Microsurgery of Vestibular Schwannoma Post-radiosurgery.

OBJECTIVES: Microsurgery of vestibular schwannoma (VS) after radiosurgery is not common. In this study, we analyze nerve functional outcomes and technical challenges associated with the microsurgery following radiosurgery of VS. MATERIALS AND METHODS: Sixteen patients underwent microsurgery at an average of 37 months (range 3-96 months) after radiosurgery. Indications of surgery included tumour progression or clinical worsening. Twelve of them had never undergone microsurgery before radiosurgery, and three had partial excision before radiosurgery. Maximum tumour diameter of all patients ranged from 23 to 51 mm, of which four were giant tumours. Operative findings and post-microsurgery clinical course, imaging and outcome were analysed. RESULTS: The tumours found at surgery were firmer, with an avascular core but increased vascularity near the surface. There were thickened arachnoid and often adhesions with surrounding structures making total excision difficult. Near total excision was employed in such cases. Eleven patients underwent gross total/near total resection. No major morbidity or death was reported. Post-surgery, eight patients had grade I/II HB facial function, four had grades III and three had grades IV/V. Of the last three, two had the same deficit preoperatively. At the last follow-up (average 50 months), all patients had a stable facial function. None of the patients have undergone any further radiosurgery/microsurgery since the last intervention. CONCLUSION: For the few patients who require microsurgery after radiosurgery, excellent tumour resection with an acceptable outcome can be achieved with proper techniques and neuromonitoring. Leaving tiny residue attached to critical structures is the key to an optimal outcome.

Correlation of Preoperative Cranial Nerve Diffusion Tensor Tractography with Intraoperative Findings in Surgery of Cerebellopontine Angle Tumors.

OBJECTIVE: Imaging to visualize nerves around tumors preoperatively could help the surgeon to plan the surgery and excise the tumor with preservation or improvement in patients' quality of life. In the present prospective study, we attempted to correlate the preoperative cranial nerves (i.e., trigeminal, abducens, facial, and vestibulocochlear diffusion tensor tractography and anatomic magnetic resonance imaging [MRI] findings) with intraoperative findings during cerebellopontine angle (CPA) tumor surgery. METHODS: The 40 enrolled patients had CPA tumors (31 vestibular schwannomas, 5 epidermoid tumors, 2 meningiomas, 2 trigeminal schwannomas). All the patients were undergoing microsurgery for the first time. They underwent preoperative MRI for anatomic and diffusion tensor imaging (DTI) data. The imaging series were postprocessed, and 3-dimensional images were obtained. The location of the involved nerves around the tumors was recorded during surgery by the senior surgeon, who was kept unaware of the results of the fiber tracking, and a correlation was performed. RESULTS: We evaluated the correlation between the DTI and intraoperative findings for the nerve location in relation to the tumor in the CPA. The correlation between the DTI and intraoperative findings for the facial, trigeminal, and vestibulocochlear nerves was 85% (34 of 40), 85% (34 of 40), and 75% (12 of 16), respectively. CONCLUSIONS: The modified technical parameters proposed could lead to better preservation of cranial nerve function, especially for patients with large tumors. To the best of our knowledge, the present study is the first systematic study of relevant cranial nerves in 40 patients with demonstration of the vestibulocochlear bundle by preoperative MRI in the most common CPA tumors using advanced MRI sequences such as diffusion tensor tractography and capturing the data in a multiplanar format.

Application of fluorescein sodium videoangiography in surgery for spinal arteriovenous malformation.

We present our recent experience with fluorescein sodium videoangiography (FLVA) in the intra-operative evaluation of a patient with conus medullaris arteriovenous malformation (AVM). To our knowledge this is the first report in the literature of use of FLVA in the surgery of spinal AVM. Intra-operative FLVA was done to identify an early filling vessel and to obliterate the site of fistulous connection. This was correlated and confirmed with simultaneous indocyanine green videoangiography (ICGVA). The conus and cauda equina roots could be appreciated and manipulated in relation to this fluorescence. Obliteration was confirmed with FLVA and correlated with ICGVA. There was no untoward reaction to the dye injection. We conclude that FLVA is a useful adjunct in the surgical treatment of conus medullaris AVMs since it is a real time, noninvasive, radiation-free, easily reproducible technique allowing surgical manipulation through the operating oculars with simultaneous visualization of surrounding critical structures.

Anterior petrosal approach for brainstem cavernoma.

Brainstem cavernomas (BC) comprise about 5-18% of intracranial vascular malformations. The annual hemorrhage rate varies depending on the study design ranging from as low as 0.25% per patient-year in a retrospective study[2] to 1.6-3.1% per patient-year in prospective studies.[45] The annual event rate is significantly higher in deep (brainstem, diencephalon) and infratentorial cavernomas when compared to their counterparts in other locations.[5] The management of BC can be conservative or surgical depending upon the mode of clinical presentation. Surgical excision of a BC is a challenge because of critical anatomy. We present a case of BC, which was totally excised with anterior petrosal approach. Anterior petrosal approach has been used for excision of BC in only 17 cases until now.[6] The use of preoperative diffusion tensor imaging, tractography, intra-operative navigation, and cranial nerve monitoring will help in reducing the morbidity.