This clinical report describes a 64-year-old woman with a bony defect in the mastoid process after mastoidectomy and who experienced vertigo on cold and windy days during winter. The patient noticed that packing a piece of paper or cotton into the defect prevented the vertigo. The patient refused surgical repair, so a silicone prosthesis was fabricated to fill the defect completely. Electronystagmography confirmed the effectiveness of the prosthesis to prevent nystagmus. Although surgical repair is ideal, prosthesis repair of the defect may prove to be effective in some patients.