The patient is a 67-year-old female who initially presented with a severe headache. She was diagnosed with migraines and imaging done at that time demonstrated a small planum sphenoidale meningioma ( Figure 2.8.1 ). Serial neuroimaging showed a growing tumor ( Figure 2.8.2 ), although this was not thought to be associated with her headaches. The patient opted for radiosurgery and underwent SRS with 9 isocenters to cover a tumor volume of 5960 mm 3 (margin dose 15.5 Gy; maximum dose 31 Gy) ( Figure 2.8.3 ).
Radiosurgery Machine
Gamma Knife – Perfexion
Radiosurgery Dose (Gy)
15.5, at 50% isodose line
Number of Fractions
1
Figure 2.8.1.
Initial postcontrast T1-weighted image showing a small planum sphenoidale meningioma.
Figure 2.8.2.
Serial image 5 years later demonstrating tumor growth.
Critical Structure
Dose Tolerance
Optic nerve/chiasm
10 Gy maximum point dose
<0.2 cc >8 Gy, goal <6 Gy
Pituitary gland
Stalk-to-gland radiation dose <0.8
Side Effects/Complications
Frequency
Visual dysfunction
<1% with a limited dose
Olfactory dysfunction
34% change in smell with >5.1 Gy
Symptomatic edema
5%–43%
Success Rate/Control Rate
Frequency
Progression-free survival
97% at 5 years, 94.4% at 10 years
Local control
71%–100% at 10 years
Patient outcome
The tumor remained stable for 5 years after SRS, with a slight decrease in tumor volume ( Figures 2.8.4 , 2.8.5 ). The patient remained asymptomatic from the tumor, but she continued to have intermittent headaches. She has not developed any visual disturbance, changes in olfaction, or signs of pituitary dysfunction or frontal lobe radiotoxicity.
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