A teenager has been arrested over the "horrendous" bashing of an elderly woman at her home in Sydney's west that left her in hospital with serious head injuries.
Police arrested an 18-year-old man on Thursday morning at a townhouse in Toongabbie, not far from the 78-year-old woman's home.
She was attacked some time on Tuesday night or early on Wednesday morning.
Police said that, in the hours after the attack, she did not seek help or tell anyone what had happened.
It was only when she attended a bank branch in Seven Hills Plaza to cancel her bank cards just before midday on Wednesday that staff saw the severity of her head injuries and called triple zero.
Paramedics treated the woman at the scene before taking her to Westmead Hospital, where she remains in a serious but stable condition.
"This is horrendous. It is not something that occurs frequently in this area, it is something that is a great concern to us," Superintendent Gary Merryweather said on Wednesday.
"Her first concern was attending to the bank to cancel her cards.
"She was obviously not thinking straight.
"The bank workers were very much alarmed at the injuries they saw and did an excellent job of attending to her."
Forensic police on Wednesday examined the woman's home, where neighbours said she had lived for the past 30 years, while officers also conducted a line search on the street.
Channel Nine filmed the teenager being led out of a townhouse with a shirt covering his head on Thursday morning.
A NSW Police spokeswoman said the teenager was taken to Blacktown police station where he was being questioned over the attack.
No charges have been laid.
