Image-Guided/Endoscopic Sinus Surgery

Updated: Sep 27, 2023
  • Author: Seth M Brown, MD, MBA, FACS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Practice Essentials

Image-guided surgery (IGS) is the use of a real-time correlation of the operative field to a preoperative imaging data set that reflects the precise location of a selected surgical instrument to the surrounding anatomic structures. Although first developed for neurosurgery, endoscopic sinus surgery (ESS) rapidly became one of the leading indications for this technology. ESS has been shown to be successful in removing diseased sinus tissue, preserving intact sinus mucosa, reestablishing sinus ventilation, reducing inflammatory response, and restoring mucosal glandular and ciliary clearance. ESS has become the treatment of choice for chronic rhinosinusitis. [1, 2, 3, 4, 5]

Image-guided surgery is one of the most significant advances in endoscopic sinus surgery since the inception of the endoscopic approach in the mid-1980s. This technology enables the surgeon to follow the anatomic dissection of the sinuses on a computer monitor in the operating room in real time. Difficult anatomic relationships can more easily be understood and treated with the assurance that the critical landmarks are secured. Although the initial expense is substantial, these procedures have minimal per-case costs. The decision whether to use an optical or an electromagnetic system is less critical than the decision to use computer technology. Both systems are widely accepted and provide excellent anatomic information. [6, 7]

All IGS systems utilize a computer workstation, video monitor, tracking system, surgical instrumentation, and data-transfer hardware. The tracking system allows the real-time determination of instrument position and is either electromagnetic (EM) or optical tracking (OT). [8]

ESS has also been used for access to pathologies of the orbital transnasally, avoiding skin incisions, such as decompression of the orbit and optic canal in Graves disease or posttraumatic optic neuropathy, lesions of the extraconal medial orbital apex or space, benign sinonasal tumors that have invaded the orbit medially, and medial orbital wall fractures. In addition, ESS has become standard procedure for mucoceles, invasive and noninvasive fungal sinusitis, silent sinus syndrome, pituitary tumors, and CSF leaks, as well as ventral skull base lesions, lesions of the petrous apex, or pterygomaxillary fossa. [2]

IGS should not be considered as a way to palliate lack of experience or understanding of sinonasal surgical anatomy but rather as an adjunctive tool designed for otolaryngologists properly trained in ESS.

There is potential risk of serious postoperative complications associated with ESS because the sinuses are adjacent to the nasolacrimal duct, orbit, optic nerve, cavernous sinus, internal carotid artery, skull base, and slope. Complications may include nasolacrimal duct and lacrimal sac injury, orbital wall injury, visual impairment, cerebrospinal fluid rhinorrhea, and hemorrhagic complications. [4]  In a study by Hassanin et al, use of IGS devices was associated with less than 3% adverse events, with the most frequent being CSF leakage, tissue damage, and nervous system injury. The most commonly reported device malfunction was imprecision. [9]  Orozco et al reported that imprecise navigation increased the likelihood of CSF leakage and navigation abortion. [10]

In neurosurgery, the primary use of image-guided surgery is to locate an intracranial lesion for resection or biopsy. In endoscopic sinus surgery, the main advantage is to avoid disrupting hazardous areas such as the brain and orbit. [11, 12, 13]

Magnetic resonance images (MRI) can also be fused directly to CT images, which is beneficial in cases that involve both otolaryngologists and neurosurgeons, as one image-guidance system can be used for navigation. CT images are better able to delineate the bony anatomy of sinonasal cavities for the nasal approach performed by the otolaryngologist, whereas the neurosurgeon will require the assistance of MRI guidance with enhanced intracranial soft-tissue definition to pursue the combined procedure. This is particularly relevant in cases that involve the pituitary and anterior skull base. [14]  The image-guidance system can create a hybrid image that has both excellent soft-tissue and bony detail.

IGS begins with obtaining a CT scan. The CT scan acquisition protocol used for the authors' needs consists of a helical, 2-mm–thickness axial CT scan with the use of a specially designed headset incorporating built-in metallic fiducial land marking. The specially designed headset allows automatic registration of the imaging to the patient's anatomy in the operating room. The imaging data set is transferred to the operating room, where it is loaded into the workstation. The images are brought up on the IGS system prior to the procedure and checked for image quality and accuracy.

(An image depicting image-guided surgery is shown below.)

Verification of accuracy using patient anatomic la Verification of accuracy using patient anatomic landmarks.

Most CT scanners provide data sets compatible with guidance systems. Radiology also has the ability to provide the required data or to transfer the images directly from the radiology station to the IGS system. These advances, as well as the decreasing cost of the technology, have allowed IGS to be available to a sizable number of otolaryngologists.

Image-guided radiotherapy (IGRT) is an advanced auxiliary radiotherapy technique. During cancer treatment, patients with oral cavity cancer (OCC) experience not only disease but also adverse effects due to radiotherapy (RT). IGRT provides the advantages of RT by precisely delivering tumoricidal doses via real-time knowledge of target volume location and achieves maximal tumor control with minimal complications, as recommended for cancer treatment. Studies have also shown that IGRT can improve clinical outcomes in terms of not only treatment side effects but also survival benefits for cancer patients. IGRT can be performed alongside various imaging methods, including CT and magnetic resonance imaging (MRI), and at different times during the radiotherapy regimen. [15]

Some studies have focused on real-time updates, which allow the preoperative images used for navigation to be updated throughout the surgery. [11, 16]  Advancements include CT, MRI fusion capability, three-dimensional CT angiography, preoperative planning software, virtual-reality (VR) tools, and augmented-reality (AR) capabilities. [8, 17, 18, 19]

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Indications and Contraindications

Initially, because of the cumbersome nature of the systems, increased operating time, and expertise required of operating room personnel, image-guided surgery was selected only by tertiary referral centers for revision or unusual sinus cases in which the anatomy was expected to be distorted. [20] As experience has been gained, image guidance has become an integral part of surgery for many otolaryngologists performing endoscopic sinus surgery, particularly in the following situations:

  • Sinus surgery in the absence of normal landmarks

  • Revision sinus surgery [21]

  • Disease that abuts the skull base [22]

  • Disease that extends into the frontal or sphenoid sinus

  • Dehiscent lamina papyracea

  • Orbital pathology

The time from anesthesia induction until completion of registration can be under 5 minutes. [23]  Computer-assisted endoscopic sinus surgery (ESS) has no absolute contraindications except for lack of experience and training. Physicians must be aware that the technique is an adjunct to surgery and does not replace surgical skills and knowledge. [24]  The relevant anatomy is that of the paranasal sinuses, orbits, and cranial base. [25]

ESS can remove diseased sinus tissue, preserve intact sinus mucosa, reestablish sinus ventilation, reduce inflammatory response, and restore mucosal glandular and ciliary clearance, and it is the treatment of choice for chronic rhinosinusitis. It is also frequently used to access orbital pathologies, such as decompression of the orbit and optic canal, lesions of the extraconal medial orbital apex or space, benign sinonasal tumors in the medial orbit, and medial orbital wall fractures. In addition, ESS has become standard procedure for mucoceles, invasive and noninvasive fungal sinusitis, silent sinus syndrome, pituitary tumors, and CSF leaks, as well as ventral skull base lesions, lesions of the petrous apex, or pterygomaxillary fossa. [5, 1, 2]

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Procedural Technique

Nasal endoscopy is performed using a 0- or 30-degree scope.  The lateral nasal wall near the uncinate and the axilla of the middle turbinate are infiltrated with 1% lidocaine with 1:100,000 epinephrine using a 3-ml syringe and 27-gauge needle. Oxymetazoline-soaked cotton pledgetts are placed in the middle meatus. [2]

Anesthesia is induced on a normal operating table. However, when electromagnetic systems are used, a thick foam mattress is needed to keep the patient off of the metal table in order to prevent interference. With systems using optical technology, the image-guided surgery (IGS) unit must be in direct line to the operating room table. [26, 27]

Registration

The critical step is the registration process. There are 3 basic paradigms to create 1-to-1 mapping between corresponding points in the operating-field volume and imaging data-set volume: paired-point registration, contour-based registration, and automatic registration (which is now rarely used). [8] Registration generates a correlation between the position of the instrument in the surgical field and the corresponding location on the CT images. The instruments are registered to show their position with respect to the orthogonal CT images of the patient. The location is materialized by a set of crosshairs on the screen that moves through the CT image data in concordance with the movement of the pointer.

Once registration is complete, the target registration error (TRE) must be assessed, which is the distance between the measured position of a tracked instrument tip (seen on the monitor) and real-world position of the instrument tip. [8]

Image-guided surgery, using optical or electromagnetic systems, accommodates for head movement. This has enormous implications for surgeons who prefer local or intravenous sedation. Prior to the advent of new systems, general anesthesia was necessary to ensure absolute fixation of the head relative to the tracking system (see the first image below). With the newer systems (see the second image below), the headset moves along with the head, so registration is maintained throughout the procedure, although frameless registration can also be performed. Therefore, any anesthetic technique may be used. [28, 29, 30, 31, 32]

Old image-guided surgery (IGS) systems used an art Old image-guided surgery (IGS) systems used an articulated arm (shown) and required the patient's head to be taped to the operating room bed.
Newer electromagnetic image-guided surgery (IGS) s Newer electromagnetic image-guided surgery (IGS) system.

With an electromagnetic system, the headset that was worn by the patient during the preoperative CT scan acquisition is again applied on the patient's head in the operating room. This correlates head position with the tracking system.

Testing of accuracy

Accuracy is verified by testing various known landmarks on the patient's face and intranasally to the images on the computer monitor (see the image below). These locations' coordinates are stored and used throughout the procedure to monitor any changes in the accuracy of the device. With most systems, these preliminary steps take less than 2 minutes with the collaboration of trained operating room staff.

Verification of accuracy using patient anatomic la Verification of accuracy using patient anatomic landmarks.

Once registered and verified, the system allows the surgeon to verify surgical position on the monitor depicting the preoperative CT scan in 3 dimensions, along with an additional frame displaying the endoscopic view of the procedure (see the image below).

Surgeon's view of the computer monitor showing the Surgeon's view of the computer monitor showing the sagittal, axial, and coronal depictions in real time of the surgery progress. The fourth window can be either the real time video or a computer 3-dimensional rendition of the surgical field.

Although technical advances have allowed navigation devices to be attached to virtually any sinus surgery instrument, the true value of the technology is that it maps out difficult anatomy at critical points in the surgery. Clearing the operative field of blood and debris and then using either a tracking pointer or a tracking curved suction to elucidate anatomic questions is most prudent for the surgeon, who may then proceed safely with the next step of surgery. The following are examples of critical points when computer guidance is of greatest assistance during surgery:

  • Localizing a difficult frontal sinus

  • Localizing a small sphenoid sinus

  • Delineating a skull base contour during a revision procedure

  • Distinguishing smooth-walled peripheral cells from surrounding landmarks

These localization maneuvers should be performed with diagnostic instruments, not surgical instruments. The use of a microdebrider with tracking is of exceptional benefit while removing nasal and sinus polyp disease.

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Results and Complications

The following observations of IGS have been consistent since the earliest cases in the authors' institution :

  • Image-guided surgery assists the experienced surgeon in delineating ambiguous or distorted landmarks. It is not a replacement for thorough anatomic training

  • Accuracy within 2 mm is the norm

  • Registration can be accomplished with minimal additional operating room time

  • Inconveniences related to logistical setups are minimal and do not affect the value of the technology

  • Image-guided surgery allows the surgeon to routinely perform a more complete exploration of the paranasal sinuses, particularly when it comes to smaller cells occupying the crevices of the sinus cavities

  • Difficult sphenoid sinus and ethmoid sinus anatomy can be approached with more surgical confidence using computer-guided dissection

  • Frontal sinus anatomy can be approached with greater confidence, particularly in the presence of a false lateral terminal cell

According to a study by Hassanin et al, adverse events with IGS occurred in less than 3% of procedures. The most frequent events were CSF leakage, tissue damage, and nervous system injury, and the most common cause was imprecision. [9] Orozco et al also reported that imprecise navigation was the most common cause of CSF leakage and abortion of navigation. [10]

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Future Advances

 

 

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