Arachnoid Cyst

Hello Im 34 years old and decided to go to the doctors because i had weakness on my left arm and a headche they did a MRI in the emeregency room and found out I had a arachnoid cyst in my head a little bit smaller than a quarter. They said that they have to keep a eye on it and they might have to drain it. It is sitting right in the back of my brain stem. Will this cause any serious problems? what is the out look for me? I dont have any other illnesses and is other wise healthy...

[CCF-Neuro-M.D.-JT]

Potential neurological problems depend on the exact location of the arachoid cyst (in your case where it pushes up against the brainstem) and whether or not it ruptures. Arachnoid cysts can either be congenital (you're born with it) or acquired as a complication of infection or trauma. SOmetimes it's jsut an incidental finding on an MRI- meaning, it doesn't really do anything or mean anything clinically significant. In most patients,the cysts remain stable and don;t rupture. But if it does rupture or begins to enlarge, producing symptoms such as headache, progressive weakness, or other neurological symptoms then surgical treatment with either drainage or excision may be indicated. The brainstem is a very elegant structure that has many functions located within it such as the nerves that control strength and sensation of the face as well as eye movements. It also contains the nerve fibers that run from the brain to the spinal cord.  If the cyst continues to grow (some do and some don't), you will likely need to think about surgical intervention depending on how much it compromises the brainstem and its functions. Talk to your PCP about getting a neurosurgery appointment and bring them your MRI for a formal review and examination. It's possible that the cyst is not causing your symptoms, but it would be best for a surgeon to follow you closely anyway, given its proximity to the brainstem. good luck.