The 24-year-old man, paralyzed "as a result of an accident," wrote down the details of the alleged abuse on a communication board because he is unable to speak, prosecutors said.
Dioscoro Flores, 39, is charged with felony aggravated criminal sexual assault in the alleged incident at the renowned Streeterville rehabilitation center at 345 E. Superior. He was ordered held on $50,000 bond.
Two times between July 4 and August 6, the nurse fondled the victim without his consent, Assistant State's Attorney LaToya Croswell said. He communicated the details to a witness, who relayed the allegation to hospital staff.
Hospital officials reported it to police, prosecutors said.
A spokeswoman at the Rehabilitation Institute said it could not disclose any information because of patient privacy.
"Patients are our first priority, and as such we provide them with quality care, compassion and respect," spokeswoman Betsy Owens said. "RIC and the employees involved have thoroughly cooperated with the authorities and will continue to do so."