- A-C: The SCITA is demonstrated using our 3D virtual model, highlighting the thalamic surface immediately exposed (A and B) and its reach along the long axis of the thalamus (C).
- D: Superior view of an anatomical dissection after removing the tentorium, showing the microsurgical corridor to the thalamus using the SCITA (green arrow).
- E and F: Posterior view of an anatomical dissection showing exposure of the inion and occipital bone and centering the craniotomy over the torcular Herophili, exposing the bilateral transverse sinuses and superior sagittal sinus. In real-life surgery, the craniotomy is extended toward the side of the thalamic pathology to utilize the slope of the superior surface of the cerebellum (lateral to the culmen) to our advantage.
- G–I: The thick arachnoid over the quadrigeminal cistern is carefully dissected, exposing the quadrigeminal plate, pineal gland, venous tributaries to the deep or galenic venous complex, and pulvinar of the thalamus laterally.
- J: A paramedian supracerebellar infratentorial corridor is developed after carefully dissecting the arachnoid and skeletonizing the tentorial veins.
- K: Panoramic dissection demonstrates the left paramedian supracerebellar transtentorial approach.
- CN IV = trochlear nerve; PCA = posterior cerebral artery.
- A paramedian variation of a midline SCITA has several advantages. It provides a more favorable angle of attack given the downward slope of the cerebellum from medial to lateral. Also, cerebellar bridging veins in the paramedian infratentorial location are smaller caliber than the ones in the midline (J). Additionally, there is lower risk for injuring the precentral cerebellar vein via this corridor. A contralateral approach allows a more direct view of posterior thalamic lesions that are a few centimeters off midline, whereas the ipsilateral approach is more appropriate for lesions close to the midline (K). If preferred, a paramedian incision and craniotomy can be made off midline on the side with the dominant extension of the tumor. We determine the surgical position (prone vs semisitting vs lateral) based on the patient’s body habitus and degree of cerebellar slope. However, obviously lateral positions allow the neurosurgeon to sit and have ergonomic advantages over prone or semisitting positions.
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