What is the definition of Arachnoid Cysts?
Arachnoid cysts are sacs filled with cerebrospinal fluid (CSF) that are located between the brain or spinal cord and the arachnoid membrane, one of the three membranes that cover the brain and spinal cord. Arachnoid cysts can be primary or secondary. Primary arachnoid cysts are congenital (present at birth), resulting from abnormal development of the brain and spinal cord during early pregnancy. Secondary arachnoid cysts are less common, and result from head injuries, meningitis, tumors, or as a complication of brain surgery. Signs and symptoms depend on the location and size of the cyst and may include headache, nausea and vomiting, seizures, hearing and visual disturbances, vertigo, and difficulties with balance and walking. Although many affected individuals develop symptoms in the first year of life, some never develop symptoms. Whether and how to treat the condition depends on the location and size of the cyst. In some cases, arachnoid cysts are part of a genetic syndrome such as Chudley-McCullough syndrome, mucopolysaccharidosis, or Marfan syndrome, where there are many other associated signs and symptoms. When treatment is recommended, it may include placing a shunt to drain the fluid; surgically removing the cyst membranes; or opening the cyst so the fluid can drain into the CSF.
What are the alternative names for Arachnoid Cysts?
- Arachnoid cysts, intracranial
- Intracranial arachnoid cysts
What are the causes for Arachnoid Cysts?
The exact underlying cause of arachnoid cysts is unknown. Primary arachnoid cysts, which are congenital (present at birth), are due to developmental abnormalities of the brain and spinal cord during the early fetal period. Secondary arachnoid cysts, which occur more rarely, are associated with head injury, hemorrhage, meningitis, tumors, or a complication of brain surgery. In some cases, arachnoid cysts are part of a genetic syndrome such as Chudley-McCullough syndrome, mucopolysaccharidosis, or Marfan syndrome, where there are many other associated signs and symptoms, related to the specific syndrome.
What are the symptoms for Arachnoid Cysts?
In some cases, arachnoid cysts do not cause any symptoms. The location and size of the cyst in each individual determine whether symptoms occur, as well as when they might begin. Most individuals develop symptoms before age 20, and especially during the first year of life.
Signs and symptoms of arachnoid cysts vary depending on where are they located around the brain, and may include:
- Hearing and visual disturbances
- Difficulties with balance and walking
Other symptoms may include:
- Accumulation of excessive cerebrospinal fluid in the brain (hydrocephalus), resulting in increased intracranial pressure
- Malformation of certain cranial bones, resulting in macrocephaly, which is an abnormally enlarged head (only in rare cases)
- Neurological signs such as developmental delays, behavioral changes, inability to control voluntary movements (ataxia), difficulties with balance and walking, cognitive impairment, and weakness or paralysis on one side of the body (hemiparesis)
Arachnoids cysts located around the spinal cord can compress the spinal cord or nerve roots and may cause symptoms such as progressive back and leg pain, and/or tingling or numbness in the legs or arms and weakness. In some cases may cause other problems such as unwanted passage of urine or stool, called urinary or fecal incontinence.
If left untreated, injuries in the brain or spinal cord may occur due to a progressive expansion of the cyst(s) or bleeding into the cyst.
What are the current treatments for Arachnoid Cysts?
Whether to treat all arachnoid cysts, as well as the method of treatment, has been a subject of controversy in the medical literature. The need for treatment depends mostly upon the location and size of the cyst, as well as whether symptoms are present. Some believe that treatment should be reserved for individuals with symptoms, while others believe that even asymptomatic cysts should be treated to avoid future complications. In the past, doctors have placed shunts in the cyst in order to drain the fluid. However, now that specialized techniques and tools allow for minimally invasive surgery, more doctors are now opting to surgically remove the membranes of the cyst or open the cyst so its fluid can drain into the cerebrospinal fluid and be absorbed.
What is the outlook (prognosis) for Arachnoid Cysts?
Even though most arachnoid cysts are congenital (present at birth), they usually do not cause any symptoms throughout an individual's life. Whether symptoms develop depends upon the size and the specific location of the cyst within the brain. Small cysts usually do not cause symptoms, and most remain constant in size. However, some do increase in size and eventually cause symptoms to appear, especially if they press against a cranial nerve, the brain, or the spinal cord.
If the cyst puts increased pressure on structures of the brain, neurological symptoms may develop. These symptoms can include developmental delays, behavioral changes, an inability to control voluntary movements (ataxia), difficulties with balance and walking and cognitive impairment. Weakness or paralysis on one side of the body (hemiparesis) has also been reported. Symptoms often resolve or improve with treatment but if left untreated, arachnoid cysts may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or bleeding into the cyst. Arachnoid cysts may also result in a subdural hematoma, most commonly after a head trauma. Rupture of an arachnoid cyst may occur spontaneously, but this is a very rare event.
Is Arachnoid Cysts an inherited disorder?
Most diagnosed cases of arachnoid cysts are sporadic - occurring in people without a family history of arachnoid cysts. However, familial cases of arachnoid cysts have been reported in the medical literature, suggesting that a genetic predisposition may play a role in some people. For example, arachnoid cysts have been reported in at least three unrelated sets of siblings. In familial cases, inheritance may be autosomal recessive.
Arachnoid cysts can also occur secondary to other disorders which may be inherited such as Marfan syndrome.