Response to Letter Regarding Article, “Ischemic Brain Injury Following Intracerebral Hemorrhage—A Critical Review”
We thank Drs Arsava and Topcuoglu for their letter and insights on obliterative arteriolar spasm at onset of intracererbral hemorrhage (ICH) as a potential mechanism of ischemia after ICH. It is difficult, however, to confirm or refute its existence on the basis of the available data. Most patients are asymptomatic before hemorrhage onset, arguing against the occurrence of ischemia before ICH onset. Coexisting ischemia and hemorrhage at onset is plausible and might be detected by acute magnetic resonance imaging, and this represents an opportunity for future research. However, the data suggesting continued incidence at 1 month argue against an acute arteriolar spasm as the main mechanism for this phenomenon.1 In addition, other mechanisms of simultaneous ischemia and hemorrhage, such as frank hemorrhagic transformation of ischemic stroke, would be more likely.
Given the authors statements are based on infarct patterns, we would also caution against overinterpreting infarct patterns and equating them with mechanisms of ischemia. For instance, borderzone infarct patterns can combine often with microembolic patterns as noted in the impaired washout hypothesis.2 The inferences are useful for hypothesis generation but require specific experimental designs to delineate actual mechanisms.
There is much to discover regarding the timing, causes, and contributing factors to decreased diffusion after ICH, and several groups are currently investigating these questions. Without longitudinal and serial magnetic resonance imaging data, it may be difficult to differentiate among these proposed mechanisms. Studies using magnetic resonance imaging early or immediately on admission with ICH (and before blood pressure lowering) may also provide some insights to whether the lesions precede or follow blood pressure lowering.
Shyam Prabhakaran, MD, MS
Andrew M. Nadeich, MD, MSPH
Department of Neurology, Northwestern University, Chicago, IL
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- © 2012 American Heart Association, Inc.