DNA test - Fuco.
Canine Fucosidosis (Fuco) is a disease which is severe, progressive and ultimately fatal. It is characterised by deteriorating signs of the nervous system that progress over a period of several months, sometimes from an early age. Signs include uncoordination and ataxia (loss of control of movement), change in temperament, loss of learned behaviour, loss of balance, apparent deafness, visual impairment and varying degrees of depression. The disease, which affects young adults, usually between 18 months and 4 years of age, is caused by a recessive mutation in the gene for the enzyme alpha-L-fucosidase. This enzyme is one of many required to break down complex compounds into simple molecules that the body can use. In affected dogs, those carrying two copies of the mutant gene, this enzyme is absent, the pathway is blocked and toxic compounds build up in the cells of the affected animal. The cells of the nervous system are particularly sensitive to these toxic intermediates.
Source of DNA Test: http://www.thekennelclub.org.uk/download/8288/dnatestsworldwide.pdf