[Sign-report: torsional nystagmus from head-shaking in patients with labyrinth lithiasis of the vertical canal].

The clinical picture of Positional Paroxysmal Vertigo (PPV) induced by vertical canal labyrintholithiasis has been clearly described, eliminating previous interpretations of pathogenesis of this disorder. The diagnosis of PPV is based on the well-known picture of positional paroxysmal Nystagmus. The Authors report a clinical sign which has not previously been reported in the literature: torsional Nystagmus induced by the Head-Shaking Test (HST). The Authors encoutered this sign in 30% of the cases of vertical canalolithiasis and in 50% of the cases diagnosed as vertical cupulolithiasis. This sign was also found in patients with a history of prior positional vertigo and in patients who, after treatment with release maneuver, no longer show clinical signs of positional vertigo. Such Nystagmus was not, however, found in the control group (normal subjects and patients suffering from other vestibular pathologies). In the present study the possible pathogenesis of this sign is discussed and some practical implications are considered.