The onset may be acute (less than 2 days), subacute (between 2 and 30 days) or chronic (more than 30 days). The clinical presentation is highly variable and includes patients with only a mild headache, others with focal neurological deficits and a few with a dramatic syndrome and a coma. Moreover the evolution can be very different with unpredictable outcome: more often it is favorable with a low mortality rate, but in some cases it can be a worse course. The aim of this study is to evaluate the correlation of some biological markers: thrombin generation test and D-Dimers (marker of fibrin generation and degradation) with the type of onset or the wide spectrum of clinical presentations or the different modes of evolution.