Paralysis:

• Paralysis may be described as derangement of neurological control over the peripheral organs.
• It denotes a condition when there is incomplete or complete loss of nervous control over any bodily functions.
• It comprises loss of sensory or motor power or both. It is characterized by total inability to perform voluntary movements.
• Paresis is state where the muscular power of contraction is weaker than normal but not lost entirely.

Classification of Paralysis:

1. Anatomical classification of paralysis:

• Cerebral paralysis:
  • It results due to:
    • Apoplexy
    • Infection of CNS
    • Tumor, cyst, abscess
    • Compression of brain
    • Encephalitis
    • Increased C.S.F pressure
    • Fracture of cranial vault
    • Cerebral thrombosis
  • Spinal paralysis

It results due to:

• Injury of spinal cord due to trauma
• Concussion of spinal cord
• Spondylopathy
• Abscess in spinal cord
• Ancylosis of vertebrae
• Fracture of vertebral column
• Intervertebral disc protrusion
• Myelitis and meningitis
• Tubercular lesion in the vertebrae
• Peripheral paralysis:

It results due to:

• Injury in nerve trunk
• Affection of the nerve endings of muscle fibres
• Rheumatic condition of muscles
• Deficiency of B-vitamins (B₁, B₆, B₁₂)
• Rheumatic condition of nerves
• Drug toxicity

2. Symptomatic classification of paralysis:

• Spastic paralysis:
  • Also known as spastic paresis
  • It is type of muscular weakness or paralysis characterized by increased muscle tone and muscle stiffness.
  • It can be seen in domestic animals and usually results from:
    • Spinal injuries: traumatic injuries from car accident, fall disrupts nerve signals controlling muscle movements, leading to muscle stiffness
    • Degenerative myelopathy: progressive neurologic disease commonly affecting certain breed of dog; German Shepherd
    • Infectious disease: Rabies, Distemper
    • Hereditary conditions: genetic mutation in some breed of cats results in spastic paralysis.
    • Toxicity: toxic substances can damage nerves resulting spastic paresis
    • Nutritional deficiencies, particularly vitamin and mineral deficiencies causes spastic paralysis.
  • Flaccid paralysis:
    • It refers to a condition where there is loss of muscle tone and muscle weakness, resulting in limp, floppy and often unresponsive limbs
    • It typically results from damage to lower motor neurons or neuromuscular junction, interrupting normal communication between nerves and muscles.
    • It results due to:
      • Botulism: It caused by bacterial toxins, interfering the release of Ach, neurotransmitter that triggers muscle contraction
      • Tick paralysis: Certain species of ticks can transmit toxins that leads to flaccid paralysis. Paralysis initiates at hindlimbs and progress forward as tick feeds.
      • Guillain-Barre syndrome: It is an auto-immune disorder affecting dogs and cats and result in flaccid paralysis.
      • Snake bite: Venomous snake bites can cause flaccid paralysis in animals due to toxins, interfering with nerve transmission.
      • Toxic plants: Ingesting certain toxic plants can lead to flaccid paralysis in animals. For example, locoweed, which is toxic to horses and other livestock, can cause muscle weakness and loss of coordination.
      • Infectious disease: Some infectious diseases, such as tick-borne illnesses, can result in neurological symptoms and flaccid paralysis in animals.

3. Lesion based classification of paralysis:

• Upper motor neuron lesion:
  • It is often referred as upper motor neuron paralysis or UMNs.
  • It is a condition affecting central nervous system, upper motor neuron
  • Upper motor neurons are located in cerebral cortex of brain and brainstem and are responsible for transmitting motor commands from brain to lower motor neuron in spinal cord.
  • This type of paralysis results in spasticity of muscles, hyperreflexia, abnormal gait, muscle atrophy, difficulty in posture and balance, loss of fine motor skills.
• Lower motor neuron lesion:
  • Lower motor neuron lesion causes lower motor neuron paralysis.
  • It is a neurological condition that affects peripheral nervous system, particularly lower motor neurons.
  • Lower motor neurons are located in spinal cord and cranial nerve nuclei. These neurons play crucial role in transmission of nerve signals from CNS to muscles
  • Paralysis resulting from lower motor neuron lesion results in flaccidity or weak limbs, hyporeflexia, loss of voluntary motor control, muscle atrophy, muscle fasciculation or twitching, incoordination, pain and discomfort in affected part.

4. Positional classification of paralysis:

• Nuclear paralysis:
  • It results due to injury of nuclei of cranial nerve or ventral horn cells of the spinal cord.
• Infra-nuclear paralysis:
  • It occurs due to injury to the axon of the cranial nerve cells or those of ventral horn cells of spinal cord.
• Supra-nuclear paralysis:
  • It results due to injury to upper part of the motor pathway.

5. Clinical classification of paralysis:

• Monoplegia: It is the term used to indicate loss of functions affecting one or few nerves. E.g, radial paralysis
• Diplegia: It is a condition in which both sides of the body are affected.
• Hemiplegia: it is the term applied to loss of functions affecting one side of body only along with anterior or posterior part of limb of that particular side.
• Quadriplegia: it is a condition where all the four legs are affected.
• Paraplegia: it is a term applied to paralysis of hind quarter. It is a distinct clinical feature in spinal cord affection.

FORMS OF PERIPHERAL NERVE PARALYSIS IN ANIMALS

Radial nerve paralysis:

• Radial nerve is one of the nerves of brachial plexus originating from spinal cord segments C₇-T₂.
• Distal radial nerve paralysis results in inability of animal to extend its carpus and digit.
• Proximal radial nerve paralysis results in inability of animal to extends its elbow, carpus, and fetlock joint to bear weight.
• This type of paralysis is also known as ‘dropped elbow’.
• It is observed in horse, cattle and occasionally in dog.

Etiology:

• Damage to nerve may result from casting of animals with rope
• Accidental restraining of forelimbs
• Prolonged recumbency in heavy animals results in distal radial nerve injury.
• Traumatic injuries such as fracture of humerus, blunt force trauma to shoulder and elbow,
• Tumor or cancer of radial nerve
• Inflammatory conditions such as radiculoneuritis or polyneuritis

Clinical Findings:

• Inability to extend elbow, carpus, fetlock
• Dragging of limbs
• Decreased muscle mass in affected limbs
• Loss of sensation in affected limb
• Pain and discomfort especially during movement
• Lameness or difficulty walking on affected limb

Diagnosis:

• Physical examination of limbs
• History of injuries, surgeries or certain medical conditions
• Neurological assessment: Characteristic wrist drop or knuckling of affected limb
• Diagnostic imaging: X-rays, CT scan, MRI helps identifying fracture, nerve compression
• Electromyography (EMG): There is abnormal electrical activity in muscle of affected limb.
• Blood test helps to identify infectious causes

Treatment:

• Rapid improvement of radial nerve paralysis can be expected in most cases with anti-inflammatory treatment.
• Patients should be confined in a generously bedded stall, and the fetlock should be protected with a bandage to prevent septic arthritis from damage to the skin over the fetlock.
• A cast up to the elbow is needed in severe cases to minimize trauma to the ventral aspect of the fetlock as the animal drags the forelimb around.
• In some cases, surgical procedures may be required to repair nerve damage or relieve nerve compression by removing tumors, repairing fractures, or decompressing the nerve.
• Physical therapy and rehabilitation exercises can help improve muscle strength and mobility in the affected limb.