Mechanisms & Levels of Injury
Avulsion, Ganglion, Roots
Mechanisms of Injury
High velocity accident, associated bone and vascular trauma may aggravate the nerve lesions.
Generally the upper roots have stronger protective anatomical structure as compared to lower roots and this can explain, in total palsies, the quite constant avulsion of lower roots
from the spine as compared to upper roots more frequently ruptured outside the spine.
Frequently the accidental impact of the upper limb with the obstacle can provoke severe bone lesion at the level of the shoulder and the nerve lesion will be situated more distally from the spine, at the level of the cords.
The association with scapula, clavicle, and humerus fractures is very frequent in these type of lesions. This fact leads to the possibility of a double level of nerve lesions that can complicate either the diagnosis and the surgical treatment.
Less frequently the plexus can be directly damaged by a cutting mechanism which is more likely provoked by a work accident or by voluntary infliction.
In these cases the nerve lesions will be less extended even if the frequent association with vascular lesions (subclavian and/or axillary artery) can seriously aggravate the prognosis rendering more urgent the surgical treatment.
Level of Injury
Faced to a traumatic brachial plexus lesion the questions we must answer to are the following:
- Which are the damaged roots?
- Which is the level of lesion? (pre or postganglionic?)
- Is there a double level lesion?
Which part of the plexus has been damaged?
Which is the level of root’s lesion?
MRI image of avulsion of C8 root