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Figures
- Fig 1.
Parasagittal and coronal T2-weighted MR images of the postmortem human brain stem. A, Canonical axial brain stem levels parallel to the anterior/posterior commissure plane that are found in Fig 2 are represented with the solid lines and On-line Fig 1 with the dashed line. Only selected brain stem substructures are labeled in coaligned sagittal and coronal images to orient the reader relative to the craniocaudal axial slice positions. The On-line Table provides a complete list of labeled anatomy for all figures, indicated by the numbers in parentheses in the legends. Note the trochlear nerve (asterisk, C) only seen in some brains.
- Fig 2.
Axial modified T2-weighted TSE images at 6 canonical levels of the postmortem brain stem orientated parallel to the anterior/posterior commissure plane. Upper row: A, cranial midbrain; B, caudal midbrain. Middle row: C, cranial pons; D, caudal pons. Lower row: E, cranial medulla, F, caudal medulla. Improved image contrast from the modified TSE sequence directly demonstrates even small structures like the medial longitudinal fasciculus (16). Note the sensory decussation of the medial lemniscus in the caudal medulla (asterisk, F). The motor decussation is demonstrated in Fig 3.
- Fig 3.
Demonstration of the corticospinal tract (asterisk) throughout the brain stem. A, Parasagittal image depicts the corticospinal tract descending within the brain stem from the cerebral peduncle to the upper cervical cord. B, Coronal image shows the course of the corticospinal tract from the posterior limb of the internal capsule to the most superior aspect of the medullary pyramids. Note in the diencephalic junction, the close relationship of the corticospinal tract to the optic tract (45) laterally and the subthalamic nucleus (46) medially. Oblique coronal (C) and oblique axial (D) images highlight the decussation of the corticospinal tracts at the cervicomedullary junction. C, The paramedian dark lines are the medial lemniscus (9), which is superficial to the corticospinal tract on this oblique axial image.
- Fig 4.
Demonstration of the medial lemniscus (asterisk) throughout the brain stem. A, Coronal image shows the change in the long-axis orientation of the medial lemniscus from anteroposterior to transverse as it ascends the medulla to the pontomedullary junction. B, Parasagittal image highlights the terminations of the medial lemniscus in the ventral posterolateral thalamic nucleus (50). C, Axial image angled anteroinferior to posterosuperior 20° relative to the ACPC plane through the inferior colliculus (6) shows the relationship of the medial lemniscus to the spinothalamic tract (12) and lateral lemniscus (22) at the lateral tegmentum.
- Fig 5.
Demonstration of the medial longitudinal fasciculus (asterisk) throughout the brain stem. A, Sagittal image depicts the dorsal course of the medial longitudinal fasciculus from its origin in the cranial medulla just superior to the hypoglossal nucleus (40) to the level of the red nucleus (3). B, Coronal oblique image that is perpendicular to the long axis of the hippocampus (structure not shown) at the level of the posterior commissure shows the terminations of the tract in the inferior walls of the third ventricle (58). This coronal image also highlights vertical columns of the central midbrain from lateral to medial: lateral lemniscus (22), superior cerebellar peduncle (7), central tegmental tract (26), and medial longitudinal fasciculus (asterisk). C, Axial cranial midbrain image angled anterosuperior to posteroinferior 20° relative to the ACPC plane highlights the close relationship of the medial longitudinal fasciculus to the oculomotor nucleus (60).
Tables
Selected measurements for 5 major brain stem white matter tracts at 3 canonical axial planesa
Tract Fig CC Cranial Medulla Mid Pons Caudal Midbrain AP TV Area AP TV Area AP TV Area CST (L) 3 51.7 ± 4.8 2.9 ± 0.6 3.7 ± 0.5 8.8 ± 2.6b 6.6 ± 1.0 6.5 ± 0.7 33.9 ± 6.8b 6.1 ± 0.6 3.5 ± 0.5 17.1 ± 3.0b CST (R) 3 51.7 ± 4.8 2.7 ± 0.3 3.3 ± 0.4 7.3 ± 1.4b 5.7 ± 0.9 6.2 ± 0.8 28.2 ± 8.1b 6.1 ± 0.8 3.2 ± 0.8 15.5 ± 5.2b ML 4 46.9 ± 3.5 5.6 ± 0.8 0.6 ± 0.1 2.9 ± 0.6 1.2 ± 0.4 4.6 ± 0.7 4.7 ± 1.9 2.0 ± 0.4 3.0 ± 0.4 4.9 ± 1.4 MLF 5 39.6 ± 3.4 1.0 ± 0.3 0.5 ± .06 0.5 ± 0.2 1.4 ± 0.3 0.8 ± 0.1 0.9 ± 0.2 3.2 ± 0.4 0.7 ± 0.1 1.9 ± 0.5 CTT 6 37.7 ± 4.0 2.6 ± 0.4 1.6 ± 0.3 3.4 ± 0.8 1.7 ± 0.2 2.1 ± 0.4 2.9 ± 0.8 3.2 ± 0.3 3.6 ± 0.4 9.1 ± 1.5 Note:—CC indicates craniocaudal; AP, anteroposterior; TV, transverse; Fig, figure; L, left; R, right.
↵a Units are millimeters or square millimeters, and data are mean ± SD, with 13 SUDC samples.
↵b All measurements of the right and left corticospinal tracts were compared separately. Cross-sectional areas trended toward small statistical differences in the medulla (P = .099) and pons (P = .063), but not the midbrain (P = .361).
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