Hello, So sorry for the loss of your daughter in law. I believe what you are referring to is a specific finding of NERVE FIBER DAMAGE to the Vagus nerve which was likely found at the level of the innervation of the diaphragm. More globally this sad case illustrates what we call CNS vasculitis and this is not frequently seen in practice but an autoimmune process begins attacking elements of the central nervous system such as cranial nerves (which the vagus nerve is one of 12 pair of such nerves), brain, and/or spinal cord. What happens is not well understood but swelling and inflammation of the blood vessels in the nervous system (in this the vagus nerve) cause damage to the point where the function is lost or altered. In your daughter-in-law s case the damage to the vagus nerve likely made her diaphragm compromised in being able to properly contract which would ve eventually resulted in pneumonia since she couldn t get good solid breaths enough to move secretions from the lungs up and out the bonchi which then, became a focus for infection to set in. The following is a very nice link to the Vasculitis Foundation s website and specifically discusses CENTRAL NERVOUS SYSTEM vasculitides which include the vagal invasion you talk about. They are an excellent group to consult and you may find more information and answers to questions regarding your daughter-in-law that can be of use to the family especially if there are children she s had who may be experiencing odd symptoms such as colds or allergies that don t seem to really go away or are not easily treated with standard medications/precautions. I ve spoken at some of their local chapter meetings on CNS vasculitides and what we look for when someone comes to us with oddball sorts of symptoms in the context of a previously active and healthy person. The devil is always in the details of such cases my dear. https://www.vasculitisfoundation.org/education/forms/central-nervous-system/ Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Dariush Saghafi, Neurologist