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Disc Herniation

- See:
       - Herniated Disc in the Child:
       - Intervertebral Discs:

- Anatomy:
    - disc herniation may vary in severity from disc protrussion to disc extrusion, to finally disc sequestration;
    - disc containment:
          - w/ a contained disc herniation, the disc material herniated through the inner annulus but not the outer annulus;
                  - the material is therefore contained, but still can distort the path of the nerve;
          - w/ a non contained herniation, the disc material penetrates both the inner and out layers of the annulus;
                  - the material may reside beneath the posterior longitudinal ligament or may penetrate through it, or can be sequestered as a free fragment;
    - posterolateral disc herniation:
          - protrusion is usually posterolateral into vertebral canal, where it may compress the roots of a spinal nerve;
          - w/ posterolateral herniation, disc will not affect nerve corresponding in number to that intervertebral discs (that nerve emerges above disc);
                  - note that each nerve emerges thru upper part of foramen and lies against body of vertebra above;
          - protruded disc usually compresses next lower nerve as that nerve crosses level of disc in its path to its foramen;
                  - hence, protrusion of fifth lumbar disc usually affects S1 instead of L5;
          - in this case, an L4-L5 disc herniation will protrude on the L5 nerve root;
    - central (posterior) herniation:
          - in the lower lumbar segments, central herniation may result in S1 radiculopathy
          - less frequently, a protruded disc above second lumbar vertebra may compress spinal cord itself or or may result in cauda equina syndrome;
    - far lateral disc herniation:
          - may compress the nerve root above the level of the herniation (hence a L4-L5 far lateral herniation may result in a L4 radiculopathy);
          - occurs in 6-10% of all lumbar disc herniations;
          - L4 nerve root is most often involved;
          - patient typically have intense radicular pain (sciatic 25% and femoral 75% of the time);
                  - when pain is femoral, sleep in the prone position is especially painful;
          - localized steroid injection:
                  - in the study by Weiner and Fraser (JBJS 1997), sustained relief of symptoms occured in 27 out of 30 patients;
          - surgical approach may consist of a muscle splitting intertransverse approach, which gives exposure of to spinal nerve and dorsal root ganglion;
    - references:
          - Foraminal and extraforaminal lumbar disk herniations.
          - Far lateral lumbar disc herniation. The key to the intertransverse approach
          - The paraspinal sacrospinatus splitting approach to the lumbar spine. 
          - Foraminal injection for lateral lumbar disc herniation

- Disc Pressure / Failure:
    - intradiscal pressure is higher when sitting than when standing;
    - sitting-leaning forward > sitting > standing > lying on side > supine;
    - rotation combined w/ flexion are the worst positions for disc injury;
    - it is elevated by bending forward, bending to side, lifting, coughing, sneezing, and straining;
    - flexion, extension, and lateral bending all produce small displacements of the nucleus;
          - asymmetric & cyclic loading combined w/ lateral bend, compression, and flexion are risk factors for disk herniation;

- Clinical Presentation and Diff Dx:
    - discogenic pain:
    - w/ radiculopathy, there should be a predominance of leg pain over back pain;

- Exam: (neurological exam and exam of the lumbar spine)
    - straight leg raise: used to diagnose L5 and S1 radiculopathy;
    - femoral stretch test: used to diagnose L4 radiculopathy;
          - this test is performed by raising the leg while the patient is prone;
    - wt relief flexion test:

- MRI of Disc Herniation:

- Natural History:
    - prognosis of disc herniation is generally good regardless of treatment;
    - patients operated on for proven disc herniations improved more rapidly than patients treated non operatively;
    - within 4-5 years both operative and non operative treatment groups will generally have comprable 
           neurologic recovery;
           - hence long term results are similar w/ or w/o surgery;
    - of all patients who sustain acute sciatica, less than 25% will require surgery;
    - despite the generally good prognosis, some patients will not recover such as this patient who had chronic 
           anterior compartment atrophy and a mild foot drop (he was never treated operatively);

- Invasive Managment:
    - epidural steroid injection:
           - best effects are found in patients whose leg pain (or radicular symptoms) are worse than back pain;
           - at least one epidural injection should probably be tried in most patients with a disc herniation since it is often the inflammation 
                   generated from the disc which causes symptoms rather than direct mechanical compression from disc material;
    - selective nerve root injection:
           - contrast radiculogram is made to ensure that the correct nerve root was being injected;
           - patient was placed prone on a fluoro table;
           - C arm is adjusted to allow visualization of the target area in posteroanterior, oblique, and lateral positions;
           - entry site should allow visualization of the lateral edge of the pars interarticularis, transverse process, and articular facets on the side to be
                   injected was selected within a few centimeters lateral to the spine;
                   - disc space at that level is typically profiled;
           - use 22-gauge spinal needle with a short bevel and consider bending the tip for easier entry;
           - injection is delivered into the anterosuperior portion of the selected lumbar foramen;
           - contrast solution is injected under fluoroscopic control inorder to verify proper needle placement and to verify absence of intravascular injection;
           - inject one cc of 0.25 % bupivacaine along with one cc of betamethasone (six milligrams per cc);

    - references:
           - The use of epidural steroids in the treatment of lumbar radicular pain. A prospective, randomized, double-blind study.
           - The Effect of Nerve-Root Injections on the Need for Operative Treatment of Lumbar Radicular Pain. A Prospective, Randomized, Controlled, Double-Blind Study
    - percutaneous discectomy
    - diskectomy
    - post operative management:

- Complications:
    - Post Operative Diskitis:

Lumbar disc excision in children and adolescents.

The form and structure of the extruded disc.

Biochemical changes associated with the symptomatic human intervertebral disk.

Lumbar disc herniation: Controlled prospective study with 10 years of observation.  

Histological changes in aging lumbar intervertebral discs. Their role in protrusions and prolapses.

Histological development of intervertebral disc herniation.

Lower-extremity sensibility testing in patients with herniated lumbar intervertebral discs.

Back pain and sciatic.     

Surgery for lumbar disc herniation: What are the choices? Murrey DB, Hanley EN. J Musculoskel Med. Jan. 1999:39.