Posterior Paramedial Parietal Approach
- Supine: The head is positioned straight and flexed 30-40 degrees, then flexed in a surgical head holder so that the parieto-occipital region is fully accessible to the surgeon. Alternatively, the patient may be positioned in the three-quarter prone position (14, 33, 41).
- Scalp incision: A parietal horseshoe skin incision is made starting at the level of the homolateral lambdoid suture, extending slightly across the midline, and centered over the superior parietal lobe.
- Craniotomy: A posterior parasagittal parietal bone flap is also centered over the superior parietal lobe 1 cm off the midline. Neuronavigation can help in localizing the superior parietal lobe.
- Cortical incision: Paramedian parietal incision 3 – 4 cm from the inter-hemispheric fissure, extending from the post-central fissure to the parieto-occipital fissure. Lateral ventricle is entered from above. The choroidal plexus is the main landmark to identify.
- Avoids the visual pathways traversing the parietal lobe and the speech areas at the junction of the parietal and temporal lobe
- Suitable for tumors of the atrium
- Access to the choroidal fissure
- Large distance if the ventricles are not dilated
- Poor visualization vessels: Early identification of the anterior choroidal artery not allowed
- Brain retraction always needed
Posterior Interhemispherical Transcallosal Approach
- Three-quarter prone: A three-quarter prone position with the operating side downward facilitates the exposure and minimizes retraction. A semi-sitting position is an alternative for positioning.
- Scalp incision: A parieto-occipital scalp incision extending across the midline is used.
- Craniotomy: Bone flap extends to the midline.
- Dural opening: The dura mater is opened in a horseshoe fashion with its pedicle toward the superior sagittal sinus.
- Interhemispheric fissure opened: The right parietal lobe’s medial surface is retracted away from the falx. The cingulate gyrus and splenium of the corpus callosum are then identified.
- Approach to the ventricle: The splenium is opened at its lateral extent, and the cingulate gyrus is incised at its posterior part. The right atrium is entered.
- For tumors extending through splenium: This approach is useful in patients with upward transependymal extension through the posterior part of the splenium.
- Avoids cortical injury: Complications of the transcortical route are avoided.
- Large tumors difficult: As hemispheric retraction is required, this approach is not suitable to large tumors.
- Hemialexia and disconnection: Section of the splenium may cause hemialexia and disconnection syndromes.
- Veins: Deep cerebral veins (Galenic system) may be on the way.