All special interest groups

Special interest group

Neurosurgery

Lead: Andrea Carai, MD

The Neurosurgery group studies how operative strategy and technique affect the risk and severity of posterior fossa syndrome (PFS), also called cerebellar mutism syndrome. In 2025 its members led the Society's consensus statement on reducing that risk, which identifies the conduct of surgery as the most important modifiable factor.1

Consensus recommendations

Surgical approach

Use an adequately sized craniotomy and whichever approach, telovelar or transvermian, gives the greatest exposure of the tumor with the least retraction.

Centralization of care

Children with posterior fossa tumors should be managed by experienced surgeons in centers with a proven track record. Where these are not available, the child should be referred.

Surgical technique

Use the ultrasonic aspirator and bipolar cautery cautiously near the ependymal surface, and avoid fixed brain retraction systems.

Extent of resection

Review preoperative imaging for adherence or invasion into critical structures (dentate nucleus, superior cerebellar peduncle, facial colliculus). Where present, consider leaving the smallest possible remnant to preserve function.

Read the consensus statement

Evidence behind the recommendations

  • Center volume. In the prospective SJMB12 cohort, children operated on at low-volume centers had 2.59 times the odds of PFS (95% CI 1.21–5.55).2
  • Approach. Early series linked vermian incision to PFS,3 but later studies, including a prospective European multicenter cohort of 500 children, found no difference between transvermian and telovelar approaches after adjustment (OR 0.88, 95% CI 0.46–1.70).4, 5, 6, 7
  • Retraction. Children who developed PFS had higher retraction scores than those who did not (2.00 vs 1.38).3 The degree of retraction may matter more than the route taken.1
  • Ultrasonic aspirator. Centers that avoided it reported lower rates of PFS; at one center, a package of changes including avoiding the aspirator and limiting retraction coincided with a fall from 39% to 11%.3, 8, 9
  • Outcomes against prediction. At a high-volume center, 3 of 18 children rated high-risk by the Rotterdam model developed PFS, against about 12 predicted.10
  • Intraoperative imaging. Ultrasound use was associated with an 18% lower incidence of PFS;6 intraoperative MRI increases gross-total resection, but its effect on PFS is not yet known.11
  • Extent of resection. In medulloblastoma, residual tumor under 1.5 cm² may not change prognosis compared with complete resection;12 whether less aggressive resection reduces morbidity will be tested in the SIOPE-MB6 trial.1
  • Neoadjuvant chemotherapy. In a single-center study of 92 children with metastatic medulloblastoma, chemotherapy before surgery was safe, increased complete resection, and may improve neuropsychological outcome.13

Open questions

The consensus statement identifies priorities for prospective research: the effect of surgical expertise, neoadjuvant chemotherapy, and extent of resection in medulloblastoma; neurophysiological monitoring of the cerebellum, which is feasible but not yet shown to reduce PFS; and perioperative medications, since dexamethasone has no proven effect and evidence for other agents comes from small series.1

Selected references

  1. Toescu SM, Pizer B, Gump W, et al. Toward reducing the risk of cerebellar mutism syndrome: consensus statement from the Posterior Fossa Society. J Neurosurg Pediatr. 2025;36:789–797. Link
  2. Khan RB, Patay Z, Klimo P, et al. Clinical features, neurologic recovery, and risk factors of postoperative posterior fossa syndrome and delayed recovery: a prospective study. Neuro Oncol. 2021;23(9):1586–1596. Link
  3. Cobourn K, Marayati F, Tsering D, et al. Cerebellar mutism syndrome: current approaches to minimize risk for CMS. Childs Nerv Syst. 2020;36(6):1171–1179. Link
  4. Grønbæk JK, Wibroe M, Toescu S, et al. Postoperative speech impairment and surgical approach to posterior fossa tumours in children: a prospective European multicentre cohort study. Lancet Child Adolesc Health. 2021;5(11):814–824. Link
  5. Pettersson SD, Kitlinski M, Miękisiak G, et al. Risk factors for postoperative cerebellar mutism syndrome in pediatric patients: a systematic review and meta-analysis. J Neurosurg Pediatr. 2022;29(4):467–475. Link
  6. Toescu SM, Samarth G, Layard Horsfall H, et al. Fourth ventricle tumors in children: complications and influence of surgical approach. J Neurosurg Pediatr. 2021;27(1):52–61. Link
  7. Onorini N, Spennato P, Orlando V, et al. The clinical and prognostic impact of the choice of surgical approach to fourth ventricular tumors in a single-center, single-surgeon cohort of 92 consecutive pediatric patients. Front Oncol. 2022;12:821738. Link
  8. Patel N, Keating G, Solanki GA, et al. Medulloblastomas, CNS embryonal tumors, and cerebellar mutism syndrome: advances in care and future directions. Childs Nerv Syst. 2023;39(10):2633–2647. Link
  9. Wells EM, Khademian ZP, Walsh KS, et al. Postoperative cerebellar mutism syndrome following treatment of medulloblastoma: neuroradiographic features and origin. J Neurosurg Pediatr. 2010;5(4):329–334. Link
  10. Bush S, Klimo P Jr, Onar-Thomas A, et al. Application of the Rotterdam postoperative cerebellar mutism syndrome prediction model in patients undergoing surgery for medulloblastoma in a single institution. J Neurosurg Pediatr. 2024;33(2):174–178. Link
  11. Adegboyega G, Momin S, Gillespie CS, et al. Intraoperative MRI in pediatric epilepsy and neuro-oncology: a systematic review and meta-analysis. J Neurosurg Pediatr. 2024;34(6):628–641. Link
  12. Keeling C, Davies S, Goddard J, et al. The clinical significance of sub-total surgical resection in childhood medulloblastoma: a multi-cohort analysis of 1100 patients. EClinicalMedicine. 2024;69:102469. Link
  13. Guerrini-Rousseau L, Abbas R, Huybrechts S, et al. Role of neoadjuvant chemotherapy in metastatic medulloblastoma: a comparative study in 92 children. Neuro Oncol. 2020;22(11):1686–1695. Link

Get involved

Society members can join this group by contacting its lead or writing to info@posteriorfossasociety.org. Not yet a member? Membership is open to clinicians and researchers working on postoperative pediatric cerebellar mutism syndrome.

Membership