BPPV: what the guideline says

Brief spinning triggered by a change in head position: seconds to under a minute, settling between triggers, provoked by rolling in bed, lying down, or looking up. Between triggers the patient is usually well. That episodic, positional shape is what separates BPPV from an acute vestibular syndrome, where the vertigo is continuous and present at rest.

The distinction matters before any test is chosen. HINTS is a battery for acute, continuous vertigo. Applying it to episodic or positional vertigo is the most common way it is misused, and it is why timing and triggers come first (TiTrATE (Newman-Toker & Edlow, 2015)).

The AAO-HNS guideline defines posterior-canal BPPV on the Dix-Hallpike: vertigo with torsional up-beating nystagmus, a latency period between the position and the onset of nystagmus, and resolution within about 60 seconds (AAO-HNS BPPV guideline (Bhattacharyya et al., 2017), Table 6).

Fatigability — a weaker response on each repeat — is a common finding rather than a criterion. The Bárány Society lists it as supportive, not diagnostic (Bárány Society criteria (von Brevern et al., 2015)). It strengthens an impression; it does not make or break one.

The direction ties to the mechanics. The vertical component beats up and the torsional component beats toward the dependent, undermost ear, matching displaced otoconia stimulating the posterior canal.

The supine head-roll test provokes the lateral canal, and the beat is horizontal rather than torsional up-beating. The guideline covers this canal and names the Lempert roll and the Gufoni maneuver for it (AAO-HNS BPPV guideline (Bhattacharyya et al., 2017)).

Geotropic and apogeotropic responses behave differently and are repositioned differently. Which side is affected is read from the relative intensity of the two roll positions, which is a bedside judgement made with the patient in front of you.

The AAO-HNS guideline does not cover the anterior canal. Claims about it therefore cannot rest on that guideline, and NeuroDash does not attach it to them.

The anterior canal is rare and produces positional downbeat with a torsional component on head-hang. Where it is treated, the deep head-hanging sequence described by Yacovino (2009) is performed the same way whichever side is involved, which is what makes it usable for a canal that cannot be lateralised. A reverse Epley is not supported for this canal, and three-dimensional simulation indicates it moves debris the wrong way (Bhandari et al., 2021).

Down-beating nystagmus on Dix-Hallpike, particularly without a torsional component, is on the guideline’s neurologic red-flag list, alongside periodic alternating nystagmus, gaze-evoked direction-switching nystagmus, baseline nystagmus with no provocation, and failure to respond to repositioning (AAO-HNS BPPV guideline (Bhattacharyya et al., 2017)).

The most reliable rule is that BPPV beats in the plane of the affected canal, in the direction that canal’s stimulation predicts. A beat that fits no canal plane is the finding that matters (Bárány Society criteria (von Brevern et al., 2015)).

Continuous vertigo at rest is a different syndrome and a different examination. There, the head impulse, nystagmus and test of skew are read together, and a normal head impulse in a patient who cannot stand is the dangerous combination (HINTS exam (Kattah et al., 2009)).

Reading these signs quickly is a skill, and it is what the rest of NeuroDash is for. The drill renders the eye movements from a kinematics engine and asks you to make the call, with the answer derived from the same parameters that drew the animation.