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Is this upbeating or downbeating ?

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Dix-Hallpike nystagmus upbeating downbeating vertical BPPV interpretation

The circled section is the Dix-Hallpike Right: Sit Head Right test. Here's the interpretation:

Upbeating nystagmus — consistent with posterior canal BPPV (right ear)

Evidence from the trace:

Looking at the circled data panel:
  • Vertical slow phase velocity: Right Eye +10.93°/s, Left Eye +17.21°/s — both positive (upward)
  • Fast Phase Direction: 251.29° — this encodes the torsional-upbeat direction
  • Frequency: 2.49 Hz, Amplitude 3.57°
  • The vertical waveforms show the characteristic burst of nystagmus early (seconds 4–10) that fatigues — a hallmark of BPPV

Why upbeating?

In posterior semicircular canal BPPV, the displaced otoconia cause ampullofugal deflection of the cupula when the head is brought to the Dix-Hallpike position. This activates the ipsilateral inferior oblique + contralateral superior rectus, producing upbeat-torsional nystagmus with:
  • Fast phase directed upward (toward the forehead)
  • Torsional component rotating the upper pole of the eyes toward the dependent (right) ear
  • Latency of a few seconds, duration <1 minute, fatigable on repeat testing

Compare with the top panel (Supine Head Ext. & Right):

That panel shows negative vertical SPV (−23.39°/s), indicating downbeating in extension — this can represent the nystagmus reversing as expected with the posterior canal mechanism, or a different positional response.

Red flag note:

Pure downbeating nystagmus on Dix-Hallpike (without a torsional component) would be a central red flag (cerebellar/brainstem lesion). The nystagmus here is upbeating + torsional, which is the classic peripheral (BPPV) pattern — reassuring.
Bottom line: The circled trace is upbeating nystagmus, consistent with right posterior canal BPPV.
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