Spinal Stenosis of the Lumbar Spine
Description:
Any
developmental of acquired narrowing of the spinal canal, nerve root canals, or
intervertebral foramina that results in compression of neural elements
Pathophysiology:
- A small
amount of canal narrowing occurs with age
- The
narrowest part of the canal is L2 – L4
- Volume
increases in flexion and decreases in extension
- Causes
of pathologic narrowing of the canal include:
- Bulging
of intervertebral discs posteriorly
- Buckling
of the ligamentum flavum posteriorly
- Encroachment
of the articular facets
- Degenerative
spondylolisthesis
- Mechanical
compression of cord results in increasing pressure in stenotic canal and:
- “neuroischemia”
– nerve fibers are nutritionally deprived by compression of small vessels
- Inflammation
of dura and exiting nerve roots results in adhesive arachnoiditis of the
pia and friction neuritis which constricts and tethers neural elements
- Reduced
permeability of hypertrophic restricts CSF flow, which provides 50% of
nutrition to nerve fibers
- Pain and
paresthesias are produced when activity increases the metabolic demands of
nerve fibers beyond what the limited delivery of nutrients and removal of
noxious substances allows
Classification:
Congenital- Example,
achondroplasia
- Acquired
– more common
- Degenerative
- Olisthetic-scoliotic
- Post-traumatic
- Post-operative
- Location
of stenosis
- Central
– hypertrophied structures put circumferential pressure around spinal
cord
- Lateral
– associated with narrowing of the foraminal canal
Signs/Symptoms
of Degenerative Spinal Stenosis:
- Most
common in elderly
- Women
> Men
- Lower
lumbar segments
- Insidious
progression of lower back, buttock, thigh pain
- Lower
extremity pain that is altered by position, relieved by rest – especially
a position of flexion of the waist
- Can
ambulate longer pushing a shopping cart (flexed body position)
- Distal
pulses should be evaluated to distinguish claudication from
neuroclaudication
Imaging:
- Plain
radiographs demonstrate
- degenerative
disc disease
- osteoarthritis
of facets
- spondylolisthesis
- narrowing
of interpedicular distance on AP
- CT scan
allows for accurate measurement of canal dimensions
- Dural
sac with diameter of less than 10mm correlates with clinical findings of
stenosis
- MRI is
now imaging modality of choice, comparable to contrast enhanced CT
Differential
Diagnosis:
- Causes
of referred pain to lower back:
- Retroperitoneal
tumors
- Aortic
aneurysms
- Peptic
ulcer disease
- Renal
lesions
- Hip and
pelvis pathology
- Psychologic
causes of low back pain
- Depression
– common in elderly
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Typical
midline decompression for spinal stenosis |
Treatment:
- Non-steroidal
anti-inflammatory medications
- Exercise
program
- Many patients
have appreciable response to NSAIDS and exercise
- Narcotics
should be avoided
- Epidural
corticosteroid injections have short-term success rate of 50% and long-term
25%
- Decompressive
laminectomy has short-term success rate between 71-85%
- Reoperation
common due to instability or recurrent stenosis
- Disc should be preserved for stability
- Prophylactic instrumented fusion should be performed if decompression will involve bilateral facet resection
