The Wales winger, who also has three Lions caps, was tackled in the air by Tigers winger Adam Thompstone and appeared to be lying unconscious on the floor after landing on his neck.
However, he passed the pitchside assessment and was allowed to return to the fray after Saints insisted he did not lose consciousness, with North later tweeting that he lay motionless in order to protect his neck.
The 24-year-old remained conscious the whole time, Saints did admit they did not have full access to the television footage of the incident while conducting the assessment.
"As at every Premiership match, the Saints' medical team has access to video footage to be used to assist the pitchside assessment of injuries," the club said in a statement.
"It is important to note this video footage is not always the full range of replay angles available to the TV viewing audience at home.
"If evidence suggesting a loss of consciousness had been available to the medical team at the time of assessment, George would not have been allowed to return to the field of play."
The club declined to give a timescale on when North would return as they await an independent assessment of the injury, his fifth since 2014, when he received four head blows in five months, including two in the Six Nations game against England in 2015.
The final head injury of those four, occurring in the Premiership match against Wasps in March 2015, forced North to take a five-month break from the sport as he recovered.
In the aftermath of the weekend’s incident, Premiership Rugby confirmed they would be reviewing the incident as part of a normal procedure.
"Every head injury incident that occurs in Aviva Premiership Rugby is assessed by an independent reviewer as part of our procedure to manage concussion," a spokesman said on Saturday.
"This is a world-leading system of assessment to ensure we take a comprehensive look at every incident which involves a potential head injury.
"Player welfare is our No 1 priority so all incidents in our 135 matches are reviewed thoroughly."
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