Arachnoid cyst 4cm discovered 7 1/2 years ago

I am a healthy 34 year old man with only an occassional sinus headache ( I do have sinuses and allergies and headaches normally occur when the weather or temp.  changes).  I recently learned from reviewing my medical records from a CT scan 7 1/2 years ago I have an arachnoid cyst of 4 cm in the left middle cranial fossa with associated hypoplasia of the left anteriortemporal lobe.  There is no hemorrage, midline shift, edema or hydrocephalus. temporal lobe.  The scan came about after I sustained a hard blow to the head while exercising. (A metal bar at the gym hit me in the head) Is this what caused it, is this a large one, do they grow and can you have a normal long healthy life?    Also is there anything to avoid or look for and could I develop seizures? ( I have never had any and get physicals every year and other then being overweight with some asthma and being near sighted I am in good health ).  Thank you

[Neuro Forum]

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 and review your CT scan, I can not tell you what the exact implications of your imaging findings are. However I will try to provide you with some useful information.

Arachnoid cysts are sacs filled with cerebropsinal fluid (CSF) which is the fluid that normally bathes the brain and spine. This fluid is normally located in the part of the brain called the subarachnoid space.

Most commonly, these are primary arachnoid cysts, cysts that are present from birth and result from a minor developmental problem that occurred while the brain was developing. Secondary arachnoid cysts are those that develop secondary to trauma, infection, or after brain sugery. It is not always possible to tell if the cyst you have is primary or secondary.

If an arachnoid cyst is deemed to be causing symptoms or is pressing on surrounding structures (which would most often be evident on your imaging), surgical opening (fenestration) of the cyst and other surgical interventions could be done to correct it, but this is rarely necessary because the vast majority of arachnoid cysts are benign, do not grow, and do not cause symptoms and do not have further consequences. Headaches in people with arachnoid cyst may or may not be related to the cyst. As you mention, seizure could theoretically happen, and they sometimes do, but there is still controversy even among epilepsy specialists what the role of arachnoid cysts are in causing seizures.

There really is not a particular activity that should be avoided in someone with arachnoid cyst; only attempts to prevent further major head trauma, as in anyone. Sometimes, re-imaging to take another look at the cyst after a few months or years may be indicated to see if it is growing, pressing on the brain, etc. It is a good idea for you to ask your physicians about more information about the cyst, what the implications of having it is, so you can have a good understanding of it; establishing care with a neurologist so that you can have a physician follow this over time is recommended.

Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.