OVERVIEW OF SPINAL CORD ANATOMY
The spinal cord begins where the medulla ends, running from the foramen magnum at the base of the skull to about the level of the first lumbar vertebra (L1) (Fig. 5–1). The spinal cord is divided into cervical, thoracic, lumbar, and sacral regions. The cervical and thoracic regions of the spinal cord correspond to the cervical and thoracic regions of the spinal column. However, the spinal cord is shorter than the spinal column, and so the lumbar region of the spinal cord actually corresponds to the lower thoracic spine, and the sacral region of the cord is housed in a short region called the conus medullaris at about the level of the L1-L2 vertebrae. Throughout the spine, dorsal roots enter and ventral roots exit through the neural foramina of the vertebrae that correspond to their spinal cord level of origin/exit. At cervical and thoracic levels, the corresponding foramina are essentially adjacent to the spinal cord levels with which they are associated. Since the spinal cord ends at L1, below L1, the lumbosacral nerve roots (cauda equina) must descend to reach their corresponding exiting foramina (discussed further in Chapters 15 and 17).
Schematic of lateral view of the spinal cord and nerve roots in relation to the spinal column. Reproduced with permission from Aminoff M, Greenberg D, Simon R: Clinical Neurology, 9th ed. New York: McGraw-Hill Education; 2015.
The lateral corticospinal tracts, dorsal column pathways, and anterolateral (spinothalamic) tracts are the three most clinically relevant pathways for clinical localization within the spinal cord. Sympathetic and parasympathetic pathways also traverse the spinal cord, and there are a number of other tracts (e.g., tectospinal, rubrospinal, vestibulospinal) that play roles in posture and motor control but are not generally assessed in clinical neurology. The spinocerebellar pathways that bring proprioceptive information to the cerebellum will be discussed in the context of the cerebellum in Chapter 8.
The lateral corticospinal tracts are lateral and posterior in the spinal cord, the dorsal columns are posterior and medial, and the anterolateral (spinothalamic) tracts are anterior and lateral (as their name suggests) (Fig. 5–2).
Schematic of axial section of the spinal cord. This schematic demonstrates the locations of the three main clinically relevant pathways and their lamination: corticospinal tracts, dorsal columns, and anterolateral (spinothalamic) tracts. Reproduced with permission from Waxman S: Clinical Neuroanatomy, 27th ed. New York: McGraw-Hill Education; 2013.
LAMINATION OF THE LONG TRACTS IN THE SPINAL CORD
Lamination refers to the arrangement of fibers within a pathway (Fig. 5–3...