Simulation Findings
Simulations of possible treatment maneuvers for this patient were created using a 3D model of the inner ear. This generic model (i.e., not specific to the patient described in this case report) was based on reconstructed images from high-resolution computed tomography of the temporal bone (Digital Imaging and Communication in Medicine files). This methodology has been described by Bhandari and colleagues.[14] The orientation of the canals and the angles between the canals were as previously reported.[15] The simulations allowed the placement of the debris in any of the canals and at variable positions within the canal. Given the uncertainty of whether the emergency department physician correctly performed the Epley maneuver on this patient, we simulated both possibilities: a correctly performed Epley maneuver and an extended Epley maneuver.
Simulation 1 (Supplemental Video 3) shows the effect of a correctly performed left ear Epley maneuver on a right ear hcBPPV. When the subject is brought to the head-hanging position in the second step of the maneuver, the debris moves through but not out of the horizontal canal away from the ampulla, which could generate a left-beating horizontal nystagmus. When the subject’s head is turned by 90o to the right side, the debris moves back through the horizontal canal toward the ampulla and could generate a right-beating horizontal nystagmus. Thus, performing the correct Epley maneuver with a hcBPPV of the opposite side causes free-floating otoconia to move within but not out of the offending horizontal SCC. The patient’s hcBPPV symptoms would likely not be resolved.
Simulation 2 (Supplemental Video 4) showed the effect of a left Epley maneuver when the head is turned by 15o more than the usual 45o in the second step of the maneuver, in a right hcBPPV. In this case, when the subject is brought to the head-hanging position, the contralateral horizontal SCC becomes nearly vertical, allowing the debris to move not only within but also out of the right horizontal SCC under the effect of gravity, thus successfully treating a hcBPPV on the contralateral side before the patient is rolled over. Note this simulation also applies to the second stage of an extended Dix-Hallpike maneuver.