[Cochlear otosclerosis and pseudo fourth turn of the cochlea].

Objective: To describe different sequences on magnetic resonance imaging (MRI) in otosclerosis with peri-cochlear involvement.

Method: MRI T1 and T2 sequences with T1 gadolinium injection and computed tomography (CT) scans with millimetric slices on axial and coronal views were obtained. The diagnosis of bilateral otosclerosis was confirmed by surgical exploration.

Results: On the CT scan, there was a fourth turn of the cochlea which appeared on the MRI T1 sequence with an intermediate signal and on the T2 sequences with a high intensity signal. After gadolinium injection, there was signal enhancement, suggestive of active otospongiosis. On the CT scan, there was another lesion in front of the cochlea with endosteal involvement. This was no however visible on the MRI, even after gadolinium infusion, in accordance with inactive otospongiosis.

Discussion: We reviewed the literature concerning MRI and results in otosclerosis.

Conclusion: MRI of the labyrinth with T1 sequences and gadolinium injection can be contributive to the diagnosis of otosclerosis to differentiate inactive from inactive otospongiosis. However, prospective studies must be conducted to confirm this hypothesis.