7.7\ Radiosurgery for Vestibular Schwannomas

7.7.1\ Discussion

Radiosurgery can be administered as a noninvasive, image-guided treatment for selected cases of vestibular schwannomas. The technique consists of applying high-dose photon radiation to the lesion from different angles. The treated tumors may continue to increase in size for up to 2 years, followed by regression (Fig. 7.60).

a

Development of high T2 signal intensity in the adjacent brain parenchyma occurs in about 30% of cases. Transient loss of enhancement and central necrosis are also common. The presence of tumor necrosis and alterations in enhancement properties do not necessarily correlate with clinical outcome. Although the changes in contrast enhancement are not predictive of clinical outcome, imaging follow-up is recommended in order to differentiate true ongoing tumor progression from transient treatment-related swelling.

b

Fig. 7.56  Radiosurgery for vestibular schwannoma. Preoperative axial contrast-enhanced T1-weighted MRI (a) shows a large right cerebellopontine mass. Postoperative axial contrast-enhanced T1-weighted MRI

(b) shows interval central non-enhancement within the mass (arrow). There is also decrease in size and mass effect on the right middle cerebellar peduncle and brainstem