Serial Follow-up MR Imaging after Gamma Knife Radiosurgery for Vestibular Schwannoma

Graphs showing the change in the ratio of tumor volume on follow-up MR examinations to tumor volume at treatment over time.

A, Tumor shows temporary enlargement.

B, Tumor shows no change or sustained regression without temporary enlargement.

C, Tumor shows repeated alternate enlargement and regression.

D, Tumor shows continuous enlargement.

Serial contrast-enhanced axial T1-weighted images (450/17/5) in a 51-year-old man. Note that the tumor shows temporary enlargement with transient loss of contrast enhancement 3 months after treatment. GKRS indicates gamma knife radiosurgery; mos., months after gamma knife radiosurgery

Serial contrast-enhanced axial T1-weighted images (450/17/5) in a 25-year-old woman. Note that the tumor shows no change in size with transient loss of contrast enhancement 6 months after treatment and thereafter the tumor shows continuous regression with recovery of contrast enhancement. GKRS indicates gamma knife radiosurgery; mos., months after gamma knife radiosurgery

Serial contrast-enhanced axial T1-weighted images (450/17/5) in a 64-year-old woman show enlargement of the cystic component and transient loss of contrast enhancement in the solid component at 3 months; regression of the cystic component, slight enlargement and recovery of contrast enhancement of the solid component, and slight regression of the overall tumor at 18 months; further enlargement of the solid component, no change in the cystic component, and regression of the overall tumor at 24 months; and remarkable regression of the tumor at 50 months. GKRS indicates gamma knife radiosurgery; mos., months after gamma knife radiosurgery

Serial contrast-enhanced axial T1-weighted images (250/25/1 at treatment, 400/15/2 at 6 months, and 400/15/4 at 12 months and 18 months after treatment) in a 55-year-old woman. Note the continuous enlargement of the tumor, although with transient loss of contrast enhancement. GKRS indicates gamma knife radiosurgery; mos., months after gamma knife radiosurgery

Serial contrast-enhanced axial T1-weighted images (250/30/1 at treatment, 400/17/3 at 7 months, 340/16/3 at 20 months, and 250/30/1 at 42 months after treatment) in a 42-year-old woman showing continuous increase in contrast enhancement without transient loss of contrast enhancement. GKRS indicates gamma knife radiosurgery; mos., months after gamma knife radiosurgery

Serial contrast-enhanced axial T1-weighted images (450/17/5 at treatment and 500/15/2 at each follow up) in a 52-year-old woman show tumor regression but almost no change in contrast enhancement. GKRS indicates gamma knife radiosurgery; mos., months after gamma knife radiosurgery

Bar graph shows the correlation between changes in tumor volume and contrast enhancement. Vol. I indicates temporary enlargement; Vol. II, no change or sustained regression; Vol. III, alternate enlargement and regression repeatedly; Vol. IV, continuous enlargement; CE. I, transient loss of contrast enhancement followed by recovery of enhancement; CE. II, continuous increase in enhancement; CE. III, no change in enhancement