Despite many advances in the management of hydro- cephalus since valve-regulated shunts were introduced longer than half a century ago, treatment of hydrocephalus without the need for implantable shunt devices remains a reasonable goal. The level of enthusiasm for the man- agement of hydrocephalus by performing endoscopic third ventriculostomy (ETV) as the initial treatment or at the time of shunt failure is increasing. Except in the very young, most patients with acute hydrocephalus can now be safely treated using this technique. 1 To date, a consensus on which patients are appropriate candidates for this procedure is lacking. 5 Some patients with hydrocephalus related to an obstructive process at the level of the sylvian aqueduct are not ideal candidates for ETV be- cause of clinical or anatomical factors. For these patients, cannulation of the sylvian aqueduct is an effective alter- native and may eliminate the need for extracranial shunt treatment. 4,6,7 In the November issues of the Journal of Neu- rosurgery and Journal of Neurosurgery: Pediatrics, two separate groups relate their experience with a new approach to treating such patients. The technique involves inserting an endoscope through the foramen of Magendie, traversing the fourth ventricle, and opening the aqueduct from below. Cannulation of the aqueduct through the fourth ventricle is not an entirely new concept. Lapras, who developed the catheter that bears his name and wrote about his experiences with its use, 2,3 inserted the device into the aqueduct from the fourth ventricle. The expansive tip at each end of the cathe- ter anchored it in the aqueduct. What is new about the tech- niques reported in the November issues is the use of mini- mally invasive techniques to open the aqueduct or to place a stent within it. The methods described in both articles are similar. In one technique a significant amount of bone is removed so that a rigid endoscope can be inserted to perform the procedure. In the other technique the procedure is attempted using a smaller, steerable endoscope, which eliminates the need for bone removal in most cases. Both articles demonstrate that the procedure is feasible and can be performed with a rela- tively low complication rate. Nevertheless, a number of questions remain. What pa- tients should be selected to undergo this procedure? What surgeon should attempt to perform such a procedure and after what training? How is this procedure tailored to the needs of individual patients? After a large number of these procedures have been performed at a great number of cen- ters, what will the rates of mortality and permanent morbid- ity be? What will the patients’ outcomes be? Is the risk of harm associated with this procedure equivalent to that asso- ciated with an ETV? Except for the last issue, these groups present some evidence to help answer these questions. The literature offers further clues. Relative to patient selection, Gawish and colleagues have defined poor candidates for ETV as patients in whom there is a narrow space between the mammillary bodies and the dorsum sellae, those in whom the basilar artery (BA) lies near the floor of the third ventricle, and those in whom the floor of the third ventricle has herniated into the sella turci- ca. If a short-segment closure of the sylvian aqueduct was found in such patients, they were selected for treatment with this innovative technique. Both groups of authors describe the risks associated with performing a third ventriculostomy, focusing particular at- tention on arterial injury and late sudden death. Unfor- tunately, neither article offers a denominator relating the percentage of patients treated with ETV or with shunt place- ment. This information would be quite helpful in analyzing selection criteria in these patients. Will a busy practice spe- cializing in hydrocephalus be likely to include a large num- ber of these patients? Fortunately, some information is available about the use- fulness of aqueductoplasty relative to ETV, albeit from a surgeon who performs the procedure from above. In an arti- cle on indications for aqueductoplasty, Miki and colleagues 4 found six patients in whom magnetic resonance (MR) im- aging studies revealed excessive risks for ETV. Of 110 pa- tients treated endoscopically, only those six patients (5.5%) underwent aqueductoplasty. Clearly patients with a Chiari malformation Type II (spi- na bifida) are not candidates for the trans–fourth ventricular J. Neurosurg. / Volume 103 / November, 2005 J Neurosurg 103:773–775, 2005 Editorial Endoscopic fourth ventricular aqueductoplasty HAROLD L. REKATE, M.D. Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 773 See corresponding articles in this issue of the Journal of Neurosurgery, pp 778–782, and in the November issue of the Journal of Neurosurgery: Pediatrics, pp 388–392.