Brenda McLaughlin, 38, told officers she believed she was targeted with a cordless drill at around 2am on Saturdaybecause she is gay.
The attack in Co Tyrone, Northern Ireland, is being treated as a hate crime.
“It is my understanding that the victim has since told medical staff that she heard the noise of the drill and felt her head being twisted,” a detective told Omagh Magistrates’ Court.
He told court there was no evidence that a drill bit was in place when the cordless power tool was later recovered or after police checked security camera footage.
The 17-year-old alleged male assailant and the victim were at Ruby’s nightclub in Strabane.
Ms McLaughlin is in a high-dependency unit at Altnagelvin Hospital in Londonderry.
“There does appear to be some sort of hole in the skull, but I cannot say how severe it is,” the detective said, adding: “The victim said she believed it was in relation to her homosexuality.”
The teenager has been accused of having an offensive weapon, a power drill.
He is also alleged to have unlawfully and maliciously caused grievous bodily harm to Ms McLaughlin or intended to do her GBH. The 17-year-old is further accused of stealing a power drill belonging to the nightclub.
The victim was discovered lying on the ground with blood coming from her head as well as having fits and seizures while lapsing in and out of consciousness. She was found by a police patrol.
District Judge Peter King said it was a “grossly violent, inexplicably violent incident”.
The accused told police he had homosexual relatives and did not bear any ill will, his solicitor Ciaran McGuinness said.
CCTV of the nightclub and the outside street showed the accused playing with the drill “as if it is a gun”, with detectives saying the footage showed the accused in possession of a drill 10 minutes before police found the victim.
The teenager has been remanded in custody and will appear by video link at Strabane Magistrates’ Court on 18 May.