Tumors

Technical possibilities have enormously improved in the field of pediatric neurosurgery in the last few decades. Microsurgical techniques are now standard operating procedure. Improved technical equipment enables gentler tumor removal and true-to-detail presentation of the brain, its membranes and vessels, which is mainly made possible by multimodal magnetic resonance imaging (MRI) which is used for precise surgical planning. The latter can also be integrated in computer systems such as neuronavigation in order to precisely adapt the planning to the individual patient. This computer-assisted surgical technique is made possible by a three-dimensional MRI. With the help of these images, a reconstruction of the head in all its anatomical sections can be reproduced on a computer. The tumor can be marked on the images and the best and gentlest access route can be virtually planned. The data are then sent to the operating room and by identifying the patient's position in the room, the neuronavigation system can display and control marked instruments in relation to the anatomy of the head on a screen. In addition, structures important for the operation such as the tumor can be displayed in the microscope's field of vision even before they appear in the operating field. This allows precisely targeted tumor identification and removal. Additional further technical development of electrophysiological methods permits intraoperative monitoring of important brain functions thus allowing these functions to be better protected during the operation. In principle, besides tumor removal, other surgical methods for treating patients which come into consideration include diagnostic operations with minimally invasive needle biopsies, drainage of tumor cysts through catheter placement and treatment for secondary cerebrospinal fluid retention in the brain using endoscopic procedures or placement of CSF shunt systems (see also under hydrocephalus).

Polycytic astrocytoma is the most common brain tumor in children. It is classified by the WHO as grade I (benign). It typically arises in the  posterior cranial fossa or midline structures. In general, these tumors of the cerebellum in the posterior cranial fossa can be surgically treated. With most localizations, surgical treatment is the first option. In the event of an incomplete tumor removal, individualized concepts, including a monitoring stance, radiation therapy or chemotherapy must be considered. Overall, the prognosis is good. If the tumor is completely removed, which, for example, is almost always possible in the posterior cranial fossa, the 10 year survival rate is almost 100% whereas even if not, the rate of survival is up to 80%.

Astrocytomas can, in rarer instances, also be diagnosed as being higher grade. These include pilomyxoid, diffuse fibrillary and anaplastic astrocytomas and glioblastomas. With these types of a tumors, an adapted multimodal therapeutic approach must be coordinated according to the protocols of the competence networks.

Medulloblastoma is the second most common brain tumor in children and is found in the posterior cranial fossa. It is classified by the WHO as grade IV as must therefore be referred to as malignant. Nevertheless, it is possible to cure it in most instances through intensive therapy. With medulloblastomas, an operation, a course of chemotherapy and in some cases radiation therapy are necessary. The treatment is coordinated based on the patient's age and the spread of the tumor in the nervous system. With the already well optimized therapeutic protocol, 10 year survival rates of over 70% can be achieved.
This tumor can also occur in the cerebral hemispheres and is then referred to as a primitive neuroectodermal tumor (PNET). A therapeutic concept similar to that used with medulloblastomas must also be followed for this tumor.

Ependymomas can occur in various locations in the brain but are most commonly found in the posterior cranial fossa. It is classified by the WHO as grade II or III. Surgery is the most viable option for treating these tumors. Complete removal is not always possible, however, since cranial nerves performing important functions can be surrounded by the tumor. Secondary options include radiation therapy and chemotherapy. These are performed based on the completeness of the tumor removal, the grade and spread of the tumor and the patient's age. If necessary, the therapeutic options must also be repeated. Depending on the defined protocol, if the tumor is completely resected, the four year survival rate is 80% and if not, up to 70%.

Craniopharyngeomas are dysontogenetic malformations which typically originate in the mid skull base region . The primary aim of treatment is extirpation of the tumor. Due to the proximity of the tumor to the neighboring structures of the optical nerves, the hormone-regulating hypohysis and the hypothalamus and the anterior cerebral arteries (internal carotid artery), protecting the brain's functions is of the utmost importance. Maintenance of these functions must be weighed against a radical tumor operation. This priority is even more applicable because histologically speaking this type of tumor is classified by the WHO as grade I and often shows slow growth. In case of tumor regrowth, a repeated operation may have to be performed. With purely cystic craniopharyngeomas, there is the option of minimally invasive catheter insertion to decrease the size of the mass or drug treatment with bleomycin inside the cyst. Radiation is used in children aged 5 and up as a supplementary option and has shown promising results in a small number of cases. Its specific therapeutic value is currently being tested as part of a multi-center study. The prognosis in terms of the 10 year survival rate is  87%.

These tumors have a diverse etiology. Most often they are  germ-cell tumors. Here we differentiate between germinomas and non-germinoma tumors. Germinomas can be diagnosed with a spinal tap and success rate for curing them with radiation and chemotherapy is high (approx. 86%). If conditions are unclear, a biopsy of the tumor will have to be performed, however.
With non-germinoma germ cell tumors, the mature teratoma treated primarily by operation often has a very high rate of therapeutic success.
The other tumors in this group (yolk sack tumor, mixed germ-cell tumors, malignant tumors, embryonic carcinomas) must first be biopsied. The diagnosis is generally followed first by chemotherapy then by an operation and repeated chemotherapy. This therapeutic concept has resulted in 70% survival rate after 5 years.

Other tumors of this region include pineal tissue tumors. A histological examination must also be performed with these tumors by means of a biopsy. Whereas benign pineocytomas can be successfully cured by operating, malignant pineoblastomas require a multimodal course of treatment comprising surgery, chemotherapy and radiation therapy.

Dysontogenetic malformations such as dysembryoplastic neuroepithelial tumors (DNT), gangliomas and harmatoma are generally benign but often cause epileptic seizures. Treatment through operation is necessary in case of tumor growth or to treat epilepsy.

Choroid plexus tumors are typically found in the cerebral ventricles and are treated with an operation. In the case of the rare malignant plexus tumor, complementary chemo- and radiation therapy are necessary.

With the atypical teratoid rhabdoid tumor (ATRT), the first step is to operate on the tumor. Subsequent chemotherapy and radiation therapy have very recently produced clear success with this malignant tumor variety.

Tumors affecting the spinal column and cord occur in children, albeit rarely. In principle, we can differentiate between various types of tumors by the location in which they occur.

Tumors which occur in the spinal cord are referred to as intramedullary tumors. The most frequent tumors in this location are astrocytomas, ependymomas, gangliomas and hemangioblastomas. Cavernomas also occur in the spinal cord. Usually neurological symptoms, pain or poor posture point to the existence of such a tumor. In almost all cases, the aim of the necessary operative treatment is to remove the tumor and secure a specific diagnosis by taking a tissue sample from the tumor. During the operation, neurophysiological monitoring is always carried out, i.e. the functions of the spinal cord are continuously monitored in order to keep to a minimum the risk of postoperative deterioration.

Extramedullary tumors are ones which form outside of the spinal cord. Since space is limited in the spinal canal, the growth of an extramedullary tumor also results to compression of the spinal cord and the exiting nerves. Frequently occurring tumors in the spinal meninges include ependymomas, neurinomas, gangliogliomas or metastases of brain tumors. Outside of the spinal meninges, the significant tumors are neuroblastomas or tumors originating from bone.

As is also the case with intramedullary tumors, the aim of a necessary operation is to remove as much of the tumor tissue as possible and to acquire a tissue sample. With tumors also affecting the bony spinal column, an important criterion is the stability of the spinal column. If the tumor growth has led to instability or deformity, then a stabilizing operation with implants must be carried out. All operations may be performed with neurophysiological monitoring, i.e. under continuous surveillance of the spinal cord functions during the procedure.  
As with brain tumors, affected children are treated in close collaboration with our colleagues from pediatric oncology, pediatric radiology, neuroradiology and spinal cord surgeons. All therapeutic steps are discussed and determined beforehand in interdisciplinary conferences in order to find the best course of treatment for every child.