Anatomical Predictors of Transcranial Surgical Access to the Suprasellar Space

Abstract

Objective The suprasellar space is a common location for intracranial lesions. The position of the optic chiasm (prefixed vs. postfixed) results in variable sizes of operative corridors and is thus important to identify when choosing a surgical approach to this region. In this study, we aim to identify relationships between suprasellar anatomy and external cranial metrics to guide in preoperative planning. Methods T2-weighted magnetic resonance images (MRIs) from 50 patients (25 males and 25 females) were analyzed. Various intracranial and extracranial metrics were measured. Statistical analysis was performed to determine any associations between metrics. Results Interoptic space (IOS) size correlated with interpupillary distance (IPD; a = 7.3, 95% confidence interval [CI] = 4.5–10.0, R 2 = 0.3708, p = 0.0009). IOS size also correlated with fixation of the optic chiasm, for prefixed chiasms (n = 7), the mean IOS is 205.14 mm2, for normal chiasm position (n = 33) the mean IOS is 216.94 mm2 and for postfixed chiasms (n = 10) the mean IOS is 236.20 mm2 (p = 0.002). IPD correlates with optic nerve distance (OND; p = 0.1534). Cranial index does not predict OND, IPD, or IOS. Conclusion This study provides insight into relationships between intracranial structures and extracranial metrics. This is the first study to describe a statistically significant correlation between IPD and IOS. Surgical approach can be guided in part by the size of the IOS and its correlates. Particularly small intraoptic space may guide the surgeon away from a subfrontal approach.

Chiasmatic Ridge: Incidence, Classification, and Clinical Implications

“…4,6,12 One of the important factors affecting the choice of surgical technique is variations of anatomical structures. 5,6,8,13 For instance, Guthikonda et al 8 classified the prechiasmatic sulcus as 4 types (narrow-steep sulcus, narrow-flat sulcus, wide-steep sulcus, and wide-flat sulcus) using the sulcal length (anteroposterior length of the prechiasmatic sulcus) and sulcal angle (the angle between the prechiasmatic sulcus and planum sphenoidale), and reported that the pterional approach might be preferred to remove meningioma in patients with narrow-steep sulcus, while a subfrontal approach (or a supraorbital approach) in patients with wide-flat sulcus. They also suggested that endoscopic endonasal techniques might be preferred in a patient with wide sulcus, while transcranial techniques in a patient with narrow sulcus.…”

“…14 For these reasons, anatomical variations of the structures including the CR may be important in terms of effective and successful surgical outcome. 5,6,8,13,20,21 Meningiomas localized in the suprasellar region may be removed with transcranial approaches from ''above,'' while with endoscopic transnasal approach from ''below.'' 8,12 The potential area beneath the CR poses a residual tumor risk during the removal of meningiomas using transcranial techniques.…”

“…Skull base tumors, especially meningiomas, frequently arise from the suprasellar region (eg, the planum sphenoidale, limbus sphenoidale, prechiasmatic sulcus, diaphragma sellae, or tuberculum sellae) 1–4 . The surgical management of the suprasellar meningiomas (eg, surgical approach choice including frontolateral, transnasal transsphenoidal, subfrontal, tailored bifrontal, transsylvian, extended bifrontal, orbitozygomatic, pterional, and supraorbital) may differ depending on tumor size (small or large), tumor location (limited to midline or spread to lateral), and anatomic features of the region (eg, prechiasmatic sulcus length and angle) 5–13 . Tumors with aggressive behavior characterized by invasion of adjacent anatomical structures may cause technical difficulties (eg, surgical approach choice) for surgeons due to anatomical variations 5,8,11,14 .…”

Craniopharyngioma surgery for rhinologists

“…Multidisciplinary management with neurosurgery, endocrinology, and radiation oncology is critical for successful care of craniopharyngioma patients. in which the optic chiasm is located over the dorsum sella, is associated with a wider surgical corridor in this location [17].…”

“…More recently, the QST system has been used to classify craniopharyngiomas as originating from below the diaphragmatic area, or in an infrasellar location (Q); from the precursor cells of Rathke's pouch in the middle or inferior segment of the pituitary stalk (S); and from precursor cells of Rathke's pouch that are located above the pars tuberalis, extending upward into the third ventricle (T), with studies indicating improved and outcomes in type S craniopharyngiomas [9,16]. Prefixed chiasm anatomy, in which the optic chiasm is located over the tuberculum sella, is associated with a narrower surgical corridor between the optic nerves whereas postfixed chiasm anatomy, in which the optic chiasm is located over the dorsum sella, is associated with a wider surgical corridor in this location [17].…”