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Arachnoid cyst
Classifications and external resources

ICD-10	Q04.6
ICD-9	348.0
OMIM	207790
DiseasesDB	33219
eMedicine	radio/48
MeSH	D016080

Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells and collagen<ref name="pn">Ariai 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)</ref> 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.<ref name="ninds">NINDS Arachnoid Cysts Information Page</ref> Arachnoid cysts are a congenital disorder<ref>Gelabert-Gonzalez M. "Intracranial arachnoid cysts", Rev Neurol., 2004 Dec 16-31;39(12):1161-6. (PMID 15625636)</ref>, and most cases begin during infancy; however, onset may be delayed until adolescence.<ref name="ninds" />

Contents 1 Classification 2 Symptoms and signs 2.1 Location-specific symptoms 3 Cause/Etiology 4 Diagnosis 5 Pathophysiology/Mechanism 6 Treatment/Management 7 Prognosis 8 Epidemiology/Prevalence 9 History 10 References

[edit] Classification

Arachnoid cysts can be intracranial (in the cranium), or on the spine. Intracranial arachnoid cysts usually occur adjacent to arachnoidal cistern.<ref name="joynt">Arachnoid cyst. (n.d.). Gale Encyclopedia of Neurological Disorders. Retrieved September 10, 2006, from Answers.com Web site: http://www.answers.com/topic/arachnoid-cyst</ref> Spinal arachnoid cysts may be extradural, intradural, or perineural and tend to present with signs and symptoms indicative of a radiculopathy.<ref name="joynt" />

[edit] Symptoms and signs

Patients with arachnoid cysts may never show symptoms, even in some cases where the cyst is large ^[citation needed]. Additionally, the symptoms experienced are not unique to this disease. 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.<ref name="ninds" /> On the other hand, a number of symptoms may result from large cysts:

• Cranial deformation or macrocephaly (enlargement of the head), particularly in children <ref name="azguide">Barker 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 0521629608)</ref>
• Cysts in the suprasellar region in children have presented as bobbing and nodding of the head called Bobble-Head Doll Syndrome.<ref name="azguide" />
• Cysts in the left middle cranial fossa have been associated with ADHD in a study on affected children.<ref>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)</ref>
• Headaches<ref name="ninds" />. While the most common symptom^{[citation needed]}, 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.<ref>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)</ref>
  • 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.<ref name="cameronad">Cameron AD. "Psychotic phenomena with migraine and an arachnoid cyst", Progress in Neurology and Psychiatry 2002 Mar-Apr 6(2) http://www.escriber.com/Progress/Features.asp? Action=View&Archive=True&ID=67&GroupID=&Page=11</ref>
• Seizures<ref name="ninds" />
• Hydrocephalus (excessive accumulation of cerebrospinal fluid)<ref name="ninds" />
• Increased intracranial pressure<ref name="ninds" />
• Developmental delay<ref name="ninds" />
• Behavioral changes<ref name="ninds" />
• Hemiparesis (weakness or paralysis on one side of the body) <ref name="ninds" />
• Ataxia (lack of muscle control) <ref name="ninds" />
• Pre-senile dementia<ref name="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) http://www.escriber.com/Progress/Features.asp? Action=View&Archive=True&ID=29&GroupID=&Page=18</ref>, 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<ref name="eld">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)</ref>:
  • Dementia
  • Urinary incontinence
  • Hemiparesis
  • Headache
  • Seizures

[edit] 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 2006, no research has been published that comprehensively maps physical and neuropsychiatric symptoms to a specific arachnoid cyst location.<ref name="dementia" />

• A supratentorial arachnoid cyst can mimic a Ménière's disease attack.<ref>Buongiorno G, Ricca G. "Supratentorial arachnoid cyst mimicking a Ménière's disease attack", J Laryngol Otol. 2003 Sep;117(9):728-30. (PMID 14561365)</ref>
• Frontal arachnoid cysts have been associated with depression.<ref name="nbn">Cummings JL, Mega MS. Neuropsychiatry and Behavioral Neuroscience, Oxford University Press, USA; 2Rev Ed, 2003 Jan 23;208. (ISBN 0195138589)</ref>
• Cysts on the left temporal lobe have been associated with psychosis.<ref>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)</ref> A left fronto-temporal cyst more specifically showed symptoms of alexithymia.<ref>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)</ref>
• Cyst on the right sylvian fissure resulted in new onset of schizophrenia-like symptoms at age 61.<ref>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)</ref>
• A patient with a cyst on the left middle cranial fossa had auditory hallucinations, migraine-like headaches, and periodic paranoia<ref name="cameronad" />
• Patients with left temporal lobe cysts had mood disturbances similar to manic depression (bipolar disorder)<ref>Heinrichs, RW. In Search of Madness: Schizophrenia and Neuroscience Oxford University Press, USA (March 29, 2001); p129. (ISBN 0195122194)</ref>

[edit] Cause/Etiology

Arachnoid cysts are most often developmental or related to trauma.<ref name="joynt">Joynt RJ. Clinical Neurology, 1994, ch44, pp105-115</ref>

[edit] Diagnosis

Diagnosis of arachnoid cysts usually only occurs after symptoms are present, and many with the disorder never develop symptoms. Or, in some cases, arachnoid cysts are found incidentally. <ref name="gale">"arachnoid cyst." Gale Encyclopedia of Neurological Disorders, The Gale Group, Inc, 2005. Answers.com 10 Sep. 2006. http://www.answers.com/topic/arachnoid-cyst</ref>

Diagnosis may include a mini-mental state examination (MMSE), a brief questionnaire-based test used to assess cognition.<ref name="dementia" />

[edit] Pathophysiology/Mechanism

[edit] Treatment/Management

Treatment for arachnoid cysts occurs when symptoms present themselves.<ref name="ninds" /> A variety of procedures may be used to decompress (remove pressure from) the cyst.

• Surgical placement of a shunt:<ref>Strojnik T. "Different approaches to surgical treatment of arachnoid cysts", Wiener Klinische Wochenschrift.[1] 2006;118 Suppl 2:85-8. (PMID 16817052)</ref>
  • An internal shunt drains into the subdural compartment.<ref>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)</ref>
  • A cystoperitoneal shunt drains to the peritoneal cavity.^{[citation needed]}
• Fenestration:
  • Craniotomy with excision^{[citation needed]}
  • Endoscope<ref>Greenfield JP, Souweidane MM. "Endoscopic management of intracranial cysts", Neurosurg Focus. 2005 Dec 15;19(6):E7. (PMID 16398484)</ref>
• Drainage by needle aspiration or burr hole. While these procedures are relatively simple, there is a high incidence of recurrence.^{[citation needed]}
• Capsular resection<ref name="eld" />

A 1994 study found surgery necessary for good outcome in patients >65 years old when the cysts began displaying symptoms.<ref name="eld2">Caruso R, Salvati M, Cervoni L. "Primary intracranial arachnoid cyst in the elderly", Neurosurg Rev. 1994;17(3):195-8. (PMID 7838397)</ref>

[edit] Prognosis

Untreated, arachnoid cysts may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or hemorrhage (bleeding).<ref name="ninds" /> With treatment most individuals with arachnoid cysts do well.<ref name="ninds" />

More specific prognoses are listed below:

• Patients with arachnoid cysts of the left temporal fossa who experienced impaired preoperative cognition had postoperative improvement.<ref>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)</ref>
• Surgery can resolve psychiatric manifestations in selected cases.<ref>Kohn R, Lilly RB, Sokol MS, Malloy PF. "Psychiatric presentations of intracranial cysts", J Neuropsychiatry Clin Neurosci 1989; 1:60-66. (PMID 2577719)</ref>

[edit] Epidemiology/Prevalence

Arachnoid cysts are seen in 4% of the population.<ref name="MassNeur">Flaherty AW. The Massachusetts General Hospital Handbook of Neurology 2000 Jan 1;105. (ISBN 068330576X)</ref> Only 20% of these have symptoms, usually from secondary hydrocephalus.<ref name="MassNeur" />

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.<ref name="nmn">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)</ref>

[edit] History

[edit] References