Corporate counsel are increasingly turning to Big Law for help with intellectual property litigation rather than to midtier firms and IP boutiques. And while they are increasingly engaging in alternative fee arrangements with their law firms for most work, they rarely do so for IP litigation, according to a recent report.

A study by LexisNexis CounselLink that analyzed $18 billion in legal invoices shows the nation's biggest firms are getting a bigger share of IP litigation work.

In 2014, firms with 750 or more attorneys got 61 percent of the billings related to IP litigation—up from 36 percent in 2011. Midtier firms, those with between 500 and 750 attorneys, got 12.6 percent. And firms with between 200 and 500 attorneys received 13.3 percent, the study found.