# Bow and lean test reconsidered: anatomy, predictions, and a data visualization method for horizontal canal BPPV

## TL;DR

This paper re-examines a diagnostic test for a type of vertigo by correcting anatomical assumptions and proposing a new visualization method to improve diagnosis accuracy.

## Contribution

The paper corrects a prior anatomical model and introduces a new method to distinguish the affected side in horizontal canal BPPV.

## Key findings

- The true anatomy of the horizontal canal leads to different nystagmus patterns than previously modeled.
- A roll maneuver from supine to prone can help identify the affected side based on nystagmus patterns.
- A new data visualization method is introduced to compactly represent these diagnostic findings.

## Abstract

In the diagnosis of horizontal canal benign paroxysmal positional vertigo, it is challenging to lateralize the affected side. The “bow and lean test,” and several methods built upon it, have been proposed. Many of these techniques are based on a model in which the horizontal canal’s putative anatomy involves an anteromedial segment. The actual anatomy has a posteromedial segment. We show that predictions of a model based on the hypothetical anatomy differ from those based on the true anatomy. We further show that the true anatomical model predicts that for a roll maneuver that begins in the supine position, going from the side-lying position to the prone position should generate different patterns of nystagmus depending on which side is affected; this should distinguish which side is affected, and thus has implications for treatment. We conclude with a data visualization method that depicts these findings compactly.