The visit to a Las Vegas hospital was a "routine follow-up" to the operation Lewis, 76, underwent in Houston on April 8, when he was fitted with the battery-powered device, said Candi Cazau, a spokeswoman for the casino showroom where Lewis has a long-term contract to perform.
The battery-powered Synergy Neurostimulation System, implanted in the lower abdomen, emits an electronic pulse through wires connected to his spinal cord that Lewis can regulate using a hand-held remote control.
In a recent interview with the Las Vegas Sun, Lewis said the device has left him pain-free for the first time in more than 30 years, and joked he also can use it to "open my garage door."
After developing a bad back from years of physically demanding comic routines, Lewis has said he had endured chronic pain since overcoming a decade-long addiction to painkillers in the 1970s.
The pain became nearly intolerable after Lewis was stricken last year with pneumonia, which forced him to cancel his Las Vegas appearances at the Orleans Hotel and Casino and to cut back the hours he spent hosting his annual Labor Day Telethon benefiting the Muscular Dystrophy Association.
A doctor friend suggested he try the relatively new pain-blocking device for his bad back, and the surgery was a success, Lewis has said.
Cazau said Lewis is currently busy writing a book about his past comedy collaboration with the late Dean Martin and will start preparing for the next MDA telethon later this month. In June, she said, he goes to Belgium to receive a lifetime achievement award.