Oksana Grigorieva was diagnosed with a concussion two days after she fought with Mel Gibson, RadarOnline.com is reporting exclusively.

The diagnosis can be a crucial part of the criminal and civil investigations into Gibson’s behavior, providing documentation for Oksana’s charges and turning her doctor into an important witness.

Oksana's Broken Teeth and The Abrasion on Baby Lucia's Face

Oksana sought treatment from her dentist on January 7 and her doctor on January 8 this year. As RadarOnline.com was first to report, Oksana has told authorities Mel punched her in the mouth and the side of the head while she held their infant daughter Lucia.