Arachnoid cyst classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: José Eduardo Riceto Loyola Junior, M.D.[2]

Arachnoid cysts may be classified according to cause into 2 subtypes/groups: primary or secondary, or according to symptoms into 3 groups.

Arachnoid cysts can be classified by cause:

• Primary: developmental cysts, formed during the formation of arachnoid membranes in utero;
• Secondary: appear after trauma, infection, hemorrhage or surgery. Much less common.^[1]

They can also be further classified regarding the symptoms that they cause, as proposed by Choi et al.:

• First group: present with hydrocephalus and intracranial hypertension;
• Second group: present with dizziness, headaches, large head, seizures, strabismus, developmental delays and skull deformation;
• Third group: minimal or no symptoms.

This classification is closely related with prognosis. Patients from the first group had significant improvement after surgery, the third group had a much smaller benefit while patients from the second group had minimal benefit.^[1]

Nabors et al. suggested classifying arachnoid cysts of the spinal cord into three types:

• Type I – extradural cysts without nerve root involvement;
• Type II – extradural cysts with nerve root involvement;
• Type III – intradural cysts.^[2]