How can we differentiate between serous and purulent labyrinthitis?

how to decide whether a lesion is paretic or irritative?
Like in this question, how can we differentiate between serous and purulent labyrinthitis?

Serous labyrinthitis is during the phase of labyrinthitis where pus has not yet formed ie before purulent labyrinthitis. In purulent labyrinthitis there is pus formation and destruction of labyrinth .

So serous is irritative whereas purulent is destructive lesion of labyrinth