Table 1. Computed tomography grading systems for otosclerosis.
| A- SYMONS / FANNING CLASSIFICATION | |
|---|---|
| CT Grading | Foci Location |
| Grade 1 | Solely fenestral |
| Grade 2 | Patchy cochlear disease (with or without fenestral involvement) |
| To basal turn (grade 2a) | |
| To middle turn (grade 2b) | |
| Around the lateral aspects of the basal, middle and apical turns (2c) | |
| Grade 3 | Diffuse and confluent cochlear involvement (with or without fenestral involvement) |
| B- ROTTEVEEL CLASSIFICATION | |
| CT Grading | Foci Location |
| Type 1 | Fenestral only (thickened footplate and/or narrowed or enlarged windows) |
| Type 2 | Retrofenestral disease (with or without fenestral involvement) |
| Double ring effect (grade 2a) | |
| Narrowed basal turn (grade 2b) | |
| Double ring effect and narrowed basal turn (2c) | |
| Type 3 | Severe retrofenestral involvement (unrecognizable otic capsule), with or without fenestral involvement |
| C- VEILLON CLASSIFICATION | |
| CT Grading | Foci Location |
| Type 1 | Isolated involvement of the footplate, which is thickened (> 0.6 mm) and hypodense (1a) |
| Anterior fenestral hypodensity ≤ 1 mm (1b) | |
| Type 2 | Anterior fenestral hypodensity > 1 mm, without contact of the focus with the cochlear endosteum |
| Type 3 | Anterior fenestral hypodensity > 1 mm and with contact of the focus with the cochlear endosteum |
| Type 4 | Anterior labyrinthine hypodensities, that is, around the cochlea (4a) |
| Posterior labyrinthine hypodensities, that is, around the semicircular channels or the vestibule (4b) | |
Abbreviation: CT, Computed tomography.