The 67-year-old woman who was hit last month by a bicycle wheel thrown from a block of flats stopped breathing on Tuesday and had to be resuscitated.
Madam Mahani Abdullah has been comatose since then, her niece, Ms Nadia Abdullah Sani, told The Straits Times yesterday.
Doctors said Madam Mahani suffered brain damage when her heart stopped, and told the family to prepare for the worst, added Ms Nadia, 36, a client services manager.
On May 16, her aunt had reportedly been on her way to play chess at a nearby senior citizens centre when the wheel hit her on the head as she walked past Block 1, Eunos Crescent.
Madam Mahani, who has two sons and a daughter who is disabled and bedridden, had to undergo spinal cord surgery at the Singapore General Hospital three days later to regain the use of her limbs.
After the operation, Madam Mahani was moved out of intensive care and managed to converse with family members, but remained very weak, said Ms Nadia.
But the elderly woman's condition took a turn for the worse this week.
"We received a call at about 1.30am on Tuesday from the doctor, who said her heart had stopped beating," said Ms Nadia.
"Thankfully, they had managed to revive her by the time we got there, but she had slipped into a coma. We are hoping for the best but we also know to be realistic."
A 16-year-old boy was arrested on the day Madam Mahani was hit. He was later charged on Saturday with committing a rash act.
The alleged culprit is the same teenager arrested in December last year in relation to a series of rash acts, in which various items - including bricks, a dumbbell and a water dispenser - were thrown down a housing block in Eunos Crescent.
The Straits Times understands that the teenager is out on bail and is scheduled to appear in court tomorrow.