Each year, strokes afflict about 600,000 Americans-killing almost 160,000 and disabling many others. Most occur without warning. Magnetic resonance imaging and arteriograms can detect conditions that presage stroke but are expensive, time consuming and sometimes painful. A new sensor that sits on the eyelid may provide a cheap, noninvasive method of screening for brain aneurysms (bulges in blood vessels that can burst, depriving the brain of blood) and for blockages that can limit blood to the brain.

Electronics engineers in Kenji Kobayashi's lab at Takushoku University in Hachioji, Japan, developed the thin plastic sensor, which detects the vibrations caused by blood flow. Aneurysms and blockages change the flow and hence the vibrations. In tests, the device accurately detected aneurysms small enough for surgeons to repair before they were likely to bleed; it also identified vessels that had narrowed by 30 percent. Additional testing is needed before the device is considered reliable enough for clinical use.