Arachnoid cyst overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Arachnoid cysts are cerebrospinal fluid cysts covered by arachnoidal cells and collagen. They develop between the arachnoid membrane and the surface of the brain. Arachnoid cysts are mostly a congenital disorder.

Classification

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

Causes

The exact cause of arachnoid cysts is not known. Researchers believe that most cases of arachnoid cysts are developmental malformations that arise from the unexplained splitting or tearing of the arachnoid membrane, being classified as primary. There are also arachnoid cysts that arise from secondary causes, such as trauma, surgery, intracranial hemorrhage and infection.

Epidemiology

Arachnoid cysts occur in about 1.2% of the general population and are more frequently seen in men than in women.

Natural History, Complications and Prognosis

Prognosis of arachnoid cyst is generally excellent and is usually associated with a benign disease course, despite being symptomatic in a few patients. Most are found incidentally, and a few may, rarely, enlarge and complicate with the symptoms previously described such as hydrocephalus, seizures, hearing loss, visual changes and cervical myelopathy.

History and Symptoms

Patients with arachnoid cysts will most likely never show symptoms, even in cases where the cyst is large. Therefore, while the presence of symptoms may provoke further clinical investigation, symptoms independent of further data cannot, and should not be, interpreted as evidence of a cyst's existence, size or location. These symptoms usually are:

• Headache;
• Nausea/Vomiting;
• Seizures;
• Skull/spine deformation;
• Developmental delays;
• Obstructive hydrocephalus;
• Hearing loss;
• Head bobbing;
• Visual changes.

Physical Examination

Physical examination is generally not very useful as most cases of arachnoid cysts are diagnosed incidentally, but in larger cysts, depending of the affected region, there may be some findings such as:

• Ataxia;
• Hearing loss;
• Visual changes;
• Protrusions from the head or spine;
• Head bobbing;
• Endocrine issues, e.g. early onset of puberty.