Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.
It sounds like you have symptoms of imbalance in addition to nasal congestion and ear stuffiness. The nasal congestion and ear stuffiness do not sound like a neurologic problem. There are many potential causes to imbalance. The sensation of feeling like you are on a boat could be an equivalent to vertigo. Vertigo can be caused by inner ear problems or could be neurologic. In the presence of a normal MRI (the mucous cyst is not concerning), this excludes the more worrisome causes of vertigo such as tumors or MS. Other potential causes could include a migraine equivalent called basilar migraine. This is usually but not always associated with headache, in addition to vertigo, nausea and sometimes other symptoms. If you have a history of headache associated with your symptoms this is one possibility.
If your symptoms are worse in the morning, if you are tired throughout the day and wake up with a feeling of not being well rested and have a headache, a sleep disorder such as sleep apnea is one consideration if you are overweight and snore. Other causes of morning stuffiness could be postnasal drip or acid reflux.
2 systemic causes of the symptoms you describe could include thyroid problems, which can be checked for with a simple blood test called TSH, and a nutritional deficiency can also cause imbalance: vitamin B12 deficiency. This can be checked for with a blood test as well.
If you have chronic neck pain or other neck problems, your sense of imbalance could be due to what is termed cervicogenic dizziness, or dizziness due to neck problems.
One method of treating a sense of imbalance is a type of physical therapy called vestibular rehabilitation. This is particularly useful if the vertigo is felt to be coming from your inner ear.
I recommend continued follow up with your neurologist and ENT physician as well as your primary doctor.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
hey anthon!
have you tried a biomagnetism treatment? its an alternative kind of treatment, i would strongly recommend it with 99% good results on the balance problem. My aunt use to have those and she took the treatment 4 times and since the first time she took it, the problem start to disapear 'till she reached the 4th session and the balance problem is now gone