A nervous system (neurological) examination will show:
If other family members are affected, this may help confirm the diagnosis.
Genetic tests can look for the defective gene that causes the disease. However, this test is not yet widely available. It is only found at certain research laboratories.
Tests such as MRI can help rule out other movement disorders and diseases.
Jankovic J. Movement disorders. In: Goetz CG, ed. Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 34.