Arachnoid cysts are cerebrospinal fluid-filled sacs that may develop between the surface of the brain and the cranial base or on the arachnoid membrane - one of the 3 membranes that cover the brain and the spinal cord. Most cases begin during infancy, however onset may be delayed until adolescence. Symptoms of an arachnoid cyst are related to the cyst size and location. Small cysts are usually asymptomatic and are discovered only incidentally. Large cysts may cause cranial deformation or macrocephaly (enlargement of the head), producing such symptoms as headaches, seizures, hydrocephalus (excessive accumulation of cerebrospinal fluid), increased intracranial pressure, developmental delay, and behavioral changes. Other symptoms may include hemiparesis (weakness or paralysis on one side of the body) and ataxia (lack of muscle control). Arachnoid cysts most often occur in males. Cerebrospinal fluid (CSF), Liquor cerebrospinalis, is a clear bodily fluid that occupies the subarachnoid space in the brain (the space between the skull and the cerebral cortex—more specifically, between the arachnoid and pia layers of the meninges). ... The human brain. ... A headache (medically known as cephalgia) is a condition of mild to severe pain in the head; sometimes neck or upper back pain may also be interpreted as a headache. ... This article is about the medical term, epileptic seizure, as distinct from psychogenic non-epileptic seizure. ... Intracranial pressure, or ICP, is the pressure of the brain, Cerebrospinal fluid (CSF), and the brains blood supply within the intracranial space. ... Hemiparesis is the partial paralysis of one side of the body. ... Ataxia (from Greek ataxiÄ, meaning failure to put in order) is unsteady and clumsy motion of the limbs or trunk due to a failure of the gross coordination of muscle movements. ...
Treatment
Treatment for arachnoid cysts is symptomatic. When symptoms warrant, the surgical placement of a shunt may be required to decompress (remove pressure from) the cyst.
Prognosis
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.
It is postulated that arachnoidcysts develop because of a minor aberration in the flow of CSF in the primordial stage of the development of the subarachnoid pathways resulting in the sequestration of an enclosed chamber or diverticulum within the perimedullary mesh.
The involved cisterns are the cistern of the Sylvian fissure, the CP angle, the ambient cistern, the cisterna magna, the prepontine and interpeduncular cistern, and the chiasmatic cistern.
Cysts are located outside the pituitary gland at the level of the pars distalis and cause ballooning and posterior bowing of the sella.
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