Imaging the future of stroke: II. Hemorrhage.

Bleeding into the brain or adjacent structures is one of the most devastating neurological conditions, incurring tremendous emotional, financial, and societal costs. Imaging is essential to differentiate variants of hemorrhage, as the clinical features may be insufficient. A comprehensive approach to hemorrhage therefore relies on imaging to disclose pathophysiology, elucidate mechanisms, and thereby open further avenues to effective treatment. Hemorrhage patterns from superficial to deep locations in the brain are surveyed in this work, noting myriad potential causes and the influential pathophysiology of arterial ischemia, venous hypertension, and microvascular dysfunction. Recent progress of imaging studies and novel techniques to evaluate hemorrhage are explored. For decades, only computed tomography was available to define a hematoma without corroborating evidence of other pathology whereas multimodal computed tomography and magnetic resonance imaging, including noninvasive imaging of brain tissue, vessels, and perfusion, have now radically altered clinical practice. Imaging of the blood-brain barrier, cerebral microbleeds, coexistent ischemia, associated vascular lesions, and markers of hemorrhage expansion is possible with routine protocols akin to diagnostic strategies for ischemic stroke. Imaging applications for hemorrhagic transformation, venous thrombosis, and microvascular disorders are considered with a perspective that balances concern for hemorrhage with prevention of ischemia as these processes are often intertwined and clinical conundrums arise. Imminent imaging advances are anticipated with increased use of detailed imaging for hemorrhage and overlap with cerebral ischemia. Numerous questions abound regarding optimal management of hemorrhage and definitive treatments are lacking, yet imaging of pivotal pathophysiology offers tremendous opportunity for future progress in combating this debilitating condition.