Internal capsule: normal anatomy and ischemic changes demonstrated by computed tomography.

The purpose of this study was two-fold: (1) to attempt to localize the different parts of the internal capsule on computed tomography (CT) axial sections and (2) to correlate clinical data and CT appearance of 25 cases of ischemic capsular lesions. Twenty-three of the ischemic lesions produced a pure motor hemiplegia. The internal capsule was studied on routine CT axial sections parallel to the canthomeatal line with 8 mm collimation before and after intravenous contrast medium injection. Absorption values of the white matter at the level of the anterior limb of the internal capsule were found to be a little higher (mean, 32 Hounsfield units [H]) when compared with the posterior limb (mean, 28 H). Lesions were classified according to the topography of the internal capsule: anterior limb (three), genu (one), posterior limb (seven), and putaminocapsulocaudate (14). CT appears to be the most sensitive and reliable method to investigate small deep cerebral infarcts since isotope scans were positive in only two of 13 cases, while angiography was positive in eight of 17 cases.