**2.3 Craniopharyngiomas**

Craniopharyngiomas are usually benign epithelial tumors originating from remnants of the Rathke's pouch, localized in the sellar or suprasellar region [30]. They are rare, with an incidence of 0.5–2 per 100,000 a year [31, 32]. They often present during childhood or adolescence and persist into adulthood [32]. They are cystic or solid or mixed cystic and solid and frequently contain calcifications (**Figure 8**) [31]. Presenting symptoms include visual field defects, pituitary hormone deficiency, and diabetes insipidus [30–32]. Craniopharyngiomas can be very challenging in terms of surgical management and can cause significant morbidity, despite their benign nature [33]. There are two distinct histological types of craniopharyngiomas. The adamantinomatous type is predominant in children, is more cystic and calcified and large, and often adherent to the brain. The less common papillary type almost exclusively presents in adults, is less infiltrative, and may be more amenable to surgery [34]. However, papillary craniopharyngiomas are well suited for stereotactic radiosurgery or fractionated stereotactic radiation therapy, as they are more radiosensitive and rarely recur after irradiation. Due to the high recurrence rate after subtotal resection, adjuvant irradiation is often warranted, with stereotactic radiosurgery or fractionated stereotactic radiation therapy [30, 35]. The main indication for stereotactic radiation therapy or stereotactic radiosurgery for craniopharyngiomas is thus when surgical control is not possible, or in case of tumor recurrence where the risks of surgery outweigh the benefits [36, 37].

#### **2.4 Vestibular schwannomas**

Vestibular schwannomas are slow-growing and benign tumors originating from the Schwann cell sheath of the cochleovestibular nerve (**Figure 9**) [38, 39]. The incidence is 1–2 in 100.000 a year [38, 39]. As the vestibular schwannomas grow, they affect hearing and balance, with unilateral hearing loss, tinnitus, and balance

**Figure 8.** *MRI scan sagittal with Gd demonstrating a mainly solid craniopharyngioma in a 16-year-old adolescent.*

**Figure 9.** *MRI scan with Gd demonstrating a small left-sided vestibular schwannoma.*

disturbances [39, 40]. With increasing tumor growth, the facial nerve can also be affected. Bilateral vestibular schwannomas with bilateral hearing loss are usually associated with neurofibromatosis type 2. Surgery is the standard treatment of vestibular schwannomas, including microsurgery and hearing preservation surgery [38]. More recently, stereotactic radiosurgery and radiation therapy have been introduced for the treatment of vestibular schwannomas with the aim of tumor control and hearing preservation, and controlled studies have found the results to

be superior to microsurgery for small tumors less than 3 cm [38–40]. Sometimes a conservative wait and scan approach is appropriate, reserving treatment in case of tumor growth or neurological deterioration.
