If you’re worried about inheriting a disease with a genetic component, testing can ease your mind, but it’s not something to undertake lightly. Neurological diseases that have a genetic component include familial ALS, early onset Alzheimer’s, and Huntington’s Disease. Of these, only Alzheimer’s and Huntington’s have tests can give you a better sense of your odds. 
The Test for Early Onset Familial Alzheimer’s Disease
If you want to learn more about the pros and cons of getting tested, there’s no better place to look that the Alzheimer’s Forum. http://www.alzforum.org/early-onset-familial-ad/diagnosisgenetics/genetic-testing-and-counseling-early-onset-familial Research on this disease can tell you the likelihood that you might get it, but it cannot say with 100 percent certainty whether you will or not. For more on this issue, check out this useful fact sheet by the NIH. http://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-genetics-fact-sheet
The Test for Huntington’s Disease
Genetic testing for Huntington’s Disease can tell you for sure if you will get the disease. That new can either ease your mind, or be devastating. Captured on National Public Radio’s “This American Life,” host Ira Glass says in his preface, “Act Two. What are you doing for the test of your life? The woman in this next story is waiting on a piece of paper that– I think it’s not an exaggeration to put it this way– is going to determine how she will spend the rest of her life. The paper that she’s waiting on is a test result–a genetic test–for Huntington’s disease.”
This is one of the most powerful radio shows I’ve ever heard. Listen to the audio because it truly conveys the anxiety of the young woman even more powerfully than the transcript does.
ttp://www.thisamericanlife.org/radio-archives/episode/509/it-says-so-right-here?act=2#play
Though I heard the program on NPR, it was originally produced by WYNC, and you can listen to their production here. http://www.wnyc.org/story/dna-secrets-what-you-want-know/
A War Correspondent Considers Fatherhood and Huntington’s
Another eye-witness account can be found in this interview with war correspondent, Charles Sabine. He says that 90 percent of Americans with a family history of Huntington’s don’t get the test because they don’t want to know. http://kuow.org/post/charles-sabine-genetic-testing
Should You Get Tested or Not?
That is a question everyone with a potentially inheritable disease will have to answer individually. There are kits on the internet that allow certain kinds of genetic testing for other inherited diseases or genetic abnormalities, such as those carried by those of Askenazi Jewish heritage, but though the test kits are readily available and inexpensive, a genetic counselor is a must.