Medulloblastoma is an undifferentiated tumor believed to arise from the primitive multipotential medulloblast, embryologically located in the external granular layer of the cerebellum. It is classically identified as a primitive neuroectodermal tumor (PNET) presenting in the posterior fossa.1
Etiology:
Rachel
In most cases, the cause of medulloblastoma is not known.
In some cases, medulloblastoma is associated with certain inherited diseases, including: Li-Fraumeni syndrome, Nevoid basal cell carcinoma syndrome, and Turcot syndrome. 2
Signs & Symptoms:
Brandon Signs and symptoms may differ from patient to patient depending on the size and location of the tumor. These symptoms inlcude:3
Headache (especially upon wakening)
Nausea/Vomiting
Fatigue
Lethargy
Imbalance or lack of coordination
Problem with writing skills
Neck tilt or double vision
Changes in personality
Seizures
Diagnostic Procedures:
Brandon Some of the basic diagnostic proceudres that are used for Medulloblastomas include both Magnetic Resonance Imaging (MRI) as well as surgical biopsy to determine tumor type and grade.3
Histology:
Ashley Medulloblastoma is a type of cerebellar tumor that is found in children and adults and stems from the cerebellar vermis. 4 The exact histologic origin isn’t clear so there are different views to describe where these tumors arise. The first opinion suggests that the tumor arises from the external granular layer of the cerebellum. 4 Precursor neurons that are found in this layer of the neurons are also found in pediatric medulloblastoma . 4 Another opinion suggests that medulloblastomas can arise from more than 1 type of cell. 4 Studies have shown that a specific calcium-binding protein and beta-tubuline isotype found in some medulloblastoma patients isn’t found in the granular layer of cerebellum. 4Research continues to explore the histology of these pediatric brain tumors as they are the most common malignant brain tumor in children.
Lymph node drainage:
Ashley Because the brain doesn't contain lymph node channels, metastasis do not occur through lymphatics.5
Metastatic spread:
Amanuel Medulloblastomas rarely metastasis outside central nervous system (CNS).6
Grading:
Amanuel According to world health organization (WHO), medulloblastomas are classified as Grade IV central nervous system tumors.7
Staging:
Lindsey Chang Staging System:8 T1: tumor < 3cm in diameter T2: tumor > or = to 3cm in diameter T3a: tumor > 3cm in diameter with extension into aqueduct of Sylvius or into the foramen of Luschka T3b: tumor > 3cm in diameter with unequivocal extension into the brain stem T4: tumor > 3cm in diameter with extension up past aqueduct of Sylvius or down past foramen magnum M0: no evidence of subarachnoid or hematogenous metastasis M1: tumor cells found in cerebrospinal fluid M2: intracranial tumor beyond primary site M3: gross nodular seeding in spinal subarachnoid space M4: metastasis outside cerebrospinal axis, especially in bone marrow and bone
Radiation side effects:
Lindsey -Growth disturbances are common; growth hormone deficiency in most long term survivors8-adverse effects may be directly related to the biologically effective dose -Gradual onset of endocrine deficits (ex: growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone) -Late optic neuropathy or brain necrosis in < 10% of cases of patients treated to doses > 60Gy -Secondary malignant neoplasms -Hyperfractionated treatments are associated with moderate acute epithelial toxicity such as otitis and radioepidermitis -Late toxicities with high dose hyperfractionated treatments: neurocognitive deficits, hearing loss, leukoencephalopathy, diffuse microhemorrhages, dystrophic calcifications on MRI
Prognosis:
Kevin Children who have a complete resection and the typical benign histology have a good prognosis. The prognosis for these cases is similar to adults.9
Treatments:
Kevin Surgery is the treatment of choice. If a tumor is only partially resected, or resection is not possible, radiation therapy can be used. However, given the significant side effects of radiation on the developing brain, especially in children under three, reoperation is a preferred strategy in some reports.10
TD 5/5:
Jenn Tissue dose associated with 5% injury rate within 5 years. (TD 5/5)11
Ear (Middle): Serous otitis 5000cGy
Ear (Vestibular): Meniere’s syndrome 6000cGy
Retina: Blindness 5500cGy
Cornea: Blindness 5000cGy
Lens: Blindness 500cGy
Salivary Glands: Xerostomia 5000cGy
Oral cavity and pharynx: Ulceration 6000cGy
Pituitary: Reduced hormone production 4500cGy
References:
Chao KS, Perez CA, Brady LW. Radiation Oncology Management Decisions. 3rd ed. Philadelphia, PA: Lippincott, Williams, and Wilkins; 2011: 719.
Signs and symptoms may differ from patient to patient depending on the size and location of the tumor. These symptoms inlcude:3
Some of the basic diagnostic proceudres that are used for Medulloblastomas include both Magnetic Resonance Imaging (MRI) as well as surgical biopsy to determine tumor type and grade.3
Medulloblastoma is a type of cerebellar tumor that is found in children and adults and stems from the cerebellar vermis. 4 The exact histologic origin isn’t clear so there are different views to describe where these tumors arise. The first opinion suggests that the tumor arises from the external granular layer of the cerebellum. 4 Precursor neurons that are found in this layer of the neurons are also found in pediatric medulloblastoma . 4 Another opinion suggests that
medulloblastomas can arise from more than 1 type of cell. 4 Studies have shown that a specific calcium-binding protein and beta-tubuline isotype found in some medulloblastoma patients isn’t found in the granular layer of cerebellum. 4 Research continues to explore the histology of these pediatric brain tumors as they are the most common malignant brain tumor in children.
Because the brain doesn't contain lymph node channels, metastasis do not occur through lymphatics.5
Medulloblastomas rarely metastasis outside central nervous system (CNS).6
According to world health organization (WHO), medulloblastomas are classified as Grade IV central nervous system tumors.7
Chang Staging System:8
T1: tumor < 3cm in diameter
T2: tumor > or = to 3cm in diameter
T3a: tumor > 3cm in diameter with extension into aqueduct of Sylvius or into the foramen of Luschka
T3b: tumor > 3cm in diameter with unequivocal extension into the brain stem
T4: tumor > 3cm in diameter with extension up past aqueduct of Sylvius or down past foramen magnum
M0: no evidence of subarachnoid or hematogenous metastasis
M1: tumor cells found in cerebrospinal fluid
M2: intracranial tumor beyond primary site
M3: gross nodular seeding in spinal subarachnoid space
M4: metastasis outside cerebrospinal axis, especially in bone marrow and bone
-Growth disturbances are common; growth hormone deficiency in most long term survivors8-adverse effects may be directly related to the biologically effective dose
-Gradual onset of endocrine deficits (ex: growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone)
-Late optic neuropathy or brain necrosis in < 10% of cases of patients treated to doses > 60Gy
-Secondary malignant neoplasms
-Hyperfractionated treatments are associated with moderate acute epithelial toxicity such as otitis and radioepidermitis
-Late toxicities with high dose hyperfractionated treatments: neurocognitive deficits, hearing loss, leukoencephalopathy, diffuse microhemorrhages, dystrophic calcifications on MRI
Children who have a complete resection and the typical benign histology have a good prognosis. The prognosis for these cases is similar to adults.9
Surgery is the treatment of choice. If a tumor is only partially resected, or resection is not possible, radiation therapy can be used. However, given the significant side effects of radiation on the developing brain, especially in children under three, reoperation is a preferred strategy in some reports.10
Tissue dose associated with 5% injury rate within 5 years. (TD 5/5)11
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