Whiplash injury is caused due to -
Whiplash injury results from acute hyperextension of the cervical spine in the region of C4-C6 vertebrae.
Note: Both hyperflexion and hyperextension (i.e. flexion followed by hyperextension) are involved in the mechanism of whiplash injury. But it is hyperextension which causes damage to the spinal cord.
A fall from a height
Acute hyperextension of the spine
A blow on top to head
Acute hyperflexion of the spine