Yes, it is possible to use an old youtube account. However, it might be simpler to create a new one depending upon the purpose. Thus it can be said that there isn't a definite yes or no response to this question. It can be simpler to rename and preserve the channel if you want to drastically alter the sort of content on it, and it has been dormant. Launching a new, independent channel could be advisable if the current one still receives lots of views and subscribers.