Definition

• Lumbosacral stenosis refers to narrowing of the lumbosacral vertebral canal and/or L7–sacral intervertebral foramina, causing compression of L7, sacral, or caudal nerves.
• Cauda equina syndrome implies pain or other clinical signs related to dysfunction of these nerves.

Pathophysiology

• Congenital-abnormal vertebral development causing narrowing of the lumbosacral vertebral canal. Transitional vertebrae and other malformations are common at this site and may contribute to (early) disease progression.
• Acquired-bony and soft tissue degenerative changes, most commonly affecting the L7 intervertebral disc, that cause stenosis of the vertebral canal and/or intervertebral foramina. Specific syndrome of sacral osteochondrosis dissecans recognized in young German shepherds.

Systems Affected

Nervous-specifically nerves from L7 caudally

Genetics

No known genetic basis

Incidence/Prevalence

Unknown

Geographic Distribution

N/A

Signalment

Signs

• Lumbosacral pain-salient feature; may be the only clinical sign; may be evident in reluctance to jump or climb stairs. Pain on pressure on, or dorsiflexion of, the lumbosacral vertebral column (often also induced during extension of hip joints).
• Pelvic limb lameness-caused by lumbar 7th and/or sacral nerve dysfunction; may progress to pelvic limb weakness, muscle wasting, and postural reaction deficits.
• Urinary and/or fecal incontinence-caused by S1–3 nerve dysfunction.
• Abnormal tail carriage, tail weakness or paralysis-results from dysfunction of caudal nerves.
• Self-inflicted lesions-most often associated with congenital lesions or cauda equina inflammation.

Causes

• Congenital vertebral malformation, including transitional vertebrae, or osteochondrosis of the cranial sacrum.
• Intervertebral disc herniation (types I and II).
• Hypertrophy or hyperplasia of the interarcuate ligament.
• Proliferation of the articular facets and/or peri-articular soft tissues.
• Subluxation at the lumbosacral junction.
• Inflammatory or neoplastic disease of the vertebral canal can produce identical clinical signs (hence “cauda equina syndrome”).

Risk Factors

Dogs, especially German shepherds, with lumbosacral transitional vertebrae have increased risk to develop the syndrome.

Differential Diagnosis

• Hip dysplasia or other orthopedic disease (notably iliopsoas injury)-distinguish via thorough orthopedic examination ± imaging.
• Chronic discospondylitis, osteomyelitis, neoplastic disease-cannot be differentiated by clinical signs alone.
• Vertebral fractures and subluxations-acute; characterized by more bilateral signs.
• Localized meningomyelitis or radiculoneuritis-usually more diffuse pain.

CBC/Biochemistry/Urinalysis

• Usually normal.
• Urinalysis-may reveal lower urinary tract infection secondary to urinary incontinence, or associated with discospondylitis.

Other Laboratory Tests

If images suggest the need, CSF analysis may aid in diagnosing inflammatory (or infectious or neoplastic) disease.

Imaging

• Radiology-commonly exhibit spondylosis at the lumbosacral junction; narrowing of the L7–S1 disc space; ventral displacement of the sacrum relative to the lumbar vertebrae; BUT interpret with caution because all these can be observed in clinically normal animals.
• CT and MRI-modalities of choice. Apparent abnormalities must be interpreted with regard to the whole clinical picture because many are also observed in normal animals.

Diagnostic Procedures

• Electromyography-denervation may be detected in muscles innervated by the nerves L7 to caudal; denervation confirms localization of the lesion but is not specific for compressive lesions.
• Slowed sciatic-tibial nerve conduction or prolongation of F wave latencies may be detected.

Pathologic Findings

• May see one or more of the following features:
  • Type II disc disease with bulging of dorsal annulus
  • Hypertrophy of the interarcuate ligament
  • Stenosis of the intervertebral foramen by soft tissue or bony proliferation compressing L7 nerve(s)
  • Ventral displacement of the sacrum in relation to lumbar vertebrae
  • Proliferation of articular facets and hypertrophy of joint capsule
  • Congenitally shortened pedicles
  • Thickened and sclerotic laminae and articular processes
  • Various vertebral malformations (not only transitional vertebrae).
• Cauda equina syndrome can also be associated with neoplasia, inflammation, infection.

Appropriate Health Care

• Urinary incontinence-in-patient for initial management.

Nursing Care

• Urinary incontinence-manual expression or catheterize the bladder until adequate voluntary control returns; monitor for urinary tract infection and administer appropriate antibiotics following culture and sensitivity.

Activity

• Nonsurgical treatment-confinement and restricted leash walks, alone or combined with systemic anti-inflammatory drugs or analgesics, or epidural injection of corticosteroids, frequently alleviate pain; clinical signs may return with increasing levels of exercise.
• If treated surgically, restrict for 6–12 weeks; then gradual return to athletic function.

Diet

Avoid obesity; excess weight increases biomechanical stress on the spine.

Client Education

• Inform client that there may be progressive neurologic impairment of the pelvic limbs, urinary and fecal incontinence, and paralysis of the tail.
• Inform client that pelvic limb lameness and self-inflicted lesions result from pain associated with nerve root irritation and/or compression.
• Discuss surgical treatment which is appropriate for cases with severe pain and may be suitable for cases with neurologic deficits (especially incontinence, which may be difficult to reverse).
• Medical management is frequently successful for animals with mild pain and/or mild neurologic deficits only.

Surgical Considerations

Several options, each focused on alleviating the specific source of the problems defined by imaging-dorsal laminectomy, lateral foraminotomy or fixation-fusion may all be effective in specifically selected cases.

Drug(s) Of Choice

• NSAIDs-e.g., carprofen 2 mg/kg q12h for 5–7 days then reducing doses until used as required.
• Gabapentin-frequently used at ∼ 20–30 mg/kg q8h may be effective (side effect: sedation).
• Epidural corticosteroid-methylprednisolone actetate 1 mg/kg (<0.5 mL total volume).

Contraindications

N/A

Alternative Drug(s)

N/A

Prevention/Avoidance

N/A

Possible Complications

• Syndrome progression, increasingly severe neurologic signs.
• Seroma formation-frequent sequela to surgery; can be effectively managed by cage rest and surgical drainage. Prevent by careful soft tissue closure.
• Adhesions between nerves and surrounding soft tissues after surgery.
• Recurrence of clinical signs following medical (commonly) or surgical (uncommonly) intervention.
• Failure of fixation-fusion implant.
• Fracture of articular process after excessive lateral bone excision at surgery.
• Infection (especially if an implant is used for surgery).

Expected Course and Prognosis

• Vary with the severity of neurologic injury.
• Majority are successfully managed medically, but need to ensure outcome matches requirements for dog's way of life; surgery remains an option.
• If low lumbar pain and mild neurologic deficits-good prognosis after surgery; 70–80% have an excellent or good outcome.
• If fecal and urinary incontinence-guarded prognosis.

Associated Conditions

Lower urinary tract infections frequently accompany urinary incontinence.

Age-Related Factors

• If a lumbosacral transitional vertebra is present, syndrome may develop 1–2 years earlier than the average dog.
• Older large-breed dogs may have concomitant diseases that also cause neurologic deficits: type II disc protrusions at other sites, degenerative peripheral nerve disease (especially Labradors), degenerative myelopathy (especially German shepherds).

Synonyms

• Lumbosacral instability
• Lumbosacral malarticulation or malformation
• Lumbosacral spondylolisthesis
• Lumbosacral spondylopathy

See Also

• Discospondylitis
• Intervertebral Disc Disease, Thoracolumbar
• Intervertebral Disc Disease-Cats

Abbreviations

• CT = computed tomography
• MRI = magnetic resonance imaging
• NSAID = nonsteroidal anti-inflammatory drug

Internet Resources

http://veterinarymedicine.dvm360.com/vetmed/Medicine/Degenerative-lumbosacral-stenosis-in-dogs/ArticleStandard/Article/detail/169902

Client Education Handout Available Online