You can read some information about the retention cyst on http://www.urmc.rochester.edu/smd/rad/neurocases/Neurocase110.htm
The case described here may not be like your, but they have attempted to describe the retention cyst. A particularly important extract of it is "....A retention cyst forms when a mucous gland of the sinus mucosa becomes obstructed. Its walls are thus defined by the epithelium of a mucous gland and duct itself, not by the walls of the sinus. There is almost always air still surrounding the retention cyst, and bony expansion and remodeling of the sinus does not often occur. They are .........incidental findings in at least 10% of people."
In your case, the sphenoid sinus cyst may not be clinically significant. At the same time, these cysts are known to bring on headache.
You may discuss about the significance of the cyst with your neurologist once.
I have been diagnosed having panthetonase kinase associated with neurodegeneration disease also found in the MRI scan an incidental mucous retention cyst in the right sphenoid area. can you explain to me what this means ? i had bolts of bad headache attack very frequently which can cause numbness from the shoulder to the head. Has this anything to do with the retention cyst ?