Posterior fossa syndrome and increased mean diffusivity in the olivary bodies

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OBJECTIVE

Posterior fossa syndrome (PFS) is a common postoperative complication following resection of posterior fossa tumors in children. It typically presents 1 to 2 days after surgery with mutism, ataxia, emotional lability, and other behavioral symptoms. Recent structural MRI studies have found an association between PFS and hypertrophic olivary degeneration, which is detectable as T2 hyperintensity in the inferior olivary nuclei (IONs) months after surgery. In this study, the authors investigated whether immediate postoperative diffusion tensor imaging (DTI) of the ION can serve as an early imaging marker of PFS.

METHODS

The authors retrospectively reviewed pediatric brain tumor patients treated at their institution, Lucile Packard Children’s Hospital at Stanford, from 2004 to 2016. They compared the immediate postoperative DTI studies obtained in 6 medulloblastoma patients who developed PFS to those of 6 age-matched controls.

RESULTS

Patients with PFS had statistically significant increased mean diffusivity (MD) in the left ION (1085.17 ± 215.51 vs 860.17 ± 102.64, p = 0.044) and variably increased MD in the right ION (923.17 ± 119.2 vs 873.67 ± 60.16, p = 0.385) compared with age-matched controls. Patients with PFS had downward trending fractional anisotropy (FA) in both the left (0.28 ± 0.06 vs 0.23 ± 0.03, p = 0.085) and right (0.29 ± 0.06 vs 0.25 ± 0.02, p = 0.164) IONs compared with age-matched controls, although neither of these values reached statistical significance.

CONCLUSIONS

Increased MD in the ION is associated with development of PFS. ION MD changes may represent an early imaging marker of PFS.

ABBREVIATIONS DTC = dentatothalamocortical; DTI = diffusion tensor imaging; FA = fractional anisotropy; GMT = Guillain-Mollaret triangle; HOD = hypertrophic olivary degeneration; ION = inferior olivary nucleus; MD = mean diffusivity; PFS = posterior fossa syndrome; ROI = region of interest; SCP = superior cerebellar peduncle.

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Article Information

Correspondence Kristen W. Yeom: Lucile Packard Children’s Hospital, Stanford University, Palo Alto, CA. kyeom@stanford.edu.

INCLUDE WHEN CITING Published online July 26, 2019; DOI: 10.3171/2019.5.PEDS1964.

D.Y. and R.J. contributed equally to this work.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    ROI placement (red circles). A: A structural T2-weighted MR image was used to cross-reference and identify the medullary olive (crosshairs) on DTI (B–D). B: Area just lateral to the medullary pyramids, indicated by the blue color (white arrows), which represents the conventional color scheme for the descending corticospinal tract, was interrogated and propagated to MD and FA maps. C and D: MD (C) and FA (D) maps. The ROI placements are shown corresponding to the expected locations for bilateral olivary regions in the medulla. Recent postoperative changes are seen in the posterior fossa. Figure is available in color online only.

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    MRI features of SCPs and hypertrophic olivary medulla. A–C: Both axial (A) and coronal (B and C) T2-weighted images were used to evaluate for abnormal signal of the SCPs. Abnormal signal is present in the right SCP (arrows, A and B). The left SCP appears slightly attenuated. Abnormal signal of the left SCP was also present on a more superior slice (not shown). Normal appearance of bilateral SCPs shown without abnormal signal (arrowheads, C). D: Example of hypertrophic olives is shown with T2 high signal on an axial image (red arrows). Figure is available in color online only.

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