Basic information
- Gives access to:
- large part of the lateral surface of the temporal lobe
Also facilitates sub-temporal routes
Keep in mind
- Consider whether the patient / location of the lesion are suitable for this type of approach)
- Study carefully available images (CT, MR) to be prepared for anatomical rarities, use different section and projection
- Try to find the best route to the lesion with an avoidance of the excessive exposure and the retraction of brain tissue, otherwise use a different approach to reach the pathology
- Keep in mind the general anatomy (skin layers, temporal muscle, skull bones, brain surface)
- Be aware of possible slight distortion of the anatomy (patient is in the supine position and the head is rotated – effect of the gravity)
- Try to project the anatomy on the skin surface
Highlights
Surface of the temporal lobe, subtemporal route
Anatomy and important anatomical landmarks
- Skull bones – the middle cranial fossa
- Roof of the zygoma
- Tragus
- Temporal muscle, temporal muscle line
- Superficial veins
- Temporal lobe
- Circle of Willis
- Cranial nerves – n. III, n. IV.
Positioning
Body positioning: supine lateral (45°), lateral (90°)
Supine-lateral or lateral position
Head positioning contralateral rotation (0°), lateral tilt (12°), flexion (10°)
Rotation: 90° rotation contralaterally; the midline must be parallel to the floor
Extension: approximately 15° to facilitate temporal lobe retraction
Contralateral bending: this helps with the subtemporal surgical perspective
Red Flags
Head over the heart level. Avoid over rotation of the neck – elevate the ipsilateral shoulder or prefer lateral position based on the freedom of the neck motility.
Surgery
1. Skin incision N°22 scalpel blade
The skin incision is performed in a “question mark” fashion. The inferior end starts anterior to the tragus, bends over the root of the pinna forming the question mark and terminates approximately over the temporal line.
2. Initial dissection of the skin flap with elevator
Skin and subcutaneous layers are separated from the superficial temporal fascia.
3. Placement of hemostatic clips
Avoiding an excessive cauterization of the subcutaneous layers mitigates the risk of impaired skin healing.
4. Skin flap elevation with elevator
The same technique of subperiosteal detachment in one layer is applied during this stage to achieve a complete exposure of the bone.
5. Incision and dissection of temporalis muscle
A “question mark” incision with monopolar cautery or scalpel and a subperiosteal dissection with periosteal elevator are performed on the temporalis muscle. Subsequently the muscle is retracted anteriorly with hooks.
6. Burr hole with perforator
Burr hole can be placed on the temporal squama. One burr hole is often sufficient.
7. Preparation of the burr holes with dura separator
This step helps to reduce the risk of tearing the dura mater during the craniotomy. The risk is higher in elderly patients because of the strong adherence between the inner table of the skull and dura.
8. Craniotomy with high-speed drill
The resultant bone flap has a square shape.
9. Edge drilling with high-speed drill
The cranial base must be drilled flat if a subtemporal route has been chosen. During drilling attention should be paid to the accidental opening of mastoid air cells. If this occurs, bone wax is used as a sealant.
10. Dural tenting sutures
Transosseous stitches are used to suspend the dura and reduce extradural bleeding.
11. Dural incision with N°10 scalpel blade and scissors
Dura should be incised starting at the superior end of the craniotomy and reflected toward the cranial base.
Microexploration
BT: Basilar Tip
PCA: Posterior Cerebral Artery
CN IV: Cranial Nerve IV, Trochlear Nerve
BV: Basal Vein of Rosenthal
CN III: Cranial Nerve III, Oculomotor Nerve
CP: Cerebral Peduncle
Closure
1. Dura reconstruction
A water-tight closure of the dura is always needed, particularly in cases of cisternal and ventricular opening. In case of dura retraction, several types of synthetic substitutes or a galea flap can be used to complete the approximation.
2. Bone fixation with microscrews
At least 3 microplates are used to guarantee the immobility of the bone flap. Immobility is necessary for osteosynthesis. For bigger craniotomies, central dural suspensions are mandatory.
3. Muscle reconstruction
Temporal muscle is sutured – this mitigates the risk of chewing problems postoperatively.
4. Subcutaneous/skin suture
Aesthetic skin reconstruction is always mandatory.
