Intraoperative Navigation

see Electromagnetic navigation.

see Intraoperative Navigation.

see Image-Guided Magnetic Thermoseed Navigation.

Intraoperative Computed Tomography.

Surgical Navigation Systems.

The more commonly available and routinely used tools for intraoperative image guidance, which are based on preoperative imaging. NN is an excellent tool for surgical planning and identification of the lesion and the surrounding vital structures but suffers from major limitations.

Neuronavigation is an established technology in neurosurgery. In parts of the world and in certain circumstances that neuronavigation is not easily available or affordable, alternative techniques maybe considered.

Neuronavigation systems, based on preoperative imaging, lacks accuracy because of brain-shift and brain-deformation.

Of 78 patients referred for intracranial arteriovenous malformation from 2005 through 2013, 31 patients were operated on with microsurgical technique. 3D Magnetic resonance angiography (MRA) with neuronavigation was used for planning. Navigated 3D ultrasound angiography (USA) was used to identify and clip feeders in the initial phase of the operation.

None of the patients was embolized preoperatively as part of the surgical procedure. The niduses were extirpated based on the 3D USA. After extirpation, controls were done with 3D USA to verify that the AVMs were completely removed. The Spetzler three-tier classification of the patients was: A: 21, B: 6, C: 4.

Sixty-eight feeders were identified on preoperative MRA and DSA and 67 feeders were identified and clipped by guidance of intraoperative 3D USA. Six feeders identified preoperatively were missed by 3D USA, while five preoperatively unknown feeders were found and clipped. The overall average bleeding was 440 ml. There was a significant reduction in average bleeding in the last 15 operations compared to the first 16 (340 vs. 559 ml, p = 0.019).

They had no serious morbidity (GOS 3 or less). New deficits due to surgery were two patients with quadrantanopia (one class B and one class C), the latter (C) also acquired epilepsy. One patient (class A) acquired a hardly noticeable paresis in two fingers. One hundred percent angiographic cure was achieved in all patients, as evaluated by postoperative DSA.

Navigated intraoperative 3D USA is a useful tool to identify and clip AVM feeders. Microsurgical extirpation assisted by navigated 3D USA is an effective and safe method for removing AVMs ¹⁾.

The method of incorporating functional data into neuronavigation systems is a promising tool that can be used in more radical surgery to cause less morbidity around eloquent brain areas ²⁾.

The use of intraoperative navigation during microscope cases can be limited when attention needs to be divided between the operative field and the navigation screens. Heads-up display (HUD), also referred to as augmented reality, permits visualization of navigation information during surgery workflow.

Mascitelli et al. retrospectively reviewed patients who underwent HUD-assisted surgery from April 2016 through April 2017. All lesions were assessed for accuracy and those from the latter half of the study were assessed for utility.

Seventy-nine patients with 84 pathologies were included. Pathologies included aneurysms (14), arteriovenous malformations (6), cavernous malformations (5), intracranial stenosis (3), meningiomas (27), metastasis (4), craniopharygniomas (4), gliomas (4), schwannomas (3), epidermoid/dermoids (3), pituitary neuroendocrine tumors (2) hemangioblastoma (2), choroid plexus papilloma (1), lymphoma (1), osteoblastoma (1), clival chordoma (1), cerebrospinal fluid leak (1), abscess (1), and a cerebellopontine angle Teflon granuloma (1). Fifty-nine lesions were deep and 25 were superficial. Structures identified included the lesion (81), vessels (48), and nerves/brain tissue (31). Accuracy was deemed excellent (71.4%), good (20.2%), or poor (8.3%). Deep lesions were less likely to have excellent accuracy (P = .029). HUD was used during bed/head positioning (50.0%), skin incision (17.3%), craniotomy (23.1%), dural opening (26.9%), corticectomy (13.5%), arachnoid opening (36.5%), and intracranial drilling (13.5%). HUD was deactivated at some point during the surgery in 59.6% of cases. There were no complications related to HUD use.

HUD can be safely used for a wide variety of vascular and oncologic intracranial pathologies and can be utilized during multiple stages of surgery ³⁾.

Intraoperative stereotactic navigation has become more available in spine surgery. Stereotactic navigation with cone-beam fluoroscopy and CT and the use of the O arm (Medtronic) 3D imaging with stereotactic computer navigation have been well described for the safe and accurate placement of pedicle screws ^{4) 5)}.

Stereotactic navigation may also be used to advance surgical treatment of spinal neoplasms. The use of image guidance has been described in surgical planning for resection of spinal tumors ^{6) 7)}.

It has been used to both plan osteotomies and to carry out minimally invasive surgical techniques. The result is to minimize the extent of surgery in the oncological patient. It is proposed that stereotactic intraoperative navigation can be of further utility in tumor resection by aiding in the localization of spinal lesions and intraoperative visualization of margins ⁸⁾.

Based on the currently available data in the peer-reviewed literature, computer assistance in the form of robotic] guidance or navigation has the potential to reduce the incidence of costly and clinically relevant postoperative revisions for screw malposition. It is essential to further investigate on a higher level of evidence if the clinical benefits of computer-assistance warrant the high acquisition and maintenance costs inherent to these systems ⁹⁾.

The use of surgical neuronavigation systems is becoming an increasingly important part of planning and performing intracranial surgery ^{10) 11) 12)}.

For such reason, it is particularly important to avoid errors during the navigation process.

However, there is an overvaluation of using these methods since in most cases they are only used for the craniotomy positioning ^{13) 14)}.

Spinal Navigation

Frameless stereotactic brain biopsy.

Allows more flexibility during microsurgical procedures. Introduced into neurosurgical routine in the late 1980s and early 1990s, several advantages of this technology have been pointed out ^{15) 16)}.

Placement of the Ommaya reservoir

Percutaneous radiofrequency trigeminal rhizotomy

Being based on preoperative acquired images it does not take into account intraoperative changes due to tumor resection, brain shift and brain deformation ^{17) 18) 19) 20)}.

Besides the benefits of neuronavigation in tumor localization, tumor resection control, skull base surgery, or in procedures close to functional important structures, several publications pointed out that one of the most valuable applications of frameless neuronavigation was the localization of the craniotomy.

To overcome the limitations of NN based on preoperative imaging, recently it has been proposed to use intraoperative imaging for meningioma surgery: MRI (iMRI), CT (iCT), intraoperative ultrasound (ioUS) and also fluorescent imaging (5-ALA) ^{21) 22) 23)}

Wagner and coworkers ²⁴⁾ showed that in 40% of the cases that had been operated on using intraoperative neuronavigation, the system was only needed to correctly define size and position of the craniotomy. This observation was confirmed in a study of Spivak and colleagues ²⁵⁾.

Integration of metabolism images into multimodal neuronavigation provide not only anatomical, but also metabolic and functional information for frameless stereotaxy, increasing diagnostic yield and avoiding postoperative neurologic deficits ²⁶⁾.

A retrospective study included a total of 34 patients treated in our Institution between June 2017 and January 2018. Surgical procedures included two groups operated under general anesthesia: microscopic transcranial approach and endoscopic endonasal approach. Preoperative and post-operative navigation accuracy was assessed by two different neurosurgeons.

After our surgical planning navigation protocol was applied, both transcranial and endonasal procedures were successfully performed under navigation guidance in all patients except one. Intraoperative and post-operative complications related to tracker mounted under the hard palate did not occur. In 33 cases a maximal tracking view and optimal navigation accuracy was achieved accounting for a successful rate of 97%.

The position of the patient tracker under the hard palate showed safety, accuracy and feasibility in 97% of our patient. In our case series, it allowed to obtain the main goal to avoid device displacement without invasiveness and postoperative discomfort of the patient ²⁷⁾.