Accuracy of a Diagnostic Algorithm for the Differential Diagnosis of Vertigo in the Emergency Department: the STANDING.

The STANDING test is a structured diagnostic algorithm based on previously described diagnostic signs or bedside maneuvers, the investigators have logically assembled in four sequential steps.

1. Assessment of nystagmus presence (spontaneous vs positional) 2) Assessment of nystagmus direction 3) Head Impulse Test (HIT) 4) Standing (SponTaneous, Direction, hIt, standiNG: STANDING)

1. First, the presence of nystagmus will be assessed with Frenzel goggles in a supine position after at least five minutes of rest. When no spontaneous nystagmus is present in the main gaze positions, the presence of a positional nystagmus will be assessed by the Pagnini test first and then by the Dix-Hallpike test (5). The presence of a positional, transient nystagmus will be considered typical of BPPV.
2. Instead, when spontaneous nystagmus is present, the direction will be examined: multidirectional nystagmus, such as bidirectional gaze-evoked nystagmus (ie, right beating nystagmus present with gaze toward the right and left beating nystagmus present with gaze toward the left side), and a vertical (up or down beating) nystagmus will be considered signs of central vertigo (Video 3).
3. When the nystagmus is unidirectional (ie, nystagmus beating on the same side independent of the gaze direction) we will performed the Head Impulse Test (HIT)(13). When an acute lesion occurs on one labyrinth, the input from the opposite side is unopposed and as a result, when the head is rapidly moved toward the affected side, the eyes will be initially pushed toward that side and, immediately after, a corrective eye movement (corrective "saccade") back to the point of reference is seen. When the corrective "saccade" is present the HIT is considered positive and it indicates non-central AV, whereas a negative HIT indicates central vertigo(14).
4. Patients showing neither spontaneous nor positional nystagmus were invited to stand and gait was evaluated. When objective imbalance was present they were suspected to have central disease.

STANDING will be performed before imaging test. STANDING results will be unknown to the attending emergency physician and to the panel of experts who will establish the final diagnosis at the end of follow-up of three months. The physician who will perform the STANDING will not know patient's clinical data, except those detectable during the STANDING test.