Dalley, 10th Edition

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Contents of Vertebral Canal

the spinal cord supplied by the anterior spinal artery (see Figs. 2.53 and 2.54). Neurons with cell bodies distant from the site of ischemia of the spinal cord will also die, secondary to the degenera tion of axons traversing the site. The likelihood of iatrogenic paraplegia depends on such factors as the age of the patient, the extent of the disease, and the length of time the aorta is cross clamped. When systemic blood pressure drops severely for 3–6 minutes, blood ow from the segmental medullary ar teries to the anterior spinal artery supplying the midthoracic region of the spinal cord may be reduced or stopped. These people may also lose sensation and voluntary movement in the areas supplied by the affected level of the spinal cord. Spinal Cord Injuries The vertebral canal varies considerably in size and shape from level to level, particularly in the cervi cal and lumbar regions. A narrow vertebral canal in the cervical region, into which the spinal cord ts tightly, is potentially dangerous because a minor fracture and/or dislocation of a cervical vertebra may damage the spi nal cord. The protrusion of a cervical IV disc into the verte bral canal after a neck injury may cause spinal cord shock associated with transient depression or abolition of re ex activity or paralysis inferior to the site of the lesion. In some people, no fracture or dislocation of cervi cal vertebrae can be found. If the individual dies and an autopsy is performed, a softening of the spinal cord may The spinal cord, spinal nerve roots, CSF, and meninges that surround them are the main contents of the vertebral canal. Spinal cord: In adults, the spinal cord occupies only the superior two thirds of the vertebral canal and has two (cervical and lumbosacral) enlargements related to innervation of the limbs. ■ The inferior, tapering end of the spinal cord, the conus medullaris, ends at the level of the L1 or L2 vertebra. ■ However, the lum terminale and spinal nerve roots from the lumbosacral part of the spinal cord that form the cauda equina continue inferiorly within the lumbar cistern containing CSF. Spinal meninges and CSF: Nerve tissues and neurovascular structures of the vertebral canal are suspended in CSF contained within the dural sac and dural root sheaths. ■ The uid- lled subarachnoid space is lined with the pia and arachnoid mater, which are continuous membranes The Bottom Line: Contents of Vertebral Canal

be detected at the site of the cervical disc protrusion. En croachment of the vertebral canal by a protruding IV disc, by swollen ligamenta ava, or resulting from osteoarthritis of the zygapophysial joints may exert pressure on one or more of the spinal nerve roots of the cauda equina. Pres sure may produce sensory and motor symptoms in the area of distribution of the involved spinal nerve. This group of bone and joint abnormalities, called lumbar spondylosis (degenerative joint disease), also causes localized pain and stiffness. Transection of the spinal cord results in loss of all sensa tion and voluntary movement inferior to the lesion. Transec tion between the following levels will result in the indicated effects: • C1–C3: no function below head level; a ventilator is re quired to maintain respiration. • C4–C5: quadriplegia (no function of upper and lower limbs); respiration occurs. • C6–C8: loss of lower limb function combined with a loss of hand and a variable amount of upper limb function; the individual may be able to self-feed or propel a wheelchair. • T1–T9 paraplegia (paralysis of both lower limbs); the amount of trunk control varies with the height of the lesion. • T10–L1: some thigh muscle function, which may allow walking with long leg braces • L2–L3: retention of most leg muscle function; short leg braces may be required for walking. (leptomeninges). ■ Because the spinal cord does not extend into the lumbar cistern (the inferior part of the subarachnoid space), it is an ideal site for sampling CSF or for injection of anesthetic agents. Vasculature of spinal cord and spinal nerve roots: Longitudinal spinal arteries supplying the spinal cord are reinforced by asymmetric segmental medullary arteries occurring at irregular levels (mostly in association with the cervical and lumbar enlargements) that also supply the spinal nerve roots at those levels ■ At levels and on the sides where segmental medullary arteries do not occur, radicular arteries supply the nerve roots. ■ The veins draining the spinal cord have a distribution and drainage generally re ective of the spinal arteries, although there are normally three longitudinal spinal veins both anteriorly and posteriorly.

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