology. The reason ABR response was normal on both sides of this patient was presumably because the tumor was only 3 mm size, ABR being less sensitive for lesion <1 cm. This indicates that a high index of clinical suspicion is required for diagnosing such conditions. The pointer toward the diagnosis was the low speech recognition scores, underscoring the importance of this simple test even in the times of sophisticated investigation armamentarium. However, good speech audiometry requires the skill of an expert audiological team.
The contrast enhancement in T1 images that is seen in cochlear schwannomas may also mimic labrynthitis,,, and hence it is the most important differential diagnosis radiologically. At the same time, labrynthitis features would be more diffuse rather than focal as in case of schwannoma. Furthermore, the enhancement would be more pronounced and less sharp in inflammatory condition of the labyrinth.
Once diagnosed, treatment options for intracochlear schwannomas include surgery, “wait, watch and scan” with serial imaging or stereotactic radiosurgery.,,, For larger tumors with vestibular symptoms, surgery is advised outright, while for smaller tumors with serviceable hearing conservative approach with serial MRI is advocated. Small tumors with severe hearing impairment (as in this case) and those with vestibular symptoms are advised surgery. Thus, the management depends on extent of the tumor, degree of hearing impairment, presence of vestibular symptoms, and the progressive growth of the tumor.
Surgical approaches include translabrynthine and transotic approaches., Transotic transcochlear approaches are advocated more because of more exposure possible. Expected complication when dissecting over the osseous spiral lamina is CSF leak, which can be quite controlled. Zhu and McKinnon  have reported a case in which transcanal excision of the tumor was done.
| Conclusions|| |
- Intracochlear schwannomas are very rarely diagnosed and require a high index of clinical suspicion
- Smaller intracochlear schwannomas (<1 cm) can be missed in ABR, and hence MRI with gadolinium contrast should be considered in suspicious cases
- Treatment mainly depends on the size of the tumor, symptoms and the degree of serviceable hearing left in the patient
- The importance of speech audiometry in suspecting a diagnosis of a retrocochlear pathology is emphasized.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]