Cardiac-induced brain tissue motion in Chiari Malformation type 1 subjects and its relationship to symptomatology, morphometrics, and surgical outcomes.

PURPOSE: To determine whether cardiac-induced brain-tissue displacement in Chiari Malformation type 1 (CMI) relates to patient symptoms, morphometrics, and surgical outcomes.

METHODS

We performed cardiac-gated phase-contrast MRI in 45 adults with CMI, converting velocity measurements to voxel-wise displacement in the cerebellum, pons, medulla, and cervical cord. We examined if displacement was correlated with each symptoms of subjects, and two anatomic measurements: tonsillar position (TP) and the ratio of neural-tissue area at foramen magnum to the area of foramen magnum. In seven patients who underwent posterior fossa decompression (PFD), we compared pre- versus post-operative displacement in seven paired scans and related changes to the Chicago Chiari Outcome Scale (CCOS).

RESULTS

No significant correlations were found between displacement and symptom reports. TP correlated moderately with displacement (r = 0.47-0.61, p < 0.002), and ratio of neural-tissue area showed modest links to cerebellar motion (r = 0.34-0.36, p < 0.02). After PFD, mean and peak cerebellar displacement decreased by 45 % and 60 %, respectively (p < 0.05), but neither pre-operative motion nor its reduction predicted CCOS scores.

CONCLUSION

While displacement increases with anatomical crowding and normalizes after surgery, it does not predict clinical symptoms or surgical outcomes. Future work should combine multiple biomechanical markers and detailed symptom scales in an effort to develop a multidimensional biomarker for guiding treatment and assessing recovery in CMI.