Q. I have a congenital arachnoid cyst at the mid posterior fossa. What should I do?

Answered by
Dr. Gursimran
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Mar 27, 2021

Hello doctor,

I had an MRI today, and the report came back saying I have a congenital arachnoid cyst at the mid posterior fossa. I had a brain MRI about a year ago, and there was no cyst. Should I be concerned, and what should I do?



Welcome to icliniq.com.

Sorry to hear about your problems and I have few questions to ask. What kind of symptoms do you have? Do you have headaches, vomiting, weight loss? Usually, congenital cyst does not grow and are harmless. They do not require treatment until there is a lot of headache or hydrocephalus. It usually does not show in your scan, and there is no need to worry.

Thank you doctor,

Online, it says that this could be linked to cancer or tumor. Is this true? Also, if I did not have it before, how have I got it now? I am also lethargic.



Welcome back to icliniq.com.

The location of the cyst in your case is in a very safe place, and there is no need to worry at all. If the location was somewhere else, like in the cortical region, then you would have symptoms. Lethargy is not a symptom of this arachnoid cyst in the posterior fossa. Serial imaging and neurologic examinations are adequate in the majority of lesions that are asymptomatic. Surgery is indicated if there are symptoms of increased intracranial pressure, seizures, focal neurologic deficits, or cognitive impairment, which you do not have. It is not linked to cancer or any progression of the cyst. This cyst could have been missed in the last scan.

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