Caroline Stockley, 27, and Wendy McGuigan, 26, allegedly left Annie Latham, 43, tied to a pipe by an apron.
When the patient was found collapsed, the nurses and their colleague, Pamela McKenzie, lied to cover it up, Birmingham Crown Court heard.
Ms Stockley, from Stoke-on- Trent, Staffordshire, and Ms McGuigan, from Argyll, Scotland, are both charged with ill- treatment of Ms Latham.
Both nurses also face a charge of perverting the course of justice along with Ms McKenzie, 42, also from Meir.
Christopher Hotten QC, for the prosecution, said that Ms Latham, who could not talk, had been admitted to Stallington Hospital, near Stoke-on-Trent, as a child. She was frequently sick and because she was not toilet trained staff often restrained her by tying her to the lavatory.
The trial continues today.