The American comedian and actor, 45, released the extract from his new book ‘A Heart That Works’ as he shared details behind his son’s death.
Delaney, known for his role in Channel 4’s Catastrophe said that hearing his son had a brain tumour was the “heaviest pain in the world”.
Rob and his wife Leah lost their son on Rob’s 41st birthday in January 2018, at just two-and-a-half years old.
In an extract published by the Sunday Times, the actor provided a heartbreaking recount of the couple coming to terms with their loss.
Only the day after Delaney and Sharon Horgan had won a BAFTA for their comedy writing on Catastrophe in 2016, Rob and Leah found out that Henry might have a brain tumour.
Delaney described that period of time and the months that followed in his book as being ‘obscured by fog’, despite being at the height of his career success.
In the extract shared by the Sunday Times, Delaney said that: “Greif drove a bus through the part of my brain where memories are stored.”
The comedian shared: “After the MRI, DR Anson confirmed that Henry had a large tumour in the back of his head, near his brain stem.
“He delivered the news calmly, and ended by saying a paediatric brain surgeon would come to see us within a few hours.
“We sank inside ourselves.”
Delaney shared that it was “The heaviest pain in the world. I felt like I had suddenly quadrupled in weight, and an oily, black whirlpool began to swirl where my heart had been.”
The American actor then explained how the family were introduced to a brain surgeon at Great Ormond Street Hospital who were going to attempt to surgically remove the tumour.
Rob Delaney also shared how Henry had only turned one-year-old less than two weeks before the diagnosis.
The family arrived at the hospital days before the surgery, with Rob describing Henry as having such a fatigued appearance that “you would normally associate with an old man”.
Delaney also shared how as the doctors prepared Henry for his operation, the couple, who had been married for 18 years, had got a hotel room nearby.
The comedian shared how the couple had had sex twice within a few hours during what he described as the “scary” period.
Rob said that he wanted to share that detail in the book to show parents “hyperventilating with anxiety” the reality of the situation.
He added that the fear of what was happening in the hospital had “manifested in sex”, saying that they just wanted to be close during that time.
Henry then spent two months in the intensive care unit and was eventually moved to the cancer ward where he received chemotherapy for several months.
Rob revealed that his “stomach filled with stones” after a check-up following an MRI scan revealed that Henry’s cancer had started to return and there were no options left.
The couple were told that their son was then expected to live for another three to six months.
Rob and Leah had three other sons and admitted in his Sunday Times article that he doesn’t know how he has continued to function after the loss of Henry.