A 12-year-old male western lowland gorilla living at the San Diego Zoo Safari Park underwent what is believed to be a first-of- its-kind surgery by UC San Diego Health physicians and is recovering well, it was announced Monday.

The Safari Park's Harter Veterinary Medical Center performed a CT scan on Mizani the gorilla, confirming he had sinusitis and mastoiditis, an infection of the large bone behind the ear that can occur in both humans and gorillas.

Veterinarians and wildlife care specialists noticed in March that Mizani was "reluctant to open his mouth fully, had a decreased appetite, and was exhibiting behaviors often associated with head pain, like holding his head while squinting his eyes," according to a statement from the San Diego Zoo Wildlife Alliance.

Following the CT scan, doctors believe he had developed the condition before he arrived at the Wildlife Park in November 2024.

Dr. Jeffrey Harris, an otolaryngologist-head and neck surgeon, and Dr. Kris Suresh, a resident fellow at UC San Diego Health, played a critical role in adapting human techniques to Mizani's skull. Humans and gorillas share many similarities anatomically, but differ in key ways.

Meghan Breen

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San Diego Zoo Wildlife Alliance

A scan of Mizani's skull showing the infection of the large bone behind the ear, Jun 30, 2026.

"Our surgical team regularly performs complex mastoid and skull base procedures but applying that expertise to a critically ill gorilla required meticulous planning," Harris said. "After carefully analyzing CT scans, we adapted our approach to account for the significant anatomical differences and proceeded with delicate microsurgery. We're proud to bring this level of specialized care beyond the traditional clinical setting and we are incredibly gratified by Mizani's recovery."

The Wildlife Alliance could not find any literature detailing a mastoidectomy ever being performed on a gorilla, leading park leaders to believe this was a world first.

According to the doctors, the surgery involved making an incision along the left side of Mizani's head to access and drain the infected area, followed by removal of portions of infected mastoid bone and tissue and careful closure of the surgical site.

The surgery was performed at the Harter Center and took around five hours from anesthesia induction through recovery. More than 20 veterinarians, physicians, registered veterinary technicians, wildlife care specialists and support staff from both organizations were involved in the tricky procedure.

"This case was particularly unique because this disease is rarely seen in gorillas, making it a valuable learning opportunity for everyone involved," said Ryan Sadler, senior veterinarian at the San Diego Zoo Safari Park. "Even after working with gorillas throughout my career, I'm still learning something new every day. Procedures like this highlight how medicine can be remarkably similar across species, while also requiring very different approaches depending on the animal. I'm incredibly proud of how quickly our team and the doctors from UC San Diego Health came together for this monumental procedure."

Mizani has recovered well, with his most recent recheck exam in June showing "significant improvement with no indication of complications," the zoo statement read. Veterinarians will continue to monitor the gorilla and he will have a follow-up recheck in a year's time unless clinical signs arise.

Mizani has returned to his troop and resumed his normal diet, activity level and daily routine, the zoo statement read.

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