The challenging enigma of vasospasm and associated clinical deterioration, despite generally successful treatments of ruptured aneurysms, have lured hundreds if not thousands of neurosurgeons and researchers toward seeking its cause, pathomechanism(s), and developing treatment. Nevertheless, despite this worldwide effort, developed numerous in vitro and in vivo models, and numbers of pathophysiological hypotheses tested, the elusive nature of vasospasm pathophysiology remains unrevealed. Over the years, we have obviously learned a lot about vessels anatomy, physiology, regulation of cerebral blood flow, etc., but it seems that as we get closer to answers we also face the old questions.

The chapters that follow are focused on continued efforts to conquer these challenges and reveal the true nature of vasospasm after aSAH. In the pursuit of this goal, they address experimental and clinical methods of vasospasm assessment, its effects, and imaging in the context of vasospasm research.