Ruptured intracranial aneurysms: has the incidence of early rebleeding been over-estimated?

Of 110 consecutive patients with ruptured intracranial aneurysms, 49 underwent delayed neurological deterioration, involving 57 episodes in all. During the first three weeks after the presenting haemorrhage less than a third of these episodes were due to confirmed rebleeding. Rebleeding episodes were found to have a "flat" distribution in time during this period, but episodes of non-haemorrhagic deterioration "peaked" between days 4-12. This peak coincides with the peak for rebleeding which was described in earlier studies on aneurysms, and it is suggested that confusion between non-haemorrhagic deterioration and rebleeding may have led to a significant over-estimate of the incidence of early rebleeding with important implications for the optimum timing of surgical intervention.