Pediatric Posterior Fossa Tumors: Diagnosis and follow up

Esther de Luis MD. PhD.

Hospital Universitario Madrid Montepríncipe-SpainClínica Universitaria de Navarra- SpainHospital San Javier Guadalajara Mexico

Pediatric Posterior Fossa Tumors

• CNS tumors are the second most common pediatric tumors being exceed only by leukemya

• Supratentorial and posterior fossa tumors occur in nearly equal frequency

• Supratentorial tumors are more frequent in the first 2-3 years of life whereas infratentorial predominate from ages 4-10 years

Objectives

• Describe the intraparenchymal posterior fossa tumors in children and their imagining findings (MR and CT) and the importance of diffusion and spectroscopy in the differential diagnosis of these tumors

• Review the most common complications that occur during treatment and the importance of the radiologic follow up

Pediatric Posterior Fossa Tumors

• The most common posterior fossa tumors in children are medulloblastoma, astrocytoma and ependymoma

• The accurate diagnosis of these lesions is important to ensure that patients receive adequate therapy and prognostic information

Medulloblastoma

• Primitive Neuroectodermal Tumor of the posterior fossa (PNET)• Tumor with neuroblastic or glioblastic elements (embryonal tumor) • May appear intraventricular its origin is vermis cerebellar

parenchyma • Children 6-11 years old• Males 2-4 times than females• The duration of symptoms is short: nausea, vomiting (area

postrema), lethargy in small children and ataxia in older• Spinal metastases are present in initial diagnosis 30% cases• Extent of disease is the most important predictive prognosis• Increased frequency: Basal cell nevus syndrome

Medulloblastoma

1 year 4 months old female. Vomiting and lethargy

Medulloblastoma

1 year 4 months old female. Vomiting and lethargy

Medulloblastoma

1 year 4 months old female. Vomiting and lethargy

Medulloblastoma

1 year 4 months old female. Vomiting and lethargy

Medulloblastoma

1 year 4 months old female. 2 months after surgery

Medulloblastoma

5 years old female.Medulloblastoma removed 2 year before. Chemo and radiotherapy

Medulloblastoma

5 years old female.Medulloblastoma removed 2 year before. Chemo and radiotherapy

Medulloblastoma

16 years old male.Medulloblastoma removed 1 year before. Radiotherapy no chemotherapy

Cerebellar Astrocytoma

• 60% of astrocytomas in children are located in the posterior fossa: 40% cerebellum and 20% in the brainstem

• Most common astrocytoma in children are of a specific type: Juvenile Pilocytic Astrocytoma (JPA): grade I WHO

• JPA most benign astroglial tumor of CNS• JPA equal frequency males and females. 70% astrocytomas in children• Peak of incidence 8 years• Older children more frequent anaplastic astrocytoma• Symptoms: early morning headache and vomiting• Originate in midline, 30% extend into cerebellar hemispheres • 25% are solid• JPA excellent prognosis 90% survival rate after 25 years• Malignant transformation is exceeding rare• Gross total resection is curative• Tumors non surgically accessible: stereotactic radiosurgery

Cerebellar Astrocytoma: JPA

15 years old female. Biopsy confirmed JPA

Cerebellar Astrocytoma: JPA

15 years old female. Biopsy confirmed JPA

Cerebellar Astrocytoma: JPA

15 years old female. Biopsy confirmed JPA

Ependymoma

• Constitute 8-12% primary CNS neoplasm in children and 8-15% posterior fossa tumors

• Ependymal cell tumors: floor and roof of fourth ventricle • WHO grade II• The relative frequency diminishes as children grow up, they can

appear at any age• In children are more common infratentorial (70%)• Slightly more frequent in males• Two age peaks: 1-5 years and four decade• Long clinical history• Nausea and vomiting, hydrocephalus (90%), torticollis, ataxia and

lower cranial neuropathies(foramen of Luschka)

Ependymoma

Ependymoma

Atypical rhabdoid teratoid tumor

• Younger age than PNET • Median age at diagnosis less than 2 years of age• Lack of response to standard therapy• Special microscopic techniques• Rhabdoid cells: small round cells (only a minority of the

tumor)• Cerebellum most common site• May spread through the subarachnoid space• Imaging similar to medulloblastoma, calcification is

common, necrosis, cysts and hemorrhage

Brainstem Tumors

• Constitute 15% of all pediatric CNS tumors and 20-30% of infratentorial brain tumors

• Peak of incidence 3-10 years of age• Different types:– Medullary tumors– Pontine tumors– Mesencephalic tumors

• Focal or diffuse• Histology: astrocytoma, ganglioglioma, lymphoma• The most frequent astrocytoma• More frequent in NF 1

Brainstem Tumors: Medullary

15 years old male. JPA confirmed

Brainstem Tumors: Pontine

9 years old male. Glioma grade II WHO

Brainstem Tumors: Mesencephalic

19 years old female. JPA

Brainstem: Quadrigeminal plate

16 years old female

Brainstem Tumors: differential diagnosis

Conclusions

• It is important to know the best imaging technique and be familiar with the most common complications that occur during and after treatment

• Radiologists play an important role not only in the diagnosis but also in the follow up of children with posterior fossa tumors

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