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Diagnosis

Obtaining a symptom history and performing a neurological examination will be your doctor’s first steps in making a diagnosis. Magnetic resonance imaging (MRI), done both with and without a contrast dye, is then used to identify the presence of a tumor in the brain. The contrast dye is given intravenously (into the vein) to enhance the pictures. By concentrating in abnormal tissue, the dye makes a tumor appear much brighter than other areas. If a tumor suspected of being a medulloblastoma is identified, an MRI of the entire spine can be done to look for tumor in that area. PET (positron emission tomography) and MRS (magnetic resonance spectroscopy) may be used to determine if what is seen on the scan is growing, live tumor as opposed to radiation effects or non growing tissue.

While scans provide important and intricate details, microscopic examination of tissue obtained during a surgical procedure, such as a biopsy or tumor removal, confirms the diagnosis. The pathologist, a doctor who specializes in studying tissue samples, will be looking for cell patterns that identify the tumor type. A pathology report usually takes about a week to be completed. It is sent to your neurosurgeon’s office, and the results then shared with you.

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Symptoms

The early “flu-like” signs of this tumor — lethargy, irritability and loss of appetite — are often so nonspecific that the disease first goes unnoticed. In infants, increased head size and irritability may be the first symptoms. Older children and adults may

experience headaches and vomiting upon awakening. Typically, the person feels better after vomiting and as the day goes on. As the pressure in the brain increases due to a growing tumor or blocked fluid passages, the headaches, vomiting and drowsiness may increase. Other symptoms depend on the nerves and brain structures affected by the tumor. Since medulloblastomas appear in the cerebellum, the center of balance and movement, problems with dizziness and coordination are common. Tumors growing close to the brain’s fourth ventricle may expand into that cavity, blocking the normal flow of cerebrospinal fluid. This can result in hydrocephalus — the buildup of cerebrospinal fluid within one of the cavities of the brain. The pressure of this buildup triggers the tumor’s characteristic symptoms: Morning headaches, nausea, vomiting and lethargy.

Children with this tumor may exhibit a clumsy, staggered walking pattern. They may also complain of visual problems. For instance, if the tumor involves the sixth cranial nerve which controls outward muscle movement of the eye, diplopia (double vision) can occur. Nystagmus (involuntary jerking of the eye) may also be a problem. While seizures are not common with medulloblastoma, other symptoms such as mild neck stiffness and a tilt of the head may occur. As many as 2 out of every 10 children with medulloblastomas may be less than 2 years of age at the time of diagnosis. In infants, symptoms can be more subtle and include intermittent vomiting, failure to thrive, weight loss, an enlarging head with or without a bulging of the soft spot of the head (fontanelle), and inability to raise the eyes upward (the so-called “sun-setting” sign).

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Incidence

About 1,000 new patients — children and adults — are diagnosed in the US each year, more often in males than females. Medulloblastoma is relatively rare, accounting for less than 2% of all primary brain tumors (tumors that begin in the brain or its coverings) and 18% of all pediatric brain tumors. More than 70% of all pediatric medulloblastomas are diagnosed in children under age 10. Very few occur in infancy or under age 1. Typically a tumor of childhood, medulloblastoma in adults is not common, but does occur. About one-third of all medulloblastomas diagnosed in

the United States are found in adults between the ages of 20 – 44. The incidence in adults sharply decreases in frequency after age 45, with very few older adults having this tumor.

Cause

Although the cause of medulloblastoma is unknown, scientists are making significant progress in understanding its biology. Changes have been identified in genes and chromosomes (the cell’s DNA blueprints) that may play a role in the development of this tumor. For example, one-third to one-half of all pediatric medulloblastomas contain a change on chromosome 17. Similar changes on chromosomes 1, 7, 8, 9, 10q, 11 and 16 may also play a part.

There are a few rare, genetic health syndromes that are associated with increased risk for developing this tumor. For instance, a small number of people with Gorlin’s Syndrome develop medulloblastoma. (Gorlin’s Syndrome is an inherited tendency to develop basal cell carcinoma in combination with other conditions.) Scientists have identified alterations on a gene called PTCH which may be the common link.

Similarly, genetic changes in the APC and TP53 genes are involved in two other inherited syndromes, Turcot and Li-Fraumeni. People with these syndromes tend to develop multiple colon polyps and malignant brain tumors.

Researchers are also exploring normal brain activity pathways, such as communication patterns among cells or genes. Changes in the genes involved in cell-signaling pathways such as SHH, WNT and ERBB, have been linked to the development of medulloblastoma. Several therapies targeted at proteins in these pathways are being studied.With increased understanding of how these genetic changes contribute to medulloblastoma, researchers may one day be able to correct or compensate for these changes.

Genetic versus Inherited

“Genetic” does not mean “inherited.” Genetic changes are those that occur in the DNA, or the inside blueprint, of a cell. No one knows what triggers these changes. Some, but not all, genetic changes can be inherited. Inherited means abnormal genes are passed from one generation to another. Medulloblastoma is not an “inherited” disease.

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Types of medulloblastoma:

_ classic medulloblastoma

_ desmoplastic nodular medullobastoma

_ large-cell or anaplastic medulloblastoma

_ medulloblastoma with neuroblastic or neuronal differentiation

_ medulloblastoma with glial differentiation

_ medullomyoblastoma

_ melanotic medulloblastoma

To a neurosurgeon, this tumor looks like a pinkish gray mass with a thickened “sugar-coating.” But under the microscope, classic medulloblastoma tissue looks like sheets of densely packed, small round cells with large colorful centers called nuclei. While this classic pattern is found in the majority of both pediatric and adult tumors, four other notable tissue patterns include desmoplastic nodular medullobastoma, which contains scattered islands of tumor cells in the tissue and small cysts; large-cell or anaplastic medulloblastoma, with large round tumor cells; medulloblastoma with neuroblastic or neuronal differentiation, in which the tumor cells look similar to abnormal nerve cells; and medulloblastoma with glial differentiation, whose cells look similar to the supportive, glial brain cells.Two other variants, medullomyoblastoma and melanotic medulloblastoma, are rarer and generally found only in children. These “histologic” tissue patterns are used for grouping and naming these tumors, and may someday be useful for targeting therapies. For now, though, the subtype of medulloblastoma does not influence the treatment plan. Significant strides have been made in diagnosing and treating medulloblastoma. Yet these tumors remain among the most challenging pediatric brain tumors.

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offers extensive brain tumor information, treatment and research updates, and patient/family storiesMedulloblastoma is a rapidly-growing tumor of the cerebellum — the lower, rear portion of the brain. Also called the “posterior fossa,” this area controls balance, posture, and complex motor functions such as speech and balance. Tumors located in the cerebellum are referred to as “infratentorial” tumors. That means the tumor is

located below the “tentorium,” a thick membrane that separates the larger, cerebral hemispheres of the brain from the cerebellum. In children, medulloblastoma arises most often near the vermis, the narrow worm-like bridge that connects the cerebellum’s two sides. In adults this tumor tends to occur in the body of the cerebellum, especially toward the edges.

Medulloblastoma is the most common of the embryonal tumors — tumors that arise from “embryonal” or “immature” cells at the earliest stage of their development. Other embryonal tumors include histologically similar tumors such as supratentorial primitive neuroectodermal tumors, central neuroblastomas, and ependymoblastomas. These tumors are now known to be molecularly different than medulloblastoma, as are other embryonal tumors such as medulloepithelioma and atypical teratoid/rhabdoid tumors.