Canis ISSN: 2398-2942

Sciatic neuropathy

Contributor(s): Paul Cuddon, Laurent Garosi

Introduction

  • Cause: pelvic (shaft of ilium or acetabulum), lumbar and sacrococcygeal fractures, foraminal stenosis, surgery in the pelvic and perineal areas (eg entrapment by a suture following perineal herniorrhaphy), retrograde intramedullary pinning of femur, intramuscular injection into caudal thigh muscles, peripheral nerve or nerve root tumor.
  • Signs: lameness or lower motor neuron (LMN) paresis.
  • Diagnosis: signs, electrophysiology, eg EMG, nerve conduction studies.
  • Treatment: nerve graft, anastomosis (neurorrhaphy), antibiotics (wound creams):
    • If sciatic nerve is entrapped by scar tissue surgical release of the nerve (neurolysis) is indicated.
    • Surgical decompression of sciatic nerve roots if lateralized (foraminal) compression.
  • Surgical stabilization of lumbar spine, or sacrum, if fracture.
  • Physiotherapy to assist with the maintenance of muscle mass and tone.
  • Prognosis: depends on severity - good to poor.

Pathogenesis

Etiology

  • Trauma, eg pelvic, lumbar, sacrococcygeal fractures.
  • Lateralized disk extrusion at the lumbosacral junction - foraminal compression of sciatic nerve root.
  • Iatrogenic, eg retrograde intramedullary pinning of the femur, acetabular fracture repair, hip surgery, perineal hernia repair, intramuscular injection into caudal thigh muscles.
  • Neoplasia (peripheral nerve or nerve root tumor).

Predisposing factors

General
  • Access to road traffic.
  • Non-traumatic conditions requiring surgical intervention near sciatic nerve, eg perineal hernia, hip dysplasia.
  • Caudal thigh IM injections.

Pathophysiology

  • Trauma/injury, nerve root tumor, or pressure from hematoma or scarring → damaged lumbosacral trunk or L7, S1 or S2 spinal nerve → variable degree of nerve damage → decreased motor and/or sensory innervation to gluteals, caudal thigh muscles, all muscles distal to stifle (depending on level of injury) → decreased sensation and spinal reflexes → neurogenic muscle atrophy of affected muscles.

Timecourse

  • Immediately after injury - loss of function of pelvic limb if trauma/irritant injection/acute disk.
  • Over 1 to 3 weeks - muscle atrophy of denervated muscles if trauma/irritant injection/acute disk.
  • Slowly progressive pelvic limb lameness leading to paresis and muscle atrophy over weeks to months if a nerve root tumor.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Barthez P et al (1994) Discography and epidurography for evaluation of the lumbosacral junction in dogs with cauda equina syndrome. Vet Radiol Ultrasound 35 (3), 152-157 VetMedResource.
  • Wheeler S J (1992) Lumbosacral disease. Vet Clin North Am 22 (4), 937-950 PubMed.
  • Newton G T (1989) Sciatic impairment following proximal femoral physeal fracture - two case reports. JAAHA 25 (3), 239-242 VetMedResource.
  • Bailey C S, Kitchell R L (1987) Cutaneous sensory testing in the dog. JVIM 1 (3), 128-135 PubMed.
  • Jacobson A, Schrader S C (1987) Peripheral nerve injury associated with fracture or fracture-dislocation of the pelvis in dogs and cats - 34 cases (1978-1982). JAVMA 190 (5), 569-572 PubMed.
  • Chambers J N, Hardie E M (1986) Localisation and management of sciatic nerve injury due to ischial or acetabular fracture. JAAHA 22 (4), 539-544 VetMedResource.
  • Gilmore D R (1984) Sciatic nerve injury in twenty-nine dogs. JAAHA 20 (3), 403-407 VetMedResource.
  • Fanton J W, Blass C E, Withrow S J (1983) Sciatic nerve injury as a complication of intramedullary pin fixation of femoral fractures. JAAHA 19 (5), 687-694 VetMedResource.

Other sources of information

  • Anor S (2013)Monoparesis.In:BSAVA Manual of Canine and Feline Neurology. Platt S R & Olby N (eds) 4th edn. BSAVA Publication, pp 328-341.
  • Gemmill T & McKee M (2012)Monoparesis and neurological causes of lameness.In:Small Animal Neurological Emergencies.Platt S R & Garosi L (eds). Manson Publishing, pp 299-315.
  • Summers B Aet al(1995)diseases of the peripheral nervous systemIn:Veterinary Neuropathology.Mosby. pp 402-501.
  • Braund K G (1994)Clinical syndromes in veterinary neurology.Mosby. pp 277-279.


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