Pediatric Posterior Fossa Tumors: Diagnosis and follow up

1. Pediatric Posterior Fossa Tumors: Diagnosis and follow up Esther de Luis MD. PhD. Hospital Universitario Madrid Montepríncipe-Spain Clínica Universitaria de Navarra- Spain Hospital San Javier Guadalajara Mexico

2. 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

3. 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

4. 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

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

6. Medulloblastoma 1 year 4 monthsoldfemale. Vomiting and lethargy

7. Medulloblastoma 1 year 4 monthsoldfemale. Vomiting and lethargy

8. Medulloblastoma 1 year 4 monthsoldfemale. Vomiting and lethargy

9. Medulloblastoma 1 year 4 monthsoldfemale. Vomiting and lethargy

10. Medulloblastoma 1 year 4 monthsoldfemale. 2 monthsaftersurgery

11. Medulloblastoma 5 yearsoldfemale. Medulloblastoma removed 2 yearbefore. Chemo and radiotherapy

12. Medulloblastoma 5 yearsoldfemale. Medulloblastoma removed 2 yearbefore. Chemo and radiotherapy

13. Medulloblastoma 16 yearsoldmale. Medulloblastoma removed 1 yearbefore. Radiotherapy no chemotherapy

14. CerebellarAstrocytoma • 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 PilocyticAstrocytoma (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 anaplasticastrocytoma • 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

15. CerebellarAstrocytoma: JPA 15 yearsoldfemale. Biopsyconfirmed JPA

16. CerebellarAstrocytoma: JPA 15 yearsoldfemale. Biopsyconfirmed JPA

17. CerebellarAstrocytoma: JPA 15 yearsoldfemale. Biopsyconfirmed JPA

18. Ependymoma • Constitute 8-12% primary CNS neoplasm in children and 8-15% posterior fossa tumors • Ependymalcelltumors: floor and roof of fourthventricle • 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)

19. Ependymoma

20. Ependymoma

21. Atypical rhabdoidteratoid 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

22. 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

23. Brainstem Tumors: Medullary 15 yearsoldmale. JPA confirmed

24. Brainstem Tumors: Pontine 9 yearsoldmale. Glioma grade II WHO

25. Brainstem Tumors: Mesencephalic 19 yearsoldfemale. JPA

26. Brainstem: Quadrigeminal plate 16 yearsoldfemale

27. Brainstem Tumors: differential diagnosis

28. 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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