Arterial Spin-Labeling Perfusion Metrics in Pediatric Posterior Fossa Tumor Surgery

Abstract

Background and purpose: Pediatric posterior fossa tumors often present with hydrocephalus; postoperatively, up to 25% of patients develop cerebellar mutism syndrome. Arterial spin-labeling is a noninvasive means of quantifying CBF and bolus arrival time. The aim of this study was to investigate how changes in perfusion metrics in children with posterior fossa tumors are modulated by cerebellar mutism syndrome and hydrocephalus requiring pre-resection CSF diversion.

Materials and methods: Forty-four patients were prospectively scanned at 3 time points (preoperatively, postoperatively, and at 3-month follow-up) with single- and multi-inflow time arterial spin-labeling sequences. Regional analyses of CBF and bolus arrival time were conducted using coregistered anatomic parcellations. ANOVA and multivariable, linear mixed-effects modeling analysis approaches were used. The study was registered at clinicaltrials.gov (NCT03471026).

Results: CBF increased after tumor resection and at follow-up scanning (P = .045). Bolus arrival time decreased after tumor resection and at follow-up scanning (P = .018). Bolus arrival time was prolonged (P = .058) following the midline approach, compared with cerebellar hemispheric surgical approaches to posterior fossa tumors. Multivariable linear mixed-effects modeling showed that regional perfusion changes were more pronounced in the 6 children who presented with symptomatic obstructive hydrocephalus requiring pre-resection CSF diversion, with hydrocephalus lowering the baseline mean CBF by 20.5 (standard error, 6.27) mL/100g/min. Children diagnosed with cerebellar mutism syndrome (8/44, 18.2%) had significantly higher CBF at follow-up imaging than those who were not (P = .040), but no differences in pre- or postoperative perfusion parameters were seen.

Conclusions: Multi-inflow time arterial spin-labeling shows promise as a noninvasive tool to evaluate cerebral perfusion in the setting of pediatric obstructive hydrocephalus and demonstrates increased CBF following resolution of cerebellar mutism syndrome.

FIG 1.

Violin plots showing changes in perfusion metrics across time points for all patients’ brain regions. The horizontal line within the plot indicates the median. Darker data points indicate patients with CMS. A, CBF derived from single-PLD ASL. B, BAT derived from multi-TI ASL. C, CBF derived from multi-TI ASL. Horizontal significance bars show false discovery rate–adjusted P values from t test pair-wise comparisons (degree sign indicates P < .1; asterisk, P < .05). Pre-op indicates preoperative; Post-op, postoperative.

FIG 2.

Sample ASL maps of a patient with a posterior fossa pilocytic astrocytoma on a midthalamic axial section. A, Single-PLD CBF maps at preoperative, postoperative, and follow-up time points. Color bar indicates milliliters/100g/min. B, Raw multi-TI ASL data show a difference in magnetization (dM) between control and label scans at selected sequentially increasing TIs at a follow-up scan. Color bar indicates arbitrary units of dM.

FIG 3.

Boxplots depicting perfusion metrics stratified by brain regions in patients with and without symptomatic HCP. A, CBF derived from single-PLD ASL. B, BAT derived from multi-TI ASL. False discovery rate–adjusted P values: Degree sign indicates P < .1; asterisk, P < .05; double asterisks, P < .01; triple asterisks, P < .001. Pre-op indicates preoperative; Post-op, postoperative.