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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Neurosurgery

Surgery and Pathology: The First Major Milestone

At a Glance

Surgery is the critical first step in treating medulloblastoma, focusing on maximal safe resection to remove as much tumor as possible. Afterward, a detailed pathology report identifies the tumor's exact molecular subgroup to guide the next phase of treatment.

Surgery is the critical first step in treating medulloblastoma. It is both a life-saving intervention to relieve pressure and the only way to obtain the tissue needed to identify the tumor’s specific molecular type [1].

The Goal: Maximal Safe Resection

In pediatric neurosurgery, the standard objective is maximal safe resection [2]. This means the surgeon aims to remove as much of the tumor as possible while protecting the vital functions of the brain [1].

Because medulloblastoma grows in the posterior fossa—a small, crowded space containing the brainstem—the tumor may be tightly attached to nerves that control breathing, swallowing, or heart rate. If removing the final piece of the tumor would cause permanent neurological damage, the surgeon may intentionally leave a small portion behind [1][2].

Defining the Terms

After surgery, a follow-up MRI (usually within 48 hours) measures how much tumor remains. This is described using two main terms [3]:

  • Gross Total Resection (GTR): No visible tumor is left on the post-operative MRI.
  • Near-Total Resection: A very small amount of tumor remains, but it is less than 1.5 cm².
  • Subtotal Resection (STR): The remaining tumor is larger than 1.5 cm².

The 1.5 cm² cutoff is a traditional standard used to help determine if a patient is “standard-risk” or “high-risk.” However, modern medicine increasingly views the tumor’s molecular subgroup as equally or more important than the amount of tumor left behind [4][5].

Posterior Fossa Syndrome (Cerebellar Mutism)

Some children experience a complication called Posterior Fossa Syndrome (PFS), also known as Cerebellar Mutism Syndrome [6]. It occurs in about 15% to 25% of children, usually appearing 1 to 2 days after surgery [7].

The hallmark of PFS is a sudden loss of speech (mutism), often accompanied by intense irritability, difficulty swallowing, and poor muscle tone [6]. While the loss of speech is usually temporary, it can be a frightening experience for families. Long-term recovery often involves challenges with coordination and emotional regulation, requiring early and consistent support from physical, occupational, and speech therapists [8][9].

Your Pathology Report Checklist

A modern pathology report is more than just a description of cells. Following the 2021 WHO guidelines, it should provide an integrated diagnosis [10]. When you review the report with your oncologist, ensure the following markers are present:

  • [ ] Histology: Does it list the cell type (e.g., Classic, Desmoplastic, or Large Cell/Anaplastic)? [11]
  • [ ] Molecular Subgroup: Is the tumor clearly identified as WNT, SHH, Group 3, or Group 4? [12]
  • [ ] TP53 Status: For tumors in the SHH subgroup, has the TP53 mutation status been checked? [13]
  • [ ] MYC Status: For Group 3 tumors, has MYC amplification been assessed? [14]

If these molecular details are missing, ask your team if the tissue can be sent for DNA methylation profiling, the gold standard for accurate classification [15][16].

Common questions in this guide

What is a maximal safe resection in medulloblastoma surgery?
Maximal safe resection means the neurosurgeon removes as much of the tumor as possible without damaging critical brain functions like breathing or swallowing. If removing the entire tumor risks permanent neurological harm, a small piece may be intentionally left behind.
What is the difference between a gross total and subtotal resection?
Gross total resection means no visible tumor remains on the post-operative MRI. Subtotal resection means a residual tumor larger than 1.5 square centimeters was left behind, usually to protect vital nerves in the brainstem.
What is Posterior Fossa Syndrome after brain surgery?
Posterior Fossa Syndrome, also called cerebellar mutism, is a complication where a child temporarily loses the ability to speak 1 to 2 days after surgery. It can also cause intense irritability, swallowing difficulties, and poor muscle tone, often requiring dedicated rehabilitation.
What information should be in a medulloblastoma pathology report?
A modern pathology report should provide an integrated diagnosis based on 2021 WHO guidelines. It must identify the tumor's cell type, its specific molecular subgroup (WNT, SHH, Group 3, or Group 4), and key genetic markers like TP53 or MYC.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Was a 'gross total resection' achieved, and what is the exact measurement of any residual tumor?
  2. 2.If my child develops Posterior Fossa Syndrome, what is the hospital's protocol for immediate rehabilitation and support?
  3. 3.Does the pathology report use the 2021 WHO classification and include molecular subgrouping?
  4. 4.Was the tumor tested for TP53 (for SHH subgroup) or MYC (for Group 3) status?
  5. 5.How will the extent of the resection and the molecular markers together determine the next steps in treatment?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (16)
  1. 1

    Evolution of neurosurgical advances and nuances in medulloblastoma therapy.

    Rechberger JS, Power EA, DeCuypere M, Daniels DJ

    Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2024; (40(4)):1031-1044 doi:10.1007/s00381-023-06239-x.

    PMID: 38112693
  2. 2

    Effects of the growth pattern of medulloblastoma on short-term neurological impairments after surgery: results from the prospective multicenter HIT-SIOP PNET 4 study.

    Schepke E, Tisell M, Kennedy C, et al.

    Journal of neurosurgery. Pediatrics 2020; (25(4)):425-433 doi:10.3171/2019.11.PEDS19349.

    PMID: 31952041
  3. 3

    Safety and efficacy of concurrent carboplatin during full-dose craniospinal irradiation for high-risk/metastatic medulloblastoma in a resource-limited setting.

    Gupta T, Sinha S, Chinnaswamy G, et al.

    Pediatric blood & cancer 2021; (68(5)):e28925 doi:10.1002/pbc.28925.

    PMID: 33533557
  4. 4

    The clinical importance of medulloblastoma extent of resection: a systematic review.

    Thompson EM, Bramall A, Herndon JE, et al.

    Journal of neuro-oncology 2018; (139(3)):523-539 doi:10.1007/s11060-018-2906-5.

    PMID: 29796724
  5. 5

    Efficacy of Carboplatin and Isotretinoin in Children With High-risk Medulloblastoma: A Randomized Clinical Trial From the Children's Oncology Group.

    Leary SES, Packer RJ, Li Y, et al.

    JAMA oncology 2021; (7(9)):1313-1321 doi:10.1001/jamaoncol.2021.2224.

    PMID: 34292305
  6. 6

    Posterior fossa syndrome-a narrative review.

    Wahab SS, Hettige S, Mankad K, Aquilina K

    Quantitative imaging in medicine and surgery 2016; (6(5)):582-590 doi:10.21037/qims.2016.10.12.

    PMID: 27942479
  7. 7

    Medical management for cerebellar mutism syndrome following posterior fossa surgery: A systematic review.

    Turkistani AN, Alsharif TH, Aldhafeeri WF, et al.

    Clinical neurology and neurosurgery 2024; (242()):108352 doi:10.1016/j.clineuro.2024.108352.

    PMID: 38823197
  8. 8

    Long-Term Outcomes Associated With Posterior Fossa Syndrome in Survivors of Childhood Medulloblastoma.

    Sarvode S, Dhaduk R, Chen Y, et al.

    JAMA network open 2026; (9(2)):e2559376 doi:10.1001/jamanetworkopen.2025.59376.

    PMID: 41712211
  9. 9

    The Pediatric Physiatric Posterior Fossa Symptoms scale: Impairments and outcome in pediatric inpatient rehabilitation for posterior fossa brain tumors.

    Wu J, Wishart BD, Cohen SE, et al.

    Neuro-oncology 2025; (27(2)):508-516 doi:10.1093/neuonc/noae199.

    PMID: 39320989
  10. 10

    Spinal Ependymomas: An Updated WHO Classification and a Narrative Review.

    Villanueva-Castro E, Meraz-Soto JM, Hernández-Dehesa IA, et al.

    Cureus 2023; (15(11)):e49086 doi:10.7759/cureus.49086.

    PMID: 38125233
  11. 11

    Vismodegib as First-Line Treatment of Mutated Sonic Hedgehog Pathway in Adult Medulloblastoma.

    Kian W, Roisman LC, Goldstein IM, et al.

    JCO precision oncology 2020; (4()) doi:10.1200/PO.19.00264.

    PMID: 32923880
  12. 12

    Medulloblastoma genomics in the modern molecular era.

    Kumar R, Liu APY, Northcott PA

    Brain pathology (Zurich, Switzerland) 2020; (30(3)):679-690 doi:10.1111/bpa.12804.

    PMID: 31799776
  13. 13

    Molecular subtypes, prognostic factors, and treatment optimization in pediatric medulloblastoma: a real-world study from China.

    Liu J, Sun Y, Li H, et al.

    Frontiers in oncology 2025; (15()):1597123 doi:10.3389/fonc.2025.1597123.

    PMID: 40809009
  14. 14

    MYC promotes group 3 medulloblastoma cell proliferation and alleviates ROS-induced cell death by upregulating transketolase.

    Wang S, Zhang D, Wang C, Liu Y

    Acta neuropathologica communications 2025; (13(1)):139 doi:10.1186/s40478-025-02051-7.

    PMID: 40581635
  15. 15

    Pathology, diagnostics, and classification of medulloblastoma.

    Orr BA

    Brain pathology (Zurich, Switzerland) 2020; (30(3)):664-678 doi:10.1111/bpa.12837.

    PMID: 32239782
  16. 16

    Advances in the classification of pediatric brain tumors through DNA methylation profiling: From research tool to frontline diagnostic.

    Kumar R, Liu APY, Orr BA, et al.

    Cancer 2018; (124(21)):4168-4180 doi:10.1002/cncr.31583.

    PMID: 30255939

This page is for informational purposes only and does not replace professional medical advice. Always discuss your child's specific surgical risks, pathology results, and treatment plan with their neurosurgeon and neuro-oncologist.

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