Congenital dehiscence in the posterior semicircular canal.
OBJECTIVE
Posterior semicircular canal dehiscence (PSCD) may be of congenital origin.


BACKGROUND
PSCD is characterized by the lack of bone coverage, which results in its lumen being exposed to the meninges of the posterior cranial fossa or to the gulf of the jugular vein. It has an incidence of 0.2%. Its presence has been associated with several well-defined entities, although a congenital origin has not been proven.


METHODS
We have analyzed, from a macroscopic, microscopic, and radiologic (computed tomography) viewpoint, the right temporal bone of a 32-week-old human fetus that presented a defect in the bone coverage located in the rear.


RESULTS
The macroscopic study showed a solution of continuity in the posterior semicircular canal, with elliptic morphology and smooth edges. This defect was 3.4 mm long with a width that varied between 0.67 mm in its apical portion and 1.42 in the basal portion. The radiologic study (computed tomography) showed the absence of bone coverage of the posterior semicircular canal, which was open to the intracranial space in the posterior fossa. Its histologic study showed good bone coverage of this canal at the expense of compact bone tissue. However, at the medial end, there is a lack of bone coverage, resulting in the lumen of the canal being open to the intracranial space. The bone edges of the defect did not present any osteoclast activity.


CONCLUSIONS
The lack of bone coverage (dehiscence) of the posterior semicircular canal in a 32-week-old fetus suggests a congenital component of bony dehiscences of this canal. Even so, this single finding does not conclusively prove the congenital component, and the dehiscence is a finding that can be part of and not by itself a syndrome.
Department of Human Anatomy and Histology, School of Medicine, University of Zaragoza, Zaragoza, Spain. jwhyte@unizar.es
Jaime
J
Whyte
Ana Isabel
AI
Cisneros
Claudio
C
Martínez
Borja
B
Gracia-Tello
Ana
A
Whyte
Rafael
R
Crovetto
Miguel Ángel
MÁ
Crovetto
D000328:Adult; D005260:Female; D005333:Fetus / Q000473:pathology; D006801:Humans; D007759:Labyrinth Diseases / Q000151:congenital* / Q000000981:diagnostic imaging / Q000473:pathology*; D011247:Pregnancy; D012665:Semicircular Canals / Q000000981:diagnostic imaging / Q000473:pathology*; D013701:Temporal Bone / Q000000981:diagnostic imaging / Q000473:pathology; D016707:Tissue Fixation; D014057:Tomography, X-Ray Computed