Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells and collagen[1] that may develop between the surface of the brain and the cranial base or on the arachnoid membrane, one of the three membranes that cover the brain and the spinal cord.[2] Arachnoid cysts are a congenital disorder,[3] and most cases begin during infancy; however, onset may be delayed until adolescence
Arachnoid cysts can be found on the brain, or on the spine. Intracranial arachnoid cysts usually occur adjacent to the arachnoidal cistern.[4] Spinal arachnoid cysts may be extradural, intradural, or perineural and tend to present with signs and symptoms indicative of a radiculopathy.[4]
Arachnoid cysts can be relatively asymptomatic or present with insidious symptoms; for this reason, diagnosis is often delayed.
[edit] Signs and symptoms
Patients with arachnoid cysts may never show symptoms, even in some 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.
Symptoms vary by the size and location of the cyst(s), though small cysts usually have no symptoms and are discovered only incidentally.[2] On the other hand, a number of symptoms may result from large cysts:
- Cranial deformation or macrocephaly (enlargement of the head), particularly in children[5]
- Cysts in the suprasellar region in children have presented as bobbing and nodding of the head called Bobble-Head Doll Syndrome.[5]
- Cysts in the left middle cranial fossa have been associated with ADHD in a study on affected children.[6]
- Headaches.[2] A patient experiencing a headache does not necessarily have an arachnoid cyst.
- In a 2002 study involving 78 patients with a migraine or tension-type headache, CT scans showed abnormalities in over a third of the patients, though arachnoid cysts only accounted for 2.6% of patients in this study.[7]
- A study found 18% of patients with intracranial arachnoid cysts had non-specific headaches. The cyst was in the temporal location in 75% of these cases.[8]
- Seizures[2]
- Hydrocephalus (excessive accumulation of cerebrospinal fluid)[2]
- Increased intracranial pressure[2]
- Developmental delay[2]
- Behavioral changes[2]
- Hemiparesis (weakness or paralysis on one side of the body)[2]
- Ataxia (lack of muscle control)[2]
- Musical hallucination[9]
- Pre-senile dementia,[10] a condition often associated with Alzheimer's disease
- In elderly patients (>65 years old) symptoms were similar to chronic subdural hematoma or normal pressure hydrocephalus:[11]
