What are the common causes, diagnostic features, and clinical implications of cervical nerve root avulsion, particularly in relation to the brachial plexus?

Cervical nerve root avulsions most commonly occur due to trauma, such as birth-related shoulder traction injuries, and often involve the brachial plexus affecting the upper extremities. Key diagnostic features include pseudomeningoceles on MRI and absent nerve rootlets on myelography. Clinically, patients may present with flail arm syndrome or Horner's syndrome if the lower roots are involved. A common pitfall is confusing it with brachial plexus neuritis, which typically lacks traumatic etiology and pseudomeningoceles.