Posterior fossa syndrome and increased mean diffusivity in the olivary bodies

Area of Science:

• Pediatric neurosurgery
• Neuroradiology
• Neuroscience

Background:

• Posterior fossa syndrome (PFS) is a frequent complication after pediatric posterior fossa tumor resection.
• PFS symptoms include mutism, ataxia, and behavioral changes, appearing 1-2 days post-surgery.
• Hypertrophic olivary degeneration (HOD) on MRI, indicated by T2 hyperintensity in inferior olivary nuclei (IONs), is linked to PFS but appears months later.

Purpose of the Study:

• To investigate if immediate postoperative diffusion tensor imaging (DTI) of the IONs can serve as an early imaging biomarker for PFS.
• To correlate early DTI findings in the IONs with the development of PFS in pediatric patients.

Main Methods:

• Retrospective review of pediatric brain tumor patients (2004-2016) at Lucile Packard Children's Hospital at Stanford.
• Comparison of immediate postoperative DTI scans from 6 medulloblastoma patients who developed PFS with 6 age-matched controls.
• Analysis of mean diffusivity (MD) and fractional anisotropy (FA) in the IONs using DTI.

Main Results:

• Patients with PFS showed significantly increased mean diffusivity (MD) in the left ION compared to controls (p=0.044).
• A trend towards increased MD was observed in the right ION of PFS patients, though not statistically significant (p=0.385).
• Fractional anisotropy (FA) in both IONs trended downwards in PFS patients, but did not reach statistical significance (p=0.085 for left, p=0.164 for right).

Conclusions:

• Elevated MD in the IONs is associated with the development of PFS in pediatric patients.
• ION MD changes detected via DTI may function as an early imaging marker for predicting PFS.
• This finding could lead to earlier identification and management of PFS.