Pediatric Medulloblastomas

, by  Anthony Joud , Jean-Claude Marchal , Olivier Klein, Pascal Chastagner , Pierre-Henri Pretat , Valérie Bernier-Chastagner , popularity : 10%
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Pathology |

IV. Epidemiology`

The incidence of medulloblastoma is 5 to 10 cases per 1 million children corresponding to approximately 150 new cases per year in France. The annual incidence is estimated at 0.5 per 100 000 children under 15 years (66). The American epidemiological surveillance (SEER) reported a decrease in the incidence of medulloblastoma, while the incidence of supratentorial PNET is increasing (42).

Medulloblastoma is observed at any age but 75% of tumors occur in children with a median age of 9 (57). Boys are more often affected than girls (sex ratio 1.5: 1). These are mostly sporadic cases but some genetic predispositions are associated with medulloblastoma: Gorlin syndrome (Basal Cell Nevus Syndrome), Li-Fraumeni syndrome, Bean syndrome (cutaneous and gastrointestinal telangiectasia), Turcot syndrome, ataxia-telangiectasia, Rubinstein-Taybi syndrome or mutation SUFU (1, 9, 20). In a study of 82 cases of medulloblastoma, a predisposing syndrome was observed in 9.7% and 28% in children aged under 14 and 3 years respectively (9)

V. Pathophysiologic Principles Of The Disease Process

MB often present with hydrocephalus secondary to compression of the CSF pathway, then cerebellar damage (static and / or kinetic cerebellar syndrome) and / or meningeal metastatic dissemination. The following can also be observed: long track affection with gait disorders, oculomotor paralysis (VI cranial nerve), other cranial nerve deficits, nystagmus, speech difficulties….

Medulloblastoma is the intracerebral tumor with the greatest propensity to metastasize. In 30-35% of cases, it is found in the CNS in the form of nodules in the brain and / or neuraxis or neoplastic meningitis. Spinal involvement may present with back pain, signs of spinal cord compression or radiculopathy. The clinical signs of meningeal metastases are those of meningitis. Medulloblastoma is the only intracerebral tumor which metastasizes outside the CNS; the most common sites being: the bone and then the bone marrow and exceptionally the lymph nodes, liver or lungs. These metastases are very rare, representing less than 5% of cases (37, 38). Such presentations demand the need for an emergency brain MRI (and of the spines if possible) to make the diagnosis of a posterior fossa space occupying lesion and rule out hydrocephalus.