Neuroendoscopy is a further advance in "adequate" minimally invasive microsurgery, which means a further reduction of damage to normally functioning tissue while maximizing the effectiveness of the impact on pathology. Endoscopy of the central nervous system, however, is more complicated than general surgical endoscopy: unlike arthroscopy or peritoneal and thoracic endoscopy, here one has to work in the ventricle or the cyst of the brain in the cerebrospinal fluid, "underwater" (except for the necessary, difficult draining in case of severe bleeding). Gas insufflation or any excess pressure with perfusion of fluids to optimize the endoscopic field of view is prohibited (except for discoscopy). Therefore, stopping bleeding (preventive measures are desirable) requires absolute precision, also, maximum sterility is required. Therefore, the sensitive CNS requires special small-diameter endoscopes, special washing techniques, and special endoscopic instruments and operating techniques.
For this, a whole system was developed for two main methods of neuroendoscopy:
- for neuroendoscopy through an air-filled cavity: in this case, the endoscopic operation is carried out through an existing, if necessary enlarged natural cavity (for example, our kit for transnasal neurosurgery) or through an artificially prepared access, for example, in endoscopically assisted or controlled microsurgery or during surgery of the carpal and cubital canals. For transnasal and endoscopically assisted surgery, we use partly the same endoscopes that are installed with a holder at an optimal distance to view the processes; work with modified microsurgical instruments is carried out around the endoscope, hemostasis and tissue ablation are carried out according to the same principles, but, for example, with special instruments, as in microsurgery (monopolar, pseudo-monopolar and bipolar coagulation, ultrasonic aspiration, etc.). For intracerebral endoscopic access using a speculum, we use transnasal mirrors with a blunt trocar and neuronavigation positioning, preferably also with a holder
For the carpal and cubital canals, the same endoscopes are used as for ventriculoscopy, with only partially modified light guide access (30° optics) and special slotted cannulas / hook knives for the (bipolar) carpal tunnel technique.
- for neuroendoscopy in the central nervous system cavity filled with CSF: Here, access to the cavity filled with cerebrospinal fluid is carried out by puncture using a guide tube ("operating tube"); in this case, a blunt trocar in the operating sheath can be introduced using neuronavigation. Also during puncture, the particularly thin Hopkins II telescope provides a "trocar tip" view through an optical obturator. Then the optics is introduced into the operating tube, which simultaneously directs special operating instruments (in the central nervous system, mainly monoportal, "coaxial" access is used).
With neuroendoscopy in a cavity filled with cerebrospinal fluid, there are again two principles:
- "Channel endoscope" ("channel endoscope"): The sheath (eg a DECQ endoscope) or the endoscope itself (eg a "miniature endoscope") has several channels that guide instruments with the appropriate diameter and are used for flushing (separate inflow and outflow!). The advantages lie in the precise guidance of the instruments and the mechanical protection of the endoscope, while the disadvantage is the small working lumen of the canals, which hardly allows the removal of the significant tumor and cystic areas or the implantation of vascular endoprostheses, as well as effective hemostasis. Therefore, we use this principle with instruments with a particularly small, atraumatic outer diameter of the whole tube <4.5 mm only for ventriculostomy and cystostomy, for example, when operating on small children; if necessary, this principle can also be combined with biopsy using well-guided, straight instruments with a diameter of 1 mm.
- "Spatial endoscope" ("space endoscope"): here, the entire cavity of the operating sheath is used for work. First, a diagnostic endoscopy is performed using a 4 mm Hopkins II endoscope for optimal quality; Along with straight optics, it is possible to use angled optics (30°, 45°, 70°), which provide a view of the entire cavity (ventricle, cyst) and can be rotated 360°. The particularly thin 2 mm endoscope leaves most of the guide channels free for surgical manipulation, allowing the use of a flushing cannula and instruments up to 3 mm. Together with the endoscope, large tumor areas can be removed, and vascular endoprostheses can also be inserted. The sensitive 6° operating endoscope, which shows the instrument in the center of the field of view, must be used with a protective case.