LAWRENCE – The 22-year-old former Lynn man who sodomized and caved in his little brother’s skull with a plastic pole four years ago was sent back to Bridgewater State Hospital for another six months.Luis Sanchez, who last lived at 139 Timson St., was found not guilty by reason of insanity in late August after Sanchez’ mother and two other witnesses gave a detailed account of the Aug. 31, 2003 attack on his then 4-year-old brother.His mother, Elba Martinez, testified that on the day of the attack, she had left Sanchez to take care of his 4-year-old half-brother to do an errand.When she returned, Sanchez met her at the front door and told her his brother was sick. Martinez went upstairs, where she found him naked, unconscious and bound at the feet and wrists.The boy was taken to North Shore Children’s Hospital and airlifted to Massachusetts General Hospital.Medical officials determined the boy’s skull had been caved in and there was evidence of an assault in the area of the child’s rectum.Police searched the home and found a broken bed and a 46-inch black plastic pole in the attic with evidence indicating it was used to rape the boy.Sanchez told police during an interview that his brother was possessed and that he brought him to the attic, tied him up and “hit him in the bum.”Superior Court Judge John Lu ruled then that Sanchez suffers from a schizophrenic disorder and is not criminally responsible for the attack. He sent Sanchez to Bridgewater State Hospital and would return for an update on his condition and medical treatment.Monday afternoon in Lawrence Superior Court another hearing was held before Judge Lu, who ruled that Sanchez should stay at Bridgewater State Hospital.Assistant District Attorney Kate B. MacDouglall said it was agreed by all parties that Sanchez be sent back to Bridgewater State Hospital due to his mental illness, which requires strict provisions and supervision because “he is a danger to others.”Now, the court will review the case every year as to Sanchez’ mental stability.