Indications
- •
Fenestration of arachnoid cysts is indicated in cysts that show significant increase in size or associated clinical symptoms. The size of an arachnoid cyst typically remains stable or increases over time, and associated symptoms are unlikely to resolve spontaneously. Symptoms may include headaches, craniomegaly, developmental delay, and seizures.
- •
Surgical treatment of arachnoid cysts that are large enough to cause mass effect but that remain asymptomatic is controversial. One option is to observe these cysts; however, many neurosurgeons believe that any arachnoid cyst causing significant mass effect should be treated to minimize the possibility of developmental adverse effects or the risk of subdural hemorrhage.
- •
If initial fenestration fails, or if the cyst is in an anatomic location that makes success with fenestration unlikely, a shunting procedure is indicated. Cyst-peritoneum, cyst-ventricle, or cyst-subarachnoid shunts all are possible shunting treatment options.
Contraindications
- •
Most arachnoid cysts do not require treatment. Small and asymptomatic arachnoid cysts should be observed clinically without any intervention.
- •
Incidentally found cysts that remain stable in size and do not have any associated symptoms or significant mass effect on surrounding neural structures should not be treated.
Planning and positioning
- •
Treatment options include open resection of the entire cyst wall, fenestration into the ventricle or subarachnoid spaces, and shunting procedures. Our first-line treatment for middle fossa arachnoid cysts involves a keyhole craniotomy and fenestration of the cyst allowing for communication with the basal cisterns.
- •
Similar fenestration procedures can be performed for cerebellopontine and retrocerebellar arachnoid cysts.
- •
Whenever possible, the procedure should be planned to fenestrate the arachnoid cyst in two locations: at an entrance site and an exit site.
Figure 50-1:
Appropriate neuroimaging is obtained to show the anatomy of the arachnoid cyst and its relationship to surrounding cerebrospinal fluid (CSF) spaces and neural and bony structures. Although the diagnosis of arachnoid cyst is most commonly confirmed with computed tomography (CT), magnetic resonance imaging (MRI) is the most sensitive study for evaluating an arachnoid cyst. The appearance is typically a well-defined nonenhancing mass that is isointense to CSF on all MRI series. This appearance differentiates them from other types of cysts that contain more proteinaceous fluid.
Figure 50-2:
Patient positioning depends on the location of the cyst. For microsurgical keyhole fenestration of middle fossa arachnoid cysts, the patient is positioned supine and in three-point Mayfield pin fixation. The head is turned so that the side with the cyst is positioned at the uppermost aspect.Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
