The lawsuit identifies the child who was severely injured and went into cardiac arrest that night as Zynae Green.
"The incident at National Harbour was a tragic accident and we are all heartbroken that Zynae Green and her family continue to suffer," MGM spokeswoman Debra DeShong said in a statement. "We are committed to continue working with the family's representative to reach a resolution. In the meantime, we will respond to this lawsuit in the appropriate venue, which is in court."
Whiting-Turner and Rosendin Electric did not immediately respond to requests for comment on the complaint.
Zynae, who turned 7 on Sunday, cannot speak, walk or move her limbs, said the family's lawyer Benedict Morelli. She is able to track people with her eyes, which she could not do a month ago, but doctors say few substantial improvements are expected, Morelli said.
"This is about the absolute need to take care of this girl for the rest of her life," Morelli said. "She'll never be much more than what she is. She'll never go to college or get married."
DeShong said MGM had offered to assist with medical expenses but had been rebuffed. Morelli said MGM has offered "nothing" to the family.
"If in fact someone said they made an offer then I would love to hear what it is," Morelli said.
According to the lawsuit, Zynae has been moved to an acute rehabilitation facility for 24-hour medical care after spending two months in the hospital.
"Her life-altering injuries will tremendously impact her and her family's lives moving forward," the lawsuit states.
The lawsuit seeks damages to cover the cost of Zynae's medical care for the rest of her life in an amount exceeding US$75,000, plus lawyer's fees.
Zynae's siblings, 5-year-old Carlos Green, and 16-year-old Monya Rosier, were also shocked by the electrified handrail and hospitalised for days from their injuries, the lawsuit states. The children's mother, Rydricka Rosier, was also shocked when she tried to pull her children off the handrail.
The claim stems from events the night of June 26, when Zynae and her family were near an outdoor fountain area on the west side of the Maryland property.
Zynae had been swinging on a lighted metal handrail that had become electrified due to improper installation and faulty wiring, according to the report of an independent engineer hired to review the incident by Prince George's officials. The bad wiring violated several county building codes and should not have passed the permitting and inspections process, according to the engineer's report.
The independent engineer described the wiring feeding the lighting on the handrail as "terrible" and some of the "sloppiest work" he had ever seen.
The engineer's report confirmed details in a preliminary assessment obtained by the Washington Post that said the handrail was improperly installed and used the wrong type of wiring for the LED lights that were on the railing. The engineer's report and the preliminary assessment said the railing was installed at too shallow a depth, allowing the handrail to wobble and fray protective coatings on wiring that exposed bare wiring that came in contact with the metal railing.
Investigators also found a device known as an LED driver - designed to cut 120 volts to 12 volts for the lighting on the underside of the handrail - failed.
When Zynae touched the electrified rail and swung her legs to touch another rail, she was jolted with 10 times the flow of electricity intended to power the lights, the county assessments stated.
Zynae went into cardiac arrest, but the property did not have a defibrillator immediately available to render emergency aid, the lawsuit asserts. Morelli said that if there had been a defibrillator on the scene that paramedics could have used right away, then Zynae would not have lost as much oxygen to her brain, and her condition might not be as bad as it is.
