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(Code CIE-9-MC: 348.0)
Arachnoid cyst, also known as leptomeningeal cysts.
Arachnoid cysts (QA) are benign pathological structures of features that could be defined as cavities filled with clear fluid similar to cerebrospinal fluid (CSF) contained within a membrane of the arachnoid histologically indistinguishable healthy.
Occur during the division of the arachnoid.
The most accepted hypothesis of impaired speech separation endomenix in the third quarter of the neonatal period. The membrane is endomenix mesenchymal tissue surrounding the neural tube. In the third quarter, when it goes through the roof of the fourth ventricle, CSF pressure waves flowing through it, the dissected into two layers and give rise to the pia mater, the arachnoid and subarachnoid space. Alterations of this mechanism may lead to the formation of separate cavities, in their growth, form cysts.
Others speak of hypotheses that are secondary to focal brain hypoplasia, which occupy the space provided or produced by alterations in the secretion of substances from the subarachnoid space to the venous system. Also, to further explain the cyst growth theories have emerged, among them the most widely 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 meningeal infections and related trauma, called side, in contrast to those for which the cause is unknown and congenital malformation is suspected, and designated as primary.
Actually they are cysts intraaracnoideos. When diagnosed at middle fossa were called "syndrome" temporal lobe agenesis. (This term is now obsolete).
Others are caused by trauma.
A simple linear fracture without immediate complications, may lead to the development of an arachnoid cyst, hence the need to maintain a proper monitoring of the evolution of fracture healing and etiological alert to the appearance of neurological symptoms.
They are a typical diagnosis of childhood, especially in the first two years of life, which represent approximately 1% of intracranial expanding lesions. The most common locations are found in various series the Sylvian fissure and posterior fossa.
5 per 1000 in autopsias.son lesions characteristic of childhood, slightly more common in males.
Also found at the spinal level but are rare.
- Sylvian fissure 49%
- APC 11%
- Supracolicular 10%
- Vermian 9%
- Sellar and suprasellar 9%
- Interhemispheric 5%
- Convexity 4%
- Clivus 3%
Simple cysts: cell line appear to be capable of CSF secretion. The middle fossa cysts appear to be exclusively of this type
Cysts can also contain complex glia, ependyma, and other tissue types.
The symptoms are variable depending on which part of the central nervous system compresses, the most striking are focal symptoms with signs of increased intracranial pressure such as headache (headache), hemiparesis, diplopia (double vision), irritability, mood swings, apathy (lack of emotions), and impaired mental performance.
Middle fossa with suprasellar supra or infratentorial diffuse hydrocephalus hydrocephalus
Epilepsy, headache, hemiparesis HTE, Craneomegalia, delayed development, visual loss, 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, nausea ...)
- Sudden deterioration: due to hemorrhage (in cyst or subdural): medial fossa cysts are prone to bleeding due to the increased possibility of bridging veins rupture, due to rupture of the cyst
- Protrusion in the skull
- Focal neurological signs.
- Incidental finding.
- Hydrocephalus (probably due to compression of the third ventricle)
- Yes, endocrine symptoms: occur by 60%. Includes precocious puberty.
- In posterior fossa usually produce nonspecific symptoms such as hearing loss and tinnitus sometimes even difficult to distinguish from
- Meniere's disease and most often characteristic cerebellar ataxias.
Are diagnosed primarily by TAC.
The ideal method MRI and diffusion sequences (better raise the differential diagnosis with neoplastic epidermoid cysts or hemangioblastomas).
- Sticos chemical astrocytomas.
- Cisterna magna large
- Cyst hidatí-dico - Cysticercosis
- Myocardial old crebral
- Cavum of midline.
It is recommended to treat only the symptoms occur regardless of location and size. Treatment is still controversial.
Treatment 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 the cyst to the peritoneum.
Method Advantages Disadvantages
Aspiration-Quick and easy drill Recurrence
Craniotomy with excision of the fenestration to wall quísticay subarachnoid or ventricular cyst Allows inspection and vascular structures. Evita in some cases permanent shunt. Reaccumulation possible and more invasive.
Simple Procedure Unit peritoneal shunt Shunt and Shunt carry risks.
Dr. J. Sales Llopis
Department of Neurosurgery, Hospital General Universitario de Alicante.