What are the other Names for this Condition? (Also known as/Symptoms)

• Arachnoid Cyst of the CNS
• Central Nervous System Arachnoid Cyst
• Leptomeningeal Cyst

What is Arachnoid Cyst? (Definition/Background Information)

• Arachnoid Cysts are uncommon benign cysts that form between the layers of the arachnoid membranes. These fluid-filled lesions may arise anywhere in the central nervous system (CNS); however, most lesions are seen near the temporal lobe and cerebellopontine angle in the brain. The involvement of the spinal cord is infrequently noted
• The meninges, which is the membranous tissue encasing the brain and spinal cord, consist of three layers, namely the outer layer (dura mater), the middle layer (arachnoid mater), and the inner layer (pia mater); together, they form the protective lining around the CNS. Arachnoid Cysts are cysts filled with cerebrospinal fluid (CSF) involving the arachnoid mater/membrane
• Arachnoid Cysts are mainly classified depending on the cause as primary and secondary; and, based on their location as cranial or spinal
  • Primary Arachnoid Cyst: It is the more common form of Arachnoid Cyst that is present at birth (congenital origin). It forms due to developmental issues during fetal growth that involves the brain and/or spinal cord
  • Secondary Arachnoid Cyst: It develops due to certain underlying factors, such as meningitis, trauma to the brain, or surgical complications. This form of Arachnoid Cyst is relatively uncommon
  • Both the primary and secondary forms can occur intracranially (cranial Arachnoid Cysts), or in association with the spinal meninges (spinal Arachnoid Cysts)
• The exact cause of formation of a primary Arachnoid Cyst is unknown; nearly 80% of these lesions are diagnosed in males. These cysts are also classified according to the location they arise from within the central nervous system. Some of these location specific types include suprasellar Arachnoid Cyst, intraventricular Arachnoid Cyst, and spinal Arachnoid Cyst
• Small Arachnoid Cysts may not present any significant signs and symptoms. However, large cystic tumors may cause headaches, memory issues, back pain, numbness, weakness of the lower extremities, or loss of bladder/bowel control, depending on the location of the tumor within the CNS
• In some cases, the treatment of Central Nervous System Arachnoid Cyst may involve surgery. In most cases, the prognosis is good with appropriate early treatment, since it is a benign lesion. Occasionally, large cysts may result in severe complications and cognitive issues, especially if these are undetected or left untreated

Who gets Arachnoid Cyst? (Age and Sex Distribution)

• Arachnoid Cysts are seen in both children and adults across all age groups. Most of the cases are diagnosed by age 20 years
• Although these are amongst the most common intracranial cysts noted, they constitute less than 1% of all intracranial masses
  • Primary Arachnoid Cysts are observed in infant children; in some cases, the manifestation of symptoms occurs even during adolescence. Some cystic lesions are even detected prenatally on imaging studies
  • Secondary Arachnoid Cyst develop secondary to an underlying cause factor, and hence, it may arise at any age
• Both males and females are affected; however, males are affected much more than females (a 4:1 male-female ratio is reported) for the primary form of Arachnoid Cyst
• No specific racial or ethnic group predilection is noted

What are the Risk Factors for Arachnoid Cyst? (Predisposing Factors)

The following factors may increase one’s risk for Arachnoid Cysts:

• A family history is a known risk factor for the primary forms of Arachnoid Cysts
• In some cases, Primary Arachnoid Cysts have been associated with certain congenital abnormalities such as:
  • Agenesis of the corpus callosum: A congenital defect affecting the formation of the brain
  • Arachnoiditis: Inflamed meningeal layers causing severe pain and other neurological issues
  • Marfan syndrome, a connective tissue disorder
  • Mucopolysaccharidosis syndrome, a group of rare genetic metabolic conditions
• Occasionally, the following factors may lead to the development of Secondary Arachnoid Cysts:
  • Head injury; it is the most common factor noted
  • Meningitis or inflammation of the meninges that may occur from various factors
  • Presence of other brain tumors in the region
  • Iatrogenic factors, such as complications (intracranial hemorrhage) that develop from invasive procedures to the brain/spinal region

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Arachnoid Cyst? (Etiology)

Arachnoid Cysts are a benign collection of cerebrospinal fluid (CSF) in the subarachnoid space, usually of congenital origin. Currently, a host of factors are thought to contribute towards its formation.

• Arachnoid Cysts can either occur sporadically, or form in association with other congenital defects or malformations of the brain and spinal cord, such as mucopolysaccharidoses or Marfan syndrome. These are therefore termed as Primary Arachnoid Cysts
• When Arachnoid Cysts develop due to other underlying conditions or factors, such as trauma, CNS tumor, infections, or complications from invasive procedures to the brain, it is termed as Secondary Arachnoid Cysts

Some experts believe that an Arachnoid Cyst is caused by a malformation/splitting of the arachnoid membranes, which causes the subarachnoid space to be filled with cerebrospinal fluid. In case of the primary form, the cause of such malformation is unknown. However, in case of the secondary form, the disruption of arachnoid membranes due to certain underlying factors may result in cyst formation. Both the primary and secondary cysts can arise in the cranial and spinal meninges

What are the Signs and Symptoms of Arachnoid Cyst?

The signs and symptoms of Arachnoid Cysts can vary from one individual to another and depends on the size and location of the cystic tumor. Most of the cysts presents symptoms at birth (congenital Arachnoid Cysts) or during infancy, typically before the child is 12 months old. Some cysts are diagnosed in early childhood, into adolescence, or even during young adulthood. Occasionally, they may even be diagnosed during pregnancy, during routine USG screening of the developing fetus.

In general, most small tumors are asymptomatic and no significant symptoms may be observed, while large tumors are known to present symptoms. In many individuals, tumors that grow slowly and remain asymptomatic, are only diagnosed during certain radiological imaging studies of the head and neck or spinal cord region, which are performed for unrelated health conditions. Sometimes, this may result in severe complications due to a delayed diagnosis, especially in children. In some rare cases, no significant symptoms are noted even from large-sized cysts.

Most of these fluid-filled lesions are observed at supratentorial locations, predominantly outside the temporal lobes, in the middle fossa (in 75% of the cases). Other Arachnoid Cyst sites include the cerebellopontine angle (CPA), cerebral convexities, ventricular system, suprasellar region, cisterna magna, and rarely, the spinal canal.

Generally, the signs and symptoms of Arachnoid Cysts depend on several factors that include:

• Size of the cyst
• Characteristics of the cyst, which is observed on imaging studies
• Exact location of the cyst within the central nervous system
• Age of the affected individual (whether it is a child or an adult)

In the brain (cranial Arachnoid Cyst), the signs and symptoms may include:

• Headaches that may be persistent and increasing in intensity; this is observed in over 65% of the cases and is the most commonly noted symptom
• Numbness and tingling sensation
• Muscle weakness; loss of strength in the arms of legs
• Lack of muscle control or ataxia
• Visual impairment such as blurred vision, double vision or poor eyesight
• Hearing impairment or hearing loss
• Speech problems; children display difficulties in understanding languages
• Fatigue and lethargy
• Lack of coordination; unsteadiness and loss of balance (vertigo)
• Increased intracranial pressure due to obstruction of CSF drainage, resulting in nausea, vomiting, headaches, and seizures, if the ventricular system is involved
• Obstruction of the CSF also leads to increased size of the head with associated complications, a condition termed as obstructive hydrocephalus
• Hydrocephalus can result in enlarged head in babies, lethargy, irritability, poor feeding, nausea and vomiting, blurring of vision, loss of balance, seizures, urinary incontinence, and growth delays, among other symptoms
• Dizziness and fainting
• Confusion
• Changes in one’s behavior; personality changes
• Mental impairment
• Memory loss
• Paralysis

In the spinal cord (spinal Arachnoid Cyst), the signs and symptoms may include:

• Presence of visible lump in the affected region
• Back pain and/or chest pain
• Numbness and tingling sensation
• Weakness of the body or lower extremities; loss of strength in the arms of legs
• Pain in the arms and legs, depending on the nerves that are compressed by the tumor
• Spinal cord compression leading to numbness and pain, due to mass effect of the tumor
• Severe cases may result in loss of bowel and bladder control
• Paralysis

The signs and symptoms of any associated or underlying condition may be noted, if present.

How is Arachnoid Cyst Diagnosed?

There are a variety of tests and exams the healthcare provider may employ to diagnose Arachnoid Cyst, which may include:

• Physical examination and complete medical history screening
• Assessment of the presenting signs and symptoms
• Prenatal ultrasound scans, which are performed during pregnancy; usually the second trimester scans reveal the presence of cysts, if any present
• Amniocentesis: A medical procedure that involves removal of a small amount of amniotic fluid from the amnion for prenatal diagnosis; it may be performed if the healthcare provider suspects any genetic abnormalities
• Alpha fetoprotein (AFP) blood test in pregnancy: A screening test that is performed to determine the apparent risk for certain congenital abnormalities, such as spina bifida or chromosomal disorders, and not to confirm any diagnosis
• Neurological, motor skills, and cognitive assessment:
  • Checking intellectual ability, memory, mental health and function, language skills, judgment and reasoning, coordination and balance, reflexes, and sensory perceptions (space, sight, hearing, touch, etc.)
  • The healthcare provider/neurologist may use the Karnofsky Performance Scale in order to assess the neurological functioning of the individual’s central nervous system (CNS)
• Electroencephalography (EEG)
• Electromyography with nerve conductivity tests
• Imaging studies that may be performed include:
  • X-ray of head and neck region or vertebral column
  • Computerized tomography (CT) scan of the head and neck region/vertebral column; CT with contrast
  • Magnetic resonance imaging (MRI) scan of the central nervous system (brain and spine); MRI with contrast agents such as gadolinium
  • Cerebral angiographic studies or MR angiography: An angiogram involves injecting dye into the bloodstream, which makes the blood vessels to appear visually on X-rays. The X-ray may show a tumor in the brain or the blood vessels leading into the tumor
  • Magnetic resonance spectroscopy: This radiological technique is used to study the chemical profile of the tumor. It is often performed with and compared to corresponding MRI scan images of the affected region
• Cerebrospinal fluid analysis, where a spinal tap or lumbar puncture procedure may be performed: This diagnostic test is used to remove a sample of cerebrospinal fluid (CSF) from the spaces in and around the brain and spinal cord. The sample is removed from the lower spinal cord using a thin needle, and it is then checked for the presence of cancer cells
• Molecular studies, if necessary

Tissue biopsy: A biopsy of the affected region (brain or spinal cord) is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy sample under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy sample under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis.

A biopsy of the affected region is rarely performed. When the biopsy is performed, it is sent to a lab for further investigations. However, in a majority of cases, the diagnosis is made using a combination of signs and symptoms and radiological studies.

A differential diagnosis to eliminate other conditions or tumor types may be considered, before arriving at a definitive diagnosis.

The clinical differential diagnosis may include:

• Dandy-Walker malformation
• Empty sella syndrome
• Porencephaly

The radiological differential diagnosis may include:

• Chronic subdural hemorrhage
• Epidermoid cyst of CNS
• Hemangioblastoma of CNS
• Neurenteric cyst
• Neurocysticercosis
• Neuroglial cyst
• Non-neoplastic cysts of CNS
• Pilocytic astrocytoma
• Porencephalic cyst
• Subdural hygroma
• Other CNS cystic tumors

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Arachnoid Cyst?

The complications of Arachnoid Cyst may include the following:

• Stress and anxiety due to fear of an intracranial or intraspinal tumor
• Congenital lesions, those that are present at birth, may cause developmental delays in the child
• Attention-deficit hyperactivity disorder (ADHD)
• Paraplegia or paralysis of the lower limbs
• Large-sized cysts may also cause skull bone malformations in infants and young children
• Severe intellectual disability; dementia including personality changes causing a reduced quality of life
• Severely affected physical and mental health may lead to the overall quality of life being greatly reduced
• Large undetected tumors can severely affect brain function and be disabling or even life-threatening, due to mass effect/compression of surrounding tissue
• Tumor rupture may cause a form of meningitis
• Miscarriage and stillbirths, may take place in very rare cases
• Occasionally, recurrence of the tumor following its incomplete surgical removal
• Damage to the muscles, vital nerves, and blood vessels, during surgery
• Post-surgical infection at the wound site

How is Arachnoid Cyst Treated?

The treatment of Arachnoid Cyst may involve the following:

• In some cases of small asymptomatic tumors, the healthcare provider may consider conservative ‘wait and watch’ measures, instead of immediately recommending surgery to remove them
• Symptomatic treatment may involve the use of antiseizure medications, painkillers, steroids (to reduce inflammation), and administration of anti-depressants
• Placement of ventriculoperitoneal (VP) shunt: It is an invasive procedure that involves the use of a medical device called a VP shunt. The device is placed in the ventricles of the brain to treat hydrocephalus, and thus helps relieve excess CSF pressure on the brain
• Generally, the treatment of choice is a complete surgical excision for large cysts. The surgeon may perform a craniotomy or use other microsurgical approaches to remove the cyst
• Other invasive procedures that may be considered include:
  • Neuroendoscopic removal of the brain cyst
  • Stereotactic aspiration and drainage of brain cyst
  • Laser-assisted endoscopic techniques
  • Osteoplastic laminotomy and laminectomy for spinal cord cysts
• Follow-up care with regular screening and check-ups are important and encouraged

How can Arachnoid Cyst be Prevented?

Currently, there are no known methods to prevent the development of Arachnoid Cyst.

• If there is a family history of the condition (primary Arachnoid Cyst), then genetic counseling will help assess risks, before planning for a child
• Genetic testing of the expecting parents and prenatal diagnosis may help in understanding the risks better during pregnancy

Even though the secondary Arachnoid Cysts have underlying causes, it is often difficult to prevent them.

What is the Prognosis of Arachnoid Cyst? (Outcome/Resolutions)

• The prognosis of Arachnoid Cyst is usually good with suitable treatment, since it is a benign cyst
• In the absence of treatment, large cysts may cause severe neurological disabilities and can even be life-threatening due to cystic hemorrhage (bleeding in the brain)
• In many individuals, an effective surgery is known to alleviate most of the pre-operative symptoms

In general, the prognosis of Arachnoid Cysts depends on a variety of factors including:

• Whether it is primary or secondary
• Whether it is intracranial or spinal
• Size of the cyst
• The combination of signs and symptoms noted

Additional and Relevant Useful Information for Arachnoid Cyst:

The following article link will help you understand other cancers and benign tumors:

http://www.dovemed.com/diseases-conditions/cancer/