Postoperative subarachnoid clots and the pattern of cerebral ischemia associated with symptomatic vasospasm

We retrospectively evaluated the presence of subarachnoid clots and the development of symptomatic vasospasm in 125 patients who had early surgical treatment of a ruptured cerebral aneurysm.

We studied 16 patients (aged 35-86 years; mean, 58.7 years) who underwent surgery 0 to 6 days (mean, 2.1 days) and then manifested symptomatic vasospasm on day 5-12 (mean, day 7.4), and 57 patients (aged 13-79 years; mean, 52.0 years) who underwent surgery 0-8 (mean, day 2.9) and did not manifest symptomatic vasospasm. The volume and location of subarachnoid clots were evaluated with computed tomographic (CT) scanning. Cerebral ischemia was evaluated clinically and also in eight patients, by measurement of cerebral blood flow (CBF) using xenon-enhanced CT. Angiographic evaluation was performed only on one patient.

Of the 16 patients with symptomatic vasospasm, the subarachnoid clots were localized, distributed thickly, or associated with intracerebral hematomas in 15 and thin in 1 at the time of admission. Fifteen patients had CT evidence of a subarachnoid clot during vasospasm. Most of the clots were near the ruptured aneurysms, but in three cases, clots were located in the remote cisterns, which were not accessible operatively. The clinical manifestations of vasospasm in these three patients correlated with the site of the clot. CBF was reduced in the territory of the involved artery in all eight patients in whom it was measured. In two of the eight cases, the reduction occurred in the territory of a contralateral artery. In contrast, in the 57 patients without symptomatic vasospasm, the subarachnoid clots were already gone or disappeared soon after surgery in most patients.

The continued presence of subarachnoid clots is an important risk factor for symptomatic vasospasm after the rupture of a cerebral aneurysm. The clot is not always located near the ruptured aneurysm, and the clinical course may be unpredictable.