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A 19 year old woman reports new imbalance. When she tries to walk, she falls to her right side. She is extremely nauseated, and has been vomiting. Your examination shows a left-beating (jerk) horizontal-rotary nystagmus in primary (straight ahead) gaze position that intensifies on left gaze but is still slightly present on right gaze. The head impulse test appears to be positive when you rapidly move her head to the right.

  • Review Topic

    Where is the lesion?

    Correct! The new imbalance, unidirectional horizontal rotary nystagmus, and the positive head impulse test strongly suggest 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.
    The vestibular imbalance explains why the patient falls to her right. 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.
    Incorrect