Prevalence of Medullary Glioblastoma
Clarification of Terminology
The term "medullary glioblastoma" requires clarification, as it likely refers to either intramedullary spinal cord glioblastoma or medulloblastoma (a cerebellar tumor), which are distinct entities with vastly different prevalence rates.
If Referring to Intramedullary Spinal Cord Glioblastoma
Intramedullary glioblastoma is an extremely rare entity, comprising only 1.4-9% of all spinal gliomas. 1
Spinal cord glioblastomas are exceptionally uncommon compared to their intracranial counterparts, with the vast majority of glioblastomas occurring in the brain rather than the spinal cord. 1
The overall incidence of glioblastoma (predominantly intracranial) ranges from 0.59 to 5 per 100,000 persons, with approximately 3.19 cases per 100,000 person-years reported in recent studies. 2, 3
Glioblastoma accounts for approximately 49% of all malignant primary brain tumors in adults, with an annual incidence of primary malignant brain tumors of approximately 7 per 100,000 individuals. 4
Given that intramedullary spinal glioblastomas represent only 1.4-9% of spinal gliomas (which themselves are rare), the prevalence of true intramedullary glioblastoma is extraordinarily low—likely fewer than 0.1 cases per 100,000 population. 1
If Referring to Medulloblastoma
Medulloblastoma has a substantially higher prevalence than intramedullary glioblastoma, though it remains relatively uncommon, particularly in adults.
Pediatric Population
Medulloblastoma accounts for approximately 10-20% of all pediatric brain tumors, with an incidence of 0.47 per 100,000 children aged 0-14 years. 5
The estimated prevalence in the United States includes approximately 1,423 pediatric cases. 5
Medulloblastoma represents only 1.8% of all brain tumors overall but is the most common malignant brain tumor type among children. 5
Adult Population
In adults, medulloblastoma is exceedingly rare, with only approximately 140 new cases diagnosed annually in the United States in patients aged ≥15 years. 5
Patients aged ≥40 years represent fewer than 30 new cases per year, accounting for less than 8% of all medulloblastoma cases. 5
The estimated prevalence in the United States includes 1,862 cases in late adolescent and young adult (AYA) patients aged 15-39 years (most diagnosed in childhood), 492 cases aged 40-64 years, and only 58 cases aged ≥65 years. 5
The overall incidence of CNS primitive neuroectodermal tumors (PNETs), which include medulloblastoma, is 0.26 per 100,000 person-years. 5
Key Clinical Distinctions
Medulloblastoma is classified as a WHO grade 4 malignant primary CNS tumor arising in the cerebellum (posterior fossa), not the spinal cord. 5
Intramedullary glioblastoma arises within the spinal cord parenchyma itself and represents a completely different pathologic entity from medulloblastoma. 1
The rarity of both conditions in adults necessitates referral to specialized centers or "centers of excellence" with expertise in managing these tumors. 5