Its not unusual to wake up with the feeling that your arm or leg has gone to sleep. You may chalk it up to just having "slept wrong." But if you wake up with feelings of numbness on one side, a difficulty talking or understanding speech, or trouble walking, the cause may be much more serious. A recent study found that one in seven strokes occur during sleep, and many of those stroke patients could have been treated had they been seen by a doctor soon after waking up. The study, published in the May 10 issue of the journal Neurology, found that at least one third of the people who with "wake-up" stroke symptoms could have been treated with the clot-busting drug tissue plasminogen activator (tPA).