Endoscopic technique a breakthrough in facial nerve schwannoma removal

Mumbai: Dr Satish Nair, Senior Consultant, ENT & Head and Neck Oncology, Apollo Cancer Centre, Bangalore, spoke to ETHealthworld’s Prabhat Prakash about the endoscopic trans canal excision of facial nerve schwannoma surgery on a 35-year-old patient who was suffering from right-sided facial weakness for the last two years. The surgery involved the principles of head and neck, lateral skull-base approach, and endoscopic techniques together to retain the entire functionality of the ear.

What causes vestibular schwannomas and who are most susceptible to them? What is its prevalence gender-wise?

Vestibular schwannomas have no specific causal factor however patients with neurofibromatosis type II (genetic disorder) can develop bilateral vestibular schwannomas. Vestibular schwannomas are usually random without any specific aetiology in about 95 per cent of cases. In less than five per cent of cases, genetic abnormalities can lead to schwannoma.

The prevalence is one in 50,000 per year. It is more common in females than in males (2:1). About 5000 new cases of vestibular schwannoma are diagnosed per year out of which 2800 are females and 2200 are men. The most common age group is 40-60 years.

What are the most effective tests for diagnosing schwannomas?

Contrast-enhanced MRI scan of the brain with special reference to the internal auditory meatus with a high-resolution CT scan is the investigation of choice for vestibular schwannoma. There are complimentary tests performed usually to find the impact of the schwannoma on the ear like Brainstem evoked auditory response (BERA), pure tone audiometry (PTA), Oto-acoustic emission (OAE) and vestibular tests. These tests can give us information regarding the degree of hearing loss and the effect of the tumour on the balance, etc but are not confirmatory tests.

How different are the head and neck, lateral skull-base approach, and endoscopic techniques as compared to the conventional methods of treating vestibular schwannomas like surgery and radiation therapy? Can this be applicable to treating malignant schwannomas as well?

The endoscopic approach is a minimally invasive technique to remove vestibular schwannoma. It does not require post-aural incision/mastoid bone drilling/brain retraction which are the mandatory steps in conventional surgery. Endoscope renders better visualisation of the structures which results in the preservation of all the critical structures around the tumour. The surgery can be performed as day care surgery and the patient can return to their normal activities after 2-3 days due to faster recovery as compared to conventional surgery which requires one week of hospital stay, mastoid bandage, hair shave and risk of brain fluid leakage (CSF leak).

Radiotherapy can be given only in tumours of small sizes. Large-size schwannomas require surgical removal. The endoscopic technique can be applied to malignant schwannomas as well however the surgery has to be followed by adjuvant radiation therapy as per international guidelines for the treatment of malignant schwannoma.

How challenging was the endoscopic trans canal excision of facial nerve schwannoma surgery? Please share your insights.

The patient was a foreign diplomat, she didn’t want any visible scar and her social life to be affected by the surgery. She also wanted her hearing to be preserved as her official and social life requires good hearing. These requirements warranted our surgical expertise to combine oncological principle, skull base approach and endoscopic technique to overcome the routine complications after the conventional open approach.

The endoscopic technique for the removal of facial nerve schwannoma has never been attempted in the literature and it confers maximum benefits without any morbidity to the patient. This is a minimally invasive technique that renders better anatomical, physiological (functional), cosmetic as well as the quality of life outcomes as compared to the open approach.