SINGAPORE - A man with a psychotic disorder hit his elderly mother repeatedly on her head, taped her mouth shut and warned her to remain silent, after she quizzed him over a trivial matter.

The 150-minute ordeal in February left Madam Manikan Santanaletchmi, 62, with swelling in the face and bruises on the legs.

Her eye condition, caused by diabetes, was aggravated, resulting in blurred vision and bleeding in the eyes. She required surgery to restore her sight before being able to continue with her daily routines.

On Thursday, Yogaraj Arumugam, 33, who also stole $1,707 in valuables from his mother during the incident, was sentenced to 26 months in prison.

The unemployed man had pleaded guilty on Tuesday to three charges, including one for breaching a personal protection order in the process. This had been issued in December 2012 due to previous instances of violence Yogaraj had committed against his mother. Further investigations revealed he had been convicted of a similar breach a month before the incident.

A community court had heard that on Feb 5, Madam Manikan was alone with Yogaraj in the HDB flat along Bukit Purmei Road that they shared. Her elder son, who also lives there, was out at the time.

The attack began after she quizzed Yogaraj on his attitude towards a caller looking for her. Yogaraj had answered but told the caller his mother had died, then hanged up.

Yogaraj then grabbed his mother's hands and slapped and punched her in the head. He also pulled her mouth by the ends towards the sides to stop her shouting, causing her to bleed. She urinated in her clothes during the beating and asked to use the toilet, but decided not to after he dragged her there but refused to let her close the door.

He later dragged her to her room and laid her on the bed, warning her to remain silent. Her mouth taped, she remained in this position for a while, before locking the bedroom door when he left to answer the doorbell. But she was unable to call for help as there was no telephone in the room.

The court spared Yogaraj caning on account of his mental condition, but said a significant jail term had to be imposed for the "brutal and prolonged" assault.

He could have been jailed for up to 10 years, fined and caned for voluntarily causing grievous hurt to his mother. The maximum penalty for theft in dwelling is seven years in jail and a fine.