Posterior semicircular canal dehiscence: first reported case series.
OBJECTIVE
To identify clinical, audiological, and vestibular characteristics of posterior semicircular canal dehiscence.


METHODS
Retrospective case review.


METHODS
Tertiary referral center.


METHODS
Twelve patients aged 2 to 67 years identified with posterior semicircular canal dehiscence.


METHODS
Patients identified by suspicious clinical history and examination, confirmed by high-resolution computed tomography. Audiological evaluation included air and bone audiometry, tympanometry, acoustic reflexes, and vestibular evoked myogenic potential testing.


RESULTS
Hearing loss was mixed in 9 patients, conductive in 2 patients, and sensorineural in 1 patient, with downward-sloping configuration being the most common. Imaging revealed that 7 of 12 patients had dehiscence into a high-riding jugular bulb and 1 patient had an enlarged vestibular aqueduct with a Mondini malformation. One patient had Apert syndrome and another patient had microtia/atresia. Vestibular symptoms were more common in the adult patients than in the pediatric patients, with chronic disequilibrium the most common complaint. Vestibular evoked myogenic potential testing confirmed dehiscence with the characteristic response of reduced threshold and higher amplitude compared with healthy patients.


CONCLUSIONS
This is the first reported series of adult and pediatric patients with symptomatic posterior semicircular canal dehiscence. Posterior semicircular canal dehiscence represents a third-window lesion manifesting as hearing loss with vestibular dysfunction. Computed tomography findings of a dehiscent posterior canal can be verified with increased vestibular evoked myogenic potential responses as in other third-window lesions. Patients found to have a high-riding jugular bulb and hearing loss should have specific inspection of the posterior canal to ensure it is not dehiscent.
Department of Otolaryngology and Communication Enhancement, Children's Hospital Boston, Boston, Massachusetts 02115, USA. Quinton.Gopen@Childrens.Harvard.Edu
Quinton
Q
Gopen
Guangwei
G
Zhou
Dennis
D
Poe
Margaret
M
Kenna
Dwight
D
Jones
D000293:Adolescent; D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology; D001844:Bone Conduction / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D007223:Infant; D007759:Labyrinth Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery; D013506:Otologic Surgical Procedures / Q000009:adverse effects; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000473:pathology; D012189:Retrospective Studies; D012665:Semicircular Canals / Q000000981:diagnostic imaging / Q000473:pathology*; D013701:Temporal Bone / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed; D014722:Vestibule, Labyrinth / Q000502:physiology; D055815:Young Adult