As a general rule, tumors that can be safely resected are considered for surgical excision. What is considered a safe resection can be arguable but usually involves a lesion for which significant neurological impairments can be avoided after its surgical removal, keeping in mind that the prognosis often correlates with the extent of resection [1, 2]. Nowadays, the mainstay of treatment of many pediatric CNS tumors including gliomas, medulloblastomas, and ependymomas is maximal surgical resection followed by adjuvant therapy in selected cases [1, 3]. There are a few exceptions to this rule: germ cell tumors of the pineal or sellar region, tumors located in eloquent areas, and low-grade tumors for which observation might be an option.

The diagnosis of germ cell tumor of the pineal or sellar region may indeed be obtained via serum and/or CSF markers. When this is the case, initial surgery can be avoided and treatment with chemotherapy initiated [4]. Second-look surgery may then be considered for residual tumor before radiation therapy is started. However, for marker-negative germ cell tumors (e.g., pure germinomas), surgery followed if needed by chemotherapy and/or radiation remains the treatment of choice. Germinomas respond very well to chemotherapy and thus surgery should be limited to a biopsy. Biopsy of a pineal region tumor can be done during endoscopic third ventriculostomy (ETV) performed in the context of hydrocephalus, as discussed below.

When a tumor is located in a zone of the brain responsible for important functions (eloquent), resection may be deemed too dangerous and nonsurgical management may be preferred. In such cases, if imaging features and/or other paraclinical investigations are sufficient to establish the specific diagnosis including the nature of the tumor, treatment can be initiated. However, if uncertainty persists, a biopsy is performed and histopathological analysis will then guide subsequent nonsurgical treatment [4]. The risks and benefits of both the surgical and nonsurgical approach should be weighted when conservative management of tumors in eloquent areas is considered.

As mentioned earlier, most pediatric CNS tumors will be amenable to surgical resection. When this is not the case and if a doubt persists on neuroimaging studies regarding the likely histopathological diagnosis, a biopsy of the lesion may be required. Various biopsy techniques have been described and choice of the appropriate method is largely influenced by tumor location.

In addition to the mass effect and infiltrative effect of the tumor itself, secondary brain insults (SBIs) can result from conditions such as hydrocephalus. Other causes of SBIs such as vasogenic edema and seizures which require medical rather than surgical treatment will not be discussed in this section.

The main mechanism of hydrocephalus in the context of CNS tumors is obstruction of the ventricular system by tumors of the posterior fossa and tumor located around the third ventricle. Signs and symptoms of hydrocephalus result from elevated intracranial pressure (ICP). These include nausea, vomiting (often in the morning), irritability, sixth nerve palsy, headaches, and a decline in mental status [1, 3]. An upward gaze deficit and other associated signs of the Parinaud syndrome can be seen with compression of the midbrain tectum by the enlarged third ventricle at the level of its suprapineal recess or via direct tumor compression. Bulging fontanelles, splayed sutures, and an increase in skull circumference are additional manifestations of elevated ICP seen in infants with open sutures.

In the presence of hydrocephalus from tumor compression, the patient’s clinical state should dictate initial management. In a stable patient with little clinical evidence of significant hydrocephalus and normal neuro-ophthalmologic examination, conservative management is recommended until tumor surgery. Contribution of vasogenic edema to the compression should warrant glucocorticoid administration acting as a temporizing measure until surgical resection. On the other hand, an unstable patient with clinical evidence of elevated ICP should undergo emergent surgery consisting of the insertion of an external ventricular drain (EVD). A catheter is inserted through a burr hole in the skull until the anterior horn of the lateral ventricle is accessed and CSF flow is observed. The EVD is connected to an external collecting device and allows the excess CSF to drain [4]. Endoscopic third ventriculostomy (ETV) is another treatment option in the face of triventricular hydrocephalus from posterior fossa or pineal region tumors.

Hydrocephalus can persist despite resection of the obstructing tumor. This is especially true for posterior fossa lesions in which persistent hydrocephalus is observed in up to 30–40 % of cases following surgical resection [4, 5]. Such patients will need permanent diversion of CSF. The two main methods for permanent diversion of CSF are the ventriculoperitoneal shunt (VPS) and endoscopic third ventriculostomy (ETV). The VPS consists of a three-part device. A proximal catheter is inserted inside the lateral ventricle. The device is then connected to a distal catheter tunnelized subcutaneously ultimately reaching the peritoneum where CSF will be freely reabsorbed. A valve is commonly inserted between the proximal and distal catheter and allows for drainage control. One of the disadvantages of VPSs includes the theoretical risk of dissemination of neoplastic cells. An ETV consists in the creation of a communication between the third ventricle and the interpeduncular cistern under endoscopic guidance within the ventricular system. This technique allows diversion of CSF flow and obviates the need of extrinsic devices such as VPSs.

Considering the risk of postoperative hydrocephalus, neurosurgeons should answer the two following questions: (1) should a shunt be inserted prior or after surgical resection and (2) which CSF diversion procedure should be performed? We recommend the following management. If validated risk factors associated with postoperative hydrocephalus such as young age (<2 years), transependymal edema, type of tumor, and moderate to severe hydrocephalus are present, a preoperative ETV can be performed to avoid long-term shunt dependency [6]. If not, the risk of developing hydrocephalus is lower and tumor resection ± the insertion of an EVD during surgical removal of the tumor should be sufficient. If an EVD has been placed, the ICP is then monitored over the following days to determine the need for permanent CSF diversion such as a VPS.

Intramedullary spinal cord tumors are rare in the pediatric population, representing 4.2 % of all CNS tumors [7]. The general approach for such tumors consists of surgical excision. Tumor debulking often leads to favorable outcome and is thus the preferred surgical option. In fact, removal of 80 % of the lesion has been associated with good survival rate in low-grade tumors (70 % at 5 years for nonmalignant lesions, which represent 80 % of these tumors) [8]. In addition to tumor removal, debulking provides specimens for histopathological analysis. Another option in the initial management of these tumors consists of a more conservative surgical resection followed by radiation therapy, which has revealed an overall comparable survival rate [9–13].

In this context, the choice between the two treatments should be guided by the risk of morbidity. Since the introduction of intraoperative physiological monitoring, morbidity rate from spinal cord surgeries has considerably decreased [14]. In addition, irradiation of the spine in children has been associated with significant side effects, including myelopathy [15], alteration of bone growth [16], and potential induction of other malignancies [17]. However, these secondary effects were mostly described with radiotherapy techniques used in the 1980s and are thus less likely to occur nowadays with modern radiation therapy.