Paresis

In the nervous system, the ability to move a limb can be compared to a computer system and the ability to print a document. The computer (brain), connecting cable (spinal cord) and printer (limb) must all communicate to produce the proper response. For example:

  • If the computer's network isn't working properly, then the signal could be inhibited from reaching a normal functioning cable and printer.
  • If the cable was severed, communication would not be linked between the normal functioning computer and printer.
  • And, a good signal flowing from the computer and cable wouldn't be able to help print the document if the printer rollers were unable to turn.

Paresis is the reduced ability and paralysis is the inability to activate motor neurons. They are signs of a myelopathy or encephalopathy in the central nervous system. In humans, paresis and paralysis are often signs of encephalopathy but are usually only signs of myelopathy in animals. Weakness is the decrease in strength of one or more muscles. It is a sign of a neuropathy and/or myopathy in the peripheral nervous system. Upon patient examination, the subtle difference between signs of paresis and weakness may be detected. This could enable a veterinarian to narrow the problem to either a spinal cord disorder or neuromuscular (i.e. nerve, muscle, and/or neuromuscular junction) disorder.

Patients showing signs of limb paresis/paralysis or weakness should be examined by a veterinarian as soon as possible; paresis can lead to paralysis which is generally considered a medical emergency.

COMMON SIGNS

  • knuckling
  • dragging leg(s)
  • abnormal gait
  • monopareseis/monoplegia
  • paraparesis/paraplegia
  • tetraparesis/tetraplegia

COMMON CAUSES: Spinal Cord Diseases (Myelopathies)

Degenerative

  • lumbosacral stenosis
  • intervertebral disk disease
  • cervical spondylomyelopathy / wobbler syndrome
  • arachnoid cyst / diverticulum
  • spondylosis deformans (rarely resulting in clinical signs)

Congenital

  • vertebral malformations
  • atlantoaxial subluxation
  • caudal occipital malformation syndrome
  • syringomyelia or hydromyelia
  • spina bifida

Inflammatory

  • Infectious:
      • Bacterial
        • diskospondylitis
        • tetanus
      • rickettsial
        • Rocky Mountain spotted fever
        • ehrlichiosis
      • viral
        • canine distemper encephalomyelitis
        • feline infectious peritonitis (FIP)
        • feline leukemia virus (FeLV)-associated myelopathy
        • rabies
      • fungal
        • aspergillosis
        • blastomycosis
        • cryptococcosis
        • coccidioidomycosis / Valley Fever
        • histoplasmosis
      • protozoal
        • neosporosis
        • etoxoplasmosis
      • parasitic

  • Immune-mediated:
      • steroid responsive meningitis / arteritis
      • granulomatous meningoencephalomyelitis (GME)

Neoplastic

  • osteosarcoma
  • fibrosarcoma
  • meningioma
  • nerve sheath tumor
  • metastatic neoplasia
  • multiple myeloma
  • lymphoma

Traumatic

  • fractures, subluxations / luxations

Vascular

  • fibrocartilaginous embolism (FCE)
  • ischemic myelopathy

Metabolic

  • degenerative myelopathy
  • degeneration of motor neurons

COMMON CAUSES: Neuromuscular Diseases (Neuromyopathies)

Degenerative

  • fibrotic myopathy

Congenital

  • congenital myasthenia gravis

Inflammatory

  • Infectious:
    • myositis
    • neuritis
    • acute idiopathic polyradiculoneuritis / coonhound paralysis
    • bacterial
      • tetanus
    • protozoal
      • neosporosis
      • toxoplasmosis
  • immune-mediated
    • acquired myasthenia gravis
    • paraneoplastic neuropathy
    • myositis
    • neuritis

Neoplastic

  • nerve sheath tumor

Traumatic

  • brachial plexus avulsion
  • peripheral nerve injuries

Toxic

  • botulism
  • organophosphate poisoning
  • tick paralysis

Vascular

  • ischemic neuromyopathy
    • aortic thromboembolism

Metabolic

  • diabetic neuropathy
  • muscular dystrophy
  • hypothyroidism