A man who hit a 19-year-old pedestrian with his Mercedes Benz on a Perth street continued home because he thought the sound of impact he heard may have been a rock or brick being thrown at his car, a court has heard.

Sophia Muiruri was a newcomer to Australia from Kenya and was crossing against a red pedestrian signal at a Subiaco intersection when she was struck by David Clarke's luxury vehicle on the night of September 16, 2015.

The woman suffered serious injuries including skull and spinal fractures, and bruising of the lungs.

She suffered serious injuries including skull and spinal fractures, and bruising of the lungs.

The WA District Court heard on Monday that Ms Muiruri underwent surgery to remove part of her skull and relieve pressure on her brain.