Magnetic Resonance Imaging Observations of the Conus Medullaris in a Korean Population

Moon, Myung Sang; Jeong, Ji Ho; Kim, Sang Jae; Kim, Min Su; Choi, Won Rak

Abstract

STUDY DESIGN: Retrospective study (level of evidence: level 3). PURPOSE: To study the anatomy of the conus medullaris in Koreans. OVERVIEW OF LITERATURE: The anatomical position of the conus medullaris is well-documented in anatomy textbooks; however, the shape of the conus in the canal rarely described. Furthermore, to our knowledge, no study in Korea has not yet assessed the shape of the conus as well as its position in the canal via cadavaric dissection and/or magnetic resonance imaging (MRI).
METHODS
MRI findings of 189 Korean patients aged 2-94 years (93 men and 94 women) were assessed. No subjects from other ethnicities were included. The method proposed by Arai and colleagues was used to assess the termination point and shape of the conus in the canal. The position of the intervertebral disc trisection of the vertebral body closest to the tip of the conus was recorded at the canal level.
RESULTS
The tip of the conus medullaris was positioned from the upper T12 body to the L2-L3 disc, mostly in L1 bodies (52.4%), followed by the L2 bodies (22.5%), the L1-L2 disc, and the L2-L3 disc (1.1%). The shape of the conus was classified as type A in 74 (39.6%), type B in 58 (31%), and type C in 55 patients (29.4%). The conus did not terminate at the L3 body in any patient. In the first decade ones (five children) conus positioned rather lowly from L1 bodies to L2-L3 disc, and no type A conus shape, and mostly type B (80%).
CONCLUSIONS
The conus medullaris was positioned mostly in the lower one-third of L1 and it in the first decades terminated lowly. No type A in the first decade one, and type B was mostly frequently formed which was followed by type C.