A healthy dental patient complains of increasing discontineous left sided facial pain. Initially no dental cause could be indentified. When the pain remains present, the 36 is endodontical treated, as this tooth is reacting on thermal stimulation. However, the pain increases. After a couple of days small vesicles occur in the left temporal area and the face. Intra-oraly a black discoularation of the lower left interdental papillea is observed with ulceration up the bony surface. Finally an acute neurodermal viral infection of the second or third branch of the trigeminal nerve with intra- and extra-oral manifestations is diagnosed.