Intracranial arachnoid cysts are very common benign lesions in children, and their incidence accounts for approximately 1% of intracranial lesions in children, 90% of which are located in the superior curtain and 60% in the middle cranial fossa (also known as lateral fissure arachnoid cysts). Because the exact pathogenesis and natural history are not fully understood, there are no guidelines for the treatment of arachnoid cysts. The vast majority of arachnoid cysts are found asymptomatically and incidentally; a few cysts can increase in size progressively and present with headache, ruptured cyst bleeding, subdural effusion, and epilepsy. For patients with symptomatic arachnoid cysts, it is recognized that they should be treated surgically; for asymptomatic patients, it is more controversial whether to give prophylactic surgical treatment.
1. Natural history of arachnoid cysts
The exact natural history of arachnoid cysts is not clear. Since the majority of patients are detected by cranial imaging, long-term neuroimaging observations can help to understand the natural course of arachnoid cysts. In a study of 11,738 children with 11 consecutive years of MRI, the detection rate of arachnoid cysts was 2.6%; among 111 children with a mean follow-up of 3.5 years, the arachnoid cysts increased in size in 11 (9.9%), decreased in size in 13 (11.7%), and remained unchanged in 87 (78.4%); low age was strongly associated with cyst enlargement, with all children >14 years old at the time of the first visit. All children >14 years of age had no cyst enlargement or new symptoms at the first visit. Another MRI examination of 48417 consecutive adults over 12 years found that the detection rate of arachnoid cysts was 1.4% (661 cases), of which 94.7% were asymptomatic and only 5.3% (35 cases) were symptomatic, with 24 of the symptomatic cases (3.6%) requiring surgical treatment. Although the majority of arachnoid cysts are asymptomatic, a small percentage of patients develop spontaneous cyst rupture or hemorrhage, which can be life-threatening in severe cases, with a rate of 6%, and arachnoid cysts >15 cm in diameter are more likely to rupture. The literature confirms that arachnoid cysts >5 cm in diameter and recent head trauma are risk factors for cyst rupture or hemorrhage.
2. Indications for surgery of arachnoid cysts
Symptomatic arachnoid cysts should be treated surgically, and the indications include.
(1) obstructive hydrocephalus due to the cyst.
(2) Increased intracranial pressure.
(3) Epilepsy clearly associated with the cyst.
(4) Focal neurological deficits.
(5) progressively enlarging cysts
(6) subdural effusion or hematoma due to cyst rupture.
It is controversial whether prophylactic surgery should be performed in asymptomatic individuals, especially for arachnoid cysts >5 cm in diameter. Proponents argue that cysts >5 cm in diameter are at greater risk of rupture and bleeding and should be treated with aggressive surgical intervention; opponents argue that the risk of rupture in larger cysts is only 6% and that surgical treatment even when ruptured and bleeding does not affect the patient’s prognosis at all.
Combined with the natural history of arachnoid cysts, asymptomatic patients aged ≤4 years, especially infants, should be reviewed semiannually with neuroimaging (CT or MRI) and actively operated on if the cyst is progressively enlarging with corresponding symptoms; if the cyst is enlarging but still asymptomatic, surgery can be considered for those >6 cm in diameter, while those ≤6 cm can continue to be observed. For patients aged >4 years, the possibility of cyst enlargement is obviously reduced, and CT or MRI can be reviewed once a year to compare whether there is any change of cyst, during which patients are advised to avoid strenuous exercise and head trauma, etc.; once symptoms such as headache and vomiting appear, cT or MRI should be reviewed promptly, and it is confirmed that cyst rupture is feasible by drilling and drainage or craniotomy to remove the hematoma.
3.Surgical methods
At present, the main surgical methods are
(1) open cranial cyst wall resection or cyst windowing surgery.
(2) endoscopic cystocephaloplasty.
(3) cyst-abdominal shunt.
A recent Meta-analysis showed no significant difference in the impact of these procedures on patients’ quality of life at 5 years after surgery.
The international surgical approach to arachnoid cysts is more often open and endoscopic. 2008 results of a survey of pediatric neurosurgery centers internationally (excluding mainland China) for surgical treatment of lateral split arachnoid cysts in children showed that 66.6% of physicians chose open cystotomy, 28.8% chose endoscopic cystostomy, and only 3 (5%) pediatric neurosurgery centers preferred cyst -There were differences in the efficacy of the three surgical procedures, in which the shrinkage rate of the cyst after craniotomy was 92% and the near total disappearance rate was 51%; the shrinkage rate of the cyst after endoscopic cystostomy was 75% and the near total disappearance rate was 39%; and the shrinkage rate of the cyst after cyst-abdominal shunt was 100% and the near total disappearance rate was 89%. In terms of cyst disappearance rate and shrinkage ratio, cyst-abdominal shunt was the most effective. However, Shim et al. reported that among 19 patients who underwent arachnoid cyst-abdominal shunt, 8 cases developed shunt dependence after surgery, with a mean of 6.1 years postoperatively, a rate as high as 42%; and in 11 of these cases in which the cyst disappeared completely, when ligation of the shunt was attempted in order to remove the shunt, it was successfully removed in 8 cases. Overall, cyst-abdominal shunts are rarely preferred by foreign pediatric neurosurgeons for the treatment of arachnoid cysts. Instead, the use of endoscopic treatment has been increasingly reported in recent years.
Unlike the choice of most pediatric neurosurgeons internationally, many hospitals in China, because of the absence of neuroendoscopy, the complications of open surgery, or other factors, prefer cyst-laparotomy for the treatment of arachnoid cysts. Cyst-abdominal shunt is widely used at home and abroad because of its simple operation, small trauma, highest cyst disappearance rate, good postoperative efficacy, low recent complications, and can be used as the final remedy for craniotomy and endoscopic surgery. Especially in the past 20 years, under the influence of domestic conference exchanges and professional journals, many hospitals have carried out cyst-abdominal shunt surgery to treat arachnoid cysts. In the past 10 years, domestic literature advocates the use of low-pressure common shunts, which can quickly achieve significant reduction or even disappearance of cysts, with a reduction or disappearance rate of up to 95%, much higher than that of open surgery or endoscopic fistula surgery, with excellent imaging and recent surgical results. However, with the prolonged application time, the long-term complications of cysto-abdominal shunt gradually emerge, including obstruction, rupture of the shunt, benign intracranial pressure increase, lacunar ventricular syndrome, shunt-dependent syndrome, etc., especially the shunt-dependent syndrome is more serious and poses the greatest threat to the children. Due to the low incidence of shunt dependency reported in the literature, it has not yet attracted sufficient attention, and many primary care hospitals are still widely performing arachnoid cyst-abdominal shunts. However, in fact, the incidence of shunt dependency is gradually increasing, from l% in early reports to 13%, and in the past 3 years, Beijing Tiantan Hospital of Capital Medical University has treated more and more patients with shunt dependency after cyst-abdominal bypass (preliminary statistics are about 20%. A small number of cases are from the early surgery of this hospital, and most of them are from outside hospitals in recent years after surgery). The rate of shunt dependency reported in foreign literature is even as high as 42%. This rate may continue to increase with time. Early on, this defect of shunt dependency could be ignored because of its extremely low incidence, but with the prolongation of time, rates as high as 13-42% have become fatal defects of cyst-laparoscopic shunt surgery.
Children who develop shunt dependency after cyst-abdominal shunt present with progressively recurrent headache, vomiting, and eye distention from six months to more than 10 years (mean 6 years) after the cyst has largely disappeared, with a short duration of intermittent weekly episodes in the early stages, followed by progressively more frequent episodes, several times a day, each lasting from several minutes to several hours, with severe headache in the later stages, significantly higher lumbar puncture pressure, fundus image CT and MRI showed lacunar ventricles. These patients are basically treated with low-pressure shunts for arachnoid cysts for several years or even up to 10 years after surgery, and the arachnoid cysts are often no longer visible on neurological imaging, and patients are often seen in neurology and are often misdiagnosed as “venous sinus occlusion Patients are often seen in neurology and often misdiagnosed as “venous sinus occlusion”, “benign intracranial pressure increase” and delayed treatment, and individual patients even go blind due to severe intracranial pressure increase and optic papilloedema.
As for the treatment of patients with shunt dependence after cyst-peritoneal shunt, it is extremely difficult at present, among which it is extremely difficult to perform ventriculoperitoneal shunt surgery in the lacunar-like ventricle, even in the large neurosurgery center can perform lacunar ventriculo-peritoneal shunt under navigation, although it can solve the problem temporarily, but the symptoms of shunt obstruction will still recur later; the rate of subungual herniation of the cerebellum in the distant stage of lumbar pool peritoneal shunt The rate of subungual herniation is extremely high. Once the ventral shunt of the lacunar ventricle becomes obstructed again, and the lumbar pool ventral shunt becomes herniated, there will be no effective treatment, which will be disastrous for both doctors and patients.
In conclusion, treatment of intracranial arachnoid cysts should be cautious, long-term follow-up observation should be the main focus for asymptomatic patients, and surgical treatment should be chosen with extreme caution; surgical modalities should be carefully chosen for symptomatic patients, and although cyst-abdominal shunt surgery has the best cyst reduction and disappearance rates and the advantages of simplicity, efficiency, and few complications, the high risk of potential shunt dependence must be faced squarely; craniotomy cyst open cyst and endoscopic cystostomy, although with lower cyst disappearance and reduction rates, can avoid distant shunt dependence.