Effect of clot removal and the different incidence of vasospasm between clipping and GDC

The removal of subarachnoid clot has been thought to be effective for prevention of cerebral vasospasm. However, it is suggested that the incidence of cerebral vasospasm is not high in the cases where ruptured cerebral aneurysms are obliterated using Guglielmi detachable coils (GDC) without clot removal. The effect of subarachnoid clot removal on the occurrence of cerebral vasospasm and the different incidence of cerebral vasospasm between clipping cases and in GDC cases are reviewed.Surgical clot removal in experimental model indicated marked preventive effect on cerebral vasospasm. However, the clinical trials of clot removal during early aneurysm surgery had failed to show satisfactory preventive effect for vasospasm, and the cumulative incidence of symptomatic vasospasm in these trials was 29%. As fibrinolytic drug, intrathecal administration of tissue plasminogen activator showed sufficient elimination of subarachnoid clot and prevention of cerebral vasospasm in the experimental studies and in the clinical case trials and nonrandomized case-control trials. However, the multi-center, randomized case-control trial showed no statistically significant effect on symptomatic cerebral vasospasm. On the other hand, the cumulative incidence of cerebral vasospasm in GDC cases was 20%. The comparative studies of the incidence of vasospasm between GDC cases and in clipping cases also showed less incidence of symptomatic vasospasm and a more favorable outcome in GDC cases. From the results of studies reviewed, the incidence of cerebral vasospasm seems less in GDC cases than in clipping cases. It should be clarified why clipping could not be dominant in the prevention of cerebral vasospasm compared to GDC.