Dalley, 10th Edition

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Contents of Vertebral Canal

Posterior spinal arteries Posterior spinal veins Anterior spinal artery Anterior spinal veins Posterior, anterior segmental medullary arteries Posterior, anterior segmental medullary veins

Sulcal artery in anterior median fissure

Posterior and anterior segmental medullary arteries

Spinal branch *

Anterior spinal artery

2

Spinal nerve

Spinal ganglion Posterior radicular artery Anterior radicular artery

Spinal branch * Pia mater Intervertebral vein Anterior radicular artery Arachnoid mater Spinal dura mater Anterior internal vertebral (epidural) venous plexus

Anterior segmental medullary artery

Anterior median fissure

Dural root sleeve Spinal nerve

Spinal branches arise from the vertebral, intercostal, lumbar, or sacral artery, depending on level of spinal cord. *

(A) Anterolateral view

(B) Anterolateral view

FIGURE 2.54. Arterial supply and venous drainage of spinal cord and spinal nerve roots. A. Spinal veins. The veins that drain the spinal cord, as well as internal vertebral venous plexuses, drain into the intervertebral veins, which in turn drain into segmental veins. B. Spinal arteries. The pattern of the arterial supply of the spinal cord is from three longitudinal arteries: one anterior lying in the anteromedian position and the other two lying posterolaterally. These vessels are reinforced by medullary branches derived from the segmental arteries. The sulcal arteries are small branches of the anterior spinal artery coursing in the anterior median ssure.

CLINICAL BOX CONTENTS OF VERTEBRAL CANAL Compression of Lumbar Spinal Nerve Roots The lumbar spinal nerves increase in size from su perior to inferior, whereas the IV foramina de crease in diameter. Consequently, the L5 spinal nerve roots are the thickest, and their foramina, the narrowest. This increases the chance that these nerve roots will be compressed if osteophytes (bony spurs) develop (see Fig. B2.9A), or herniation of an IV disc occurs.

subarachnoid space. This technique shows the extent of the subarachnoid space and its extensions around the spinal nerve roots within the dural root sheaths. High-resolution MRI has largely supplanted myelography. Development of Meninges and Subarachnoid Space Together, the arachnoid and pia mater form the leptomeninges (G., slender membranes). They develop as a single layer from the mesenchyme sur rounding the embryonic spinal cord. Fluid- lled spaces form within this layer and coalesce to produce the subarachnoid space (Persaud & Torchia, 2025). The origin of both pia and arachnoid from a single membrane is re ected by the numerous arachnoid trabeculae passing between them (see Fig. 2.49). In adults, the arachnoid is thick enough to be manipulated with forceps. The delicate pia mater gives a shiny appearance to the surface of the spinal cord but is barely visible to the unaided eye as a distinct layer.

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Myelography

Myelography is a radiopaque contrast procedure that allows visualization of the spinal cord and spi nal nerve roots (see Fig. 2.51B). In this procedure, CSF is withdrawn by lumbar puncture and re placed with a contrast material injected into the spinal