Arachnoid cyst

(Código CIE-9-CM: 348.0)

arachnoid, 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 in some cases related cysts meningeal and injuries, 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 ” de de agenesis temporal. (This term is now obsolete).

Others are caused by trauma.

An fracture Simple linear, without immediate complications, can cause the development of an arachnoid cyst, hence the need to maintain a proper monitoring of the evolution of consolidation fracture and an etiologic alert to the onset 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 symptomatology is variable depending of the central compress, the most striking are other & shy; focal symptoms with signs of intracranial hypertension, as are headache ( headlong), hemiparesis,diplopia (double vision), irritability, mood swings, apathy (emotionless), and impaired intellectual performance.

Trench Media suprasellar with fuzzy supra or infratentorial hydrocephalus hydrocephalus

,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:

You Might Also Like ...

160 Replies

  1. 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

  2. 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.

  3. Good Morning, I would guide would please, my baby a year ago he made a resonance for his conduct since it is challenging and disruptive opposition, besides having headaches. Does It Have 9 years now. In resonance it came out that has a arachnoid cyst 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.

  1. 10 February 2013

    … [Trackback]…

    […] Find More Informations here: […]…

Leave a Reply