Limb Paresis & Weakness

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

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:

Immune-mediated:

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)