I found this source but i don't know whether it is what you are after.
Thrandiul’s sudden scars reflect a little emphasized of Tolkien’s lore:
elves’ “Fëar” (a metaphysical concept analogous translatable as
“soul”) occasionally influences the “Hröa” (the fleshly, physical
body), particularly under moments of extreme stress. This can
manifest as extreme physical changes that reflect the mind’s state, in
this case deep war scars.
Edit : I have also found this reference which seems to state that Tolkien made no reference to the Scars on Thralduin's face in the books.
Thranduil's scars are decidedly non-canon. According to
Tolkien's texts, the last battle Thranduil saw (up to setting in
The Hobbit) was that of the last alliance at the end of The Second
Age. However, in the 1900's of the Third Age, according to text,
the "serpents of the north" were fought and mostly slain. In
all likelihood, Peter Jackson is taking creative liberty with the
story. On a more symbolic note, the scars could represent the pain
Thranduil has endured in war (he watched his father die in the battle
of the last alliance).