Recent discoveries on chromosomal loci and mutations in familial neurodegenerative conditions have expanded our knowledge about the basic cellular mechanisms involved in neurodegeneration. These have provided us with the option of genetic testing to establish a more precise diagnosis in symptomatic individuals with or without an obvious family history. Presymptomatic (predictive) and prenatal diagnosis are possible for several movement disorders, including some of those discussed here, although a detailed discussion of molecular genetic testing is beyond the scope of this chapter. A recent review on this subject was published by the Movement Disorders Society Task Force on Molecular Diagnosis (88). Molecular genetic testing can be readily performed in affected individuals presenting with parkinsonism with ataxia (SCA2 and SCA3), dystonia (DYT1), and chorea (HD). The genetic tests for these conditions are commercially available. Appropriate genetic counseling can be provided by a neurologist requesting such tests. However, presymptomatic and prenatal molecular testing, if requested by family members, should be performed by experienced personnel in specialized genetic centers. Clinical geneticists can also help locate laboratories where molecular genetic testing can be performed for parkinsonian patients in whom known mutations are suspected. Testing for such mutations is currently performed only on an experimental basis.
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