3D Models Related Images

Comparison of the Retrosigmoid and the Various Modifications of the Presigmoid Exposure

Surgical Correlation

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G, Deep exposure with the minimal mastoidectomy with retraction of the vestibulocochlear and glossopharyngeal nerves, to be com-pared with the retrosigmoid approach shown in C. The exposure is similar to that obtained with the retrosigmoid approach. H, Retrolabyrinthine approach in which more extensive drilling of the mastoid has been completed to expose the osseous capsule of the semicircular canals. I, The dura has been folded forward after completing the retrolabyrinthine exposure. The exposure differs little from that obtained with the minimal mastoidectomy exposure shown in F and G. J, The exposure with the posterior canal partial labyrinthectomy is similar to that achieved with the minimal mastoidectomy. K, The partial labyrinthectomy has been extended by removing the superior canal in addition to removal of the posterior canal. L, The infratentorial exposure does not differ significantly from that achieved with the minimal mastoidectomy, as shown in F and G. Removal of the superior canal reduces the required temporal lobe retraction and aids in the exposure along the middle fossa floor and petrous apex. M, Translabyrinthine exposure in which the semicircular canals and the vestibule have been removed. This adds the internal auditory canal to the exposure, but does not improve the exposure of the structures medial to the meatus, as compared with the minimal mastoidectomy or even the retrosigmoid approach. N, The facial nerve has been transposed posteriorly out of the field and the cochlea has been removed to complete the transcochlear approach. This approach greatly improves access to the front of the brainstem, clivus, and basilar artery, but is done at the cost of a temporary or permanent facial paralysis and loss of hearing. (Images courtesy of AL Rhoton, Jr.)

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