[Effectiveness indices in "Particle Repositioning Maneuver" by Parnes and Price-Jones]

The Parnes and Price-Jones "Particle Repositioning Maneuver" (PRM) was used to treat Paroxysmal Positional Vertigo (VPP) in 36 consecutive cases, studying both any induced secondary nystagmus and any persistent Paroxysmal Positional Nystagmus (PPNy) upon repetition of the Hallpike positioning after 15 minutes (re-test). The purpose of the study was to evaluate the ability to use secondary Ny and the retest to predict maneuver effectiveness. Although the PRM was quite effective (PPNy disappeared in 86% of the cases after a single session), the low observation frequency reduced the feasibility of using secondary Ny. On the other hand the systematic introduction of the Hallpike re-test into clinical practice does not offer the desired cost/benefit ratio because of the time required to prevent false negatives due to PPNy fatigue. In fact, secondary Ny was only evoked in 12 out of 36 cases (33%) and of these only 9 out of 36 (25%) presented direction congruous with canalolith release (liberating Ny). The predictive value of evoked liberating Ny appeared further reduced by the persistence of PPNy upon subsequent re-testing in two cases and in one case by the persistence of the disorder upon follow-up. The Hallpike test appears a more reliable indicator of effectiveness as it proved in agreement with subsequent clinical findings in 80% of the cases. The present results lead one to conclude that, when using PRM in cases where no secondary liberating Ny was found (75%), we should rely on the high effectiveness of this procedure (86% of the cases resolved in a single session) rather than perform a Hallpike retest. Thus it is possible to select a small number of patients (22%) still presenting PPNy (positive retest) and requiring repetition of the therapeutic maneuver.