Arachnoid cyst

Name = Arachnoid cyst

Caption =
DiseasesDB = 33219
ICD10 = ICD10|Q|04|6|q|00
ICD9 = ICD9|348.0
OMIM = 207790
MedlinePlus =
eMedicineSubj = radio
eMedicineTopic = 48
MeshName = Cyst,Arachnoid
MeshNumber = D016080

Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells and collagenAriai S, Koerbel A, Bornemann A, Morgala M, Tatagiba M. "Cerebellopontine angle arachnoid cyst harbouring ectopic neuroglia", "Pediatr Neurosurg." 2005 Jul-Aug;41(4):220-3. (PMID 16088260)] 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. NINDS Arachnoid Cysts Information Page] Arachnoid cysts are a congenital disorder, [Gelabert-Gonzalez M. "Intracranial arachnoid cysts", "Rev Neurol.", 2004 Dec 16-31;39(12):1161-6. (PMID 15625636)] 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.Arachnoid cyst. (n.d.). Gale Encyclopedia of Neurological Disorders. Retrieved September 10, 2006, from Web site:] Spinal arachnoid cysts may be extradural, intradural, or perineural and tend to present with signs and symptoms indicative of a radiculopathy.

Arachnoid cysts can be relatively or present with symptoms; for this reason, diagnosis is often delayed.

igns 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. On the other hand, a number of symptoms may result from large cysts:
*Cranial deformation or macrocephaly (enlargement of the head), particularly in childrenBarker RA, Scolding N, Rowe D, Larner AJ. "The A-Z of Neurological Practice: A Guide to Clinical Neurology" Cambridge University Press 2005 Jan 10, p61. (ISBN 0-521-62960-8)]
*Cysts in the suprasellar region in children have presented as bobbing and nodding of the head called Bobble-Head Doll Syndrome.
*Cysts in the left middle cranial fossa have been associated with ADHD in a study on affected children. [Millichap JG. "Temporal lobe arachnoid cyst-attention deficit disorder syndrome: role of the electroencephalogram in diagnosis", "Neurology" 1997 May;48(5):1435-9. (PMID 9153486)]
*Headaches. While the most common symptom,Fact|date=January 2007 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. [Valença MM, Valença LP, Menezes TL. "Computed tomography scan of the head in patients with migraine or tension-type headache", "Arq Neuropsiquiatr." 2002 Sep;60(3-A):542-7. (PMID 12244387)]
**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.Cameron AD. "Psychotic phenomena with migraine and an arachnoid cyst", "Progress in Neurology and Psychiatry" 2002 Mar-Apr 6(2) [ Action=View&Archive=True&ID=67&GroupID=&Page=11] ]
*Hydrocephalus (excessive accumulation of cerebrospinal fluid)
*Increased intracranial pressure
*Developmental delay
*Behavioral changes
*Hemiparesis (weakness or paralysis on one side of the body)
*Ataxia (lack of muscle control)
*Musical hallucination [Griffiths TD. "Musical hallucinosis in acquired deafness. Phenomenology and brain substrate.", "Brain", 2000 Oct;123 ( Pt 10):2065-76. (PMID 11004124)]
*Pre-senile dementia,Richards G, Lusznat RM. "An arachnoid cyst in a patient with pre-senile dementia", "Progress in Neurology and Psychiatry", 2001 May-June;5(3) [ Action=View&Archive=True&ID=29&GroupID=&Page=18] ] 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:Yamakawa H, Ohkuma A, Hattori T, Niikawa S, Kobayashi H. "Primary intracranial arachnoid cyst in the elderly: a survey on 39 cases", "Acta Neurochir (Wien)." 1991;113(1-2):42-7. (PMID 1799142)]
**Urinary incontinence

Location-specific symptoms

:"The following list of location-specific symptoms should be interpreted in the context of what they represent: results from several independent, unrelated studies. As of September 2006update after|2007|09|30|COMMENT = See if any articles published after last "as of" date discuss location-specific symptoms, no published research comprehensively maps physical and neuropsychiatric symptoms to a specific arachnoid cyst location."

*A supratentorial arachnoid cyst can mimic a Ménière's disease attack. [Buongiorno G, Ricca G. "Supratentorial arachnoid cyst mimicking a Ménière's disease attack", "J Laryngol Otol." 2003 Sep;117(9):728-30. (PMID 14561365)]
*Frontal arachnoid cysts have been associated with depression.Cummings JL, Mega MS. "Neuropsychiatry and Behavioral Neuroscience", Oxford University Press, USA; 2Rev Ed, 2003 Jan 23;208. (ISBN 0-19-513858-9)]
*Cysts on the left temporal lobe have been associated with psychosis. [Alves da Silva J, Alves A, Talina M, Carreiro S, Guimarães J, Xavier M. "Arachnoid cyst in a patient with psychosis: a case report" "Annals of General Psychiatry" 2007, 6:16) [] ] [Vakis AF, Koutentakis DI, Karabetsos DA, Kalostos GN. "Psychosis-like syndrome associated with intermittent intracranial hypertension caused by a large arachnoid cyst of the left temporal lobe", "Br J Neurosurg." 2006 Jun;20(3):156-9. (PMID 16801049)] A left fronto-temporal cyst more specifically showed symptoms of alexithymia. [Blackshaw S, Bowen RC. "A case of atypical psychosis associated with alexithymia and a left fronto-temporal lesion: possible correlations", "Can J Psychiatry" 1987 Nov;32(8):688-92. (PMID 3690485)]
*Cyst on the right sylvian fissure resulted in new onset of schizophrenia-like symptoms at age 61. [Cullum CM, Heaton RK, Harris MJ, Jeste DV. "Neurobehavioral and neurodiagnostic aspects of late-onset psychosis", "Arch Clin Neuropsychol." 1994 Oct;9(5):371-82. (PMID 14589653)]
*A patient with a cyst on the left middle cranial fossa had auditory hallucinations, migraine-like headaches, and periodic paranoia
*Patients with left temporal lobe cysts had mood disturbances similar to manic depression (bipolar disorder) [Heinrichs, RW. "In Search of Madness: Schizophrenia and Neuroscience" Oxford University Press, USA (March 29, 2001); p129. (ISBN 0-19-512219-4)]


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. According to the medical literature, cases of arachnoid cysts have run in families (familial cases) suggesting that a genetic predisposition may play a role in the development of arachnoid cysts in some individuals.

In some cases, arachnoid cysts occurring in the middle fossa are accompanied by underdevelopment (hypoplasia) or compression of the temporal lobe. The exact role that temporal lobe abnormalities play in the development of middle fossa arachnoid cysts is unknown.

In a few rare cases, intracranial arachnoid cysts may be inherited as an autosomal recessive trait. In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.

In a few rare cases, spinal intradural arachnoid cysts may be inherited as an autosomal dominant trait.

Some complications of arachnoid cysts can occur when a cyst is damaged because of minor head trauma. Trauma can cause the fluid within a cyst to leak into other areas (e.g., subarachnoid space). Blood vessels on the surface of a cyst may tear and bleed into the cyst (intracystic hemorrhage), increasing its size. If a blood vessel bleeds on the outside of a cyst, a collection of blood (hematoma) may result. In the cases of intracystic hemorrhage and hematoma, the individual may have symptoms of increased pressure within the cranium and signs of compression of nearby nerve (neural) tissue.

Arachnoid cysts can also occur secondary to other disorders such as Marfan’s syndrome, arachnoiditis, or agenesis of the corpus callosum. (For more information on these disorders, choose the specific disorder name as your search term in the Rare Disease Database.) []


Diagnosis is principally by MRI. Frequently, arachnoid cysts are incidental findings on MRI scans performed for other clinical reasons. In practice, diagnosis of symptomatic arachnoid cysts requires symptoms to be present, and many with the disorder never develop symptoms.

Additional clinical assessment tools that can be useful in evaluating a patient with arachnoid cysts include the mini-mental state examination (MMSE), a brief questionnaire-based test used to assess cognition. Myelograms are contraindicated for people with arachnoid cysts.


Treatment for arachnoid cysts occurs when symptoms present themselves. A variety of procedures may be used to decompress (remove pressure from) the cyst.

*Surgical placement of a cerebral shunt: [Strojnik T. "Different approaches to surgical treatment of arachnoid cysts", "Wiener Klinische Wochenschrift." [] 2006;118 Suppl 2:85-8. (PMID 16817052)]
**An internal shunt drains into the subdural compartment. [Helland CA, Wester K. "Arachnoid cysts in adults: long-term follow-up of patients treated with internal shunts to the subdural compartment", "Surg Neurol." 2006 Jul;66(1):56-61; discussion 61. (PMID 16793443)]
**A cystoperitoneal shunt drains to the peritoneal cavity. [Park SW, Yoon SH, Cho KH, Shin YS. "A large arachnoid cyst of the lateral ventricle extending from the supracerebellar cistern—case report", "Surg Neurol" 2006 Jun;65(6):611-14. (PMID 16720186)]
**Craniotomy with excision [Gangemi M, Colella G, Magro F, Maiuri F. "Suprasellar arachnoid cysts: endoscopy versus microsurgical cyst excision and shunting", "Br J Neurosurg" 2007 Jun;21(3):276-80. (PMID 17612918)]

**Various endoscopic techniques are proving effective, [Greenfield JP, Souweidane MM. "Endoscopic management of intracranial cysts", "Neurosurg Focus." 2005 Dec 15;19(6):E7. (PMID 16398484)] including laser-assisted techniques. [Van Beijnum J, Hanlo PW, Han KS, Ludo Van der Pol W, Verdaasdonk RM, Van Nieuwenhuizen O. "Navigated laser-assisted endoscopic fenestration of a suprasellar arachnoid cyst in a 2-year-old child with bobble-head doll syndrome", "J Neurosurg." 2006 May;104(5 Suppl):348-51. (PMID 16848093)]
*Drainage by needle aspiration or burr hole. While these procedures are relatively simple, there is a high incidence of recurrence.Fact|date=January 2007
*Capsular resection
*Pharmacological treatments may address specific symptoms such as seizures or pain.

A 1994 study found surgery necessary for good outcome in patients >65 years old when the cysts began displaying symptoms.Caruso R, Salvati M, Cervoni L. "Primary intracranial arachnoid cyst in the elderly", "Neurosurg Rev." 1994;17(3):195-8. (PMID 7838397)]


Untreated, arachnoid cysts may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or hemorrhage (bleeding). With treatment most individuals with arachnoid cysts do well with the double edge sword of developing surgical arachnoiditis which can cause its own specific problems and can lead to "popping" another cyst.

More specific prognoses are listed below:
*Patients with arachnoid cysts of the left temporal fossa who experienced impaired preoperative cognition had postoperative improvement. [Wester K, Hugdahl K. "Arachnoid cysts of the left temporal fossa: impaired preoperative cognition and postoperative improvement." "J Neurol Neurosurg Psychiatry" 1995 Sep;59(3):293-8. (PMID 7673959)]
*Surgery can resolve psychiatric manifestations in selected cases. [Kohn R, Lilly RB, Sokol MS, Malloy PF. "Psychiatric presentations of intracranial cysts", "J Neuropsychiatry Clin Neurosci" 1989; 1:60-66. (PMID 2577719)]


Arachnoid cysts are seen in 4% of the population.Flaherty AW. "The Massachusetts General Hospital Handbook of Neurology" 2000 Jan 1;105. (ISBN 0-683-30576-X)] Only 20% of these have symptoms, usually from secondary hydrocephalus.

A study that looked at 2,536 healthy young males found a prevalence of 1.7% (95% CI 1.2 to 2.3%). Only a small percentage of the detected abnormalities require urgent medical attention.Weber F, Knopf H. "Incidental findings in magnetic resonance imaging of the brains of healthy young men", "J Neurol Sci." 2006 Jan 15;240(1-2):81-4. Epub 2005 Oct 26. (PMID 16256141)]


ee also

* Acoustic Neuroma
* Arachnoiditis
* Brain Tumors, General
* Dandy-Walker Syndrome
* Empty Sella Syndrome
* Epidermoids
* Midline Caves of the Brain
* Porencephaly
* Syringomyelia
* Bobble-Head Doll Syndrome
* Hyperprolactinemia
* Panhypopituitarism
* Arnold-Chiari Malformation


External links

*Patient support sites::* [] :* [ Arachnoid Activist]

* [ Video of endoscopic fenestration procedure]
* [ Video of MRI scan showing two arachnoid cysts]

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