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Nervous system

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herniation of nucleus pulposus (HNP)

focal protrusion of disc material secondary to rupture of annulus fibrosus confined within the posterior longitudinal ligament

location:

  • L4/5 (35%); L5/S1 (27%); L3/4 (19%); L2/3 (14%); L1/2 (5%); thoracic spine affected in 3:1000 disc operations
  • posterolateral (49%): weakest point (posterior longitudinal ligament tightly adherent to posterior margin of disc)
  • posterocentral (8%)
  • lateral/foraminal (<10%)
  • intraosseous/vertical (14%): "Schmorl node"
  • extraforaminal/anterior (29%): commonly overlooked
  • bilateral: on both sided of the posterior ligament

findings:
  • disc (low T1) displaces posterior ligament/epidural fat (high T1)
  • enlarged (edematous) nerve root: "trumpet sign"

see:
degenerative disc disease
extradural mass

Yong H. Hahn, MD  -  2 February 1995
Last updated:  1 October 2013


 

Related CHORUS documents:
degenerative disc disease
bulging disc
Schmorl node
cervical disc herniation
extradural mass
disc sequestration

 

Copyright © 2013, Charles E. Kahn, Jr.