Arachnoid Cysts: Spider or Disorder?

By Neda Brinster

Don't be confused...the Arachnoid Cyst is not a spider but a congenital malformation affecting the brain and spinal cord. The Arachnoid Cyst is a membrane sac that fills with spinal fluid between the brain and spinal cord. The cyst forms on the arachnoid membrane, a thin, spider web-like material covering the brain and spinal cord. Most arachnoid cysts form outside the temporal lobe in the middle of the cranial fossa of the skull. Although rare, an arachnoid cyst can also develop near the spinal cord.

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Formation:

Arachnoid cysts usually form on the brain and are called intracranial arachnoid cysts. These cysts rarely form on the spinal cord, called spinal arachnoid cysts. Most Arachnoid cysts, called the middle fossa region, grow in front of the ears. Others grow behind the eyes, the Suprasellar region, and on the base of the skull, the posterior fossa.

Symptoms:

Symptoms usually develop before the age of 20 and the first years of life. However, some people with an arachnoid cyst never develop symptoms.

Depending on the location and classification of the arachnoid cyst, symptoms vary. They include headaches, nausea and vomiting, seizures, and vertigo.

Symptom Classifications:

Middle Fossa Region

- Vision problems

- Weakness, fatigue, paralysis

- Developmental delays and changes in behavior

Suprasellar region:

- Vision problems

- Affects the endocrine system

- Uncontrollable head-shaking

Spinal Cord:

- Numbness and tingling in the feet

- Muscle spasms

- Paralysis and movement issues

- Back pain and scoliosis

Treatment:

Without treatment, large arachnoid cysts may cause serious and permanent nerve damage. However, depending on the size and location of the cyst, symptoms may never present and surgery is not always necessary. Three types of treatment procedures are usually used: endoscopic procedures, open craniotomy fenestration, and shunting.

Endoscopic procedures: a small, thin tube with a camera is used to create a smaller incision and drain the spinal fluid.

Open craniotomy fenestration: part of the skull is removed to drain the fluid, and the body absorbs this fluid over time.

Shunting: a tube is inserted into the cyst, which remains in place. This helps drain the fluid but can also cause other complications such as blockage and infection.

Citations:

“Arachnoid Cyst.” Arachnoid Cyst - an Overview | ScienceDirect Topics, https://www.sciencedirect.com/topics/neuroscience/arachnoid-cyst.

“Arachnoid Cysts.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, https://www.ninds.nih.gov/health-information/disorders/arachnoid-cysts#:~:text=What%20are%20arachnoid%20cysts%3F,the%20brain%20and%20spinal%20cord.

“Arachnoid Cysts: What Are They, Location, Causes & Symptoms.” Cleveland Clinic, https://my.clevelandclinic.org/health/articles/6023-arachnoid-cysts.