Step 1: Two named stress ulcers must be told apart - Curling ulcer follows severe burns, while Cushing ulcer follows an intracranial insult.
Step 2: In Cushing ulcer, a space-occupying brain lesion or traumatic head injury elevates intracranial pressure. This overstimulates the vagus nerve via its nuclei, flooding the stomach with acid and creating deep ulcers that may perforate.
Step 3: Among the choices, head injury is the trigger that raises intracranial pressure. Burns point to Curling, not Cushing, and the remaining options are non-specific.
\[\boxed{\text{Head injury}}\]