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Logo of jkneurosocJournal of Korean Neurosurgical SocietyJournalInstructions for AuthorsOn-line Submission
J Korean Neurosurg Soc. 2010 June; 47(6): 433–436.
Published online 2010 June 30. doi:  10.3340/jkns.2010.47.6.433
PMCID: PMC2899030

Endoscopic Management of Cranial Arachnoid Cysts Using Extra-Channel Method

Myung-Hyun Kim, M.D., Ph.D.corresponding author1 and Hae-Dong Jho, M.D., Ph.D.2



Arachnoid cysts (ACs) can be cured by making the definite and wide communication between the cyst and arachnoid space using endoscopy, but often it is impossible only through the usual working-channel (intra-channel) procedures. We discuss and propose a more valuable endoscopic technique with the presentation of our series of cases.


We treated 9 patients with cortical AC in various locations with extra-channel endoscopic techniques. The patients ranged in age from 3 years to 60 years (mean age, 37.2 yrs). The follow-up period ranged from 12 to 26 months (mean follow-up duration, 17.2 months). All patients had large AC compressing the adjacent brain with clinical symptoms or signs. The authors performed extensive fenestration via single burr hole with the aid of endoscope. Being bypassed the rigid endoscope, through the space between the shaft of endoscope and guiding cannula (extra-channel method), fenestration procedures were done in the dry fields.


Eight (88.9%) patients had been treated successfully with endoscope. One patient required shunt procedure. Among the eight patients who were treated with endoscopic procedure, 6 patients (66.7%) showed cyst reduction, and two (22.2%) showed disappearance of cyst.


We suggest that extra-channel method will be simple and easy to perform using more valuable instruments with wider working area, and may promise better results compared to the conventional intra-channel endoscopic procedures.

Keywords: Cranial arachnoid cyst, Endoscopic procedure, Fenestration


Arachnoid cysts (ACs) are intra-arachnoid collections of cerebrospinal fluid (CSF)8), and are regarded as a developmental abnormality of the arachnoid, originating from a splitting or duplication of this membrane19). Surgical treatment is necessary for patients with raised intracranial pressure and corresponding clinical symptoms. Many operative procedures for the control of ACs have been recommended, however it remains controversial as to which is the best method. Recently, endoscopic procedures have been recommended as the first surgical option for cerebral AC1,5,6,12,13,18). Several kinds of endoscopic procedures have been reported according to the location of lesion12,13). We describe our technique and it is compared with the others.


Clinical materials

Details of each case are given in Table 1. Five cysts were located in the posterior cranial fossa, three in the middle cranial fossa, and one in parietal region. All patients showed clinical manifestations of increased intracranial pressure requiring prompt surgical intervention and corresponding radiological findings. We operated on all patients with extrachannel endoscopic method.

Table 1
Clinical characteristics of 9 patients with cerebral arachnoid cysts

Surgical technique (extra-channel endoscopic method)

All procedures were performed under general endotracheal anesthesia. The field of operation was prepared and draped to allow immediate open microsurgical intervention in cases of complications. We used a rigid endoscope (Karl Storz, Germany) with or without frameless stereotaxy (Stealth, USA).

A burr hole was made according to the best trajectory guided by frameless stereotaxy. After dural opening, the outer membrane was coagulated and incised. The endoscopy with self-cleansing system equipped sheath (Buxter, USA) was inserted freehand into the cyst to explore. After orien-tation, endoscope was fixed by modified Greenberg retractor. The fluid content in the cyst was sucked out and fenestration procedure was started. The whole procedures was performed through the relatively the wide space between the shaft of endoscope and margin of burr hole. Through this space, we could use various endoscopic instruments, monopolar Bovie-sucker (Valleylab, USA), dissectors, forceps and scissors (Fig. 1A, B, ,3B),3B), including even the microscopic instruments. Usually, cysto-cisternostomy was performed by creating one or more wide openings to the cyst. Closure was done as usual manner.

Fig. 1
Operative findings in case 3. A : Arachnoid cyst located in the sylvian region showing a third cranial nerve (III) through its semi-transparent membrane and a tiny hole on the outer surface of cyst. B : After extensive fenestration, a third nerve and ...
Fig. 3
Schematic drawing of our endoscopic extra-channel procedures. A : Intra-channel method. We can work only through the narrow instrument channel (long, ended arrow) of endoscope, so working area will be small (white round area), and instrument will be limited. ...

Unlike conventional intra-channel endoscopic method (Fig. 3A), we could use almost every kind of endoscopic instruments and several kinds of microscopic instruments during extrachannel method (Fig. 3B). Furthermore, every procedure was done in dry fields, which gave us more clear operative fields, convenient hemostasis.


The follow-up periods were ranged from 12 to 26 (mean 17.2) months. Symptoms were relieved in all patients, but one patient required shunt. There was no mortality and morbidity as a result of this procedure. The follow-up magnetic resonance images or computed tomography scans revealed a decrease in the size of the cysts (Fig. 2). The operation time was from 1 hour to 2 hours and the hospital stay was only 1 day.

Fig. 2
Radiologic findings in case 3. A : Coronal T1-weighted magnetic resonance image revealing an arachnoid cyst in the middle cranial fossa with compression of lateral ventricle and midline shifting. B : Coronal T1-weighted magnetic resonance image obtained ...


Arachnoid cysts most probably arise by way of anomalous splitting and duplication of the endomeninx4) and the concept of a ball-valve mechanism in the expansion of AC has attained broad agreement11,14). Becker et al.2) found a positive correlation of relative AC volume to age in large arachnoid cysts and argued in favor of the existence of a subgroup of expansile lesions. A subgroup of large AC appears to expand with time, while the majority of small AC remains unchanged.

Controversy exists concerning the treatment of ACs. There is no doubt that surgical treatment is necessary for patients with raised intracranial pressure and corresponding clinical symptoms, even if the communicating type, and those complicated by intra-cystic or subdural hemorrhage. ACs combined with subdural hematoma or fluid collection should be followed-up24) and if communication is inadequate, they should be considered as a surgical candidate. Conservative management can be considered for those patients complaining of mild symptoms or presenting cranial deformity alone. Diagnostic evaluation should include, after the initial identification of intracranial ACs, the detection of mass effect, determination of the type of communication between cyst and subarachnoid space, and recognition of the presence, location and severity of obstructive hydrocephalus and cisternal block10).

ACs have been treated by cyst fenestration/resection13,16) or by cystoperitoneal shunting5,8), however, controversy continues regarding which surgical treatment is best. Furthermore, both procedures have some limitations to be the first line of treatment for AC3,5,7,9-11,15,16,18,22,23). Endoscopic techniques can replace open surgery or shunting procedures with similar or even better results. Many authors have been regarded endoscopic fenestration as the first option of treatment1,5,6,8,12,18,20,21).

To treat AC, fenestrations need to be definite and large enough to communicate the cyst and intact cisternal spaces freely without re-closure. Usual enodoscopic technique (intra-channel) is making one or more fenestrations using various endoscopic instruments through the limited instrumental channels of endoscopy1,5,6,8,13,18,20,21). This may be successful, but often there can be difficulties to control bleeding and manipulate the cyst wall because the instruments should be handled only via long, narrow channels. The continuous movement of the endoscope to control the trajectory of instruments may cause troublesome bleeding and disorientation. Moreover, surgery in the wet field will cause more light reflection and air-fluid level what make us difficult to see underlying structures through the cyst wall, and we cannot see any more even by the presence of minor bleeding (Fig. 3A). But in the dry field, the structures opposite to the cyst can be seen more clearly, which are crucial for the fenestration procedures under the similar situations. The larger instruments can be handled more easily, through the wider space between the endoscope and guiding cannula, instead of long, narrow instrument channels (Fig. 3B). Also, we can dissect the cyst wall from the underlying structures like usual microscopic surgery. In this point, our technique is similar to the 'endoscope-guided microneurosurgery', proposed by Hopf and Pereczky12). Whereas we perform all our endoscopic procedures through the single burr hole without microscope in their procedure, they need a small craniotomy and use the endoscope as an assistance of microscope, 'looking around the corner'.

Still there are some limitations in our procedure. First, as shown at Fig. 3B, the effective working area will be eroded by endoscope itself. This 'hidden area' will not hinder the operation itself, but may block the prompt approach to the certain area of endoscopic field. It can be overcome by replacement of endoscope. Secondly, the limited illumination and view angle of endoscope can make 'blind spots' in the corner of operation fields, especially in the lesion with complex, large cavity. Finally, the surgeons cannot look behind along the shaft of endoscope. This may cause unexpected harmful events during endoscopic procedures. The imaging technology will be advanced day after day17). We hope that in the future, the clinical application of microvideo camera can rescue us from these troubles (Fig. 3C).

Although the follow-up period is too short to make statements on long-term outcome, the authors recommend extrachannel endoscopic approach for treatment of arachnoid cysts. Should the endoscopic procedure be failed, established treatment options can subsequently be performed without additional risk.


We conclude that extra-channel method will be simple and easy to perform with using more valuable instruments. It can give us wider working area, and promise better results to the conventional intra-channel endoscopic procedures.


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