Following an approximately 4×4cm craniotomy and retraction of the dura of the temporal lobe, exposure of the superior surface of the petrous bone and performance of procedures on the petrous bone or brainstem.

A middle cranial fossa procedure is undertaken for facial paralysis due to a longitudinal fracture, or for Bell palsy; it is also carried out in different neurotologic procedures such as acoustic neuroma surgery.

The critical anatomical structures in the middle cranial fossa approach are indicated in the diagrams. The relationship of these critical structures to one another is highlighted. The diagrams show the superior view, as in the approach through the middle cranial fossa, of the anatomical structures in the left surgical site.

BC: Basal turn of cochlea

CP: Cochleariform process

GSPN: Greater superficial petrosal nerve

I: Incus

IAC: Internal auditory canal

LFN: Labyrinthine facial nerve

M: Malleus

SSC: Superior semicircular canal

SVN: Superior vestibular nerve

TFN: Tympanic facial nerve

V: Vestibule

VFT: Vestibulofacial triangle

Following dissection of the soft tissues, the temporal bone is ready for the procedure. In the first stage, the cortical bone at the zygomatic root is drilled with a large burr. During the operation, the craniotomy and temporal lobe retraction must be done beforehand.

II: 7mm cutting burr

MIL: Zygomatic root

EAC: External auditory canal

SSP: Superior surface of petrous bone

ZR: Zygomatic root

The anterior part of the cortical bone at the zygomatic root has been removed. The important anatomical areas and structures located on the superior surface of the petrous bone are indicated in the figure.

AE: Arcuate eminence

HF: Hiatus facialis

MP: Meatal plane

TG: Trigeminal ganglion

TT: Tegmen tympani

Working with the same burr, the posterior part of the cortical bone at the zygomatic root is extirpated. In this way, the cortical bone of the squamosa is brought to the same level as the superior surface level of the petrous bone, allowing better exposure of the deep structures, and in the operation, less retraction of the temporal lobe.

There are very few recognizable surgical landmarks in middle cranial fossa approach because the anatomical structures are hidden within the bone. For this reason, each additional landmark is important. The microsurgical instrument in the figure is pointing to one of these landmarks, the arcuate eminence.

The tegmen tympani, which is located lateral and posterior to the hiatus facialis, is another key landmark to be noted in this procedure. The microsurgical instrument in the figure is pointing to this landmark.

The blue-line technique will be carried out on this temporal bone. Using first a medium-sized cutting burr and then a diamond burr, the arcuate eminence is drilled beginning posteriorly and going anteriorly, and the blue line of the superior semicircular canal is identified.

II: 3–4mm cutting and diamond burrs

MIL: Arcuate eminence

MMA: Middle meningeal artery

TG: Trigeminal ganglion

TN: Trigeminal nerve