Arachnoid cysts are

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

covered by arachnoidal cells and

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

that may develop between the surface of the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

and the cranial base or on the arachnoid membrane, one of the three meningeal layers that cover the brain and the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

. Primary arachnoid cysts are a

congenital disorder A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

whereas secondary arachnoid cysts are the result of head injury or trauma. Most cases of primary cysts begin during infancy; however, onset may be delayed until adolescence.

Signs and symptoms

Patients with arachnoid cysts may never show symptoms, even in some cases where the cyst is large. 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, location, or potential functional impact on the patient. Symptoms vary by the size and location of the cyst(s), though small cysts usually have no symptoms and are discovered only incidentally. On the other hand, a number of symptoms may result from large cysts: * Cranial deformation or

macrocephaly Macrocephaly is a condition in which circumference of the human head is abnormally large. It may be pathological or harmless, and can be a Heredity, familial genetic characteristic. People diagnosed with macrocephaly will receive further medical ...

(enlargement of the head), particularly in childrenBarker RA, Scolding N, Rowe D, Larner AJ. ''The A-Z of Neurological Practice: A Guide to Clinical Neurology''

Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...

2005 Jan 10, p61. () * Cysts in the suprasellar region in children have presented as bobbing and nodding of the head called bobble-head doll syndrome. * Cysts in the left middle cranial fossa have been associated with

ADHD Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple ...

in a study on affected children. *

Headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...

s. 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. ** 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.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
*

Seizure A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

s *

Hydrocephalus Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within the brain, which can cause pressure to increase in the skull. Symptoms may vary according to age. Headaches and double vision are common. Elderly adults with n ...

(excessive accumulation of cerebrospinal fluid) * Increased

intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adu ...

Developmental delay The term developmental delay can refer to: *Global developmental delay, an umbrella term used when children are significantly delayed in two or more areas of development *Specific developmental disorder, a classification of disorders characterize ...

* Behavioral changes * Nausea * Dysdiadokinesis *

Hemiparesis Hemiparesis, also called unilateral paresis, is the weakness of one entire side of the body (''wikt:hemi-#Prefix, hemi-'' means "half"). Hemiplegia, in its most severe form, is the complete paralysis of one entire side of the body. Either hemipar ...

(weakness or paralysis on one side of the body) *

Ataxia Ataxia (from Greek α- negative prefix+ -τάξις rder= "lack of order") is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in e ...

(lack of muscle control) * Musical

hallucination A hallucination is a perception in the absence of an external stimulus that has the compelling sense of reality. They are distinguishable from several related phenomena, such as dreaming ( REM sleep), which does not involve wakefulness; pse ...

* Pre-senile

dementia Dementia is a syndrome associated with many neurodegenerative diseases, characterized by a general decline in cognitive abilities that affects a person's ability to perform activities of daily living, everyday activities. This typically invo ...

,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
a condition often associated with

Alzheimer's disease Alzheimer's disease (AD) is a neurodegenerative disease and the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances, symptoms can include problems wit ...

* In elderly patients (>80 years old) symptoms were similar to chronic

subdural hematoma A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrou ...

or normal pressure

hydrocephalus Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within the brain, which can cause pressure to increase in the skull. Symptoms may vary according to age. Headaches and double vision are common. Elderly adults with n ...

: ** Dementia **

Urinary incontinence Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a significant effect on quality of life. Urinary incontinence is common in older women ...

** Hemiparesis ** Headache ** Seizures

Location-specific symptoms

* A supratentorial arachnoid cyst can mimic a

Ménière's disease Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected in ...

attack. * Frontal arachnoid cysts have been associated with depression.Cummings JL, Mega MS. ''Neuropsychiatry and Behavioral Neuroscience'', Oxford University Press, USA; 2Rev Ed, 2003 Jan 23;208. () * Cysts on the left temporal lobe have been associated with

psychosis In psychopathology, psychosis is a condition in which a person is unable to distinguish, in their experience of life, between what is and is not real. Examples of psychotic symptoms are delusions, hallucinations, and disorganized or inco ...

. A left fronto-temporal cyst showed symptoms of

alexithymia Alexithymia, also called emotional blindness, is a neuropsychological phenomenon characterized by significant challenges in recognizing, expressing, feeling, sourcing, and describing one's emotions. It is associated with difficulties in attachme ...

. * Cyst on the right

sylvian fissure The lateral sulcus (or lateral fissure, also called Sylvian fissure, after Franciscus Sylvius) is the most prominent sulcus (neuroanatomy), sulcus of each cerebral hemisphere in the human brain. The lateral sulcus (neuroanatomy), sulcus is a deep ...

resulted in new onset of

schizophrenia Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...

-like symptoms at age 61. * A patient with a cyst on the left

middle cranial fossa The middle cranial fossa is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull ...

had auditory

hallucinations A hallucination is a perception in the absence of an external stimulus that has the compelling sense of reality. They are distinguishable from several related phenomena, such as dreaming ( REM sleep), which does not involve wakefulness; pse ...

migraine Migraine (, ) is a complex neurological disorder characterized by episodes of moderate-to-severe headache, most often unilateral and generally associated with nausea, and light and sound sensitivity. Other characterizing symptoms may includ ...

-like headaches, and periodic

paranoia Paranoia is an instinct or thought process that is believed to be heavily influenced by anxiety, suspicion, or fear, often to the point of delusion and irrationality. Paranoid thinking typically includes persecutory beliefs, or beliefs of co ...

* Patients with left temporal lobe cysts had mood disturbances similar to

manic depression Bipolar disorder (BD), previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that each last from days to weeks, and in some cases months. If the elevated m ...

(bipolar disorder) and were known to show outward aggression

Causes

The exact cause of arachnoid cysts is not known. Researchers believe that most cases of arachnoid cysts are developmental malformations that arise from the unexplained splitting or tearing of the arachnoid membrane. In some cases, arachnoid cysts occurring in the middle fossa are accompanied by underdevelopment (

hypoplasia Hypoplasia (; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ.temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe is involved in pr ...

. The exact role that temporal lobe abnormalities play in the development of

middle fossa The middle cranial fossa is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull ...

arachnoid cysts is unknown. There are some cases where hereditary disorders have been connected with arachnoid cysts. Some complications of arachnoid cysts can occur when a cyst is damaged because of minor

head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inj ...

. Trauma can cause the fluid within a cyst to leak into other areas (e.g., subarachnoid space). Blood vessels on the surface of a cyst may tear and bleed into the cyst (intracystic

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, ...

), increasing its size. If a blood vessel bleeds on the outside of a cyst, a collection of blood (

hematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is ...

) may result. In the cases of intracystic hemorrhage and hematoma, the individual may have symptoms of increased pressure within the cranium and signs of compression of nearby nerve (neural) tissue. Some scientists debate whether arachnoid cysts are a true congenital condition or if this should be separated from secondary cysts. A recent study shows differences in communication between the arachnoid cyst and the subarachnoid space by CT cisternography. A comparison of arachnoid cyst fluid and CSF in a series of patients show differences in chemical composition. Arachnoid cysts can also occur secondary to other disorders such as

Marfan syndrome Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with dolichostenomelia, long arms, legs, Arachnodactyly, fingers, and toes. They also typically ha ...

arachnoiditis Arachnoiditis is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the central nervous system. The outermost layer of the meninges is the dura mater (Latin for hard ...

, or

agenesis of the corpus callosum Agenesis of the corpus callosum (ACC) is a rare birth defect in which there is a complete or partial absence of the corpus callosum. It occurs when the development of the corpus callosum, the band of white matter connecting the two hemispheres ...

Diagnosis

Temporale Arachnoidalzyste links CT axial

Diagnosis is principally by

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and rad ...

. Frequently, arachnoid cysts are incidental findings on MRI scans performed for other clinical reasons. In practice, diagnosis of symptomatic arachnoid cysts requires symptoms to be present, and many with the disorder never develop symptoms. Additional clinical assessment tools that can be useful in evaluating a patient with arachnoid cysts include the mini-mental state examination (MMSE), a brief questionnaire-based test used to assess

cognition Cognition is the "mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...

Classification

Arachnoid cysts can be found on the brain or on the

spine Spine or spinal may refer to: Science Biology * Spinal column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoology), ...

. Intracranial arachnoid cysts usually occur adjacent to the arachnoidal cistern.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 Spinal arachnoid cysts may be extradural, intradural, or perineural and tend to present with signs and symptoms indicative of a

radiculopathy Radiculopathy (; ), also commonly referred to as pinched nerve, refers to a set of conditions in which one or more nerves are affected and do not work properly (a neuropathy). Radiculopathy can result in pain (radicular pain), weakness, altered se ...

. Arachnoid cysts may also be classified as primary (congenital) or secondary (acquired) and have been reported in humans, cats, and dogs. Arachnoid cysts can be relatively

asymptomatic Asymptomatic (or clinically silent) is an adjective categorising the medical conditions (i.e., injuries or diseases) that patients carry but without experiencing their symptoms, despite an explicit diagnosis (e.g., a positive medical test). P ...

or present with insidious symptoms; for this reason, diagnosis is often delayed.

Treatment

Most arachnoid cysts are asymptomatic and do not require treatment. Treatment may be necessary when symptomatic. A variety of procedures may be used to decompress (remove pressure from) the cyst. * Surgical placement of a

cerebral shunt A cerebral shunt is a device permanently implanted inside the head and body to drain excess fluid away from the brain. They are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid (CSF). If ...

: ** An internal shunt drains into the subdural compartment. ** A cystoperitoneal shunt drains to the

peritoneal cavity The peritoneal cavity is a potential space located between the two layers of the peritoneum—the parietal peritoneum, the serous membrane that lines the abdominal wall, and visceral peritoneum, which surrounds the internal organs. While situated ...

. * Fenestration: **

Craniotomy A craniotomy is a surgery, surgical operation in which a bone flap is temporarily removed from the Human skull, skull to access the Human brain, brain. Craniotomies are often critical operations, performed on patients who are suffering from brain ...

with excision ** Various

endoscopic An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

techniques are proving effective, including laser-assisted techniques. * Drainage by needle aspiration or burr hole. * Capsular resection * Pharmacological treatments may address specific symptoms such as seizures or pain.

Prognosis

Most arachnoid cysts are asymptomatic, and do not require treatment. Where complications are present, leaving arachnoid cysts untreated may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or

(bleeding). However, with treatment most individuals with symptomatic arachnoid cysts do well. More specific prognoses are listed below: * Patients with impaired preoperative

had postoperative improvement after surgical decompression of the cyst. * Surgery can resolve psychiatric manifestations in selected cases.

Epidemiology

Arachnoid cysts are seen in up to 1.1% of the populationFlaherty AW. ''The Massachusetts General Hospital Handbook of Neurology'' 2000 Jan 1;105. () with a gender distribution of 2:1 male:female. Only 20% of these have symptoms, usually from secondary

. 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.

References

External links

{{DEFAULTSORT:Arachnoid Cyst Congenital disorders Central nervous system disorders