Effect of continuous drainage of cranial arachnoid cysts into the ventricular system by stereotactic placed catheters

Background: Surgical treatment of intracranial arachnoid cysts (iACs) is challenging. Microsurgical resection, endoscopic fenestration and cysto-peritoneal shunting are the most frequently used methods, each implying their own drawbacks. Stereotactic-guided cysto-ventricular drainage has been described as an alternative method. Here we describe our experience with this technique and how we conducted volumetric measurements to evaluate the effect of permanent drainage.Methods: Standardized stereotactic planning was performed. The planned trajectory included both the iAC and the ventricle system. The catheter was shortened to the defined length and was further fenestrated along its planned course through the iAC to allow drainage into the ventricular system. Clinical and radiological control was performed on outpatient basis after a mean follow-up of 2 (1-3) months. The overall mean follow-up was 32 months (6-59). The measurement of the cyst volume was conducted by the ABC/2-method.Results: Six patients with symptomatic arachnoid cysts (4 f, 2 m) were treated between 2010 and 2016. The overall postoperative reduction in cyst volume at the first follow-up was 36.04% (at the long-term follow-up: 38.57%). Decrease of the midline-shift was achieved in all cases and averaged 57.83% (long term: 81.88%). Clinical improvement of related symptoms could be achieved in all patients (4 patients were symptom free, two patients had alleviated symptoms). There was no case of over-drainage. The catheter had to be removed after 6 months in one case due to infection.Conclusions: We demonstrate successful symptom control and volume reduction in a small series of iACs by continuous drainage into the CSF-system through stereotactic placed catheters. This method may facilitate a self-regulated egress of entrapped cyst fluid in symptomatic patients without risk of over-drainage. A literature survey of the success rate and the complications of this approach is provided. It is concluded that this minimally- invasive method may be an alternative to established fenestration techniques especially for patients with arachnoid cysts that aren't directly adjacent to a cisternal or ventricular CSF space.