Surgical treatment of intracranial arachnoid cyst in adult patients
Background: Intracranial arachnoid cyst (IAC) is a benign cystic lesion filled with cerebrospinal fluid (CSF). Different surgical treatments were evaluated to determine the most effective technique among several. Materials and Methods: A consecutive series of 68 adult patients (43 males, mean age 30.3 years, range 18-42 years) with IAC were surgically treated between January 2004 and January 2011. The cysts were supratentorial in location in 53 and infratentorial in 15 patients. Symptoms at presentation, location of the IAC, surgical treatment modalities, and postoperative complications were evaluated. Results: Of the 51 patients with headache, 44 (86.27%) patients had complete relief of the headache, five (9.80%) patients had significant improvement, and two (3.92%) had no worthwhile change. Three of the four patients with hydrocephalus and gait disturbances had relief of the symptoms and one patient had significant improvement. Of the five patients with cognitive decline and weakness, three (60.00%) patients showed improvement, and two (40.00%) patients had no significant change. Five (62.50%) of the eight patients with epilepsy had seizure remission, two (25.00%) patients had non-disabling seizures, and one had no change. Follow-up computed tomography (CT) scans showed variable change in the mass effect of IAC in 68 patients; cystic size was significantly reduced in 51 patients, no significant change in two patients of supratentorial arachnoid cysts. Cystic size was reduced in seven patients, but no significant change was observed in eight patients of infratentorial cysts. Three patients with enlarged head circumference had no further increase in the head circumference. Conclusion: Adult patients with IAC symptoms should be treated efficiently. Surgical treatment is associated with significant improvement in the symptoms and signs.
Keywords: Arachnoid cyst, cystocisternostomy, cystoperitoneal shunt, cystoventriculostomy, endoscopy
Intracranial arachnoid cyst (IAC) is a benign cystic lesion filled with cerebrospinal fluid (CSF),  and the presenting symptoms depend on the location and mass effect of the cyst and include headache, gait disturbances, cognitive decline, weakness, and epilepsy. Major treatment approaches for symptomatic IAC include microsurgical resection of the arachnoid cyst wall, craniotomy for microsurgical fenestration, combined craniotomy for microsurgical fenestration, and communication between cysts and a ventricle or a neighboring cistern (cystoventriculostomy or cystocisternostomy), endoscopic fenestration, combined endoscopic fenestration and cystoventriculostomy or cystocisternostomy, cystoperitoneal shunt, and stereotactic aspiration. We report our experience with 68 adult patients with IAC.
Medical records and outpatient charts of all adult the 68 patients with IAC symptoms, who underwent surgical treatments between January 2004 and 2011, were retrospectively analyzed for age, sex, presenting symptoms, associated abnormalities, psychomotor status, electroencephalography (EEG), treatment modality, complications, and follow-up. All diagnoses were confirmed by neuroimaging during surgery and histopathological examination.
Of the 68 patients, 43 males and 25 females and the age range was between 18 and 43 years (mean age 30.3 years). The cyst location was supratentorial in 53 and infratentorial in 15 patients. All the patients with epilepsy were on regular antiepileptic drug therapy for 6 years to 14 years. The present symptoms included: Headache, in 51 (75%), hydrocephalus and gait disturbances in four (5.88%), cognitive decline and weakness in five (7.35%), and epilepsy in eight (11.76%).
Of the 53 (77.94%) supratentorial cysts, 21 (39.62%) were in the, 24 (45.28%) in the middle cranial fossa, 3 (5.66%) in the intraventricular region, 4 (7.55%) in the pineal area, and 1 (1.19%). in the cerebral convexity On neuroimaging mass effect was found in 66 (97.06%) of 68 cases in the form of neighboring sulcus shallowing or disappearance, sylvian fissure neighboring vascular shifting, ventricle depression, and midline shifting.
A total of 51 cases underwent regular EEG. Mild abnormalities were observed in 19 patients, moderate abnormalities in 14 patients, severe abnormalities in 13 patients, and no abnormality in five patients. Additional video-EEG monitoring was performed in all patients with epilepsy, and the presence of epileptic foci strongly conformed to the cyst location.
Selection of an individual surgical strategy for IAC mainly depends on the symptoms, location, cyst volume, intracapsular pressure, and postoperative ability of cooperation. Patients were grouped into three groups depending on the type of surgical procedure done [Table 1].
Group I microsurgical craniotomy group
This procedure was done in 29 (42.65) patients. One patient with cerebral convexity cyst and three patients with middle cranial fossa cysts underwent total cyst wall excision. Five patients with middle cranial fossa and four patients with infratentorial IAC underwent significant cyst wall excision. Eight patients with sylvian fissure cyst and five patients with middle cranial fossa cyst underwent combined microsurgical fenestration and cystocisternostomy. One patient with cyst in the intraventricular region and two patients with cyst in the pineal area underwent microsurgical fenestration and cystoventriculostomy. Additional anterior temporal lobectomy and neighboring cortical thermocoagulation was performed in two and six patients with epilepsy, respectively. Such operations were executed according to the findings of epileptiform discharges detected by intraoperative electrocorticography (ECoG) monitoring [Figure 1].
Group II endoscopic group
This procedure was done in 36 (52.94%) patients: 13 patients with sylvian fissure cyst, 10 patients with middle cranial fossa cyst, two patients with intraventricular region cyst, two patients with the pineal area cyst, and in nine cases of infratentorial cyst. All patients were treated after 2008 and underwent endoscopic fenestration and cystoventriculostomy or cystocisternostomy [Figure 2].
Group III cystoperitoneal shunting group
This procedure was done in three (4.41%) patients. One patient with IAC in middle cranial fossa and two patients with infratentorial arachnoid cyst were selected for cystoperitoneal shunting.
Of the 51 patients with headache, 44 (86.27%) had complete relief from the symptom, five (9.80%) patients had significant improvement, and two (3.92%) patients had no change. Three of the four patients with hydrocephalus and gait disturbances had complete improvement in their symptoms and patient had significant improvement. Of the five patients with cognitive decline and weakness, three (60.00%) patients had improvement and two patients had no change. Five (62.59%) of the eight patients with epilepsy had seizure remission, 2 (25.00%) patients had significant improvement, and 1 (12.50%) patients showed no change. According to the Engle class, 87.50% of patients had either seizure freedom or non-disabling seizures [Table 2].
No operative mortality in our series was recorded. Complications observed were discussed under each surgical group.
Microsurgical craniotomy group
Subdural hematoma occurred in five patients; hematoma evacuation was done in one patient and others were managed conservatively. Subdural hygroma occurred in four patients and all were observed conservatively. Follow-up revealed a significant reduction in volume and no mass effect. Meningitis occurred in two patients, which was treated with proper antibiotics. A follow-up after more than 1 year revealed secondary hydrocephalus in one patient whose postoperative computed tomography (CT) scan showed presence of blood in basilar cisterns. This patient underwent another shunt operation. Neither CSF leakage nor a new neurologic dysfunction was observed.
Subdural hematoma and subdural hygroma were observed in three and five patients, respectively. All the patients were managed conservatively. CSF leakage from an incision occurred in one patient, who was treated with reinforced suture and tight head bandages for 10 days. One patient had a transient ptosis probably related to third nerve palsy. Secondary hydrocephalus was observed in two patients after a follow-up of more that 15 months; post-operative CT scan indicated presence of blood in the lateral ventricles. These patients underwent another shunt operation.
Cystoperitoneal shunting group
Hydrocephalus recurred in one patient after a follow-up of more than 2 years and had another shunt operation.
The follow-up period of the microsurgical craniotomy group ranged between 15 months and 8 years (mean 3.8 years), that of the endoscopic surgery group between 12 and 24 months (mean 16 months), and that of the cystoperitoneal shunt group between 17 months and 8 years (mean 2.7 years). All patients underwent regular CT scans every 3 months in the first post-operative year. CT scan was performed annually after the first post-operative year.
Follow-up CT scans showed that the mass effect due to IAC in 68 cases had been alleviated to varying degrees, cystic size was significantly reduced in 51 patients, and no significant change was observed in two patients with supratentorial arachnoid cysts. Seven patients with infratentorial cysts showed a marked reduction in size, whereas eight patients exhibited no significant changes. In three patients with enlarged head circumference, there was no increase in the head circumference.
Two (6.89%) patients from the microsurgical craniotomy group and two (5.56%) patients from the endoscopic group had another shunt operation. The shunting device for one patient in the cystoperitoneal shunting group was changed.
The operative indication and the best surgical management for patients with IAC remain controversial. Incidental finding of IAC following extensive application of neuroimaging have been reported. In addition, numerous issues on the management of asymptomatic lesions have been raised. ,,, In this study, we reviewed the data of the symptomatic IAC and focused on the selection of appropriate surgical management. Neurosurgeons agree that patients with IAC with symptoms of intracranial hypertension, intractable seizures, and focal neurologic deficits warrant surgical management. ,, The selection criteria for surgical management mainly depend on clinical manifestations at presentation, signs, location, volume, age, intracapsular pressure, and the distance between the lesion and the neighboring ventricle or cistern. We performed microsurgical craniotomy, endoscopy, and cystoperitoneal shunting during the study period. Patients were totally selected to undergo microsurgical craniotomy or cystoperitoneal shunting for lack of an endoscopic technique before 2008. The following operations were mostly conducted by endoscopy.
We selected microsurgical craniotomy for patients with arachnoid cysts located in the cerebral convexity or whose preoperative diagnosis was cystic tumor, cyst-related epilepsy, or lack of endoscopic facility. Total resection of the small arachnoid cyst or partial resection of the cyst wall could be performed as much as possible for full fenestration. The combined use of microsurgical fenestration and cystoventriculostomy or cystocisternostomy was performed simultaneously. Microsurgical craniotomy provides a full space to manipulate ECoG monitoring to capture epileptiform discharges and confirm the epileptic foci. This approach also allows performing another procedure called focus excision or cortical thermocoagulation. No significant difference in therapeutic effect and reoperation rate between microsurgical craniotomy and endoscopy was observed in this study. The reoperation rate in the microsurgical craniotomy group (6.89%) was significantly lower than that in the cystoperitoneal shunting group (33.33%). Microsurgical craniotomy was more invasive than either endoscopy or cystoperitoneal shunting. However, compared with the other two methods, the microsurgical technique can obtain greater control of hemostasis because of the ability to use bipolar forceps. A full space ensures the ability to perform another operation for cyst-related diseases, especially in cyst-related epilepsy. Extensive and mature application of endoscopic technique is expected to replace microsurgical craniotomy treatment gradually; however, the latter technique is more efficient for cortical arachnoid cysts, cyst-related epilepsy, or cysts with preoperative diagnosis showing the possibility of a cystic tumor, according to previous studies. 
Endoscopic treatment is the newest technology among the three methods mentioned above. This treatment involves the use of a high-definition and stereo vision system to observe the arachnoid cyst and its neighboring structures. In addition, the technique provides an easy and minimally invasive method of performing cystoventriculostomy or cystocisternostomy. We used a retractable film to form an inner channel to control the shifting of a neighboring cerebral tissue or vessels, ensure that the flushing liquid flows continuously and unobstructed as well as lessen the possibility of injury between the cerebral tissue and the hard passage. The materials used showed that endoscopy gained similar therapeutic effects with low reoperation rate to microsurgical craniotomy group for IAC. Therefore, endoscopy is a safe and effective therapeutic modality for all kinds of IAC, especially those located in the suprasellar and quadrigeminal regions as well as the posterior fossa. ,,
Only three patients had undergone this method, and only one patient had this surgical treatment after we had endoscopy. We chose cystoperitoneal shunting for the middle-fossa IAC with a significant volume to avoid over drainage and fierce variation in intracranial pressure, lessen the occurrence rate of epidural or subdural hematoma, and fully informed the possibility of reoperation for alternating the shunt device. This patient had his reoperation for alternating the shunt device during the follow-up time of 1 year. The other two patients showed satisfactory outcomes without complications. We avoided shunt placement as the first treatment option in our review of literature and material and methods section.  If cystoperitoneal shunt is necessary for alleviating the symptoms or avoiding complications caused by the fierce variation of intracranial pressure, the use of a cystoperitoneal shunt with an adjustable valve is highly recommended. ,
Advancing technology provides us a new choice of treatment for IAC. However, no gold standard criteria exist for different individuals. We conclude that the endoscopic approach is highly effective for most cases of IAC, especially for cysts in the suprasellar and quadrigeminal regions, as well as posterior fossa. Microsurgical craniotomy is recommended for cortical arachnoid cysts or cysts with the possibility of a cystic tumor or cyst-related epilepsy. Cystoperitoneal shunting is effective for large-volume cysts, particularly by using the shunt device with an adjustable valve.
[Figure 1], [Figure 2]
[Table 1], [Table 2]