inability to sneeze

In 1997, I had a period of a month or more where I could not sneeze; I would have the urge to sneeze, build up to the sneeze, but it would not come out. Then, I went back to "normal" sneezing. Then several years later, I had the same thing again, for over a month, but again, went back to "normal" sneezing. Now, over two years since the last episode, I have been experiencing the same thing again, for around 6 weeks. I even caught a cold, but my sneezes would come on with the inhalation and the AH but would never complete themselves with the CHOO. I read somewhere that this could be a symptom of a tumor on the medulla. Wouldn't there be other symptoms in conjunction with just that one symptom? I have no other symptoms and am a healthy 28 year old female. What I am looking for is this: Is there some explanation you can give me as to what causes this or could this just be "normal?" It is very frustrating, but as long as it is nothing serious like a tumor, I could stop thinking about it. I know sneezing is a reflex, and supposedly, from what I have read, once it starts, my brain should just automatically finish the sneeze. Thank you for your time.

[National Jewish]

This is definitely within the realm of normality.  Many people, especially if they begin to think about the sneeze sequence, will get hung-up and not sneeze.  This has been happening for 8 years or so.  No tumor, benign or malignant would ever behave this way, this long.