Herniated Nucleus Pulposus Flashcards
Comprises the cartilaginous joint between adjacent vertebral bodies
-allows for mobility between adjacent vertebrae
Intervertebral disk
The intervertebral disk functions as a
Shock absorber
The outer portion of the intervertebral disk
Anulus fibrosis
Composed of rings of fibrocartilage and fibrous connective tissue with a high collagen content
Anulus fibrosis
The inner portion of the intervertebral disk is the
Nucleus pulposus
Gelatinous in character, contains few cells, and is rich in proteoglycans
Nucleus pulposus
There is a high water content bound in the nucleus pulposus, and this provides
Turgor (rigidity) to the disk
Serves the function of distributing pressure throughout the disk when the vertebral column is weight bearing (i.e. upright posture)
Nucleus Pulposus
What happens when you are standing upright?
Water is squeezed out of nucleus and the nucleus gets thinner
When not weight bearing (i.e. when reclined), water returns to the nucleus and the disk gets
Thicker
The thinning of the nucleus from water loss due to upright posture explains why we are
Taller in the morning than at night
With age, there is a loss of proteoglycans in the nucleus pulposus and therefore the amount of bound water is
Reduced
The loss of proteoglycans, and therefore water, from the nucleus pulposus explains what phenomenon of aging?
We get shorter
The nucleus pulposus is not centrally positioned in the disk, but rather it is positioned towards the
Posterior side of disk
Thinner posteriorly than it is anteriorly because of position of nucleus pulposus
Anulus fibrosus
What can happen with degeneration of the anulus fibrosus and with pressure applied to the intervertebral disk during movement?
Anulus ruptures and nucleus pulposus can herniate through anulus
Because the anulus is thinner posteriorly and because flexion of the spine stretches the posterior portion of the anulus and squeezes the nucleus pulposus posteriorly, the nucleus is much more likely to herniate in a
Posterior direction
However, because the posterior midline of the disk is reinforced by the posterior longitudinal ligament, the nucleus is most likely to herniate in a
Posterolateral direction
This posterolateral herniation can result in impingement on the roots of spinal nerves in either the
Lateral portion of vertebral canal, or in intervertebral foramen
Compression of the spinal nerves (or spinal roots) may result in
Sensory/motor disturbance
The location of these clinical findings will be in regions of distribution of these spinal nerve fibers known as
Dermatomes (for sensory findings) and myatomes (for motor findings)
Formed by the apposition of adjacent intervertebral notches, i.e. the inferior notch of one vertebra with the superior notch of the next
Intervertebral foramen
Anteriorly, the borders of the intervertebral foramen are
Body of vertebra above, intervertebreal disk, and body of vertebra below
Posteriorly, the borders of the intervertebral foramen are the
Inferior articular facet of vertebra above, superior articular facet of vertebra below, and zygopophyseal joint
Superiorly and inferiorly, the boundaries of the intervertebral foramen are
Pedicles
A spinal nerve passes through each
Intervertebral foramen
Named according to which intervertebral foramen it passes through
A spinal nerve
At thoracic and lumbar levels, the nerve takes the name of the vertebra
Above the foramen
Where does the L1 nerve pass through?
The foramen between L1 and L2
At cervical levels, the nerve takes the name of the vertebra
Below the foramen
Where does the C3 nerve pass?
The foramen between C2 and C3
Where does the C8 nerve pass?
The foramen between C7 and T1
Because the lumbar spinal nerve roots descend a considerable distance through the vertebral canal from their origin at the spinal cord to their exit at the intervertebral foramen, they exit through the
Upper portion of the foramen
Forms the anterior border of the lower portion of the foramen
Intervertebral disk
Thus, lumbar spinal nerves exit through their intervertebral foramina above the level of the
Intervertebral disk
Therefore, it is likely that a small herniated nucleus pulposus at lumbar levels will not impinge on the
Spinal nerve exiting that foramen
Will impinge on the nerve roots that are in the lateral recess of the vertebral canal, getting ready to exit through the next lower intervertebral foramen
Lumbar nuclear pulposus hernia
Thus, a herniation of L3/L4 disk is likely to impinge on the roots of the nerve that will exit between
L4 and L5, (i.e. the L4 nerve)
Says that if a herniated nucleus pulposus impinges on one spinal nerve, the nerve that will be impinged has the same name as the vertebra below the disk
The “clinical rule”
The foramen is smaller and so the nerve occupies most of the foramen of
Cervical vertebrae
At the cervical level, the disk forms the anterior border of the middle of the foramen, so the nerve impinged by the hernia is the nerve that
-explains why the “clinical rule” holds for cervical vertebrae
Passes through that foramen
A herniation of the C5/C6 disk is likely to impinge on the
C6 nerve
May impinge on multiple nerves or nerve roots or even impinge on the spinal cord if above the L2 vertebral level
Larger or more medial hernias
Forms the posterior border of the intervertebral foramen
Zygaphosphyseal joint
Pathologies of the zygaphosphyseal joint may impinge on the
Nerve
Similarly, thickening of the zygapophyseal joint capsule or of the ligamentum flavum may impinge on
nerve roots in the
Foramen or canal
What are two types of stenosis?
- ) Foraminal stenosis
2. ) Central Stenosis
The narrowing of an intervertebral foramen
Foraminal Stenosis
May be caused by a herniated nucleus pulposus, arthritic changes of zygaphosphyseal joints, inflammation or scarring of the foramen, or other reasons
Foraminal Stenosis
Results in compression of spinal nerves
Foraminal stenosis
The narrowing of the vertebral canal
Central stenosis
Causes compression of the contents of the vertebral canal such as the spinal cord, the cauda equina, or individual spinal nerves, roots, or groups of nerves or roots
Central stenosis
A region of skin that receives its sensory innervation from a single spinal nerve
Dermatome
A lesion of one or more spinal nerves or dorsal roots will result in sensory symptoms that are referred to the
Dermatomes corresponding to the injured nerves or roots
A group of skeletal muscles that receive their motor innervation from a single spinal nerve or ventral root
Myotome
Although these motor nerve fibers may reach these muscles by way of various different peripheral nerves, nonetheless, they all arise from the
Anterior horn cells within a single spinal cord segment
A lesion of one or more spinal nerves or ventral roots will result in motor symptoms (e.g. paresis, paralysis) in the muscles of the myotome corresponding to the injured
Spinal nerves or ventral roots
Failure of pump mechanisms that pump water and waste products out of the nucleus pulposus and water and nutrients in can result in
Back pain
May impinge on rootlets of multiple nerves below the level of the disk
Herniated nucleus pulposus
Osteophytes from osteoarthritic zygapophyseal joint can encroach on intervertebral foramen and impinge on
Spinal nerves
What are other names for the following sensory symptoms?
- ) Tingling
- ) Reduced sensation
- ) Total numbness
- ) Paresthesia
- ) Hypesthesia
- ) Anesthesia
