What Causes The Inability To Complete A Reflex Sneeze?
No reason for alarm.
Detailed Answer:
I read your question carefully and I understand your concern.
However I think you shouldn't worry about it. There are some very rare occasions where loss of the ability to sneeze is due to a brain lesion in an area of the brain stem called the medulla. However almost always there are other accompanying symptoms as it is a region with a high concentration of brain nuclei and nerve fibers, so loss of sneeze reflex would not be an isolated manifestation. A MRI can be scheduled to put your mind at rest but I am really confident it will turn out to be normal.
Most times it is related to psychological causes and the fact that you're building anxiety over it may in turn affect the issue. So you should relax as nothing needs to be done, no harm will come out of it.
I remain at your disposal for other questions.
Glad to have been of help.
Detailed Answer:
Wishing you good health.