What is an arachnoid cyst?
Arachnoid cysts are the most common type of brain cyst. They are congenital lesions that occur as a result of the splitting of the arachnoid membrane. The cysts are fluid-filled sacs, not tumors, appearing in one of the three layers of tissue covering the central nervous system.
Symptoms of arachnoid cysts
Most cysts that will become symptomatic do so in early childhood. Specific symptoms depend on the location of the cyst, but can include:
- mass protrusion in the skull
- focal neurological signs secondary to pressure of surrounding structures
- developmental delay
- hydrocephalus due to obstruction of normal cerebrospinal fluid (CSF) circulation
- endocrine symptoms such as early onset of puberty
- head bobbing
- visual impairment
Arachnoid cysts that do not cause symptoms or impact surrounding areas do not require treatment, no matter where they are located or how large they are. Otherwise, surgery is recommended.
How are arachnoid cysts diagnosed?
CT or MRI scans can be used to decide on the best treatment.
Treatment for arachnoid cysts
A very simple, fast and minimally-invasive treatment is burr hole drainage of the cyst. There is a high rate of recurrence and return of symptoms with this procedure, however.
A craniotomy can also be performed to remove the cyst wall and ensure normal communication with the cerebrospinal fluid pathways. This is a more invasive procedure, but allows for direct inspection of the cyst. Another option is the minimally-invasive endoscopic fenestration of the cyst, where the physician drains the cyst with a needle.
Shunting of the cyst is the simplest surgical procedure. A patient becomes dependent on the shunt, however, which can cause complications.