Correct! The combination of new falling, unidirectional horizontal rotary nystagmus, and a positive head impulse test strongly suggests an acute right peripheral vestibulopathy. It has upset the balance between the right and left vestibular pathway inputs. The right-sided lesion produces a drift of the eyes toward the right, which is met by compensatory leftwardly directed saccades, making up a left jerk nystagmus. The nystagmus remains left-beating in all three positions of horizontal gaze, a feature relatively unique to acute peripheral vestibulopathy.  

The positive head impulse test, which can be difficult to interpret in the presence of nystagmus, supports a peripheral lesion.   A common cause for this condition is “vestibular neuritis/neuronitis,” attributed to a virus. It can be frightening to patients and examiners and very unpleasant. In that condition, there is good evidence of reactivation of herpes simplex type 1 virus in the vestibular ganglia. A large trial showed no benefit of anti-viral therapy, but symptoms resolved more quickly in patients treated with prednisone 1mg/kg for 10 days. Therefore, steroid is often prescribed once the diagnosis is ascertained. Meclizine is also often prescribed for nausea.

In this patient, the manifestations rapidly lessened and disappeared completely within 10 days.