Spinal Stenosis

Definition

• narrowing of osteoligamentous canal &/or intervertebral foramina w/ compression of the thecal sac &/or nerve roots

Classic Findings

• middle-aged and older adults
• back & lower extremity pain
• precipitated by standing and walking & aggravated by hyperextension
• congenital narrowing of the spinal canal as a contributing factor in many
• 2° degenerative changes to further narrow the lumbar canal
• myelographic block in the midlumbar region with the characteristic degenerative hypertrophic changes about the discs, facets & ligamentous structures

Classification

1. Anatomic

• most common in the lumbar region > cervical stenosis > rarely in the thoracic spine
  • cervical - central or foraminal
  • thoracic - central (rare)
  • lumbar - central, lateral recess, foraminal, extra-foraminal (far out): most common type

Central Stenosis

• canal narrowing to 10mm on plain X rays
• dural sac transverse area of < 100mm2 correlates well with stenosis

Lateral Recess

• bounded laterally by the pedicle, posteriorly by the superior facet & anteriorly by the posterolateral surface of the vertebral body & adjacent disc
• on CT this space is normally 5mm, if < 2mm it is stenotic

Foramen

• borders - inferior edge of cephalad pedicle, the pars, inferior & superior facet dorsally, superior edge of the caudad pedicle & vertebral body & disc ventrally
• best seen on CT sagittal reconstruction views & MRI

Far out compression (Wiltse)

• predominently seen with spondylolisthesis
• compression of L5 root by the TP against the ala of the sacrum

2. Pathologic

a. congenital-developmental

• idiopathic
• achondroplastic, scoliosis, kyphosis, congenital spondylolisthesis
• usually central stenosis

b. acquired

1. degenerative & inflammatory
   • central, lateral recess or foraminal
   • OA, inflammatory arthritis, DISH, scoliosis, kyphosis
   • degenerative changes are usually in the region of the facet joints & bilateral
   • L4/5 > L5/S1 > L3/4
2. spondylolisthetic/spondylolytic
3. iatrogenic
   • postlaminectomy, post fusion
4. post-traumatic
5. metabolic
   • Paget's, fluorosis
   • Forester's disease, DISH

Tiles’ modifiers

• I - segmental
• II - generalized
  
  • less pain relief following surgery
• most common type is caused by degenerative disease
  etiology of degenerative stenosis:
  - hypertrophy of the superior facets
  - progressive disc degeneration w/ resultant hypermobility or instability in the joints
  - hypertrophy & calcification of ligamentum flavum
• canal diameter is bigger in flexion than extension

Clinical

History

• age of onset of symptoms characteristic
• early 30’s - congenital or developmental stenosis
• mid 50’s - degenerative stenosis
• most common
• females 3-5x more often
• insidious development of symptoms
• may be exacerbated by trauma or heavy activity

Clinical symptoms

Back pain

• ache & stiffness
• in buttocks & thigh - differentiate from hip pain!!!
• activity or hyperextension aggravates, rest relieves

Leg pain or radicular pain

• Two types

• Sciatica
• usually one leg
• sharp pain in a specific dermatomal distribution
• reflex changes or motor weakness may occur
• L5 root commonly involved - weakness of EHL & tib.ant.
• Neurogenic claudication (pseudoclaudication)
• pain, numbness, tingling, weakness cramping or burning in the leg
• usually both legs affected
• begins in the low back or at the buttocks & radiates into the legs (down to knees, later foot)
• no specific dermatomal distribution
• walking or standing precipitates, sitting & leaning forward or lying down alleviates pain

• neurogenic claudication is NOT relieved by standing still - vascular claudication is
• claudication is more common in central stenosis
• lateral recess or foraminal stenosis may mimic OA of the hip

Peripheral neuropathy should also be differentiated

• diabetes common
• pain worse at night, no relation to activity
• “stocking glove” distribution
• confirmed with nerve conduction studies - prolonged

Urinary dysfunction

• uncommon in spinal stenosis 3-4%
• usually incontinence

Physical examination

Look

• protective posture - forward bending
• muscle wasting - leg or back
• scar from previous surgery

Palpation

• localised tenderness rare
• discomfort “deep down” within the muscles
• distal pulses strong - exclude vascular claudication

Movements

• good flexion, limited extension with pain
• hip screening - exclude hip pathology!!!
• SLR test usually negative
• associated disc herniation if positive

Neurological examination

• power usually normal or minimal loss
• reflex testing often unreliable - loss common in elderly
• sensory deficit uncommon - mostly L5/S1 dermatome
• if diffuse - more likely peripheral neuropathy

Plain X-ray

• AP, lateral & oblique views
• standing if scoliosis or spondylolisthesis
• flexion-extension views for instability
• look for degenerative changes, spondilolysis-listhesis, instability etc.

Myelography

• has been the “gold standard” in confirming dg
• dye should be water-soluble (Omnipaque, Isovue)
• “hourglass” constriction at one or more levels
• unilateral extradural defect at L4/5 or L5/S1 if disc herniation

Advantages

• visualise the whole lumbar spine to the conus medullaris
• clinical experience
• dynamic study - hyperextension can be performed, which accentuates the stenosis

Disadvantages

• invasive
• side effects (headache, nausea, seizures, allergy etc.)

CT scan

• accurately shows size & shape of the spinal canal
• visualise the lateral recess & neuroforamen
• identify pathological levels below a complete block
• myelo + CT - 91% accuracy for stenosis

MRI

• sagittal, transverse & coronal cuts
• T1- & T2-weighted images
• non-invasive & very accurate

Electromyography (EMG)

• evaluates the physiology of the nerve roots (only lower motor neuron dysfunction)
• bilaterally positive EMG in stenosis

Nerve conduction studies

• differentiate radiculopathy from peripheral neuropathy

Somatosensory evoked potentials (SSEPs)

• usually for inraoperative monitoring in scoliosis & major reconstructive spinal surgery
• stress SSEPs - reduced amplitudes after walking stress

Differential diagnosis

• Disc herniation
• Spondylolisthesis
• Infections
• Tumours

Non-operative treatment

• similar to degenerative disc dx.

1. Limited activity
• not bedrest - heart & lung rehabilitation
• reduced lifting, twisting & repeated forward bending
2. Physiotherapy
• deep heat, US & massage
• traction has little effect
• exercise program (stationary bicycle, treadmill, swimming, brisk walking)
3. Lumbosacral corset, brace
• provides abdominal support & restricts lumbar motion
• weakens abdominal muscle tone if > 6 weeks - abdominal muscle exercise
• use in car or when up & about for a prolonged period
• not during sleeping or normal household activities
4. Anti-inflammatory medication (NSAIDs)
• short term basis - reduce symptoms
• risk of renal failure, abdominal complains
• muscle relaxants - tend to sedate pts. - Lioresal° 5-10 mg tds (up to 25 mg tds)
5. Antidepressant drugs
• at low dosages effect on neurogenic-type pain and sedative effect at night-time
• amitriptyline Trepiline° 25-50 mg at night
6. Epidural steroid injections
• for symptomatic relief

Operative treatment

Indications

• failure of conservative Rx. - increasing pain
• patient’s inability to tolerate decreased lifestyle
• accurate diagnosis with imaging
• surgical expertise

Decompression

• midline or selective
• anterior (cervical) or posterior
• decompression is by laminectomy (wide or limited = laminotomy), medial facetectomy with or without disc excision
• Laminectomy may be preferable in older patients with severe, multilevel stenosis, whereas fenestration procedures, consisting of bilateral laminotomies and partial facetectomies that preserve the midline structures, are an alternative in younger patients with intact discs.

Decompression with fusion

• Controversial
• Fusion is required if excessive bony resection compromises stability or if isthmic or degenerative spondylolisthesis, scoliosis, or kyphosis is present
• Other important indications for fusion include adjacent segment degeneration after prior fusion and recurrent stenosis or herniated disc after decompression.

Cervical stenosis

• operative treatment varies from extensive anterior decompression to extensive laminoplasty to multiple laminectomies

Outcome of surgery

• radiological findings only are not an indication for surgery
• surgery does not garantee pain relief - about 70% improvement can be expected
• neurological findings do not tend to dissappear after surgery
• best results are in patients with localized disease
• patients whose symptoms are improved by postural changes tend to do better

Because the primary complaint often is back pain and some leg pain, pain relief after surgery may not be complete. Most series report a 64% to 91% rate of improvement, with 42% in patients with diabetes, but most patients still have some minor complaints, usually referable to the preexisting degenerative arthritis of the spine. Neurological findings, if present, improve inconsistently after surgery. In a series reported by Guigui et al., only 30% had complete improvement in motor symptoms after laminectomy, with 58% regaining grade 4 strength or better at a mean follow-up of 3 years. Reoperation rates vary from 6% to 23%. Prognostic factors include better results with a disc herniation, stenosis at a single level, weakness of less than 6 weeks' duration, monoradiculopathy, and age younger than 65 years. Reversal of neurological consequences of spinal stenosis seems to be a relative indication for surgery unless the symptoms are acute.

Adjacent Segment Degeneration

• degeneration occurs adjacent to a fusion in 35% to 45% of patients because of the ensuing hypermobility of the unfused joint. Lehmann et al. reported a 45% prevalence (15 of 33) of adjacent segment instability, defined as more than 3 mm of translation, and a 42% occurrence of spinal stenosis (14 of 33), usually above the fusion
• Adjacent segment breakdown may cause symptoms that require surgery in 30% of patients. Pathology, including spinal stenosis, herniated nucleus pulposus, and instability, may require treatment years after successful surgery.