Two masked men forced their way into the 77-year-old's house where the pensioner was sleeping, woke him and demanded the keys to an Audi on the drive.
They then dragged him out of bed and punched and kicked him multiple times before leaving empty-handed.
The victim suffered serious injuries including broken ribs, a dislocated shoulder and a cut lip.
He has since suffered a bleed on the brain, which doctors believe could be due to the assault, and remained in hospital three days after being attacked.
Police are now appealing for information regarding the raid, which took place between 1.20am and 1.45am on Thursday, in Moor Green Lane, in Birmingham.
A spokesman for West Midlands Police said: " Our investigations are in the early stages, but so far there is no CCTV covering the location. However we are asking people to think back if anything seemed unusual at that time, or to check their CCTV to see if there is anything from around that time that might help with our investigation.
"We are also urging anyone who may know these people, who have caused these horrible injuries to this man, to do the right thing and hand them in."
Anyone with information can call West Midlands Police on 101, quoting crime reference number 20/1757136/21.