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.