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

• Congenital Arachnoid Cyst
• Primary Arachnoid Cyst of the Central Nervous System
• Primary Arachnoid Cyst of the CNS

What is Primary 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). The involvement of the spinal cord is infrequently noted. Arachnoid cysts are classified depending on the cause as either primary or secondary
• 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 filled with cerebrospinal fluid (CSF) involving the arachnoid mater/membrane
• Primary Arachnoid Cyst 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
• The exact cause of formation of a Primary Arachnoid Cyst is unknown; however, nearly 80% of these lesions are diagnosed in males. The cysts are classified according to the location they arise from within the central nervous system
• Small-sized Primary 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 Primary Arachnoid Cysts 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 Primary Arachnoid Cyst? (Age and Sex Distribution)

• Primary Arachnoid Cysts are usually observed in infant children. It is reported that between 60-90% of the primary cysts’ present symptoms during childhood
• In some cases, the manifestation of symptoms occurs even during adolescence
• Both males and females are affected; however, males are affected much more than females (a 4:1 male-female ratio is reported)
• No specific racial or ethnic group predilection is noted

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

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

• A family history is a known risk factor for these cysts
• In some cases, an association with certain congenital abnormalities is noted that include:
  • 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
  • Diastematomyelia, a type of spinal cord malformation
  • Marfan syndrome, a connective tissue disorder
  • Mucopolysaccharidosis syndrome, a group of rare genetic metabolic conditions
  • Spina bifida
  • Syringomyelia (a form of syrinx)

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 Primary 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
• Primary 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, Marfan syndrome, or spina bifida

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. The primary cysts can arise in both the cranial and spinal meninges.

What are the Signs and Symptoms of Primary Arachnoid Cyst?

The signs and symptoms of Primary 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 (congenitally) 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. Other sites include the cerebellopontine angle (CPA), cerebral convexities, ventricular system, suprasellar region, cisterna magna, and rarely, the spinal canal.

In the brain (cranial arachnoid cyst), the signs and symptoms may include:

• Headaches that may be persistent and increasing in intensity
• 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 Primary Arachnoid Cyst Diagnosed?

There are a variety of tests the healthcare provider may employ to diagnose Primary 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 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

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 Primary Arachnoid Cyst?

The complications of Primary 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 Primary Arachnoid Cyst Treated?

The treatment of Primary 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 Primary Arachnoid Cyst be Prevented?

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

• If there is a family history of the condition, 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

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

• The prognosis of a Primary 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 a Primary Arachnoid Cyst depends on a variety of factors including:

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

Additional and Relevant Useful Information for Primary Arachnoid Cyst:

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

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