MOTION OF THE CEREBELLAR TONSILS IN CHIARI TYPE-I MALFORMATION STUDIED BY CINE PHASE-CONTRAST MRI

We studied the effects on CSF dynamics at the foramen magnum and the c linical significance of the abnormal tonsillar motion in 14 patients w ith Chiari type I malformation and 14 control subjects using cine phas e-contrast MRI. Dynamic MRI consisted of axial and sagittal cine phase -contrast sequences. CSF and tonsillar motion were qualitatively and q uantitatively evaluated, and the subarachnoid space at the foramen mag num measured. In Chiari patients, cine phase-contrast MRI detected the abnormal pulsatile motion of the cerebellar tonsils, which produced a selective obstruction of CSF flow from the cranial cavity to the spin e. The amplitude of the tonsillar pulsation and the severity of the ar achnoid space reduction were associated with the symptom of cough-stra in headache, but not with the presence of syringomyelia. The finding o f abnormal valve dynamics of the cerebellar hernia revealed by cine ph ase-contrast MRI conforms to the pathophysiologic mechanisms suggested in pressure register studies and opens a new possibility in the presu rgical assessment of Chiari patients with exertional symptoms.