抄録
We retrospectively studied the mechanisms of development and enlargement of cyst following gamma knife surgery (GKS) for arteriovenous malformation (AVM) in 25 (15 males and 10 females) patients who developed cysts at 1.1–16 years after GKS. Cysts contained a nodular lesion enhanced with gadolinium-DTPA in 12 patients, and were associated with so-called expanding hematoma with severe surrounding brain edema in 10 patients. Magnetic resonance imaging with gadolinium-DTPA was not performed in three patients. Fourteen patients were treated with craniotomy, and two with placement of the Ommaya reservoir. One patient underwent both placement of the Ommaya reservoir and craniotomy. Spontaneous regression of the cyst was observed in one patient, and nine patients were treated conservatively. Two patients were lost to follow up. Histological examination showed proliferation of dilated vessels with fibrinoid degeneration associated with exudation of protein and bleeding. These findings were compatible with late radiation change. Increased vascular permeability at the vessel wall may be important in cyst formation and enlargement. Histological findings of nodular enhancement and expanding hematoma were essentially similar in terms of late radiation change.
Our study suggests the optimum treatment for cyst formation following GKS for AVM is cyst opening and removal of late radiation change lesion through craniotomy.
