Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Arterial dissection at young age is often related to a disorder of the connective tissue which may well be hereditary. Of course it s hard to diagnose them online as there are many different connective tissue disorders involving different organs, at times they can t be classified as they are limited to only one family. So to check that possibility it is first started with a general physical exam to check for particular constitution types, abnormalities of the skin and joint elasticity, bone length etc. Genetic testing may be done for some known conditions. If nothing abnormal is observed skin biopsy may show connective tissue changes. Whether a connective tissue disorder is evidenced or not though, from a practical point of view the only thing which can be done to prevent stroke would be to avoid traumatic events and taking Aspirin. Unless there is a genetic diagnosis though I wouldn t recommend starting Aspirin in a 9 year old. Hope I have answered your query. Let me know if I can assist you further.