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
The following list includes some of the more common signs associated with limb paresis/paralysis and weakness and is not all-inclusive.
- knuckling
- dragging leg(s)
- abnormal gait
- monopareseis/monoplegia
- paraparesis/paraplegia
- tetraparesis/tetraplegia
COMMON CAUSES: Spinal Cord Diseases (Myelopathies)
The following list includes some of the more common diseases associated with limb paresis/paralysis and weakness and is not all-inclusive.
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
- Bacterial
- 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)
The following list includes some of the more common diseases associated with limb paresis/paralysis and weakness and is not all-inclusive.
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
This information is meant to be a guide and not a substitute for veterinary care.
Always follow the instructions provided by your veterinarian.