Neuropathies

Neuropathies are frequently seen disorders in cats and dogs and are divided into motor, sensory and vegetative neuropathies. the hallmark of a neuropathy is the loss of a part of the reflex arch involved. the most common are neuropathies of the motor system. Sensory neuropathies do occur but are very rare. and although vegetative disorders have been described they are difficult to diagnose properly in a clinical setting. partly because they may provoke only limited clinical signs.

If the neuropathy affects the skeletal nerves we tend to speak of a polyneuropathy. in these animals we will see generalised, symmetrical abnormalities. if only the motor function is lost (a so called lower motor neuron disease) the clinical presentation will be that of paresis or paralysis of one or more legs. a neurological examination will reveal in principle depressed or absent reflexes. When cranial nerves are affected such as the trigeminal or facial nerves more pronounced specific signs will be noticed.

Based on the pathology polyneuropathies can also be divided into three groups, according to the morphological changes:

1. Myelinopathy in which there is a degeneration of a myelin sheath, the axon is unaffected, but may degenerate later on. Demyelinisation can occur at any level, distal or proximal and results in acute functional disturbance. remyelinisation is often quick and functional recovery will occur. acute polyneuritis is a typical form of myelinopathy(1).

2. Axonopathy in which there is a degeneration of an axon, secondary followed by degeneration of the myelin sheath. Degeneration starts at the distal end of the affected axon and progresses towards the proximal end. the most lengthy axons are most frequently affected. if the disease exists for a longer period of time, regenera- tions become visible. Disorders develop gradually and recovery takes a lot of time. Examples of axonopathies are metabolic, toxic and heriditary polyneuropathies (2, 3).

3. Neuronopathies in which the initial changes take place in the cell body of an affected neuron. if these changes are severe, the cell dies and loss of function is complete and permanent. this type of polyneuropathy is very rarely seen in cats and dogs (4).