A window into the whole story: temporal bone plasmacytoma presenting with a mobile third window

A 63-year-old man presented with imbalance when coughing due to a respiratory tract infection. He had a history of multiple myeloma with a plasmacytoma of the left temporal bone. Examination revealed a positive leftward head impulse test, no spontaneous nystagmus, left-beating positional nystagmus, and left-beating Valsalva-induced nystagmus. Videonystagmography, audiology, and comprehensive vestibular function tests revealed a subtotal left peripheral audio-vestibular loss. Temporal bone computed tomography showed an unchanged bony erosion of the left labyrinth from 2 years prior. Vertigo subsided after treatment of the respiratory tract infection. Although no tumor progression was evident, coughing had triggered a preexisting third mobile window to declare itself.