Rare Brain Surgery Gives Cat New Lease on Life

Most diabetic cats receive 1-2 units of insulin daily to successfully manage the disease. For Mars, a 10-year-old domestic short-hair cat, 20 units a day wasn’t working. He also couldn’t walk very well and seemed headed for an early death. The cause? A brain tumor on his pituitary gland. The solution? An intricate surgery performed at a Bend veterinary hospital.

“It’s done overseas, in other countries, but it’s not common here because of the level of expertise and also the level of equipment you need for it,” said Katie Sedivic, director of brand and marketing for the Veterinary Referral Center of Central Oregon, where a large team practiced on cadavers and with specialized equipment to prepare for the Transsphenoidal Hypophysectomy.

Mars’ brain tumor was causing his pituitary gland to produce excess growth hormone, dramatically increasing his insulin needs, enlarging his heart and causing neurological effects that resulted in him walking on his hocks and unable to jump and or high five his owner, as he’d done all his life. Earlier attempts to shrink the tumor through medication and radiation were unsuccessful. His owner searched for a cure. She found it in Bend.

The orange feline traveled from Hoboken, New Jersey, in May for the surgery performed by VRCCO’s Dr. Annie Chen-Allen, who received her veterinary degree from Texas A&M University and completed her neurology residency at Washington State University, where she then taught and practiced for 17 years. She was assisted by Dr. Dani Madson, VRCCO’s neurology intern, numerous other VRCCO specialists and its critical-care team. Also on hand were two of Chen-Allen’s longtime mentors and WSU experts, Dr. Tina Owen, a U.S. pioneer in the TSH surgery, and Dr. Linda Martin, a critical-care specialist. Owen, Martin and Chen-Allen have more than a decade of experienceperforming the surgery as part of WSU’s pituitary surgery team.

“She brought them both to Bend for this first surgery to optimize success for everybody,” Sedivec said. “As Dr. Chen-Allen likes to say, it was a full orchestra of people to make it go successfully. The surgery itself is very, very complex and has zero margin for error.”

The VRCCO team trained for two months on specialized equipment, including a 3D camera and Stryker drill. Additionally, VRCCO’s 3D printing expert, Dr. Mauricio Dujowich, created templates using cadaver CT scans so surgeons could perfect the delicate procedure. The pituitary gland, which is about the size of a green pea, sits at the base of the brain, encased by blood vessels. The two-part surgery involves first drilling a 6-millimeter access hole in the skull, and then the second, longer surgery involves using a small 3D camera that zooms in on the area so surgeons can see the gland and tumors. Post-surgery, patients require continuous monitoring to ensure their body is working correctly without the gland. Some patients can have difficulty regulating sodium post-surgery, Sedivic said, which can cause dangerous, even deadly outcomes. Additionally, patients typically require lifelong steroid supplementation and thyroid management, but the surgery typically significantly reduces insulin needs, as it has in Mars’ case.

Mars and his owner also utilized VRCCO’s medical-travel program, which Sedivic said has expanded as they’re seeing “a big increase of cases from outside Central Oregon, because we offer things that you don’t find in other places, and also because our facility is pretty high-tech, so you can come to one facility and get all of your needs met.”

VRCCO has a dedicated staff member who plans logistics and scheduling for traveling patients, including working with several local partner hotels to provide lodging and crafting plans for pet-friendly food, outings and other necessities pet owners might need while in Bend.

“We put a lot of work into making the experience as stress-free as possible,” Sedivic said.

Since the surgery, Mars’ insulin use has returned to normal, and he’s now jumping onto stools and high fiving his relieved owner.

Mars chills out, in the capable care of his talented medical team. Credit: VRCCO

“It was nerve wracking to bring Mars in for such a complex procedure, but the entire team at VRCCO made us feel safe and cared for from day one,” said Yisi, Mars’ human who declined to give her last name. “Dr. Chen-Allen and her team are remarkably professional, highly experienced, and very organized every step of the way. They went above and beyond, providing us prompt updates multiple times a day and treating Mars with immense patience and gentleness. Despite a very challenging surgery, they never gave up on him and successfully removed the tumor, giving Mars a second chance at life. We came in feeling anxious but left with complete trust in their care — even Mars came home more relaxed and comfortable with his future vet visits than ever before. We are forever grateful to everyone at VRCCO.”

This article appears in Central Oregon Pets Fall 2026.