QUANTITATIVE CINE-MODE MAGNETIC-RESONANCE-IMAGING OF CHIARI-I MALFORMATIONS - AN ANALYSIS OF CEREBROSPINAL-FLUID DYNAMICS

QUANTITATIVE CINE-MODE MAGNETIC resonance imaging of the craniocervica l junction was performed in 17 patients with a Chiari 1 malformation t o evaluate cerebrospinal fluid (CSF) dynamics, including 8 patients wh o underwent surgery. The cine-mode magnetic resonance images of these patients were compared with those of 12 normal pediatric and adult sub jects. The craniocervical junction was imaged by 16 cardiac-gated velo city-encoded images arranged in a cine loop. These images allowed the measurement of both the magnitude and direction of CSF velocity. Veloc ity measurements were made in four regions of interest-the foramen Mag endie, the foramen magnum, and ventral and dorsal to the spinal cord a t C2-and were plotted in relation to the cardiac cycle to produce a CS F velocity profile. All patients who underwent surgery had the same pr ocedure: a posterior fossa craniectomy with C1 laminectomy, lysis of a rachnoid adhesions, and duraplasty. Normal subjects had unobstructed f low around the craniocervical junction: a short period of cranial CSF flow was followed by a sustained period of caudal CSF flow. Patients w ith tonsillar herniation of more than 5 mm had obstructed CSF flow, de creased CSF velocity, and shorter periods of caudal CSF flow. These pa tients also had preferential cranial CSF flow as compared with the con trols. Postoperatively, there was a substantial increase in both the v elocity of CSF flow and in the period of caudal CSF flow in the forame n magnum. The postoperative changes mirrored the velocity profiles of the normal subjects. These changes in CSF velocity and direction corre lated with a more normal-appearing foramen magnum, a reduction in syri nx size, and an improvement in symptoms.