Lateral stenosis is defined as an entity in which a nerve root, dorsal root ganglion, or spinal nerve is entrapped in its pathway. In the case of degenerative changes the nerve
Fig. 4 Lateral stenosis with intraforaminal osteophyte causing nerve entrapment
Fig. 4 Lateral stenosis with intraforaminal osteophyte causing nerve entrapment root can be subject to compression secondary to the disc collapse by approximation of the pedicles due to the decrease in disc height. Furthermore, hypertrophy of the facet joint or other osteophytic changes can compress the root at its entrance in the foramen or in the foramen itself (Fig. 4). Whereas anteriorly McNab spurs (traction osteo-phytes at the insertion level of Sharpey fibers) are the rule in spondylosis, they seldom occur posteriorly. However, when present they participate in the narrowing the both the central and the lateral canal. Other osteophytes can be found such as those resulting from the calcification of an arthrosynovial cyst (Fig. 5). It appears that degenerative lesions are also often present in the middle zone or exit zone of the L4-L5 and L5-S1 foraminal pathways .
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