Hi-Tech Tools in Skull Base Surgery

3D Endoscopy

• Endoscopes are part of the armamentarium of skull base surgeons, in both pure endoscopic and microsurgical endoscope-assisted approaches.1,2

• The lack of three-dimensionality of the two-dimensional (2D) endoscope has been compensated by the introduction of the three-dimensional (3D) endoscope systems,^3–5 with large applications in transsphenoidal surgery.^6,7

Advantages: 3D deepness of the surgical field, faster training curve for nonexperts.

Disadvantages: dizziness, fatigue, eyestrain,^3,8 cost, excessive magnification in some cases. The models that do not offer high definition lack fine differentiation of the colors of different structures.

Image-Guided and Robotic Skull Base Surgery

Neuronavigation technology has great advantages in skull base surgery, by fusing computed tomography (CT) and magnetic resonance imaging (MRI) and yielding real-time multiplanar images and 3D reconstructions for orientation during the approaches.

• Image guidance systems are optically based or work by means of electromagnetic tracking devices.

• Intraoperative CT and MRI offer real-time updates of the surgical results. Intraoperative MRI suites require dedicated instruments, such as nonferro-magnetic surgical instrumentation, and they are still in limited use because of their very high costs.

• Ultrasound-based navigation systems enable intraoperative navigation and visualization of different structures at lower costs than with intraoperative CT/MRI, with applications in open skull base surgery as well as in endoscopy.9–11

• Intraoperative navigation systems can be integrated with virtual endoscopy in endonasal transsphenoidal surgery, providing additional anatomic information and improving surgical orientation, especially in the presence of anatomic variants.^12,13

• Robotic surgery, such as the da Vinci^® surgical system (Intuitive Surgical Inc., Sunnyvale, CA) or the neuroArm^® (University of Calgary, Canada),¹⁴ which is an MR-compatible image-guided robot, enables free-hand surgery for multiple purposes, facilitating a precise, bimanual, tremor-free surgical dissection under microscopic 3D visualization. In the otolaryngology–head and neck surgery field, robotic surgery is used above all for transoral robotic surgery procedures,^15–18 with some limited case reports in skull base surgery by means of extended approaches (e.g., incision of soft palate and resection of hard palate). Its adoption and application in skull base surgery is currently limited by the size of the robotic arms and the instruments.

• Modifications of the Da Vinci robotic arms and concentric tube robotic instruments with needle-sized tentacle-like arms are currently under investigation for their use in robotic transnasal skull base surgery.¹⁹

Ultrasonic Surgical Aspirator

The available ultrasonic surgical aspirators include the Cavitron ultrasonic aspirator (CUSA; Valleylab, Boulder, CO), the Sonopet ultrasonic aspirator (Stryker, Kalamazoo, MI), and the Sonastar ultrasonic aspirator (Braun, Aesculap, Center Valley, PA). These tools use different technologies, and the interested reader should refer to the technical information provided by the manufacturers.

• A titanium tip oscillates at a frequency of 23 to 25 kHz (ultrasound), disintegrating tissue and, at the same time, aspirating it through a central channel.²⁰

• The level of irrigation, suction, and vibration can be set on the control counsel; a foot switch is used to activate the device.

• Different settings and several tip variations can be used for different kinds of tissues, including bone. By using low level of irrigation, the heat generated allows the aspirator to be used for cutting and/or coagulating.²¹

• Standard CUSA displacement: 10 to 350 µm.²²

• The manipulation of the hand piece provides “tactile feedback,” which is useful when treating difficult tumors, such as skull base meningiomas and schwannomas.²¹

• Specific microprobes and modified hand-pieces enable the use of ultrasonic aspiration in transsphenoidal surgery,23–26 facilitating the resection of the clinoid processes, clivus, odontoid process, and crista galli via the endonasal route.²⁷

• Ultrasonic aspirators have been shown to provide safe, quick, and effective devascularization of dura mater attached to the brain in cases of reoperation,²⁸ confirming its potential use in skull base surgery as well.

• Ultrasonic bone aspirators are safe, quick, and effective tools in orbital surgery,^29,30 turbinoplasty,³¹ skull base osteoma,³² and facial nerve decompression.³³

• Advantages: ultrasonic aspirators are very useful for debulking tumors and for partial hemostasis, as in the central debulking of vestibular schwannomas without damaging the capsule.

• Disadvantages: Ultrasonic aspirators are expensive tools. The disposable tip is also a disadvantage in that it adds to the cost.

The normal saline irrigating solution of the CUSA may be replaced by H₂O₂ (3%), offering an uninterrupted delivery of peroxide to the tumor at the same time as the ultrasonic aspiration is being done, potentially reducing blood loss in vascular tumors.^34,35

Water-Jet Dissection

Water-jet dissection has been shown to be useful for resection of brain tumors, with preservation of vessels and cranial nerves,³⁶ although it has not been standardized for use in skull base surgery.

• The pulsed laser-induced liquid jet (LILJ) is a hybrid technique in which the photoacoustic energy of the laser is used to provide high-flow kinetic energy in the water jet.^3,4

• An LILJ consists of a bayonet-shaped catheter incorporating a jet generator surrounded by a suction tube, with the jet energy source provided by a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser system. The laser pulse forms a large vapor bubble in the water flow and provides an expansion of the confined vapor bubbles, causing a high-velocity pulsed liquid jet (velocity ~ 20 m/s).

• The temperature of the water jet remains below 37°C (41°C is the temperature reported to cause neuronal damage^37,38).

• An LILJ has been shown to provide precise dissection of skull base tumors (pituitary adenomas, meningiomas, craniopharyngiomas), with the great advantage of sparing perforators around tumors and preserving visual function.^39,40

Laser

Used since the 1960s, lasers have wide application for surgical removal of intracranial tumors. It is also used in skull base surgery and endoscopic transsphenoidal approaches.

• The laser wavelength is absorbed by water. The laser is used to vaporize and coagulate small vessels.

• Lasers can be conveyed through a flexible optical fiber (diameter ~ 1 mm) and can be set at different powers, exposure times, and in pulsed or continuous wave.

• The neodymium (Nd):YAG laser has a wavelength of 1,060 to 1,340 nm. It is widely used in neurosurgery,41,42 although it has deep penetration and entails the risk of tissue injury.^43,44

• The CO₂ laser has also been used in neurosurgery⁴⁵, with the same limits of thermal dispersion in the tissue.⁴⁶ The problem of thermal dispersion is less relevant in endonasal surgery, and CO₂ laser can be used for pedicled nasoseptal flap tailoring.⁴⁷

• The thulium laser, initially used for third ventriculostomy, has a more limited penetration and diffusion, in comparison with the other kinds of lasers, and higher cut precision.⁴⁸

• The thulium laser is used in meningioma surgery for debulking, shrinking, and coagulating the tumor as well as its basal implant.^49–51

• Lasers can be used under continuous irrigation to reduce the thermal damage on the peritumoral structures.

• In comparison to the CUSA, the thulium laser adds to the debulking/shrinkage of the tumor as well as the coagulation of the tissue and small vessels, avoiding the use of the ultrasonic aspirator with a bipolar.

Surgical Anatomy Pearl

Cranial nerves and vessels around the tissue should be protected with cottonoids.

Only gold members can continue reading. Log In or Register to continue