REDUCTION OF HEMORRHAGE RISK AFTER STEREOTAXIC RADIOSURGERY FOR CAVERNOUS MALFORMATIONS

The benefits of radiosurgery for cavernous malformations are difficult to assess because of the unclear natural history of this vascular les ion, the inability to image malformation vessels, and the lack of an i maging technique that defines ''cure.'' The authors selected for radio surgery 47 patients who harbored a hemorrhagic malformation in a criti cal intraparenchymal location remote from a pial or ependymal surface. Of these, 44 patients had experienced at least two hemorrhages before radiosurgery. The mean patient age was 39 years; six patients had pre viously undergone attempted surgical removal. The malformation was loc ated in the pons/midbrain in 24 cases, the medulla in three, the thala mus in nine, the basal ganglia in three, deep in a parietal lobe in fo ur, and deep in a temporal lobe in four. Patients had sustained initia l hemorrhages from 0.5 to 12 years prior to radiosurgery (mean 4.12 ye ars). In these patients, who were not typical of the majority of patie nts with cavernous malformations, there were 109 bleeds before radiosu rgery in 193 prior observation-years, for a 56.5% annual hemorrhage ra te (including the first hemorrhage), or an annual rate of 32% subseque nt to the first hemorrhage. The mean follow-up period after radiosurge ry was 3.6 years (range 0.33-6.4 years). The proportion of patients wi th hemorrhage after radiosurgery was significantly reduced (p < 0.0001 ), as was the mean number of hemorrhages per patient (p = 0.00004). In the first 2 years after radiosurgery, there were seven bleeds in 80 o bservation-years (8.8% annual hemorrhage rate). In the 2- to 6-year in terval after radiosurgery, the annual rate decreased to 1.1% (one blee d). After radiosurgery, 12 patients (26%) sustained neurological worse ning that correlated with imaging changes. In eight patients these def icits were temporary; two underwent surgical resection and died. Two p atients had new permanent deficits (4%). A significant reduction was o bserved in the hemorrhage rate after radiosurgery in patients who had deep hemorrhagic cavernous malformations, especially after a 2-year la tency interval. This evidence provides further support to the belief t hat radiosurgery is an effective strategy for cavernous malformations, especially when located within the parenchyma of the brainstem or die ncephalon.