Large medical device makers have fallen in love with neurovascular devices with both their hearts and their heads. In June, Covidien (NYSE: COV) announced its purchase of ev3 (Nasdaq: EVVV), and now Johnson & Johnson (NYSE: JNJ) has joined the mix, picking up Micrus Endovascular (Nasdaq: MEND) for $480 million.

At $23.40 per share, the all-cash deal is only a 5.5% premium to Friday's closing price, but the company has been on fire lately -- up 50% this year alone -- partially in anticipation of a potential purchase after rival ev3 was purchased.

The price certainly isn't like the bottom feeding we've seen from Johnson & Johnson recently, but it's not horribly expensive either. Micrus turned a profit for the first time during its last fiscal year, although Johnson & Johnson thinks the purchase might be slightly dilutive to its earnings this year.

Expect that to change quickly, though, as the health-care giant leverages its size. The neurovascular devices, which treat vascular issues in the brain after strokes, should complement Johnson & Johnson's other neuro devices well.

Boston Scientific (NYSE: BSX) also has a neurovascular business, but the new competition from heavyweights might not be as bad as it sounds. The company is in the midst of yet another restructuring, which could include selling off its neurovascular division. If Covidien's and Johnson & Johnson's moves spur other medical device makers such as Medtronic (NYSE: MDT) and Abbott Labs (NYSE: ABT) to join in the mix, Boston Scientific might be able to get a premium for the division.

According to the National Stroke Association, nearly 800,000 people have strokes each year in the U.S. With an aging population, that number is only going to grow. Jumping in now looks like a good move for Covidien and Johnson & Johnson. Perhaps Boston Scientific should think twice before giving it up.