Assessing stapes piston position using computed tomography: a cadaveric study.
OBJECTIVE
Temporal bone computed tomographic (CT) scanning in the postoperative stapedotomy patient is inaccurate in assessing stapes piston position within the vestibule.


BACKGROUND
Poststapedotomy patients that have persistent vertigo may undergo CT scanning to assess the position of the stapes piston within the vestibule to rule out overly deep insertion. Vertigo is a recognized complication of the deep piston, and CT evaluation is often recommended. The accuracy of CT scan in this setting is unestablished.


METHODS
Stapedotomy was performed on 12 cadaver ears, and stainless steel McGee pistons were placed. The cadaver heads were then scanned using a fine-cut temporal bone protocol. Temporal bone dissection was performed with microscopic measurement of the piston depth in the vestibule. These values were compared with depth of intravestibular penetration measured on CT scan by 4 independent measurements.


RESULTS
The intravestibular penetration as assessed by computed tomography was consistently greater than the value found on cadaveric anatomic dissection. The radiographic bias was greater when piston location within the vestibule was shallower. The axial CT scan measurement was 0.53 mm greater, on average, than the anatomic measurement. On average, the coronal CT measurement was 0.68 mm greater than the anatomic measurement. The degree of overestimation of penetration, however, was highly inconsistent.


CONCLUSIONS
Standard temporal bone CT scan is neither an accurate nor precise examination of stapes piston depth within the vestibule. We found that CT measurement consistently overstated intravestibular piston depth. Computed tomography is not a useful study in the evaluation of piston depth for poststapedectomy vertigo and is of limited value in this setting.
Hahn
Yoav
Y
Department of Otolaryngology-Head and Neck Surgery, University of California-Davis Medical Center, Sacramento, California 95817, USA.
Diaz
Rodney
R
Hartman
Jonathan
J
Bobinski
Matthew
M
Brodie
Hilary
H
D002102:Cadaver; D006801:Humans; D008416:Mastoid / Q000033:anatomy & histology; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D013199:Stapes / Q000000981:diagnostic imaging*; D013201:Stapes Surgery; D014057:Tomography, X-Ray Computed; D014717:Vertigo / Q000601:surgery; D014722:Vestibule, Labyrinth / Q000000981:diagnostic imaging*