Lumbar Stenosis

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- Discussion:
    - spinal stensosis is a narrowing of the lumbar spinal canal and/or neural foramina;
    - results in compression of the cauda equina and lumbar nerve roots, producing neural root ischemia and neurogenic claudication;
    - compression of neural structures also compresses vascular supply of nerves so that symptoms are predominately those of neural ischemia;
    - because both neural canal and the neural foramen are narrowed w/ spine in extension & opened in flexion, neural compression is most often temporary;
    - pain induces patients to change position and relieve nerve pressure before permanent neurologic damage is done;
    - although degenerative spondylolisthesis is common cause of stenosis, 10% of adults > 65 yrs may have this finding & many are asymptomatic; 
    - patients are usually 50 years or older; 
    - radicular symptoms may be unilateral or bilateral with or without back pain
    - standing and walking up inclines increase pain;
    - sitting and lying on side with the hips and knees flexed relieve pain as does leaning over a shopping cart.
    - pain occurs when the patient is upright and particularly when walking; 





    - typical symptom is leg pain, numbness, and weakness developing after patient walks a predictable distance;
    - patient seeks relief by sitting, leaning forward to "relieve pressure" putting his foot on a raised rest, or lying down;
    - common denominator is changing the position of the spine from extension to flexion;
    - dx of spinal stenosis is made by eliciting h/o of pseudoclaudocation, positive spinal Phalen test, and imaging confirming stenosis;
    - Phalen test may be specific;
             - this test attempts to reproduce symptoms of leg pain, weakness, or numbness by causing neural ischemia;
             - w/ pt upright, bend the patient into extension for a full minute;
             - this should accentuate the spinal stenosis;
             - positive test will produce a crescendo of leg symptoms followed by rapid relief of these symptoms when the patient flexes forward,
                    places his hands on examination table, and places one foot on stool; 

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- Radiographs:
    - disk space narrowing is a poor predictor of symptoms;
    - instability:
           - normal anterior and posterior translation from L1 to L5 is about 8% of length of vertebral body or about 4 mm;
           - note that the typical degenerative changes of osteophyte formation, decrease in disc height, and ligament calcification will serve to limit motion;
    - Myelogram:
           - myelogram with the patient in extension may offer the best information on location of stenotic areas;
    - CT scan:
           - evaluate for lateral stenosis & central stenosis;
           - cross-sectional dural areas of < 100 mm2 denote stenosis;
           - clinical syndrome of lumbar stenosis correlates more closely w/ anteroposterior diameter of the dural sac;
           - dural sac w/ AP diameter of < ten millimeters  is consistent w/ clinical syndrome of lumbar stenosis;
    - MRI:
    - references:
           - Role of computed tomography and myelography in the diagnosis of central spinal stenosis.
           - Role of computed tomography and myelography in the diagnosis of central spinal stenosis. J Bone Joint Surg (Am) 1985;67A:240-246.
           - Radiologic diagnosis of degenerative lumbar spinal instability.             x

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- Surgical Treatment:
    - indications for fusion:
            - w/ no segmental instability, arthrodesis may not be required, (assumming that posterior elements have not been destabilized);
            - degenerative spondylolisthesis;
    - positioning:
            - be particularly certain that there is no pressure on abdomen which would compress the vertebral venous plexus;
    - decompression:
            - laminae are minimally trimmed for exposure;
            - includes widening of lateral recess;
            - removal of medial rim of facets;
    - postero-lateral fusion:
            - see: fusion of the spine 

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   - references: 

- Treatment of cervical spondylotic myelopathy by enlargement of the spinal canal anteriorly, followed by arthrodesis. 
- Bone regrowth after surgical decompression for lumbar spinal stenosis. 
- Lumbar foraminal stenosis: critical heights of the intervertebral discs and foramina. A cryomicrotome study in cadavera. 
- Increase of motion between lumbar vertebrae after excision of the capsule and cartilage of the facets. A cadaver study. 
- Laminectomy with and without spinal fusion. 
- Postdecompression lumbar instability. 
- Morbidity and mortality in association with operations on the lumbar spine. The influence of age, diagnosis, and procedure. 
- Neurologic complications and lumbar laminectomy. A standardized approach to the multiply-operated lumbar spine. 
- Repeat decompression of lumbar nerve roots. A prospective two-year evaluation. 
- Degenerative lumbar spinal stenosis. Decompression with and without arthrodesis. 
- The outcome of decompressive laminectomy for degenerative lumbar stenosis. 
-  A Comprehensive Study of Patients with Surgically Treated Lumbar Spinal Stenosis with Neurogenic Claudication. 
- Perioperative Complications of Posterior Lumbar Decompression and Arthrodesis in Older Adults.