Basic information
Allows the dissection of a large portion of the Sylvian fissure, and hence provides access to the anterior circulation and part of the posterior circulation.
- Assess to:
- The anterior cranial fossa
- Peri- and suprasellar regions
- Anterior third of the frontal and temporal opercula
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, carotido-optic triangle, the circle of Willis)
- 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
Anatomy and important anatomical landmarks
- Skull bones – frontal, sphenoid, temporal, parietal, zygomatic, zygomatic arch, pterion
- Sphenoid wing
- Tragus, temporal muscle line
- Temporal muscle, facial nerve, superficial temporal artery, middle meningeal artery
- Brain surface (temporal, frontal lobe)
- Sylvian fissure
- Carotico-optic triangle, carotico-oculomotor triangle
- Circle of Willis
- Contralateral structures (optic nerve, carotid artery)
Highlights
Sylvian fissure, circle of Willis, optic nerve
Positioning
- Supine position
- Head rotation may change based upon the exact position of the area which must be exposed
Body positioning: supine (0°), supine lateral (45°)
Head positioning: contralateral rotation (40°), lateral tilt (10°), extension (12°)
Red Flags
Avoid over-rotation of the neck by elevating the ipsilateral shoulder. Head over the heart level. Regardless the position of the target, the malar eminence must always be the highest point of the operating field.
Surgery
1. Skin incision N°22 scalpel blade
2. Initial dissection of the skin flap with elevator
3. Placement of hemostatic clips
4. Skin flap elevation with elevator
5. Dissection of temporal muscle
6. Burr hole with perforator
7. Preparation of the burr holes with dura separator
8. Craniotomy with high-speed drill
9. Edge drilling with high-speed drill
10. Dural tenting sutures
11. Dura incision with N°10 scalpel blade and scissor
Microexploration
A1: Anterior Cerebral Artery, First Segment
AComA: Anterior Communicating Artery
A2: Anterior Cerebral Artery, Second Segment
ICA- Bif: Internal Carotid Artery (ICA) bifurcation
M1: Middle Cerebral Artery, First Segment
MCA-Bif: Middle Cerebral Artery) bifurcation
M2: Middle Cerebral Artery, Second Segment
PComA: Posterior Communicating Artery
CN I: Cranial Nerve I, Olfactory Nerve
CN II: Cranial Nerve II, Optic Nerve
CN III: Cranial Nerve III, Oculomotor Nerve
Chiasm: Optic Chiasm
MTR (anterior third): Mesial temporal region (anterior third)
Limen: Limen Insulae
Insula: Insula
ACP: Anterior Clinoid Process
PCP: Posterior Clinoid Process
LW: Lesser Wing