Abstract and Introduction
Resection remains the mainstay of treatment for craniopharyngiomas with the goal of radical resection, if safely possible, to minimize the rate of recurrence. Endoscopic endonasal and microscopic transcranial surgical approaches have both become standard methods for the treatment for craniopharyngiomas. However, the approach selection paradigm for craniopharyngiomas is still a point of discussion. Choosing the optimal surgical approach can play a significant role in maximizing the extent of resection and surgical outcome while minimizing the risks of potential complications. Craniopharyngiomas can present with a variety of different sizes, locations, and tumor consistencies, and each individual tumor has distinct features that favor one specific approach over another. The authors review standard cranial base techniques applied to craniopharyngioma surgery, using both the endoscopic endonasal approach and traditional open microsurgical approaches, and analyze factors involved in approach selection. They discuss their philosophy of approach selection based on the location and extent of the tumor on preoperative imaging as well as the advantages and limitations of each surgical corridor, and they describe the operative nuances of each technique, using a personalized, tailored approach to the individual patient with illustrative cases and videos.
Craniopharyngiomas are rare, slow-growing neoplasms that originate from a region of embryonic tissue around the pituitary stalk, with an incidence of 0.13 cases per 100,000 people every year. They represent approximately 2%–5% of all primary brain tumors and have a bimodal presentation in children aged 5–14 and adults aged 55–65 years. Although craniopharyngiomas are histologically benign, they threaten to compress and impair vital neighboring neurovascular structures, including the optic nerves and chiasm, hypothalamus, and pituitary stalk and gland. Because of their intimate involvement with critical structures, resection of these lesions can be associated with considerable risks of morbidity. Nevertheless, surgery remains the first line of therapy and offers the best chance of radical resection and oncological cure.[16–20,28,56,59] Advances in skull base approaches, modern microsurgical and endoscopic techniques, neuroimaging, and hormone replacement therapy, however, have allowed for safer gross- or near-total resection in the modern neurosurgical era with gross-total resection rates ranging from 72.7% to 90%.[14,18,19,22,24] In cases where tumor is adherent to critical structures such as the optic nerve, hypothalamus, or perforating vessels, achieving a maximal safe resection or near-total resection (> 95%) is the goal for preservation of neurological function. Although craniopharyngiomas are not strictly tumors of skull base origin, their anatomical relationship with critical basal neurovascular structures often requires a skull base approach to maximize the surgical corridor for optimal oncological resection.
A variety of different skull base approaches can be used to access craniopharyngiomas, each with distinct advantages and limitations. Traditional open transcranial approaches include midline approaches (transbasal subfrontal and frontobasal interhemispheric), anterolateral approaches (pterional, orbitopterional, orbitozygomatic, frontolateral, and supraorbital eyebrow), and lateral approaches (combined petrosal and subtemporal).[19,20,24,44,47,54] Alternatively, the transnasal route via the extended transsphenoidal (microsurgical) approach offers a direct trajectory to the sellar and suprasellar space for strictly midline tumors.[13,29,40,41] More recently in the last decade, the purely extended endoscopic endonasal approach (EEA) via the transplanum transtuberculum corridor has become a useful and effective route for removing craniopharyngiomas in the retrochiasmatic space extending superiorly into the third ventricle.[5,7–10,22,23,31,33,35–37,42,45] Lastly, purely intraventricular craniopharyngiomas situated in the third ventricle and/or lateral ventricles may be better accessed with transcortical or transcallosal intraventricular approaches.
Approach selection is largely dependent on tumor location, extent of pathology, tumor consistency, relationship to the optic chiasm, relationship to the pituitary stalk, involvement of the third ventricle, history and details of prior surgeries, and lastly, the surgeon's preference based on personal experience and comfort. Various authors have classified craniopharyngiomas based on the location, their relationship to the pituitary stalk, or their position along the vertical hypophyseal axis.[33,53,54] While these classification systems can assist with surgical approach selection, it is important to recognize the limits of such systems, as it is possible for craniopharyngiomas to extend into multiple regions, which increases the surgical complexity. Accordingly, a combined approach using more than one corridor may be necessary for extensive craniopharyngiomas involving multiple anatomical compartments that are not amenable to one isolated approach. Therefore, a personalized, tailored approach to the individual tumor based on multiple factors is crucial in determining the treatment strategy.
In general, when selecting the optimal approach based on anatomical location, consideration should be taken to choose an approach that not only has the shortest direct route to the tumor, but also optimizes exposure and visualization of the tumor interface with critical structures in order to avoid damage to surrounding vital structures, such as the pituitary stalk, hypothalamus, optic chiasm, and perforating vasculature. Although there is debate between open transcranial (above) and endoscopic endonasal (below) approaches for various skull base lesions, there has been an increased acceptance of EEA for suprasellar and retrochiasmatic craniopharyngiomas.[5,7–10,22,23,31,33,35–37,42,45] In a recent systematic literature review of surgically treated craniopharyngiomas, the endoscopic cohort had a significantly greater rate of gross-total resection (66.9% vs 48.3%) and improved visual outcome (56.2% vs 33.1%) than the open transcranial cohort, while the rate of CSF leakage was higher in the endoscopic cohort (18.4% vs 2.6%). However, this type of study presents various limitations due to the heterogeneity in the literature. For example, the tumor diameter was greater in the transcranial group, which suggests that smaller midline tumors may have been preferentially selected for endoscopic endonasal surgery.
The goal of this paper is to review 5 main categories of microscopic and endoscopic operative approaches for craniopharyngiomas (anterolateral transcranial, midline transcranial, extended transsphenoidal, intraventricular, and lateral transcranial), discuss advantages and limitations of each that factors into optimal approach selection, and present technical pearls and nuances with respect to maximizing tumor resection and avoiding complications, with clinical case correlates and illustrative operative videos.
Neurosurg Focus. 2016;41(6):e5 © 2016 American Association of Neurological Surgeons