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Congenital and Inherited Anomalies of the Nervous System: Introduction |  |
| Congenital defects of the CNS are, by definition, present at birth. Some congenital defects are known to be inherited, others are caused by environmental factors (toxic plants, nutritional deficiencies, viral infections); for many, the cause is unknown. In those animals born with a well-developed nervous system (foals, calves, lambs, pigs), the clinical signs of a congenital neurologic disorder may actually be recognizable at birth. Kittens and puppies are born with a less
well-developed nervous system, and in those species, neurologic signs may not be apparent until they begin to walk. In some instances, clinical signs of an inherited disorder are not seen until the animal is an adult, even though the defect has obviously been present since birth. |
| Congenital lesions can be categorized according to the primary region of the CNS affected:
Forebrain disorders (cerebrum and thalamus) primarily result in clinical signs such as visual disturbances, changes in mental status or behavior, abnormal movements or postures, and seizures.
Cerebellar disorders usually result in an intention tremor and incoordination (dysmetria) of both the head and limbs.
Spinal cord disorders do not affect cerebral function and normal coordination of head movement but produce motor dysfunction or proprioceptive deficits, including either dysmetria or reduced paw position sense in more than one limb. (See also
diseases of the spinal column and cord,
Diseases of the Spinal Column and Cord: Introduction.)
Peripheral nerve and muscle disorders can result in signs of weakness and ataxia similar to those seen in spinal cord disease. In addition, they often cause widespread disturbance of reflex function, pain sensation, or marked muscle atrophy.
Multifocal disorders result in combinations of signs from more than one of these categories of neurologic deficits. |
