Hello, 

Thanks for reaching out! If you'd like to send a photo, that could be helpful. 

I would recommend scratching the stems to see if the branches are still alive (they will be green if so). If they are alive, they will hopefully re-leaf. Make sure to deadhead, and pay attention to fertilizer and watering. Here is a great UMN Extension article with more information: https://extension.umn.edu/trees-and-shrubs/lilacs

Good luck!