Objective: To establish success- or failure-predicting factors in Semont maneuver in the treatment of benign paroxysmal positional vertigo.
Study design: Prospective study.
Setting: Referral center, institutional practice, ambulatory care (outpatient clinic).
Patients: A consecutive sample of 135 patients diagnosed with unilateral benign paroxysmal positional vertigo of posterior semicircular canal for 3 years (September 2007 to August 2010).
Intervention: Semont maneuver.
Main outcome measures: Duration of the latency period and nystagmus status with the Dix-Hallpike test. Presence or absence of orthotropic nystagmus in the second position of the Semont maneuver. Effectiveness of the Semont maneuver (cure versus no cure).
Results: The Semont maneuver is effective in 73% of the patients. Orthotropic nystagmus was present in 67% of the cases and absent in 33%; when we found orthotropic nystagmus, the maneuver was effective in 81% of the patients, but only in 57% if this nystagmus was not present (Fisher's exact test, p = 0.004; odds ratio, 3.308; 95% confidence interval, 1.492-7.334). The maneuver's efficacy and the presence of orthotropic nystagmus were not affected by the duration of nystagmus status in the Dix-Hallpike test. The duration of the latency period had no effect on the maneuver's efficacy, but it did affect the appearance of orthotropic nystagmus (Mann-Whitney test, p = 0.016).
Conclusion: The presence of orthotropic nystagmus in the second position of the Semont maneuver indicates a good prognosis, but its absence does not necessarily mean that the maneuver will fail. Orthotropic nystagmus is more common in patients with shorter latency periods, suggesting that its appearance is related to cupulolithiasis mechanisms.