Medulloblastoma: Age Distribution and Neurological Presentation
Medulloblastoma is most common in children under 10 years of age, with peak incidence in the pediatric population (0-14 years), though it can occur in adults during their 3rd and 4th decades of life. 1, 2
Age Distribution
- Pediatric predominance: Medulloblastoma accounts for 10-20% of all pediatric brain tumors and is the most common malignant brain tumor in children 1, 3
- Peak age: Most cases occur before 10 years of age, with the highest incidence in children aged 0-14 years 2, 4
- Incidence rate: 0.47 per 100,000 children aged 0-14 years in the United States 3
- Adult cases: While much less common, medulloblastoma can occur in adults, typically in the 3rd and 4th decades of life (ages 20-40 years) 2
- Gender: More frequent in males across all age groups 2
Age-Related Molecular Subtype Patterns
- WNT-activated tumors: Most common in children aged 7-14 years 3
- SHH-activated tumors: Can occur across age groups, including adults 3, 5
Neurological Signs and Symptoms
The neurological presentation is dominated by signs of increased intracranial pressure and cerebellar dysfunction, with symptoms typically developing over less than 3 months. 6, 2
Signs of Increased Intracranial Pressure (Most Common)
These occur because medulloblastoma typically arises in the cerebellum or fourth ventricle, causing obstruction of cerebrospinal fluid flow: 6, 2
- Headache (often worse in the morning)
- Nausea and vomiting (particularly morning vomiting)
- Papilledema on fundoscopic examination
- Lethargy and altered mental status
- Macrocephaly (in infants with open fontanelles)
Cerebellar Signs
Due to the tumor's predilection for the cerebellar vermis and hemispheres: 6, 2
- Ataxia (truncal and/or appendicular)
- Dysmetria (impaired coordination of movements)
- Intention tremor
- Dysdiadochokinesia (inability to perform rapid alternating movements)
- Nystagmus
- Dysarthria (scanning speech)
Cranial Nerve Deficits
From brainstem compression or invasion: 2
- Sixth nerve palsy (abducens nerve, causing diplopia)
- Facial weakness (seventh nerve involvement)
- Hearing loss (eighth nerve involvement)
Signs of Leptomeningeal Dissemination
Present in approximately 33% of cases at diagnosis: 2
- Back pain (from spinal metastases)
- Radicular pain
- Lower extremity weakness
- Bowel or bladder dysfunction
- Cauda equina syndrome
Timeline and Pitfalls
- Symptom duration: Typically brief, usually less than 3 months from onset to diagnosis 6, 2
- Critical pitfall: The rapid progression of symptoms requires urgent neuroimaging; do not delay MRI if clinical suspicion is present 1
- Imaging requirement: MRI of both brain AND spine with gadolinium contrast is mandatory at diagnosis to detect leptomeningeal dissemination, which occurs in one-third of cases and dramatically affects prognosis and treatment stratification 1, 2