Arachnoid cysts

Arachnoid cysts (ASCs) are cysts filled with cerebrospinal fluid (a fluid-filled "sac") within the arachnoid membrane, one of the meninges that surround our brain. It is still unclear exactly how arachnoid cysts develop and why they can grow larger. It is assumed that so-called primary arachnoid cysts are the result of maldevelopment due to cyst formation in the 2nd or 3rd trimester of pregnancy. In rare cases, AZs are acquired, so-called secondary AZs, for example after a traumatic brain injury or after a cerebral haemorrhage in premature infants. AZs account for around 1% of all brain lesions and occur in around 1.4% to 2.6% of the population, in ¾ of cases in children. Boys are more frequently affected than girls. In principle, ASCs can occur anywhere in the brain. A rough distinction is made between AD in the area of the cerebrum (a so-called supratentorial AD), AD in the ventricular system (a so-called ventricular AD) and AD in the area of the cerebellum (so-called infratentorial AD). The treatment of CSCs differs depending on the location of the cyst and the type of symptoms.

In most cases, ASCs are detected by chance during imaging of the head. As the brain forms and develops around the cyst during childhood development, symptoms or deficits are often absent. Symptoms occur in approximately 7% of cases, particularly when the cyst increases in size and a high pressure gradient develops within the cyst, which in turn causes pressure on the surrounding structures. In addition, hydrocephalus (hydrocephalus) can form, which can also lead to symptoms of intracranial pressure. Rarely, an ASC can rupture or haemorrhage, which in turn can lead to symptoms. In the case of symptoms, headaches are the most common. Other symptoms include developmental delays, neurocognitive deficits, seizures, visual disturbances, hormonal imbalances or a protrusion of the skull bone (due to pressure).

Normally a AZ random discovered during imaging of the head. The imaging the Choice, to diagnose and evaluate the AZ is the Magnetic resonance tomography (MRT). If the fontanel is still open (usually up to the age of 6-12 months)an ultrasound can also be used for diagnosis. MRI imaging should always be performed before starting treatment. AZ can also be diagnosed and treated during pregnancy (intrauterine). observed become. As a rule, the intrauterine diagnosis of an AZ is not a reason for a termination of pregnancy or for an early delivery.

ASCs that do not cause symptoms are usually followed up by imaging and surgery is rarely necessary. If the ASC becomes larger, new symptoms appear, or a haemorrhage or cyst rupture occurs, then surgical treatment of the cyst is recommended. The treatment depends on the localisation and the symptoms of the cyst. The aim of the operation is to reduce the pressure that has built up within the cyst. In principle, there are 3 surgical options available today: "open" fenestration of the cyst, endoscopic cyst fenestration or insertion of a cysto-peritoneal shunt. As a rule, we favour the minimally invasive endoscopic technique.

• Endoscopic "minimally invasive" Technology: In the endoscopic technique, the cyst is removed via a minimally invasive approach using either the normal cerebral ventriclesystem (ventricles) so that the cerebrospinal fluid can flow into the ventricles and be absorbed and reabsorbed from there. can. Alternatively, we connect the cyst with the so-called cisterns, which in turn belong to the outer cerebral ventricle system that surrounds the brain. In addition, the endoscopic technique can be used to possible Hydrocephalus during the same operation. The endoscopic technique is now considered the method of choice for treating an ASC. With the endoscopic technique wed the child is placed on its back. Then an approx. 3-4 cm skin incision is made, under which an approx.. 1,3 cm hole is drilled. Afterwards the meninges are opened and a small tube is inserted into which the endoscope (a long rod with a camera attached to it) is contained in the Cyst advanced. UFrom the camera's point of view becomes a hole (fenestration) towards the ventricle or the cistern (so-called Stomia). Finally, it will be ensured that a regularflow from the AZ into the surrounding cerebrospinal fluid system is guaranteed. The hole is then in the The skull bone is closed and the skin sutured together. The entire operation is carried out using a computer-controlled navigation system, which helps us with the orientation around and in the Cyst helps, carry out the fenestration in the right place.
• Microsurgery "open" Technology: The microsurgical technique has the same aim as endoscopic surgery. As endoscopic surgery is minimally invasive, it is generally preferred at the UKBB and therefore the microsurgical technique has taken a back seat. With the microsurgical technique wed the child is positioned on the back, a ca. 5-6cm skin incision is made and a A hole about 5 francs in size was drilled into the child's skull bone. The meninges are then opened and the AZ is cut open (fenestration). Finally, it is ensured that a regularflowfrom the AZ into the surrounding cerebrospinal fluid system is ensured and the skull bone and skin are closed again. The entire operation is performed using a computerised navigation system that helps us to locate the cyst.
• Cystoperitoneal Shunt: The Cystoperitoneal Shunt (ZPS) was the standard therapy for AZ for a long time, is however, due to the newoEndoscopic methodbeen replaced. Today, the ZPS is mainly used in Clinics with little expertise in neuroendoscopy or in countries with a lack of resources. With an unsuccessful endoscopicn Treatment is alsoäto a endoscopic Fenestration a ZPS inserted. The child is placed on its back and a skin incision of approx. 2-3cm is made. Then wed a 1.1cm hole was drilled into the skull cap and a siliconekatheter is inserted into the cyst. This catheter is then to a valve connected. This valve regulates the amount of Fluid that flows from the cyst into should drain into the abdominal cavity. The valve can by means of a magnet through the skin (without surgery) as desired strong can be adjusted. An additional silicone tube is then an das valve connected and under the skin to in the abdomen and inserted into the abdominal cavity under endoscopic vision. This allows fluid from the cyst to enter the abdominal cavity. derived and are absorbed and excreted by the body. The shunt usually remains in place for the rest of the patient's life.

During the entire hospitalisation, your child will be looked after by our Team of the paediatric neurosurgery at the UKBB. Your child is admitted one day before the operation, wed by our team and the anaesthetists (anaesthesia) re-examined and can thensleep at home if you wish. The next day wed Your child undergoes surgery and is then transferred to the intensive care unit for monitoring or in the Recovery room. On the day of the operation, one of our parent carers from the Parent Support Service (BELOP) at UKBB will be at your disposal. 

You accompany the parents, until the child has fallen asleep and show the parents where to wake up again becomes. In between, they help Ito find their way around the hospital. Complications after a Operation from AZ are rare. As soon as your child no longer needs close monitoring (usually on the following day)it depends on the kpaediatric surgical bedsstation. As a rule, Iyour child after 3-5 days from the operation and may also in this period home exit. You can be with your child during the entire time and contact the team at the paediatric neurosurgery turnwho will be with you every day for the and your child.

As a rule AZ benign, i.e. if they are asymptomatic and do not grow significantly, can them can be observed over a period of years. If surgery is necessary, the prognosis is also very good, as the complication rate of surgery is very low. As a rule, the AZ despite the operation exist, which Symptoms form, however often back as the pressure within the Zyste reduced was. Rarely can The opening that was made during endoscopic or open cyst fenestration, close again. 

In suchcases another operation may be necessary. After a zystoperitoneal shunt can lead to mechanical problems such as blockage or breakage of the catheter. come. In These cases usually require a revisionoperation is necessary. After surgical treatment of an AZ, no further subsequent therapies are required. Clinical monitoring is often carried out for a few years and If there are no problems, the treatment can be completed.

• Soleman J, Kozyrev DA, Constantini S, Roth J. Surgical treatment and outcome of posterior fossa arachnoid cysts in infants. J Neurosurgeon Paediatrics. 2021;28(5):544-552. doi:10.3171/2021.5.PEDS21119
• paediatrieschweiz.ch/die-behandlung-von-intrakraniellen-arachnoidalzysten-in-kindern/
• Ebel F, Greuter L, Mariani L, Guzman R, Soleman J. Intracranial Neuroendoscopy in Children and Adults: Where Do the Differences Lie? World Neurosurgeon. 2023 Jun 2:S1878-8750(23)00756-8. doi: 10.1016/j.wneu.2023.05.110.