Robotic Endoscopic Neurosurgical Interventions

Endoscopic procedures, as part of a transnasal pituitary adenoma resection (intervention through the nose to the base of the skull to remove tumors) or ventriculostomy (punctiform opening of a brain chamber to create a bypass circuit for the cerebrospinal fluid), are among the most frequent neurosurgical interventions performed worldwide. The endoscope (ancient Greek: "observe inside") is used for the precise examination of cavities in the context of these minimally invasive interventions. It consists of a rigid tube (diameter approx. 4mm) which transmits the image information of the object or room to be examined through a lens system inside the endoscope shaft to the eyepiece. The light required for the procedure is transmitted from the light source to the tip of the endoscope via the connected light guide, also inside the shaft, through fiber optic bundles.

During neurosurgical interventions, the endoscope is usually guided manually by a second operator. The problem with this manual guidance is the constantly necessary implementation of minimal corrective movements or clouding of the lens due to tissue contact. In case of long lasting interventions, there are also signs of fatigue which lead to unwanted movements of the endoscope. Due to the resulting limited precision and trauma to surrounding tissues, complications and inconclusive results can occur.

In the last 10 years, different surgical devices have been developed to increase procedural accuracy in the field of neurosurgery. For instance, a group presented an automated approach with redundant navigation for minimal invasive extended transsphenoidal skull base surgery successfully performed on cadaveric heads. Furthermore, an assistance system for extended endoscope transsphenoidal skull base surgery has been developed which allowed the simultaneous use of two instruments under endoscopic view. Another approach was to use a force controlled robotic system on bone specimen to increase accuracy for bone milling.

In cooperation with two industrial partners, the COMET Center ACMIT (Austrian Center for Medical Innovation and Technology) developed the MicroMate guidance device that also forms the base for the Stealth AutoGuide system from Medtronic plc. MicroMate is a modular guidance system for surgical invasive tools which provides a precise, submillimetric (<0.1 mm) trajectory alignment according to the predefined navigation data. The setup is based on the iSYS1 robot system, also developed by ACMIT, and on input gained in the course of a clinical trial that has been conducted at the Department of Neurosurgery, Medical University of Vienna 4-10. Notably, none of the two setups mentioned above does impinge on the surgical procedure by itself, nor does it advance any object into the patient. The neurosurgeon remains in control of the instruments during the whole procedure.

The robot used in this study (EndoGuide v2 by ACMIT Gmbh) uses exactly the same mechanical and electronic components as the MicroMate/Stealth AutoGuide system. The only difference between the two CE/FDA certified robots and the EndoGuide platform is a firmware extension to provide a tool pivoting function that allows the endoscope to be rotated around any point along the endoscope shaft. The rotation of the endoscope thus gives the user different views of the area to be viewed.

Aim of the Project The aim of the present study is to evaluate the feasibility and clinical value of the EndoGuide robotic guidance device for intraoperative trajectory alignment in endoscopic neurosurgical procedures (transnasal transphenoidal surgery; ventriculostomy) as compared to the standard freehand method.

With the intraoperative application of the robot the investigators expect:

• an increase in the accuracy of endoscopic interventions and thus a reduction in intervention- related morbidity,
• a reduction in trauma and thus also in secondary bleeding in the context of endoscopic interventions.

Rationale Null hypothesis: There is no significant difference between the accuracy of the endoscopic guidance using the robotic guidance device and the accuracy of the manual method. Primary hypothesis: The intraoperative application of the robotic guidance device for precise trajectory alignment significantly increases the accuracy of navigation-guided endoscopic procedure as compared to the standard manual method and thereby reduces procedure-related morbidity.

1. Hypothesis: The intraoperative application of the robotic guidance device for endoscopic neurosurgical procedures is feasible.
2. Hypothesis: The intraoperative application of the robotic guidance device increases procedural safety.

Objectives Main Objective: Assessment of Target Error as a Measure for Accuracy The target error (TE) measured in mm, corresponds to the distance between the true (surgically performed) trajectory that has been aligned by the robot and the preoperatively defined trajectory stored on the navigation system.

Using fusion of routine pre- and postoperative radiological images, this distance can be calculated with the navigation system software. Study data will be saved in a password-protected data-base only accessible for study personnel.

Secondary Objectives

Additionally to accuracy, the investigators will test for the following measures:

• Rate of procedure-related adverse effects (e.g. hemorrhages)
• Total procedure time (time from skin incision to suture) and setup time (time from positioning the patient to skin incision)