Placebo effect in surgery for Meniere's disease: a three-year follow-up study of patients in a double blind placebo controlled study on endolymphatic sac shunt surgery.

In a previously published double blind, placebo controlled study, the efficacy of an endolymphatic sac-mastoid shunt was compared with a purely placebo operation (mastoidectomy) in controlling the symptoms in 30 patients with typical Meniere's disease. Minor differences could be demonstrated after one year between patients with the shunt versus the sham operation, but the greatest difference was between the pre- and postoperative scores, and both groups improved significantly. It was concluded that the impact of the various endolymphatic sac shunts upon the symptoms in patients with Meniere's disease is highly unspecific, and that the 70% improvement in both our groups was most likely caused by a placebo effect. The patients have now been regularly followed for a minimum of 3 years and the symptoms registered whenever present. The results of hearing tests, the patients' own evaluation, and the investigator's evaluation (while still unaware of the type of operation in each patient) show that the 3-year results are the same as our results from the first year: no significant difference could be found between the two groups.