Abiotrophy

Abiotrophy is a process of degeneration, with progressive loss of viability, affecting cells of the central nervous system. Abiotrophy is a degenerative pathological process that occurs in histological elements. Particularly studied is the abiotrophy affecting nerve cells, known, depending on the district involved, as cerebral abiotrophy and cerebellar abiotrophy.

Abiotrophy arises without any apparent recognized cause and, according to current knowledge, it occurs simply because the cells have reached the natural biological reproductive limit of their life span.

The abiotrophy causes, depending on the areas of the brain affected, different clinical pictures; among the best known abiotrophies are the dementias on a neurodegenerative basis, such as Alzheimer’s disease, frontotemporal dementia of Pick, Huntington’s chorea (with prevalent involvement of the cerebellum), the fatal familial insomnia (due to thalamic lesions), Creutzfeldt-Jakob encephalopathy. The most frequent congenital abiotrophies, sometimes with familial distribution, are those localized mainly in the cerebellum, although they are accompanied by degenerative lesions of other brain districts: they are almost always associated with lesions of the optic nerve or retina, psychic hypoevolutism, myoclonic type motor disorders. Acquired human abiotrophies are often identified as prion diseases.

Cerebellar abiotrophy or cerebellar ataxia

Cerebellar cortical abiotrophy or cerebellar ataxia, is a condition that occurs in several dog and feline breeds. The animal develops a progressive form of corticocerbellar degeneration that has a characteristic of incoordination, called cerebellar ataxia, which is manifested by exaggerated movement. Clinical symptoms often arise insidiously and evolve chronically and progressively. Characteristic is the incoordination that is more pronounced during changes of direction and the ascent or descent of stairs.

In some breeds there may be forms of corticocerebellar degeneration that appear at birth (Beagle, Samoyed, Portuguese Podengo).

Other times the appearance of symptoms occurs a few weeks after birth (Kerry Blue Terrier, Rough-coated Collie, English Bulldog, Border collie, Labrador, Italian Hound, Lagotto, Schnautzer, Bavarian Mountain Hound, Poodle, Siamese or European cat), in some breeds may occur late, even in adulthood (Amstaff, Épagneul Breton, Setter Gordon).

The evolution of the disease is also very variable, there are cases in which very quickly the animal is no longer able to coordinate, to maintain the station, even to drink or eat, while in other subjects the gait defects are much milder and do not make the animal unable to move.

Cerebellar abiotrophy is due to a genetic defect that leads to the degeneration of neurons in the cerebellum that have an inhibitory function and control over movement (in particular, the primary lesion is at the expense of Purkinje cells). Lacking this function, the animal shows exaggerated and uncontrolled movements.

The transmission of cerebellar abiotrophy is presumably genetic of autosomal recessive type.

The Amstaff is the breed that recently has been the focus of attention of scholars, as the case history in these animals is particularly high. The onset of symptoms occurs between 18 months and 9 years, with greater concentration between 4 and 6 years.

The definitive diagnosis can be confirmed only with the pathological anatomy, but in addition to the clinical suspicion, the history of the animal and the course of the disease, as well as the characteristic presence in some breeds, in advanced cases, changes in the structure of the cerebellum can be shown on MRI examination. For the American Staffordshire Terrier the gene mutation responsible for cerebellar degeneration has been highlighted, and a genetic test has been developed to allow an early diagnosis and a proper selection of animals to decrease the incidence of the disease (about 40% of European Amstaff seem to be carriers of the disease and about 7% are affected).

In the sick animal there are two mutated alleles of the gene that encodes for arylsulfatase G (homozygosity), while in the healthy carrier there is only one mutated allele (heterozygosity). It is therefore possible to perform a DNA test to highlight the mutation and obtain crosses of animals with healthy offspring.

The symptoms usually worsen until the inability for the animal to move and feed and the prognosis is bleak. There is no definitive cure for the disease, but the animal can be helped and supported as long as possible in walking, using physiotherapy and walking aids.

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