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  • Role of Gamma Knife Radiosurgery in the Treatment of Sixth Nerve Schwannomas

    Final Number:

    Lakshmi Prasad MBBS; Manish S. Sharma MBBS, MS, MCh; Shashank Sharad Kale MBBS, MS, MCh, MD; Deepak Agrawal MBBS MS MCh; Manmohan Singh MCh; Ashok Kumar Mahapatra MD; Bhawani S. Sharma; Shailesh Gaikwad

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2012 Annual Meeting

    Introduction: Abducent nerve schwannomas are very rare and till date, only 34 cases have been reported. Very limited literature exists for the optimal management of these rare tumours. The present study aims to assess the role of gamma knife radiosurgery for the treatment of this rare pathology.

    Methods: Retrospective study from 1998-2010. All patients received primary GKRS using a Leksell model B unit using contrast MR images. Regular clinical and radiological follow ups were obtained.

    Results: There were seven patients (3 males and 4 females). All were primary lesions. Mean age group was 39.7 yrs (17-60) years. All had isolated sixth nerve palsy; five were on the right and 2 were on left side. Five of these tumors were located in pre-pontine region while 2 tumors were located in the cavernous sinus. Mean duration of symptoms was 6.5 months (range 3-18 months). The mean tumor volume was 4.25 cm3 (range 2-10.3 cm3). Median dose of 12 Gy was given with a prescription isodose of 50%. One patient was lost to follow up while both clinical and radiological follow up were available for the remaining 6 (83%) patients with a mean follow up duration of 23.5 months (8-42 months). Symptoms remained stable in 3 patients (50%) and improved in 3 patients (50%). MRI at follow up showed stable tumour size in 3 patients (50%) and reduction in 3 patients (50%) thus achieving a tumour control rate of 100% for the available patients with follow up. One patient (16%) experienced transient worsening of diplopia 2 months after GKRS which resolved with conservative treatment in the next 3 months.

    Conclusions: GKRS is a safe and effective treatment modality with excellent tumour control rates and 50% chances of relieving diplopia. It might be considered as the initial treatment of choice for this rare pathology.

    Patient Care: Gamma knife radiosurgery can be considered as the first line treatment for these rare neoplasms with excellent tumour control rates and no new onset cranial nerve/ other neurological deficits. Unnecessary surgical intervention and its resultant complications can hence be avoided if appropriately considered

    Learning Objectives: This study validates the effectiveness of GKRS for these rare neoplasms as with the more common vestibular and trigeminal schwannomas, with excellent tumour control and cranial nerve preservation rates. This might be considered as the treatment of choice for these rare tumors.

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