[Latency times and preadmission procedures]

During focal cerebral ischemia, irreversible changes occur at the core of the lesion, whereas energy metabolism and ion homeostasis are preserved in the surrounding penumbra. Not all brain cells are killed at the start of a stroke; some are destroyed hours or days later, usually by toxins released during the early stages. Time is therefore the critical factor in treating acute ischemic stroke. Early management by the neurologist is associated to better functional outcome and shorter hospital stays. Patient evaluation and treatment must therefore take place as soon as possible.