Arachnoid cyst

(Código CIE-9-CM: 348.0)

Arachnoid cyst, also known as cysts leptomeningeal.

Arachnoid cysts (QA) are benign pathological structures of features that could define as clear fluid filled cavities similar to cerebrospinal fluid (LCR), contained within a membrane indistinguishable histologically healthy arachnoid.

Occur during the division of the arachnoid.

The most accepted hypothesis speaks of changes in the separation of endomenix in the third quarter of the neonatal period. The membrane is endomenix mesenchymal tissue surrounding the neural tube. In the third quarter, when the roof of the fourth ventricle is broken, CSF pressure waves flowing through it, the dissected into two layers and result pial, arachnoid and subarachnoid space. Alterations of this mechanism may lead to the formation of separate cavities that, growth in, form cysts.

Other hypotheses are saying that are secondary to focal brain hypoplasia, in which occupy the space provided or produced by alterations of the secretion of substances from the subarachnoid space to the venous system. Also, to explain the subsequent growth of the cyst were raised various theories; between them, the most accepted, because there are cases where it has been demonstrated in vivo, is the formation of valve mechanisms . Have also been described in the literature sometimes cysts associated with meningeal infections and trauma, called secondary, as opposed to those for which the cause is unknown and suspected congenital malformation, and designated primary.

Really it is intraaracnoideos cysts. When diagnosed at the level of middle fossa were called ” sindrom ” temporal lobe agenesis. (This term is now obsolete).

Others are caused by trauma.

A simple linear fracture, without immediate complications, can cause the development of an arachnoid cyst, hence the need to keep proper monitoring of the evolution of fracture healing and an etiological alert to the appearance of neurological symptoms.


Constitute a typical diagnosis of childhood, especially in the first two years of life, which represent approximately 1% of intracranial expansive lesions. The most common locations found in various series are the Sylvian fissure and posterior fossa.

5 by 1000 autopsias.son characteristic lesions in childhood, slightly more common in males.

Also found at the spinal level, although they are rare.


  • Cisura de silvio 49%
  • APC 11%
  • Supracolicular 10%
  • Vermiano 9%
  • Sellar and suprasellar 9%
  • Interhemisférico 5%
  • Convexity 4%
  • Clivus 3%

Histological types

Simple cysts: Cell line appear to be capable of secretion CSF. The cysts of the middle fossa speak exclusively of this type

Complex cysts that may also contain glia, epéndimo, and other types of tissue.

Quiste Aracnoideo

Quiste Aracnoideo

Clinical Presentation

The symptoms are variable depending compress part of the central nervous system, the most striking are other & shy; focal symptoms with signs of intracranial hypertension, as are headache (head pain), hemiparesis,diplopia (double vision), irritability, mood swings, apathy (emotionless), and impaired intellectual performance.

Trench Media suprasellar with fuzzy supra or infratentorial hydrocephalus hydrocephalus

Epilepsy,headache,hemiparesia HTE,Craneomegalia,late development,loss of visual acuity,precocious puberty HTE,craneomegalia,late development

Most cysts are symptomatic in infancy.

Can be diagnosed by the presence of:

  • Symptoms of increased intracranial pressure (Headache, sickness…)
  • Epilepsy.
  • Sudden deterioration: due to bleeding (in cyst or subdural): pit medial cysts are prone to bleeding due to the increased possibility of rupture of bridging veins; due to rupture of the cyst
  • Protrusion in the skull
  • Focal neurological signs.
  • Incidental finding.
  • Hydrocephalus (Probably due to compression of the third ventricle)
  • Endocrine symptoms: occurring in a 60%. Includes precocious puberty.
  • Visual impairment
  • In posterior fossa usually produce nonspecific symptoms such as hearing loss and tinnitus sometimes even difficult to distinguish from Meniere's disease and the most characteristic often cerebellar ataxias.


Are diagnosed primarily by TAC.

The ideal method of diffusion MRI sequences (Maybe it will raise the differential diagnosis with epidermoid cysts or neoplastic hemangioblastomas).

Differential diagnosis

  • Cystic astrocytomas.
  • Wemer cistern
  • Hydatid cyst – Cisticercosis
  • Myocardial old crebral
  • Porencefalia.
  • Hollow Line Media.


Size is recommended to treat only the symptoms that occur regardless of the location and. Treatment is still controversial.

Therapeutic options have endoscopic fenestration or craniotomy into the ventricle or subarachnoid space and the implantation of a shunt.

Probably the best treatment consists in the derivation of cyst peritoneum.

Method Advantages Disadvantages

Aspiration- drill and fast Recurrence

Craniotomy with excision of the quísticay wall fenestration to subarachnoid or ventricular space allows inspection of the cyst and vascular structures. Evita in some cases permanent shunt. Possible re-accumulation and more invasive.

Cystoperitoneal Simple Derivation Procedure Unit Shunt and risks of carrying Shunt.

Dr. J. Sales Llopis

Department of Neurosurgery, University General Hospital of Alicante.

To consult:

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175 Replies

  1. Hi I have a grandson 9 years he took a T.A.C. and the result is that found one arachnoidal Cyst right parietal convexity of approximately 16mm diameter anteroposterior with adjacent bone remodeling pariental

  2. Rocio Torres says:

    I am soul I have an arachnoid cyst and since ten years and lived with very strong and frequent pain d head stammer my speech was very often now I have forty, and learned not to get upset ,not to get angry and q this makes q detonate a crisis d pain lasts q around d ten days m afraid to come to convulse and q doctors m told q might happen my question is this cyst can affect hearing and q took several days with an upset is not a buzz is more like a feeling something walks dq

  3. Hola Dr. How is it going.. I am a medical student and I have a project q about arachnoid cysts and found no information about the incidence in Ecuador.. I would like to help me with any bibliographic reference where to find history in Ecuador and its provinces

  4. Hello , Good afternoon, My son did an MRI and found an arachnoid cyst in left frontal temporal side, so far it has not presented any symptoms , but it shows altered , I would like to know what kind of treatment there, and damage I can cause him

  5. Hello, Doctor, please my grandson had surgery in May 2015 a quieste in the temporal lobe arachnoid I left with the method of cerebral endoscopy, in the last resonance 3 December 2016, came a subdural hygroma has, which tell me that we have to operate, the question is ; Is the hygroma is a consequence of the cyst, always happens? Do I say we have to put a valve to cistoperitoneo , a doctor says that for five years and another says for life? I'm confused hopefully I can help me and give me a light….. Since one do you recommend for craniotomy and another endoscopy

  6. Hello!!These cysts cause problems learning? This had a student with a diagnosis of frontal arachnoid, the girl never convulsed, it is very frequent headaches. It has learning problems. It will be for the diagnosis?I wait for answers. Greetings To You!!

  7. Silvana Costanzo says:

    I wanted to know whether there can be changes in behavior because of these arachnoid cysts, in the posteromedial region of the left cerebellar fossa. Thank You

  8. Hello excellent doctor your space, my daughter 13 years was diagnosed with a small cyst arachnoidal right cerebellar cistern measuring bulb 18 x 11 mm.en its axial axis slightly larger and tonsillar ectopia left in the normal limit, I wonder what that means because the doctor should review the resonance is not available. thank you

  9. my brother has 21 years a 10 present day severe headache in the posterior region,nausea,Vertigo ,vomiting and feeling very tired character also changes with ease . He underwent a scan and was diagnosed with a cyst . but the neurologist did not indicate any medication we attended another neurologist who indicated nimodipine and relaxing . my question is that will be the most effective treatment

  10. Good afternoon, I have my daughter 17 years with arachnoid cyst at the level of the left frontal region, to the 13 years was discovered after a crisis, MRI was performed annually but recently I suffered another very strong that lasted almost ten days crisis and had to be hospitalized with nausea, loss of balance , dizziness, uncontrolled head, speech problems and without remembering the days each episode , He was treated her as suffering from benign positional vertigo paraxistico. My concern is whether there is a specific treatment for this not to occur as it comes by surprise and produce in their daily lives disorder to their obligations and daily tasks as well also a state of fear or after depression of these episodes to her and the family. Thank You

  11. hello my son found him arecnoideo benign cysts in the anterior medial contour of the middle cranial fossa izuierda 25×12 mm ( no evidence of adema or Encephalomalacia.) The study was conducted by that ledio conbulsiones ( 2 times within 24 hours) but the child had a high fever in his throat infecion.
    the doctor only half the temperador s as medicine. and he told us that must be taken into observation. by MRI every year to see if the cyst growth. but I want to know more about this problem as:
    if all children who have cysts have future problems
    or if some may have and has no problems
    DEQ ue sizes are more problems that provovan
    or especially if there is a high percentage of out well when a surgery rezlizarle.

    please I could guide more, because the truth I am very concerned

  12. Hello good day.. my baby combulsiona without fever or anything and to a study carried out TAC having a arachnoid cyst in the left temporal fossa reaching
    Approximately the same diameter in transverse direction of 2.3cm by 2cm diameter anteriposterior. At the moment this medicated but I need to know if this cyst need surgery or if you will harm my baby please

  13. day moxa says:

    Hello I have 23 years old, I have a congenital brain cyst on the left side of the brain which affected me right psychomotor. But I had a normal life, just over a year with work, the study convulse and neurologist said it was so strong stress by living. Phenytoin that would be fine but be careful to hit in the head or having a lot of stress, I returned to no longer convulse, I miss even one year of anticonvulsant therapy, but sometimes it hurts too much head, me marieo, although I thought it was because of myopia my eyes but it is becoming more common, I do not want to worry my parents and make them spend on studies.

  14. Good Morning, I would guide would please, my baby a year ago made him a resonance for their behavior because it is challenging and disruptive opposition, besides having headaches. Does It Have 9 years now. At resonance came an arachnoid cyst that has in the left parietal brain.
    The neurosurgeon said that for now is not operated, but measures 4.5 cm diameter.
    Which worries me greatly, because he said to operate for the time being, but he has trouble speaking, pronouncing the R, It has a delayed development of 2 years was diagnosed in a Psychodiagnosis , and attention deficit hiperactivad, I thank you please help me, because I am very concerned, since in Uruguay where we are, They have told us that is “normal”, but I see that my son is suffering. Thank You.

  15. humberto says:

    Hello I have my grandfather 81 ala years time who underwent an MRI the result of the interpretation is as follows :
    multiple pulse sequences were performed T1, T2 , FLAIR , Diffusion , AND , getting multiplanar images which shows :
    ocupativas symmetrical brain parenchyma lesions not identified, with decrease in brain volume widely , grooves comprominencia .
    draws attention aranoideo the presence of cyst in the left parietal region , with measures 20x18x21 mm.
    the nuclei of the base with adequate volume and intensity as well as morphology concervados .
    the optic chiasm , pituitary gland and pituitary stalk with volume and signal intensisad consercados .
    corpus callosum present without alteriaciones in their morphology
    the supratentorial ventricular system with bulging breaks , increased volume of compensatory and sisternas way to the base with increased volume .
    mesencefalo , pons and medulla unchanged .
    craniocervical junction is concervada and normal caraccteristicas.
    cerebellar hemispheres and vermis size , form , situation and normal signal intensity .
    the fourth ventricle is Central and adequate volume .
    no restriction areas are observed to superspreading .
    After administration of intravenous contrast material , no zones are observed normal refuerso .
    estruccturas unaltered orbits .
    estruccturas of the internal auditory canals are symmetric and normal signal intensity .
    the tissue is normal .
    decrease in brain volume in relation to cortico subcortical atrophy
    arachnoid cyst in the left parietal region.
    suggested correlation with clinical studies.

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