Findings
Axial HRCT sections of temporal bone reveal small lucent foci in fissula ante fenestram bilaterally (solid arrows). Oval window and stapes foot plate are also noted (dotted arrows). Middle ear cavities, bony ear ossicles and mastoid air cells are normal.
Diagnosis
Fenestral Otosclerosis
Summary
- Otosclerosis is a unique autosomal dominant otodystrophy of the otic capsule. It is also called ‘otospongiosis’ as it is characterised by replacement of the normal ivory-like enchondral bone by spongy vascular bone.
- It is a cause of conductive, mixed or sensorineural hearing loss in the 2nd to 4th decades of life.
- Otosclerosis is categorised into two types, fenestral and retrofenestral or cochlear. Retrofenestral otosclerosis rarely occurs without fenestral involvement.
- The more common fenestral type of otosclerosis typically occur in the region of the fissula ante fenestram, which is located just anterior to the oval window.
- The classical imaging appearance of cochlear otosclerosis on HRCT is a distinctive pericochlear hypodense double ring (which is also known as the 4th ring of Valvassori).
- The treatment of fenestral otosclerosis is primarily surgical with stapedectomy and prosthesis insertion.
- Patients with retrofenestral otosclerosis are treated medically using fluorides, but may derive significant benefit from cochlear implantation.
Further reads
- Purohit, B., Hermans, R., & Op de Beeck, K. (2014). Imaging in otosclerosis: A pictorial review. Insights into imaging, 5(2), 245–252. https://doi.org/10.1007/s13244-014-0313-9
- Lee TC, Aviv RI, Chen JM, Nedzelski JM, Fox AJ, Symons SP. CT grading of otosclerosis. AJNR Am J Neuroradiol. 2009 Aug;30(7):1435-9. doi: 10.3174/ajnr.A1558. Epub 2009 Mar 25. PMID: 19321627; PMCID: PMC7051554.
Have a vision to collaborate?
Let's Connect
Try a complimentary trial to have a glimpse of our services
