Prolapsed Intervertebral Disk

Disk Radiology
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Thecal Sac Prolapse Impingement Upon The Thecal Sac

Fig. 11.53 Disk prolapses are classified according to location/ direction: a A lateral prolapse (arrow) can impinge upon the spinal nerve root lateral to the neuroforamen. b Foraminal prolapse (arrow) compresses the spinal nerve directly within the foramen. c A paramedian prolapse (arrow) is frequently located in the lateral recess, where it impinges upon the nerve. d The median prolapse (arrow) tends to compress the spinal cord itself. e Prolapsed diskal tissue in this case has lost its communication with the intervertebral space above (sequester; arrow), as can be seen on this myelographic image. The lower radicular sleeve of L5 is configured normally with a slim spinal root nicely outlined by positive intrathecal contrast. The superior radicular sleeve of L4, in contrast, appears compressed and the spinal nerve root is thickened. At the level of the intervertebral disk space there is no extrinsic impression of the thecal sac.

When diskal tissue loses its connection to the disk it originated from, this is called a sequester or fragment. Sequesters do not usually recede under conservative therapy (Fig. 11.53e) and are thus more often treated surgically.

Degenerative neuroforaminal stenosis: In the cervical region, degenerative foraminal stenosis is primarily caused by osteoarthritic hypertrophic changes of the uncoverteb-ral joints (Fig. 11.54a); in the lumbar region, it is caused by osteoarthritis of the facet joints (Fig. 11.54b) and by hypertrophy of the ligamentum flavum (Fig. 11.54c).

Synovial cyst: The synovial cyst, a diverticulum of the facet joint, can also impinge on the spinal nerve roots (Fig. 11.55). In that instance it must be excised surgically. Synovial cysts are, however, difficult for the surgeon to find because they may rupture very easily during surgical exploration. Later, the cystic space may seal itself off again during the postoperative healing, with a potential undesirable effect: cyst and symptoms recur.

Schwannoma: Peripheral schwannomas follow the course of the spinal nerve root through the intervertebral foramen, assuming a dumbbell shape in the process (Fig. 11.56). Intravenous contrast administration is necessary to differentiate it from a prolapsed disk.

I Degenerative Neuroforaminal Stenosis a Hypertrophy of the uncovertebral joints

Hypertrophy The Ligamentum Flavum
c Hypertrophy of the ligamentum flavum
Hypertrophy The Ligamentum Flavum

b Osteoarthritis of the intervertebral joints r

Fig.11.54a The uncovertebral joints are located directly adjacent to the cervical intervertebral neuroforamina. Hypertrophic degenerative changes in these joints may cause foraminal stenosis as seen here on the right side. b Expansion of the posterior facet joints (arrows) has a similar effect in the lumbar region. Hypertrophic degenerative disk disease with diskal bulging at these levels (note the vacuum phenomenon!) further aggravates the situation. c The frequently associated hypertrophy of the ligamentum flavum (arrow) further increases the degree of stenosis affecting the intervertebral foramen.

I Synovial Cyst

Flavum Ligamentum Spinal Cord

Fig. 11.55a On this axial Tl-weighted MR image a small mass is seen in the spinal canal directly adjacent to an intervertebral joint (arrow). b Only after contrast administration can the thin synovial membrane be distinguished, which clarifies the true character of the lesion.

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