“Silent” cerebral infarction due to vasospasm after SAH
Objective. To determine frequency, impact on outcome, and determinants of clinically silent infarcts after aneurysmal subarachnoid hemorrhage (SAH) due to vasospasm. Methods. We prospectively studied a cohort of 326 patients with acute SAH. Delayed cerebral ischemia (DCI) was defined as (i) a new focal neurological deficit or decrease in level of consciousness otherwise unexplained, or (ii) a new infarct revealed by follow-up CT scans (within day 2–14 post hemorrhage) without other explanation. Angiography confirmed vasospasm in all patients. Results. DCI occurred in 18% (59/326) of patients. Of the 59 patients with DCI, 14 (24%) patients had an infarct on CT attributed to vasospasm without clinical deterioration, 25 had clinical symptoms and an infarct on CT, and 20 had clinical symptoms only. Compared to patients with symptomatic vasospasm, patients with “silent” infarcts more often had a Hunt-Hess score of 4–5 (64% vs. 27%, p=0.023), and blood in the 4th ventricle was found more often on the admission CT scan (86% vs. 45%, p=0.012). Variables that did not differ between symptomatic and asymptomatic patients included cisternal blood scores, hydrocephalus (bicaudate index), or edema on admission CT scans; aneurysm location; location of vasospastic infarcts; mean APACHE-2 scores; and mean TCD values. DCI patients without clinical symptoms had higher mortality at 3 months when compared with patients with clinical symptoms (60% vs. 14%, p=0.006). Conclusions. Clinically “silent” infarction occurs in approximately 25% of SAH patients with DCI, and is particularly common in poor grade patients with IVH. Because ischemia and infarction may go undetected in poor grade patients, prophylactic triple-H therapy, routine follow-up angiography with prophylactic angioplasty, and new monitoring techniques (e.g. continuous EEG) may lead to improved outcomes in these patients.