The Spinal Cord: A Review of Functional Neuroanatomy

doi:10.1016/j.ncl.2012.09.009

Neurologic Clinics

Volume 31, Issue 1, February 2013, Pages 1-18

https://doi.org/10.1016/j.ncl.2012.09.009 Get rights and content

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Key points

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The spinal cord is located within the spinal canal but does not extend the entire length of the vertebral canal.
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The spinal cord is incompletely divided into 2 halves by a deep anterior median fissure and a shallow posterior median sulcus.
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The anatomic organization of ascending and descending pathways in the spinal cord often allows precise longitudinal and transverse localization of the pathologic process.
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Disproportion between the length of the spinal cord and the length of the bony spinal

Gross anatomy of spinal cord

The spinal cord is located within the spinal canal but does not extend the entire length of the vertebral canal. The spinal cord length is about 45 cm in men and 43 cm in women and its width ranges from 1.27 cm in cervical and lumbar regions to 64 mm in the thoracic region. There are 20 or 21 pairs of denticulate ligaments that constitute a surgical landmark for the anterolateral segment of the spinal cord. Caudally, the spinal cord is anchored by filum terminale, which is a nonneural membrane

Meninges

Dura mater, arachnoid, and pia mater are the membranes covering the spinal cord from the most superficial layer to that closest to the spinal cord, respectively (see Fig. 2B). The outer of the 2 cranial dural layers serves as the cranial periosteum and at the foramen magnum the inner layer separates to descend as the dural sleeve of the spinal cord. The epidural space separates dura from the vertebral canal and contains a layer of fat that can be useful as a magnetic resonance imaging landmark.

Longitudinal divisions

The spinal cord is incompletely divided into 2 halves by a deep anterior median fissure and a shallow posterior median sulcus (Fig. 4). The anterior median fissure contains a double fold of pia mater, and its floor is the anterior (ventral) white commissure. More laterally is the anterolateral sulcus, marking the exit of the ventral roots. The posterior median sulcus is a shallow septum, on either side of which lies the posterolateral sulcus, the site of the posterior nerve roots entry. Three

Spinal roots and nerves

The dorsal roots consist of several types of afferent fibers somatotopically organized such that the largest diameter fibers are medial to the smaller ones (see Fig. 4). These largest afferent fibers (Ia and Ib) are heavily myelinated fibers that conduct the afferent limb of muscle stretch reflexes and carry information from muscle spindles and Golgi tendon organs. Medium-sized fibers (A-beta) convey impulses from mechanoreceptors in skin and joints. Small, thinly myelinated A-delta and C-type

Internal anatomy of the spinal cord: gray matter

The gray matter of the spinal cord is an H-shaped structure in the transverse section of the spinal cord with 2 symmetric halves connected by a narrow bridge or commissure composed of gray and white matter through which runs the central canal (see Fig. 4). The central canal is a continuation of the fourth ventricle. Lined with ciliated columnar epithelium, it is filled with cerebrospinal fluid. Encircling the columnar epithelium is a band of neuroglia, the substantia gliosa. The ratio of gray

Architectural lamination of the spinal cord gray matter

Rexed’s cytoarchitectural studies of the spinal cord gray matter are the basis of the conventional gray matter division into the 10 eponymic laminae enumerated as Rexed’s laminae I to X. Laminae I to IX are arranged from dorsal to ventral, whereas Lamina X consists of a circle of cells around the central canal (see Fig. 4, also diagrammed in Fig. 5). Some of the laminae correspond to specific cell types with functional significance. Thus, Lamina II corresponds to the substantia gelatinosa and

Descending Fiber Systems

The corticospinal tract, arising from the precentral motor cortex, is the largest and most significant descending tract of the human spinal cord (Fig. 6).¹ Almost 90% of the corticospinal tract fibers decussate in the lower medulla to form the lateral corticospinal tract, whereas 8% of the nondecussating descending fibers form the anterior corticospinal tract and 2% of noncrossing fibers generate the uncrossed lateral corticospinal tract. The uncrossed fibers of the anterior corticospinal tract

Clinical approach to patient with spinal cord problem

The anatomic organization of ascending and descending pathways in the spinal cord described earlier often allows precise longitudinal and transverse localization of the pathologic process. Such localization not only directs diagnostic imaging procedures efficiently to the appropriate site but also offers early etiologic clues because many disease processes preferentially produce specific patterns of spinal cord dysfunction. For example, “tractopathies” such as dorsal column dysfunction occurs

Noncompressive myelopathies

Noncompressive myelopathies include most neuropathologies that initiate in the intramedullary compartment although noncompressive and intramedullary are not synonymous terms, as significant inflammatory or infectious conditions can expand the cord.⁴

Clinical clues of a noncompressive myelopathy include the following:

1.
Radicular and bone pain uncommon
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Dysesthetic pain: the patient will use words to describe associated paresthesias, such as burning, tingling, or tightness
3.
Late UMN with diffuse LMN at

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References (6)

J.H. Kaas et al.
Cortical and subcortical plasticity in the brains of humans, primates, and rats after damage to sensory afferents in the dorsal columns of the spinal cord
Exp Neurol
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P.W. Nathan et al.
Long descending tracts in man. I. Review of present knowledge
Brain
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C.J. Hodge et al.
The spinothalamic tract
Crit Rev Neurobiol
(1990)

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