Nick Cannon continues to grieve baby son's death from brain cancer as he recalls thinking Zen only had a 'sinus infection'

Nick Cannon has given his first interview since the sudden death of his five-month-old son from a brain tumour.

The talk-show host opened up about his grief in a new interview with People, recounting to the magazine the signs he and his girlfriend, model Alyssa Scott, sensed something was amiss with baby Zen.

Cannon recalls Zen being "super calm' baby but in the days after his birth in June, the couple felt his breathing patterns seemed off.

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"It sounded like he had fluid in his lungs, like a sinus infection or something," the 41-year-old told People. "[The doctors] didn't think it to be anything too concerning."

However, weeks later doctors found Zen's head was "growing a little too quickly" and by the time Zen was two months old, he was diagnosed with a glioma, a rare and aggressive form of brain cancer. Doctors then placed a shunt in his skull to drain the excess fluid and help alleviate pressure, but the tumours continued to grow.

"We started asking, 'Is there a way to prevent this? If not, how long do we have?' " Cannon recalled. "The conversations quickly turned to, 'How can we give him the best life for the time that he does have?' It could be weeks, it could be months, it could be years."

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With this fact in mind, Cannon and Scott decided against chemotherapy for their son as they "didn't want him to suffer". Cannon is no stranger to chemo as he endured the treatment himself when previously diagnosed with the autoimmune disease lupus.

"We could have had that existence where he would've had to live in the hospital, hooked up to machines, for the rest of the time," he said.

"From someone who's had to deal with chemotherapy before, I know that pain. "To see that happen to a 2-month-old, I didn't want that."

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Sadly, Zen's health took a turn for the worse over Thanksgiving weekend, with Cannon recalling his baby boy "gasping for air" and not breathing for "maybe five to 10 seconds at a time". Baby Zen died days later on December 5 in his parents' arms.

"We had a short time with a true angel. My heart is shattered," Cannon said. " I wish I could have done more, spent more time with him, taken more pictures. I wish I could have hugged him longer."