Medulloblastoma is a serious brain tumor, primarily affecting children. It is the most common malignant brain tumor in children, accounting for approximately 15% to 20% of all pediatric brain tumors. This aggressive tumor develops in the cerebellum, a region at the back of the brain responsible for balance and coordination.
Understanding Medulloblastoma
Medulloblastoma originates in the cerebellum, the part of the brain located at the base of the skull, which plays a significant role in motor control. This tumor is classified as a malignant, embryonal tumor, meaning it arises from primitive cells and can grow rapidly, often spreading to other areas of the brain and spinal cord through the central nervous system. While it primarily affects children, with a common diagnosis age between 3 and 8 years, it can also occur in adults.
The classification of medulloblastoma has evolved, now incorporating molecular subgroups: WNT-activated, SHH-activated (Sonic Hedgehog), Group 3, and Group 4. These molecular classifications are based on distinct genetic and transcriptional profiles, offering insights into the tumor’s biology and behavior. For instance, SHH-activated medulloblastoma is more prevalent in children under three, while Group 3 tumors are more common in males and frequently metastatic.
Molecular subgrouping provides prognostic information and helps guide tailored treatment strategies. While WNT and SHH subgroups are named after their prominent signaling pathways, the biology of Group 3 and Group 4 is still being delineated. These molecular insights continuously shape how medulloblastoma is understood and addressed in clinical practice.
Identifying Medulloblastoma
Medulloblastoma often manifests through symptoms related to increased pressure within the skull or issues with cerebellar function. Common signs include headaches, particularly in the morning, which may improve after vomiting. Nausea, general tiredness, and problems with balance or coordination, such as difficulty walking, dizziness, or clumsiness. Vision changes, like double vision, or changes in personality or behavior.
When a brain tumor is suspected, diagnosis begins with a thorough neurological examination, assessing reflexes, muscle strength, and various brain and spinal cord functions. Imaging techniques include Magnetic Resonance Imaging (MRI) of the brain and spine, which is the preferred method to visualize the tumor’s location, size, and extent. MRI with contrast agents, such as gadolinium, is useful for detecting tumor spread within the cerebrospinal fluid (CSF) and along the neuroaxis.
A definitive diagnosis requires a biopsy, where a tissue sample is removed, often during surgery, and examined under a microscope. This pathological analysis confirms medulloblastoma and identifies its characteristics. A lumbar puncture (spinal tap) also collects CSF for analysis, checking for cancer cells that may have spread to the spinal fluid. These tests collectively help stage the tumor and formulate a comprehensive treatment plan.
Treatment Approaches for Medulloblastoma
Treatment for medulloblastoma typically involves a multi-modal approach. The initial step is often surgery, aiming for maximal safe resection of the tumor. The goal is to remove as much of the tumor as possible while minimizing neurological damage. If hydrocephalus (a buildup of cerebrospinal fluid) is present, a shunt may be placed to relieve pressure before the main tumor removal surgery.
Following surgery, radiation therapy is a standard component, particularly craniospinal irradiation (CSI), which targets the entire brain and spinal cord. This widespread radiation is necessary due to the tumor’s tendency to spread through the central nervous system. A higher “boost” dose is often delivered to the primary tumor site or posterior fossa. Advances in techniques, such as proton therapy, are increasingly used to minimize damage to healthy tissues and reduce long-term side effects.
Chemotherapy is also commonly administered, either concurrently with radiation or afterward, to eliminate cancer cells. Common drugs used include cisplatin, vincristine sulfate, cyclophosphamide, and lomustine. These medications stop tumor cell growth, division, or spread. Treatment plans are tailored based on factors like the child’s age, the tumor’s size, its molecular subgroup, and risk stratification. For instance, reduced radiation and chemotherapy may be considered for patients with WNT-driven medulloblastoma, which has a more favorable prognosis.
Life After Medulloblastoma Treatment
The prognosis for medulloblastoma has significantly improved, with current childhood survival rates in the United States ranging from 70% to 80% when the tumor has not spread. Even with successful treatment, long-term follow-up care is important due to potential late effects. Regular monitoring includes ongoing imaging (such as MRIs) and neurological assessments to detect any recurrence or new issues.
Survivors may experience long-term side effects, including cognitive impairments (such as difficulties with processing speed, attention, and working memory), endocrine deficits (leading to growth problems or thyroid dysfunction), and hearing loss. There is also a small risk of developing secondary cancers later in life, often related to the radiation therapy received.
To support survivors, rehabilitation services (physical, occupational, and speech therapy) may address motor skill or communication challenges. Educational support and psychological counseling can help manage cognitive and emotional adjustments. Long-term, sometimes lifelong, follow-up is recommended to monitor potential effects and provide timely interventions, ensuring the best quality of life for survivors.