Avoidance or minimization of complications in the endoscopic treatment of hydrocephalus, like any other surgical procedure, requires the operator to understand the intricacies of the relevant anatomy, the steps of the procedure to be performed, and the advantages as well as limitations of the instruments to chosen for use.

Beginning with the layout of the operating theatre, the location of the surgical bed, the surgical assistants, the surgical equipment and instruments, and the monitors must be considered. It is important to ensure that the surgeon is able to comfortably work about the patient’s head while simultaneously visualizing the endoscopic view via monitors without placing themselves in an uncomfortable or disadvantageous position. Concurrent with this, the assistant must be able to follow the progression of the procedure while being able to aid the surgeon without spatially interfering with the operator’s tasks.

In positioning the patient, the operator must choose in such a way as to take into consideration that which will facilitate visualization of the surgical objective but also maximize the ergonomic advantage for the surgeon. This includes the height of the bed, how the patient’s head is angled or rotated, as well as how the patient’s head is supported (donut on bed versus horseshoe versus pin fixation). When choosing how to position the patient’s head, the approach and site of the burrhole to be used must also be considered. The goal in this instance is in understanding the objectives of the surgery, choosing a burrhole location that provides a trajectory allowing the operator to maximize visualization of the target structures and simultaneously minimizing the scope’s movement and avoiding unnecessary pressure on sensitive structures. Large, sweeping motions of the endoscope while within the ventricle should be avoided as these can cause direct injury to the traversed cortex as well as the structures that reside in the blind spot of the endoscope such as the blood vessels or the fornices [6, 27, 32, 33].

The surgeon should ensure that the appropriate instruments needed are present in the operating theatre and functioning appropriately. Time should be taken to ensure the endoscope camera is aligned properly to help with maintaining surgical orientation; the surgeon must also ensure that the optics of the endoscope provide for adequate image quality and the light source is sufficiently bright before beginning a procedure. Further, the surgeon must determine if the appropriately sized instruments are present. Consider, for example, the case of an ETV. How extensively is the foramen of Monro dilated? Is the endoscope chosen of adequate diameter to traverse the foramen safely? Attempting to traverse the foramen of Monro with an inappropriately large endoscope places the fornix and thalamus at risk for injury, as well as the associated vascular structures such as the choroid plexus, septal vein, and caudate vein. Is the angle of the endoscopic optics (e.g., 0°, 12°, or 30° scope) appropriate to allow simultaneous visualization of the appropriate structures and working instruments to pass down the working channel?

Continuing with the example of an ETV, how and where is the operator anticipating fenestration of the floor of the third ventricle? At risk with this maneuver are the thalamus and hypothalamus laterally, mammillary bodies, corticospinal tracts, and the remainder of the brain stem posteriorly, the infundibulum and optic apparatus anteriorly, and the oculomotor nerve as well as the basilar artery with its associated arterial branches beyond the ventricular floor. Ideally, a point in the midline, halfway between the infundibular recess and mammillary bodies, should be chosen to minimize injury to the adjacent structures (particularly the hypothalamus, infundibulum, and brain stem structures). Blunt fenestration using a Fogarty balloon or Bugbee wire may reduce the risk of a vascular injury but alternatively may increase the risk of hypothalamic injury [27]. Alternatively sharp fenestration utilizing a closed dissection forceps, a bipolar cautery, or a contact laser is thought to reduce the risk of hypothalamic injury associated with traction upon the floor of the third ventricle but in turn may increase the risk of injury to the vascular structures and cranial nerves deep to the ventricular floor, or result in thermal injury to surrounding tissues [6, 7, 27, 28].

Along these same lines, when performing an aqueductoplasty, choosing the adequate scope size and optic angle is essential not only for passing the foramen of Monro but also for visualizing the outlet to the aqueduct of Sylvius. Further, when dilating or stenting the aqueduct, the size of the balloon to be used, along with the amount of liquid or air used to inflate the balloon, and the outer diameter of the stent to be placed must be carefully considered. The tectum, comprising the roof of the aqueduct, is exquisitely sensitive to pressure, and the resultant injury to extraocular gaze, particularly vertical gaze, can be easily encountered [23–25, 27, 31, 34].