Arachnoid Cyst

The disease is related to the following processes:  congenital and has an incidence of about  12 / 100.000.

Overview

Arachnoid cysts are fluid filled sacs that develop between the region of the central nervous system and the arachnoid membrane. These lesions are usually present from birth and are benign in nature. The sacs are filled with cerebrospinal fluid and in severe cases may require surgical draining.

Arachnoid cysts in most cases do not produce any symptoms and cause no harm. However, in situations when the cysts enlarge it can be a cause of potential discomfort for the individuals. When the symptoms turn severe and the cyst begins to affect the functioning of the central nervous system then surgical procedures may have to be employed for removal of the cyst.

Etiology

Arachnoid cysts are divided into two categories: primary and secondary (acquired). The primary cysts are congenital in nature, which means that the cysts are present from birth. Some studies point that the malformation is an embryologic defect in asymmetric cell division during early neural development [1].

Secondary or acquired type of arachnoid cysts occur as a result of injury or a disease condition. These also develop as a secondary condition to neoplasm, hemorrhage or surgical procedures governing the brain and spinal cord. The following are the various causative factors that give rise to arachnoid cysts:

  • Meningitis, a type of brain infection characterized by inflammation of the sac that surrounds the spinal cord and the brain.
  • Surgery of the brain or the spinal cord.
  • Injury to the brain or spinal cord.
  • Head injury.

In addition to the above mentioned causative factors, certain research trials have also indicated a genetic link for development of arachnoid cyst. This indicates that parents with arachnoid cyst are likely to pass on the faulty genes to their children.

Epidemiology

Arachnoid cysts affect about 1.1 % of the population and more commonly strikes the male population with the male to female ratio being 2:1. About 20% of these individuals would experience symptoms as a result of secondary hydrocephalus.

Sex distribution
Age distribution

Pathophysiology

The brain is surrounded by several layers of tissues that cover and protect the organ. The arachnoid membrane is one of these tissues layers and protects the brain and the spinal cord.

Arachnoid cysts are lesions that occur in the region between the arachnoid membrane and brain. These cysts are filled with cerebrospinal fluid and contain no solid component or epithelial lining. The cysts are benign in nature and are not tumors.

Prognosis

When the arachnoid cysts are diagnosed on time and promptly treated, the prognosis is usually favorable. However, untreated cysts may enlarge in size and cause permanent damage to the neurological function. With surgical intervention the prognosis is good with restoration of cognitive functioning.

Complications

Untreated arachnoid cysts can cause the following serious and life threatening complications:

  • Seizures
  • Severe headache
  • Developmental delays
  • Impairment of the motor function
  • Loss of vision
  • Hydrocephalus characterized by accumulation of fluid in the skull
  • Failure to thrive 

Presentation

In many cases, small arachnoid cysts do not produce any symptoms. However, when the cysts grow in size they can present the following signs and symptoms:

  • Severe, migraine like headache
  • Lethargy
  • Nausea
  • Dizziness 
  • Vertigo
  • Difficulty or loss of hearing [2]
  • Spasms accompanied by seizures
  • Impaired coordination
  • Head bobbing
  • Changes in vision 
  • Muscle twitching
  • Hallucination 
  • Developmental delay
  • Macrocephaly characterized by enlargement of head
  • Ataxia 
  • Increased intracranial pressure
  • Manic depression
  • Schizophrenia 
  • Periodic paranoia
  • Auditory hallucinations
  • Alexithymia 

In the elderly population, some additional grave symptoms have also been noticed. These include:

Workup

Imaging studies such as magnetic resonance imaging (MRI) are done to diagnose arachnoid cyst [3]. It is usually the method of choice as it can discretely exhibit the exact location and extent of arachnoid cyst. Such a diagnostic procedure also provides information regarding the relationship of the cyst to its neighboring regions.

For children, cranial ultrasonography is usually employed for detecting arachnoid cyst [4]. It is a non-invasive procedure that fits well for infants and provides appropriate detection of the cyst.

Angiography is yet another diagnostic tool for detecting cystic masses; however CT scan and MRI can provide the same information in a non- invasive manner.

Microscopy of the arachnoid cyst membranes reveals a bilayer wall of outer and inner membrane surrounding the cyst cavity [5].

Treatment

Surgical procedure is often the treatment of choice when the cysts enlarge and begin producing symptoms. In majority of the cases, clinicians treat patients with symptoms and surgical intervention is employed for draining the fluid and excision of the mass [6]. In some other cases, clinicians prefer treating even those patients without symptoms in order to avoid development of secondary complications in the long run.

However, arachnoid cysts that remain asymptomatic since birth may not need any surgical intervention at all [7]. The following are the various type of surgical procedures employed for treating arachnoid cysts:

  • Method of burr hole or needle aspiration is done to drain the fluid from the cyst. The chances of recurrence of the cysts are higher with this method.
  • Neuroendoscopic cystocisteronostomy of the arachnoid cyst for fluid drainage [8].
  • Neurosurgery is done wherein multiple holes are made so that the fluid gets drained off continuously. This may be done by open craniotomy or by MRI assisted method of cyst drainage [9].
  • Use of shunt to drain off the fluid accumulated in the cyst [10]. However, this method has several complications such as scarring, infection and obstruction associated with it.

Prevention

So far no guidelines have been developed to prevent arachnoid cyst. However, timely diagnosis and initiation of treatment can help prevent the onset of complications.

Patient Information

Definition

Arachnoid cysts are fluid filled masses that develop in the region between the brain and arachnoid membrane. Such a condition is more common in infants being present at the time of birth. Males are more affected than females. It has also been estimated that about 1.1% of population develops arachnoid cysts.

Cause

In majority of the cases, arachnoid cysts are present from birth and genes are known to play foul. However, in cases of acquired arachnoid cysts, these masses develop as a result of injury or any surgery concerning the brain or spinal cord.

Symptoms

Many a times, arachnoid cysts are asymptomatic. In cases when the cysts grow in size the affected individuals experience headache, lethargy, changes in vision, hearing loss, loss of motor skills, depression, hallucinations and alexithymia. Elderly individuals with arachnoid cysts may also experience urinary incontinence, dementia and hemiparesis in addition to other symptoms.

Diagnosis

MRI scan is usually the method of choice for detecting arachnoid cysts. It helps in providing accurate information regarding the nature and exact location of the cyst.

Treatment

Patients with enlarged cysts and symptoms are usually the potential candidates for surgery. The cysts are drained and in many cases the masses removed.

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References

  1. Doherty D, Chudley AE, Coghlan G, Ishak GE, Innes AM, Lemire EG. GPSM2 mutations cause the brain malformations and hearing loss in Chudley-McCullough syndrome. Am J Hum Genet. Jun 8 2012; 90(6):1088-93.
  2. Doherty D, Chudley AE, Coghlan G, Ishak GE, Innes AM, Lemire EG. GPSM2 mutations cause the brain malformations and hearing loss in Chudley-McCullough syndrome. Am J Hum Genet. Jun 8 2012; 90(6):1088-93.
  3. Hu XY, Hu CH, Fang XM, Cui L, Zhang QH. Intraparenchymal epidermoid cysts in the brain: diagnostic value of MR diffusion-weighted imaging. Clin Radiol. Jul 2008; 63(7):813-8. 
  4. Slovis TL, Canady A, Touchette A, Goldstein A. Transcranial sonography through the burr hole for detection of ventriculomegaly. A preliminary report. J Ultrasound Med. Apr 1991; 10(4):195-200.
  5. Van Tassel P, Cure JK. Nonneoplastic intracranial cysts and cystic lesions. Semin Ultrasound CT MR. Jun 1995; 16(3):186-211.
  6. Zeng L, Feng L, Wang J, Li J, Wang Y, Chen J, et al. Comparative study on two surgical procedures for middle cranial fossa arachnoid cysts. J Huazhong Univ Sci Technolog Med Sci. Aug 2008; 28(4):431-4.
  7. Hughes G, Ugokwe K, Benzel EC. A review of spinal arachnoid cysts. Cleve Clin J Med. Apr 2008; 75(4):311-5.
  8. Tsutsumi S, Kondo A, Yasumoto Y, Ito M. Asymptomatic huge congenital arachnoid cyst successfully treated by endoscopic surgery--case report. Neurol Med Chir (Tokyo). Sep 2008; 48(9):405-8.
  9. Kollias SS, Bernays RL. Interactive magnetic resonance imaging-guided management of intracranial cystic lesions by using an open magnetic resonance imaging system. J Neurosurg. Jul 2001; 95(1):15-23.
  10. Algin O, Hakyemez B, Gokalp G, Korfali E, Parlak M. Phase-contrast cine MRI versus MR cisternography on the evaluation of the communication between intraventricular arachnoid cysts and neighbouring cerebrospinal fluid spaces. Neuroradiology. May 2009; 51(5):305-12.

  • Diffusion-weighted MR imaging of the brain: value of differentiating between extraaxial cysts and epidermoid tumors. - JS Tsuruda, WM Chew, ME Moseley - American Journal of , 1990 - Am Roentgen Ray Soc
  • Aseptic meningitis following posterior fossa surgery in children - PW Carmel, RAR Fraser, BM Stein - Journal of neurosurgery, 1974 - thejns.org


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