A Brighton man was found lying on a pavement with a serious head injury early on Saturday (16 July).
The 39-year-old was found in Chatham Place, Brighton, near the junction with Howard Terrace, close to the Seven Dials.
He was taken to Hurstwood Park Neurosciences Centre in Haywards Heath for an emergency operation.
The man cannot remember how he ended up injured and Sussex Police said that detectives did not whether he had been attacked.
He is thought to have been walking home after a night out in town and is believed to have walked past Brighton Railway Station although his exact route is unknown.
Detective Sergeant Helen Paine, of Brighton and Hove CID, said: “The man remains in a serious condition in hospital and we are working to establish exactly how he may have received this injury.
“We would like to hear from anyone who may have seen this male walking in Brighton between 4am and 6.30am on Saturday.”
The man, who was found at about 6.30am, was described as a thinly built white man with dark hair.
He was wearing a black jacket, blue jeans and white trainers.
Anyone with information is asked to contact Sussex Police on 0845 6070999 or the independent charity Crimestoppers anonymously on 0800 555111.
