MR Imaging of the Craniocervical Junction 209

Craniocervical junctions in 35 abnormal and 10 normal subjects were studied with a 0.5 T superconducting magnetic resonance imaging system. Sagittal spin echo with 30 msec echo times and 500 msec repetition times constituted the most informative imaging plane and sequence. The anterior aspect of the foramen magnum was well delineated; the posterior margin was less constant in appearance. Compression and distortion of the medulla and upper cervical cord by bony and extramedullary lesions were seen easily. Intramedullary cysts were differentiated from solid tumors, but ventricular communication was evaluated less successfully because of partial-volume effect of the sections. Cerebellar ectopias were detected in some asymptomatic patients.