Sung Ho Jang (DTI), have contributed to research on somatotopy at the supratentorial level.9,10,12,15,32,33 However, only a few DTT studies have reported on somatotopy in the human brain- stem.11,16,18 In the current study, I reviewed the literature on somato- topic location and arrangement at the brainstem of the hu- man brain. Relevant studies were identified using the fol- lowing electronic databases (Pubmed and MEDLINE) from 1966 to 2011. The following key words were used: CST, somatotopy, brainstem, cerebral peduncle (CP), mid- brain, pons, and medulla. I limited this review to human studies of the CST and excluded studies of the corticonu- clear or the corticobulbar tract. Ultimately, nine studies were selected for this review.8,11,16-19,21,34,35 MIDBRAIN Many studies using the Wallerian degeneration phenome- non on brain CT or MRI,23-25,28-31,36 direct brain stimulation study during surgery,27 pedunculotomy for control of invol- untary movements,37,38 or DTT18,39,40 have demonstrated the location of the CST at the CP of the human brain. Studies reporting that the CST was located in the middle portion of the CP have been a general trend;23,24,29,30,36 on the other hand, some textbooks or studies have suggested more spe- cific data: the middle three-fifths,1 middle half,31 or middle two-thirds.22 However, three recent DTT studies provided visual data suggesting that the CST was located in the mid to lateral portion of the CP.18,39,40 As for the somatotopic location and arrangement of the CST, many neuroanatomy textbooks have shown mediolat- eral arrangement of somatotopies for the arm and leg.1,22 However, there has been a shortage of studies that elucidated somatotopic anatomy in detail.18,34 In 1967, Mantinez, et al.34 investigated somatopic anatomy using a direct brain stimula- tion study during stereotactic surgery in more than 700 pa- tients. They found face predominance from 7 to 12 mm be- hind the anterior commissure, and maximal response for the upper limb at 14 mm and at 19 mm for the lower limb. They reported an antero-posterior somatotopic arrangement from the face to the upper and lower limbs, rather than a medio-lateral arrangement at the upper CP. Since the intro- duction of DTT, one DTT study has reported on the somato- topic arrangement of the CST at the CP.18 In 2008, Park, et al.18 attempted to demonstrate the somatotopic arrangement at the CP of nine normal human brains. They found that the CST showed transverse orientation in the mid to lateral por- tion of the CP, and that hand fibers were located medial to foot fibers. Therefore, they concluded that somatotopic ar- rangement for the hand and leg showed medio-lateral ori- entation at the CP. Table 1. Previous Studies on Somatotopical Location and Arrangement in the Brainstem of the Human Brain Location Authors Pubyliecaartion Subject No. Method Results Midbrain Martinez et al.34 700 Direct stimulation study Pons Park et al.18 Schneider and Gautier35 Bassetti et al.8 Tohgi et al.21 Schmahmann et al.19 Marx et al.17 Hong et al.11 Medulla Kwon et al.16 1967 2008 1994 1996 1996 2004 2005 2010 2011 9 (normal) Diffusion tensor tractography 17 (stroke) Clinico-radiological study 21 (infarct) Clinico-radiological study 36 (infarct) Clinico-radiological study 25 (infarct) Clinico-radiological study 41 (infarct) Clinico-radiological study 25 (normal) Diffusion tensor tractography 30 (normal) Diffusion tensor tractography Antero-posterior somatotopic arrangement (face-upper limb-lower limb) Medio-lateral somatotopic arrangement (hand-foot) Arm somatotopy : antero-medial Leg somatotopy : postero-lateral Hand somatotopy : ventro-medial Hand somatotopy : dorso-medial Leg somatotopy : ventro-medial Hand somatotopy : ventro-medial Leg somatotopy : dorso-lateral No somatotopical difference of arm and leg Hand somatotopy : ventro-medial Leg somatotopy : dorso-lateral Hand somatotopy : medial Leg somatotopy : lateral 554 Yonsei Med J http://www.eymj.org Volume 52 Number 4 July 2011