Medical imaging, such as a CT scan or MRI scan, can show atrophy of the caudate nuclei early in the disease, as seen in the illustration to the right, but these changes are not, by themselves, diagnostic of HD. Cerebral atrophy can be seen in the advanced stages of the disease. Functional neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), can show changes in brain activity before the onset of physical symptoms, but they are experimental tools and are not used clinically. Predictive genetic testing
Because HD follows an autosomal dominant pattern of inheritance, a strong motivation exists for individuals who are at risk of inheriting it to seek a diagnosis. The genetic test for HD consists of a blood test, which counts the numbers of CAG repeats in each of the HTT alleles. Cutoffs are given as follows:

At 40 or more CAG repeats, full penetrance allele (FPA) exists. A "positive test" or "positive result" generally refers to this case. A positive result is not considered a diagnosis, since it may be obtained decades before the symptoms begin. However, a negative test means that the individual does not carry the expanded copy of the gene and will not develop HD. The test will tell a person who originally had a 50% chance of inheriting the disease if their risk goes up to 100% or is eliminated. Persons who test positive for the disease will develop HD sometime within their lifetimes, provided they live long enough for the disease to appear.
Since scapular fractures impair the motion of the shoulder, a person with a scapular fracture has a reduced ability to move the shoulder joint. Signs and symptoms may be masked by other injuries that accompany the scapular fracture. Causes
Usually, it takes a large amount of energy to fracture the scapula; the force may be indirect but is more often direct. The scapula is fractured as the result of significant blunt trauma, as occurs in vehicle collisions. About three quarters of cases are caused by high-speed car and motorcycle collisions. Falls and blows to the shoulder area can also cause the injury. Crushing injuries (as may occur in railroad or forestry accidents) and sports injuries (as may occur in horseback riding, mountain biking, bmxing or skiing) can also fracture the scapula. Scapular fracture can result from electrical shocks and from seizures: muscles pulling in different directions contract powerfully at the same time. In cardiopulmonary resuscitation, the chest is compressed significantly; scapular fracture may occur as a complication of this technique. Anatomy
The scapula has a body, neck, and spine; any of these may be fractured. The most commonly injured areas are the scapular body, spine, neck, and glenoid rim; the scapular body or neck is injured in about 80% of cases. Fractures that occur in the body may be vertical, horizontal, or comminuted (involving multiple fragments). Those that occur in the neck are usually parallel to the glenoid fossa.