DTI fiber tractography of cerebro-cerebellar pathways and clinical evaluation of ataxia in childhood posterior fossa tumor survivors
Children and young adolescents with chronic surgical cerebellar lesions show persistent balance control problems during standing when lesions affect the deep cerebellar fastigial and adjacent interposed nuclei. The purpose of this study is to confirm that the same lesion sites are also associated with permanent signs of trunkal ataxia during sitting. A second aim is to demonstrate that examining the postural control of patients while sitting or standing on a foam cushion may constitute a simple clinical exam yielding results commensurate to a more involved dynamic posturography exam. Balance control was assessed in 16 patients after surgery of a benign cerebellar tumor in chronic state and healthy age- and gender-matched control subjects. Using an ultrasound-based kinematic recording system, trunkal and shoulder sway was measured during sitting and standing in different conditions. High-resolution MRI scans were acquired in the cerebellar patients. Voxel-wise statistical lesion symptom mapping was performed to compare lesioned areas between affected and unaffected patients in a given condition using χ 2 tests. During sitting, 56% of cerebellar patients exhibited trunkal sway outside the range of healthy controls, and 87.5% of cerebellar patients revealed abnormal sway patterns during standing. Abnormalities were most pronounced when visual information was absent, and somatosensory information became unreliable and/or when the base of support along the medio-lateral axis was minimized during tandem stance. Lesion symptom mapping revealed that pathological values in the behavior data were more likely in patients with surgical lesions involving the fastigial nuclei (NF) and adjacent interposed nuclei (NI). In patients with surgery <1-year lesions of the inferior cerebellar vermis also had an impact on balance function. Our results corroborate previous evidence that the extent of permanent damage to the deep cerebellar nuclei greatly impacts on the recovery on balance function.