Published online by Cambridge University Press: 26 August 2009
Non-traumatic intracranial hemorrhage (ICH) accounts for 10-15% of all strokes, but up to 25% of more severe strokes. The etiology of ICH in the vast majority of patients is arterial hypertension (63.5%), followed by coagulopathies (15%) and vessel malformations (8.5%), and less frequently amyloid angiopathy, vasculitis, intoxications, cavernoma, or cerebral venous thrombosis. In the hyperacute emergency assessment (< 6–12 h) computed tomography (CT) is the diagnostic standard and modality of choice to differentiate between hyperacute ICH and ischemic stroke. In general, MRI at this stage is considered to be of little value for the diagnosis of intracerebral or subarachnoidal hemorrhage, and many authors claim that the sensitivity of MRI for detecting hyperacute ICH is poor. Throughout the chapter we arbitrarily defined hyperacute as (< 12 h), acute (12 h to 7 d), subacute (7 d to 3 mo) and chronic (> 3 mo) stages. While hyperacute ICH is hyperdense on acute CT scans with progressing time and hematoma degradation, there is a loss of density and the ICH may appear isodense or hypodense. MRI is far superior to CT in the subacute and chronic stages especially with regard to concomitant or underlying pathology. In a study of 129 patients with ICH Steinbrich et al. found sensitivities of 46% (MRI) and 93% (CT) in the hyperacute and acute stage but 97% (MRI) and 58% (CT) in the subacute and 93% (MRI) and 17% (CT) in the chronic stage.