Learning objectives
To describe CT and MR findings of Superior Semicircular Canal Dehiscence (SSCD) associated to Tegmen Tympani Defect (TTD) and encephalocele in patients studied for conductive hearing loss.
Background
SSCD
Superior Semicircular Canal Dehiscence (SSCD) is described as the absence of the bony covering of the superior semicircular canal.
This creates a virtual third mobile window,
other than the oval and round existing ones,
and the sound is transmitted to the vestibular system causing vertigo by excitation of the cupula creating dizziness and nystagmus.
This third window also leads the sound away from the cochlea and hence causes conductive hearing loss in some individuals.
It also may remain asymptomatic.
Superior canal dehiscence probably arises...
Findings and procedure details
We present findings on CT performed for conductive hearing loss in two patients showing associated SSCD with tegmen tympani defect.
In our patients we observed absence of the bony coverage of the superior semicircular canal,
tegmen tympani defect and meningoencephalocele in the middle ear in contact with the inner-ear bones.
Both,
encephalocele with bone fixation and SSCD can be a cause of conductive hearing loss.
We have used a 64 multidetector scanner in bone window with axial,
coronal and oblique reconstructions of the petrous bone.In...
Conclusion
Superior semicircular canal dehiscence might coexist with tegmen tympani defect and must be suspected by the radiologist.
Both can be bilateral or unilateral,
asymptomatic or cause several auditory or vestibular manifestations.
It is imperative a careful evaluation of the superior semicircular canal in conductive hearing loss studies,
looking for SSCD and associated TTD with small encephaloceles or CSF leak signs.
Personal information
Dr.Ana María García Correa.
MD Department of Radiology,
Hospital Universitari Sagrat Cor.
Barcelona- Spain.
[email protected]
Dr.
Elisenda Grivé Isern.Chief,
Division ofNeuroradiology.
Hospital Universitari Sagrat Cor.
Barcelona - Spain.
References
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Braca et al.
Cerebrospinal Fluid Leakage from Tegmen Tympani Defects Repaired via the Middle Cranial Fossa Approach.
J Neurol Surg B Skull Base.
2013 Apr; 74(2): 103–107.
2.
Crovetto M,
Whyte J,
Rodriguez OM,
et al.
Anatomo-radiological study of the superior semicircular canal dehiscence.
Radiological considerations of superior and posterior semicircular canals.
Eur J Radiol 2010;76:167Y72
3.
Banerjee A,
Whyte A,
Atlas MD.
Superior canal dehiscence: review of a new condition.
Clin Otolaryngol.
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4.A.
Tsunoda,
O.
Terasaki.
Dehiscence of the bony...