Evaluation of Chiari I malformation by magnetic resonance imaging

Magnetic resonance imaging (MRI) was performed in 22 patients with Chiari I malformation using a Toshiba MRT-15 A scanner with a 0.15 T resistive magnet. A spin-echo (SE) technique with repetition time (Tsub(r)) of 500 msec and echo time (Tsub(e)) of 40 msec was used in all cases. Syringomyelia was associated with 12 patients (55 %), and hydrocephalus was seen in 5 patients (23 %). Two patients had past histories of meningocele. Craniovertebral junction bony anomalies were present in 9 patients; pathologic conditions included 8 basilar impression, 3 occipitalization, 2 C 2-3 fusion and 1 spina bifida at C1. Scoliosis was notided in 7 out of radiologically confirmed 17 cases. Measurement of basal angles was performed on midsagittal images of MRI by Welcker method. Mean basal angles of Chiari malformation was 138 degree, and was greater than that of 56 normal results. MRI was useful in the evaluation of the ventricular size, the position of the cerebellar tonsils, the degree of compression of the upper cervical cords and the status of the spinal cord, particularly whether a syringomyelic condition exists. Without known hazard, MRI was a modality of choice for the diagnosis of the Chiari malformation. (author)