Medulloblastoma

Medulloblastoma is the most common malignant brain tumor in children and originates in the cerebellum. It arises from immature cells during brain development; therefore, it is particularly more common during childhood when brain development is ongoing (ages 3-8). It is classified as Grade 4 (highest grade) and is a fast-growing tumor. It is more common in males than females. With modern treatments, survival has improved significantly; however, this varies depending on the tumor's molecular subgroup.

Medulloblastoma is classified into four main molecular subgroups based on genetic characteristics. These subgroups differ in terms of treatment response and prognosis: one subgroup has a relatively favorable prognosis while others can achieve good results with less radiation and chemotherapy; some subgroups follow a more challenging course and require more intensive treatment. Therefore, determining which subgroup the tumor belongs to is crucial for planning treatment and predicting prognosis. This determination is made through detailed examination of the tissue obtained during surgery.

Surgery is a fundamental step in treatment; the extent of tumor resection is one of the most important factors affecting prognosis. The tumor is removed as completely as possible through surgery via the cerebellum. Today, microsurgical techniques and intraoperative neuromonitoring are used. After surgery, temporary speech and swallowing difficulties, balance and mood changes may occur; this usually resolves in most children within several months. Fluid accumulation due to the tumor typically resolves after tumor removal.

Because medulloblastoma tends to spread through cerebrospinal fluid, radiation therapy is delivered to the entire brain and spinal cord. The dose is adjusted according to the patient's risk group. When possible, proton therapy, which delivers less radiation to healthy tissues, is preferred. Early side effects may include fatigue, nausea, skin irritation, and hair loss; long-term side effects may include slowed learning and attention, growth and hormone problems, and hearing loss. Therefore, especially in infants under three years of age, this radiation therapy is avoided as much as possible.

In infants under three years of age, radiation therapy can have serious effects on brain development, so it is delayed or avoided as much as possible. Treatment is planned as complete tumor resection followed by intensive chemotherapy. Chemotherapy may be longer in this age group. Radiation therapy is only considered if the disease cannot otherwise be controlled or if it recurs. Long-term developmental and hormonal follow-up is crucial in these children.

In certain medulloblastoma subgroups, newer drugs targeting specific cellular signaling pathways may be considered. These drugs are particularly evaluated when disease recurs and in cases with appropriate genetic characteristics. However, these drugs are not suitable for every subgroup; some genetic characteristics indicate they should not be used because they may not provide expected benefit. In children, their use is carefully evaluated as they can affect growth. Research in this area is ongoing.

Yes, medulloblastoma tends to spread to other regions of the brain and spinal cord through cerebrospinal fluid. Metastatic disease can be detected in some patients at diagnosis. The presence or absence of metastatic disease determines the patient's risk group; if spread is present, more intensive treatment is required and prognosis is usually more challenging. Therefore, spinal cord MRI and cerebrospinal fluid examination are mandatory at diagnosis; this ensures treatment is planned correctly from the start.

The tumor can recur at varying rates depending on the subgroup. Recurrence typically occurs within the first few years, most commonly at the original tumor site or along the spinal cord. When recurrence happens, the prognosis is usually more challenging. Treatment options include repeat surgery if appropriate, radiation to previously unirradiated areas, different chemotherapy regimens, and research protocols. During this process, supportive care to maintain quality of life is also important.

Medulloblastoma treatment (surgery, radiation, and chemotherapy) can lead to some long-term problems. Learning difficulties, memory and attention problems; growth and hormone deficiencies (particularly growth hormone and thyroid hormone); balance and coordination problems; and hearing loss may occur. Additionally, there may be a small increase in the likelihood of developing a second tumor in later years. Therefore, long-term follow-up spanning multiple disciplines including neurology, endocrinology, psychology, and rehabilitation is required after treatment.

Medulloblastoma treatment is a long and challenging process; preserving quality of life is extremely important. Physical therapy (for balance and coordination) and occupational therapy supporting activities of daily living can be helpful. Special education and support programs for learning difficulties; appropriate treatments for hormone deficiencies; hearing aids may be needed for hearing problems. Psychological support for the child and family, school adaptation, and participation in social life should not be overlooked during the process. Regular follow-up is vital both for early detection of disease recurrence and for managing side effects.