Dr Balagopal, Medical Superintendent, told PTI that the patient's condition was now 'stable'. Both his hands have been amputated and he sustained minor head injuries.
A case has been registered against the unidentified men under IPC sections 326 (voluntarily causing grievous hurt by dangerous weapons or means), 341 (punishment for wrongful restraint) and 34 (acts done by several persons in furtherance of common intention).
The Government Railway police will probe the case.
The incident, which occurred in the General compartment of the Thiruvananthapuram-Mangalore Malabar Express, came to light after the man regained consciousness last night.
As per the victim's preliminary statement, he boarded the train at Aluva to go to Kollur Mookambika temple in Mangalore.
He found the four inebriated men misbehaving with a woman. When he objected they left, but returned after some time, beat him up and threw him out of the compartment when the train reached Cheruthurthy early yesterday.
The man, hailing from Idukki, works in an Event Management company.