Enlargement of the cortical mastoidectomy until all the neighboring structures have been completely skeletonized. There is no specific classification or terminology for this procedure in the surgical literature. It may be called extended cortical mastoidectomy.

This procedure is an intermediate stage in neurotologic procedures such as translabyrinthine surgery. It may be also carried out during intact canal wall surgery for chronic otitis media.

Dissection is continued in the same bone in which a cortical mastoidectomy, posterior tympanotomy and epitympanotomy have been carried out. The dural plates of the middle cranial fossa and sigmoid sinus, and the digastric ridge have already been exposed. The bone around the sinodural angle is carved out with a medium-sized cutting burr.

II: 3–4mm cutting and diamond burrs

MIL: SS and MCF dural plates

DR: Digastric ridge

EAC: External auditory canal

MCF: Middle cranial fossa (dural plate)

SS: Sigmoid sinus (dural plate)

The bone at the sinodural angle has been drilled and the sinodural angle skeletonized. It is important to keep in mind that intracranially this angle corresponds to the superior petrosal sinus.

SDA: Sinodural angle

In the next stage, the interlabyrinthine, retrolabyrinthine, and retrofacial cells are exenterated by means of differentsized cutting burrs.

II: 2–3mm cutting burr

MIL: Hard bone of labyrinth

ILC: Interlabyrinthine cells

RFC: Retrofacial cells

RLC: Retrolabyrinthine cells