IMG-01. LONGITUDINAL SIGNAL CHANGES IN THE DENTATE AND INFERIOR OLIVARY NUCLEI IN PATIENTS WITH CEREBELLAR MUTISM SYNDROME

Cerebellar mutism syndrome (CMS) is a complication of posterior fossa surgery with an acute impairment in speech, and long-term neurocognitive deficits. Lesion mapping studies suggest the cognitive symptoms are associated with dentatorubrolivary damage¹. We hypothesize that CMS patients will demonstrate more longitudinal MRI signal abnormalities in the dentate and inferior olivary nuclei as compared to non-CMS patients.

MRI brains on 40 pediatric medulloblastoma patients between 2013-2015 were retrospectively reviewed by a neuroradiologist blinded to the diagnosis at pre-operative and immediate, 6-month, 12 month and most recent post-operative time points. The dentate and inferior olivary nuclei were scored for restricted diffusion, T1 and T2 hypo-and hyperintensity. A linear regression with different scores on CMS status (YES vs NO) was applied, after adjusting for age.

In the dentate nuclei, there was significantly higher T2 hypointensity in the CMS group on immediate (difference is 0.4084, p=0.0467) and most recent (difference is 0.7190, p=0.0386) post-operative MRIs. The CMS group had significantly higher T1 hyperintensity on the 1-year (difference is 0.9254, p=0.0108) and most recent (difference is 1.3291, p<0.001) post-operative MRIs. In the inferior olivary nuclei, there was significantly higher T2 hyperintensity on the 6-month (difference is 0.71, p=0.0045) and 1-year (difference is 0.6356, p=0.0162) post-operative MRIs.

The immediate post-operative findings are suggestive of a hemorrhagic, rather than an ischemic process in the dentate nuclei. On long-term follow up, the signal changes in the dentate and the inferior olivary nuclei represent dystrophic mineralization and hypertrophic degeneration, due to inflammation and axonal degeneration within the dentatorubroolivary tract² References: 1. Albazron, Fatimah M., et al. “Pediatric postoperative cerebellar cognitive affective syndrome follows outflow pathway lesions.” Neurology 93.16 (2019). 2. Perreault, Sebastien, et al. “Time-dependent structural changes of the dentatothalamic pathway in children treated for posterior fossa tumor.” American journal of neuroradiology 35.4 (2014).