1.What is a triple ventriculostomy? The cerebrospinal fluid circulates from the bilateral ventricles to the third ventricle and then through the only narrow pathway in the posterior part of the third ventricle, the midbrain aqueduct, to the fourth ventricle. EndoscopicThirdVentriculostomy (ETV) is a procedure in which a pathway is artificially created at the base of the anterior third ventricle using a ventriculoscopic technique to divert cerebrospinal fluid from the third ventricle to the anterior pontine pool, thus solving the problem of obstruction of cerebrospinal fluid circulation at the stage of the middle cerebral aqueduct and the fourth ventricle. The ETV pattern is shown (image adapted from the Internet), in which the ventriculoscope is drilled through a 2-cm-diameter hole next to the frontoparietal midline, and the ventriculoscopic fistula is inserted into the ventricles through the frontal cortex to open the base of the three ventricles (the red circle at the end of the ventriculoscope in the figure) and divert the cerebrospinal fluid from the three ventricles to the anterior pontine pool. The figure shows the intraoperative view of the base of the triple ventricle fistula (image adapted from the internet): (A) The balloon is extended into the ventricle through the sheath of the mirror and the balloon is propped open at the base of the triple ventricle to perform the fistula. (B) A manually opened foramen is visible at the base of the triventricular space after fistula. 2. What are the advantages of a fundoplication? The advantage of ETV is that it avoids carrying a tube and is more in line with the physiological structure of human cerebrospinal fluid circulation than ventriculo-abdominal shunt. In recent years, with the development of neuroimaging, optical technology, microsurgical instruments and stereotactic neuronavigation system, rigid ventriculoscopy and flexible ventriculoscopy have been gradually promoted, making the surgical method of triventriculostomy constantly updated and the indications broadened. At the same time, endoscopic tricompartmental fundoplication can also be performed with hyaline septal fistula (to resolve lateral ventricular inaccessibility on both sides), midbrain aqueduct dilation and shaping (to resolve midbrain aqueduct stenosis), choroid plexus electrocautery (to resolve excessive secretion of cerebrospinal fluid from the choroid plexus), and tumor biopsy (to clarify the tumor nature of obstructive hydrocephalus caused by tumors). Soft ventriculoscopy has a wider range of exploration and is more suitable for complex hydrocephalus management. 3.What is the effectiveness of triple ventriculostomy? Overall, endoscopic treatment is currently effective in more than 2/3 of children with hydrocephalus, and can resolve more than half of all hydrocephalus in children, thus avoiding shunts. The best indications for ETV include obstructive hydrocephalus in infants and children older than 6 months of age, with an effectiveness rate of more than 2/3. For infants younger than 6 months of age, the overall effectiveness rate is approximately 1/3, because the cerebrospinal fluid circulation is not yet mature in infants younger than 6 months of age, and some congenital hydrocephalus is often associated with anomalies in the floor of the three ventricles and multilayered arachnoid structures in the anterior pontine pool, which affect the effectiveness of the fistula. The reason for this is that traffic hydrocephalus is caused by the obstruction of cerebrospinal fluid absorption, while the main problem solved by triventricular base fistula is the lack of circulation. The ETVSS (ETV Score, ETVSUCCESSSCORE) can be used as a reference to predict the efficiency of ETV in general before surgery. The figure shows the ETVSS, which is used to predict the efficiency of ETV (image translated from: KulkarniAVetal.JPediatr.2009) 4. ETV surgery is generally safe, but a certain percentage of complications can occur. Serious complications include intraoperative bleeding, bradycardia, and sometimes forced abortion of the procedure. Other complications include postoperative subdural effusion, subcutaneous effusion, cerebrospinal fluid leak, postoperative transient seizures, fornix contusion, and fistula closure. The operative mortality rate is 0-1%. The biggest problem with ETV surgery is that a proportion of hydrocephalus does not resolve postoperatively, which is differentiated on a case-by-case basis. If the hydrocephalus resolves once after ETV and then worsens again, it may be due to fistula closure, which can be explored by ventriculoscopy again, and if the fistula is found to be closed again, another fistula can be performed, but there is still a possibility of reclosure. If the intraoperative fistula is exact but the hydrocephalus is not significantly relieved after surgery, it is more likely that a ventriculo-abdominal shunt will be required.