Anatomically, brainstem is constituted of medulla oblongata, pons and
mesencephalon. Traumatic lesions of brainstem most commonly occur on
pontomedullary junction. There are several possible mechanisms of
pontomedullary lacerations. The first mechanism includes impact to the chin,
with or without a skull base fracture, and most often leads to this fatal
injury, due to impact force transmission through the jawbone and
temporomandibular joint. The second mechanism includes lateral and posterior
head impacts with subsequent hinge fractures, where occurrence of
pontomedullary lacerations in these cases may depend on the energy of impact,
as well as on the exact position of the fracture line, but less so on the
head?s movement. The third mechanism includes frontoposterior hyperextension
of the head, due to frontal impact, concomitant with fractures or
dislocations of upper spine. In the fourth mechanism, there is an absence of
direct impact to the head, due to the indirect force of action after feet or
buttocks?first impact. Most of these cases are accompanied by ring fractures
as well. In situations such as these, the impact force is transmitted up the
spinal column and upper vertebrae, and telescopically intruded into the
skull, causing brainstem laceration. The jawbone and other facial bones can
act as shock absorbers, and their fracture could diminish the energy transfer
towards the skull and protect the brain and brainstem from injury. In all the
cases with pontomedullary laceration posterior neck dissection should be
performed during the autopsy, since upper spine injuries are often associated
with this type of injury.
Functional appliance treatment in children with morphologic deviations in the upper spine
