Pediatric Movement Disorders - Dystonia

Workup

The investigation of dystonia depends on the specific type of dystonia. Most hemidystonia is caused by a localized injury to the brain, often at or before birth. Therefore, with dystonia that involves one side of the body, a magnetic resonance image (MRI) of the head often shows the problem area(s).

In some cases, an old injury is seen as a region of damaged brain tissue. In other cases, it appears that one side of the brain is smaller than the other, presumably due to prior injury and loss of cells.

In many cases, dystonia is without obvious cause and the symptoms begin before the age of 24 years, and then become progressively worse. In these cases, there may be a genetic mutation in the DYT1 gene. If no other cause is evident, then the child should be tested for the presence of this gene, particularly if symptoms began in the foot and progressed to other areas of the body.

Other genetic tests may be ordered. The tests that are selected are based on the particular symptoms and whether or not other family members are affected. It is important to exclude metabolic causes for dystonia, as many of these diseases are treatable. Dopa-responsive dystonia (DRD) is a rare disorder of the enzyme pathway responsible for synthesizing dopamine. DRD is tested by measuring chemicals...

• In the cerebrospinal fluid, obtained by doing a spinal tap
• In the blood, following an oral dose of phenylalanine (known as the phenylalanine loading test)

Many neurologists forego testing for DRD and make a diagnosis based on the rapid resolution of symptoms with very low doses of oral dopamine. Other metabolic disorders, such as Wilson's disease, amino acid or organic acid disorders, and lysosomal storage diseases may be tested for in certain children. (See section on Etiologies.) An MRI is helpful during the workup for many metabolic diseases. This imaging technique may show whether or not there is destruction of part of the brain, a stroke, or a tumor.