Vestibular Schwannoma (Acoustic)

Patient: A 63 yr old man was initially seen by the Dept of Otolaryngology for assessment of progressive hearing loss in five years prior to the neurological consult.

Presenting Problem: MR imaging at inital Oto evaluation showed a small focal area of enhancement in the right internal auditory canal measuring a few millimeters in size. It was felt he had a small vestibular schwannoma. The patient subsequently lost all hearing in the right ear. He was followed with serial MR imaging. The patient's MRI scan of the head that was done two years later showed growth in the enhancing lesion in the right internal auditory canal. It then measured about 1.5 cm in length.

Given the increased growth of the lesion in the right internal auditory canal, the patient was referred to neurosurgery for consideration of Gamma Knife radiosurgery. The patient did not decide to proceed at that time.

The patient returned six months later and decided to proceed with radiosurgery treatment after discussion of options, which included: observation, microsurgical resection, or Gamma Knife radiosurgery. The rational for treating the lesion with radiosurgery was discussed. It was explained that we could not guarantee radiosurgery would control growth of the tumor. Potential risks such as injury to the facial nerve or facial dysesthesias were reviewed. The patient was also seen by radiation oncology and decided to proceed with the Gamma Knife procedure.

Radiosurgery Treatment: The patient arrived at the Gamma Knife Center accompanied by his wife and underwent bilateral supraorbital and occipital nerve blocks with local anesthesia. The Leksell frame was then applied to his skull without difficulty. After the patient's scalp radii measurements were determined; he was taken to the radiology floor. He underwent a CT scan of his head as well as a gadolinium enhanced MRI scan of the head at 1 mm thick sections. The neuroimaging studies were transferred to the computer in the Gamma Knife Center. Treatment planning was then done.

The patient's right-sided vestibular schwannoma was contoured. The volume of the contoured tumor measured 321 cubic mm. It was simulated to treat the tumor with 14 Gy at the 50% isodose line. The 50% prescription isodose line encompassed 96% of the contoured tumor. The dose volume histograms as well as the treatment plans were reviewed and accepted.

The patient was placed on the Gamma Knife at the appropriate stereotactic coordinates. He received the radiosurgery as described in the treatment plan. He tolerated the procedure well. The Leksell frame was removed. The patient was released for home later that afternoon.

Clinical Outcome: At the six-month follow-up after radiosurgery the patient was doing well. Patient denied any new symptomatology.

At his 18 months post surgery visit, he returned for an MR scan. He states he has had some occasional dizzy spells as before. He has had no problems with numbness in his face or weakness. The lesion on the MR measured about 1 cm in size and was slightly smaller compared with his prior study at he time of the Gamma Knife.

The patient has continued to do well without any facial weakness or numbness. The patient will continue to have regular checkups.