Torsional nystagmus during head thrust test

A female patient with a BPPV background successfully treated with maneuvers shows in the previous examination and subsequently a rotatory nystagmus of short duration when performing head thrust. Possible causes?

Head

Pathologic Nystagmus

Head Impulse Test

Vertigo

Vestibular Diseases

Joaquín Guerra Gómez

Thanks for your answers. Head shaking was always normal, head impulse test not (torsional nystagmus on the left side, the BPPV was on the left too). In the subsequent visit, positional maneuvers where normal, but head impulse test STILL revealed a torsional nystagmus on the left side. What would be the explanation of it?