Injury to medulla oblongata may prove fatal.

Medulla oblongata is the region of the brain that controls all the involuntary activities. 

Vital activities such as heartbeats, respiration, vasomotor activities, peristalsis, etc. Are under the control of medulla oblongata. 

When medulla oblongata is injured, all these vital functions are instantly stoped. 

Therefore, injury to medulla oblongata causes sudden death.