Skin Incision
- An arch line is marked with a pen from the root of the zygoma to the midline.
- For better cosmetic, starting the incision in between 35 and 40 mm anterior to the tragus, where the skin folds, as is done in a facial lift. The patient’s hairline is set as the anterior limit of the incision to avoid noticeable scars.
- The incision is staged into short segments and hemostasis is achieved before proceeding with the next segment. Homeostatic Raney clips are applied to the scalp edges as needed.
- Skin incision
- From superior temporal line → midline
- Cut down to bone
- Including the pericranium and galea aponeurotica (if the pericranium does not need to be preserved).
- From Zygoma → Superior temporal line
- Cut down to superficial temporalis fascia
- A two-layer dissection of the scalp is performed elevating the scalp apart from the temporalis muscle, exposing the superficial temporalis fascia to proceed with an interfascial or submuscular dissection afterwards.
- Cutting too far back from root of zygoma can cut into the TMJ
Reflexion of scalp and galea
Frontalis branch
- Aka Temporal branch
- The frontal branches of the facial nerve course in a fat pad in the anterior temple area between the superficial layer of temporalis fascia and the galea, where they could be damaged during in the subgaleal elevation of the scalp flap.
- Pitanguy line facial nerve protection during pterional approaches
- 0.5 cm below tragus and 2 cm above eye brow, along zygoma to lateral orbital rim location of frontalis branch of facial nerve
- Ways to protect the nerve
- If only the superficial and not the deep fascia is elevated
- The superficial temporalis fascia covers the temporalis muscle and attaches it to the superior temporal line and to the zygomatic arch.
- Before attaching to the zygomatic arch the superficial temporalis fascia splits in two layers
- Superficial
- Deep
- The fronto-temporal branch of the facial nerve runs in a fat pad within the two layers of the superficial temporalis fascia.
- With the skin flap elevation, the superficial layer of the temporalis fascia and the superficial temporal fat pad are exposed.
- The superficial layer of the superficial temporalis fascia is incised in an arching fashion and elevated together with the underlying fat pad that contains the facial nerve.
- If required and if retraction on the skin flap will be prolonged, the dissection can continue down until the arch of the zygoma.
- Preserving the fat pad will prevent injuring the nerve from retraction pressure. Finally, the fat pad is carefully retracted anteriorly and the temporalis muscle covered by the deep layer of the superficial temporalis fascia is exposed.
- Mr Laraway: Stay on the deep layer of the temporal fascia: i.e. stay as close as to the muscle surface will keep the frontotemporal branches safe.
- If both layers of the temporal fascia are elevated and reflected downward.
- The temporalis muscle is incised and elevated together with the superficial temporalis fascia without proceeding with the interfascial dissection.
- Compared with the interfascial technique, the submuscular dissection lowers the risk of facial nerve injury but restricts the working space.
- In both interfascial and submuscular dissections, the deep temporal artery — branch from the internal maxillary artery — may be preserved as the main blood supply for the temporalis muscle.
Interfascial
Subfascial/submuscular dissection technique
Superficial temporal artery
- The temporal artery can be injured at the most caudal part of the skin incision during pterional craniotomy
- Blunt dissection down to the level of the temporalis fascia is used in this region to preserve the superficial temporal artery.
- The skin flap is elevated and retracted anteriorly and the superficial temporalis fascia is exposed
- Sacrificing the superficial temporal artery can compromise the vascularization of the skin flap. A well-vascularized skin flap is important to achieve good cosmetic results and is also important in those cases when adjuvant radiotherapy will be needed.
Temporal muscle mobilisation
- The temporal muscle must be detached from the calvarium:
- To expose the anterior temporal fossa area:
- The muscle must be detached from its anterior and superior insertion and folded downward and backward, as in the classic pterional approach.
- ROK:
- Detach the anterior temporalis muscle from the (superior/inferior) temporal line
- Follow this as back as needed (the whole craniotomy)
- At the posterior margin of the skin incision cut caudally towards the zygoma
- Anteriorly Cut down at the Keyhole and reflect muscle inferior and anteriorly
- To expose the posterior temporal fossa area:
- Necessary to section a small anterior portion of the muscle parallel to the zygomatic arch, but this may result in masticatory symptoms and cosmetic deformity.
- Freeing the muscle from its posterior and superior insertions and mobilizing it anteriorly allows exposure of medium and posterior part of the middle fossa only,
- To expose the whole temporal fossa
- Detaching the muscle from its superior, anterior, and posterior attachments, plus sectioning the zygomatic arch and displacing it downward with the masseter, allows the temporal muscle to be reclined downward through the breach in the arch.
- The temporalis muscle is incised along the superficial temporal line, dissected subperiosteally and elevated laterally.
- Careful subperiosteal elevation of the muscle using a sharp periosteal elevator offers the best chance of preserving the neural innervation, arterial supply, and venous drainage of the muscle, which courses directly on the periosteal surface
- Hot cutting current to elevate the delicate neural and vascular structures on the deep surface of the muscle → in atrophy of the muscle → masticatory symptoms + a poor cosmetic result.
- It is important to keep 1 cm cuff of muscle attached to the bone for posterior reattachment.
Craniotomy
- Depending on the surgeon’s preferences and the tumor location, one to five burr holes are drilled for the craniotomy. We suggest placing as many as three burr holes, and under the muscle for better cosmetic results:
- Keyhole
- Located
- Above the fronto-sphenoidal suture
- Below the superior temporal line
- Posterior to the fronto-zygomatic suture.
- The keyhole has the anterior fossa dura in its upper margin and the periorbita in its lower margin. The inset shows the burr holes and bone flap.
- At the most posterior point just below the superior temporal line (and below the muscle cuff).
Flattening sphenoid wing
- Drill Medial sphenoid wing
- Too aggressive removal of sphenoid ridge can lead to injury of the
- 3rd nerve
- Orbit
- Bridging deep anterior cerebral vein
- Meningo-orbital band
- Needs to be cut
- Medial limit of medial sphenoid wing
Step wise pterional craniotomy procedure for exposing the temporal lobe
A., artery; Cent., central; Fiss., fissure; Front., frontal; Frontozygo., frontozygomatic; Inf., inferior; M., muscle; Mid., middle; N., nerve; Postcent., postcentral; Precent., precentral; Squam., squamosal; Sup., superior; Supramarg., supramarginal; Temp., temporal; V., vein; Zygo., zygomatic.
- Skin incision, which extends more posteriorly above the ear than with the usual pterional craniotomy.
- The scalp and temporalis muscle have been elevated to show the bone flap for a temporal lobectomy.
- The bone flap, centered below the squamosal suture, will be smaller if only a transsylvian or transbasal or direct temporal lobectomy is needed and will be larger if cortical mapping and electrocardiography are to be carried out.
- A cuff of fascia remains attached along the superior temporal line to aid in a closure.
- In this exposure, the superficial layer of temporalis fascia has been incised and folded down with the galea to preserve the branches of the facial nerve to the frontalis muscle, which course on the outer surface of the temporalis fascia.
- Subfascial approaches in which both the superficial and deep layers of temporalis fascia are elevated to preserve the branches of the facial nerve.
- The authors prefer the interfascial shown in B. It is best to avoid cutting into the muscle, which may result in scarring, atrophy, cosmetic deformity, and disorders of mastication.
- The careful handling of this muscle is important in obtaining a good cosmetic result. The arterial supply, venous drainage, and nerve supply all course on the deep surface of the muscle directly on the periosteal surface of the bone.
- Using a hot cutting current to elevate the muscle will often damage the muscle’s nerve and vascular supply with resulting temporalis atrophy and a poor cosmetic result.
- It is best to elevate the muscle using careful subperiosteal dissection with a sharp periosteal elevator.
Exposure of the right temporal lobe used in cases in which the preoperative studies have clearly defined a lesion in the medial temporal lobe and there is no need to expose the area above the sylvian fissure.
- More extensive exposure above the sylvian fissure is used if cortical mapping and electrocardiography are needed to define the extent of resection and the seizure focus.
- Pterional exposure used for the transsylvian-transinsular and transsylvian-transcisternal approaches.
- The insert shows the site of the scalp incision.
- Magnetic resonance imaging scan with image guidance showing the operative trajectory both before and after dividing the zygomatic arch.
- The green image shows the trajectory obtained if the zygomatic arch remains and the muscle is folded downward over the upper edge of the arch.
- The yellow image shows the lower trajectory obtained after dividing the zygomatic arch and folding the muscle down between the divided edge of the arch.
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