We presented our series of intracranial arachnoid cysts. Most of our patients were male and adults. Fenestration was the most preferred technique and 90% of patients were improved after surgery. Subdural effusion and wound dehiscence were most common complications, but we not observed re-closure of cyst fenestration. In addition, there is no mortality in our series.
Arachnoid cysts are benign and cystic intracranial lesions which were more often diagnosed in children than adults. They constitute approximately 1% of all intracranial mass lesions. Most of them are located in the supratentorial region and middle cranial fossa. But they may also occur in the posterior fossa, cerebellopontine angle and spinal region [6, 8, 9].
These cystic lesions are usually asymptomatic but, in some patients, symptoms may develop such as nausea, vomiting, headache, neurological deficits and seizures. Radiological techniques such as CT scan and MRI are widely used for the diagnosis of intracranial arachnoid cyst [6, 7].
Management of arachnoid cysts is still controversial today. Follow-up is the main option in patients with incidentally diagnosed arachnoid cyst. Enlargement of the arachnoid cyst may be seen in every period of life because of a slit valve mechanism, an osmotic gradient, or cerebrospinal fluid (CSF) production by the cyst walls [10]. It is well known that the rate of cyst enlargement is very low in asymptomatic arachnoid cysts during the follow-up period. Meanwhile, periodical radiological imaging is also indicated in asymptomatic patients for the risk of obstructive hydrocephalus and intracystic hemorrhage, especially in the pediatric population [10].
There are mainly 2 different surgical approaches for the treatment of arachnoid cysts as cyst fenestration and cystoperitoneal shunt [2, 6]. Cystoperitoneal shunts divert CSF from the cysts to the abdomen, helping decrease of the intracranial or intracystic pressure [5, 11]. This technique is a safeand practical procedure and most neurosurgeons are familiar with shunting. But shunt is a mechanical device and patient becomes dependent to shunt. In addition, it carries many risks such as obstruction, infection and overdrainage. Cyst fenestration using either microsurgical or endoscopic technique decreases CSF pressure within the cyst and allows brain expansion especially in young children [12–15]. Microsurgical technique may also help larger cyst wall removal in association with fenestration [16]. Other advantages of microsurgical technique are direct inspection of the cyst borders and vital neurovascular structures, adequate biopsy sampling, multiples fenestration sites especially in multilocular arachnoid cysts [17]. Endoscopic fenestration is a minimally invasive method and aims to fenestrate the cyst with basal cisterns or ventricular system. But cyst fenestration may not be satisfactory with endoscopic technique because it is performed using a narrow corridor and rapid cyst wall closure may occur especially in children. It is obvious that the cyst wall removal is not satisfactory using endoscopic technique. Moreover, surgical area in endoscopic technique is very limited because of the proximity of the neural and vascular structures in basal cisterns [18]. Gangemi et al. performed pure endoscopic fenestration in 18 patients and concluded that suprasellar, quadrigeminal and posterior fossa arachnoid cysts are the best candidates for pure neuroendoscopic approach [18]. They also pointed out that cortical cysts are best treated by microsurgical fenestration or shunting. Hall et al. performed a retrospective study in 82 patients and emphasized that endoscopic and microsurgical approaches cysts produce comparable clinical and radiological outcomes in arachnoid cysts [19]. But endoscopic fenestration is associated with a shorter length of hospital stay. Today, arachnoid cysts are frequently treated with endoscopic fenestration procedure. Cystoperitoneal shunts are usually reserved for patients who did not benefit from the fenestration alone. But the shunt dependence is the main disadvantage of cystoperitoneal shunts. In our series, we performed cystoperitoneal shunt in only 2 patients who were previously underwent endoscopic fenestration in another center. Fenestration or combined fenestration+shunt were the main surgical approaches in our series and we obtained 90% success after surgery.
Combined technique such as endoscopic fenestration and cystoperitoneal shunt placement in the same operation is another surgical option for neurosurgeons. The importance of this technique is related to the fact that the shunt can induce the collapse of the cyst and that the endoscopic fenestration could make it possible to remove the shunt, avoiding the phenomenon of shunt dependence. Mottolese et al. reported combined use of endoscopic fenestration and a cystoperitoneal shunt in 35 pediatric patients and they pointed out that this is a short and useful procedure for the treatment of arachnoid cysts in all locations [15]. In our series, we performed cyst fenestration and shunt placement in the same session in 8 (18.18%) patients. These patients were also children because of the avoidance of cyst wall re-closure. But we did not removed shunts in case of cyst collapse because of continuous CSF diversion and improvement of the symptoms.
There are also some studies suggesting that surgery did not contribute to the treatment of arachnoid cysts. Kim et al. reported long-term outcome of patients with large sylvian arachnoid cyst in 60 children and they concluded that there is no difference in the outcomes between the surgery and non-surgery groups regardless of the size of the arachnoid cysts when patients had no hydrocephalus or papilledema [13]. Our surgical indications are same with Kim et al., as we also operated patients with the signs of increased intracranial pressure or seizure due to cyst.
Arachnoid cysts should not be operated until they become symptomatic. Meanwhile, close follow-up with periodical MRIs is required in order to detect any cyst enlargement or intracystic hemorrhage. Severe headache, convulsion, and nausea-vomiting are alert signs for patients with arachnoid cysts. Electroencephalography may be used for the detection of any abnormal electrical discharges secondary to cysts. But this test is not a criterion for the decision of surgery. Cyst fenestration is the main option for surgical treatment. It may be performed using either endoscopic technique with a small burr hole or microsurgical technique with craniotomy. The decision usually depends on the cyst size and presence of increased intracranial pressure. Large cysts with midline shift or intracystic hemorrhage especially in children require microsurgical approach with craniotomy. Removal of a large cyst wall is crucial for adequate cerebral decompression. Moderate or small arachnoid cysts which are presenting with seizure in adult patients are best candidates for endoscopic fenestration through a small burr hole.
This study describes our institutional experience over a 9-years period. The major limitation of our study is the retrospective nature. Lack of comparison group and small number of patient are other limitations.