What are the first signs a neuro looks for if there has been dramatic significant damage to all nerve cells throughout the body ?

Nerve damage: This question is very general and a complicated topic for discussion. To simplify the answer I would say it depends on which nerve cell is damaged, Peripheral or central. Central cells are located in our brain and spinal cord and base on the location of them their function is different and therefore their damage manifests differently and this is true for the peripheral one,too.