Computer-assisted neurosurgical navigational system for transsphenoidal surgery--technical note.

Transsphenoidal surgery carries the risk of carotid artery injury even for very experienced neurosurgeons. The computer-assisted neurosurgical (CANS) navigational system was used to obtain more precise guidance, based on the axial and coronal images during the transsphenoidal approach for nine pituitary adenomas. The CANS navigator consists of a three-dimensional digitizer, a computer, and a graphic unit, which utilizes electromagnetic coupling technology to detect the spatial position of a suction tube attached to a magnetic sensor. Preoperatively, the magnetic resonance images are transferred and stored in the computer and the tip of the suction tube is shown on a real-time basis superimposed on the preoperative images. The CANS navigation system correctly displayed the surgical orientation and provided localization in all nine patients. No intraoperative complications were associated with the use of this system. However, outflow of cerebrospinal fluid during tumor removal may affect the accuracy, so the position of the probe when the tumor is removed must be accurately determined. The CANS navigator enables precise localization of the suction tube during the transsphenoidal approach and allows safer and less-invasive surgery.     

Surgeon's position for transsphenoidal surgery--technical note.

Transsphenoidal resection of pituitary tumors is usually performed with the surgeon standing on the patient's right side. However, this configuration is awkward when the tumor extends to the right and access may be hindered if the patient has poor nuchal flexibility or a large chest due to giantism or acromegaly. The surgeon stood on the left side of the patient during transsphenoidal surgery in five selected cases. The position on the left provided good access to the tumors with minimal changes in technique.     

Image fusion for skull base neuronavigation. Technical note

An automatic image fusion module (BrainLab, Munich, Germany) is used for the fusion of the magnetic resonance (MR) imaging and computed tomography (CT) data sets. The procedure of image fusion takes 5 minutes prior to surgery. The image fusion of CT and MR imaging data visualizes the skull base and tumor margins clearly. Color display of the different data sets allows the tumor and the skull base to be distinguished easily. The fused CT data in bone window mode provides useful additional information on the osseous skull base.     

Transciliary subfrontal craniotomy for anterior skull base lesions. Technical note.

Microsurgical approaches are the procedures of choice for high-risk patients with lesions requiring surgical treatment. The use of a microscope reduces the extent of the surgical invasion, thus minimizing the handling of healthy tissues. The authors present a surgical approach described for the first time in 1981, which has been used for the past 17 years in more than 260 patients with different tumors and vascular lesions of the anterior cranial fossa. The modification set forth in this article makes better exposure possible, allows more space for instrument handling, and improves cosmetic results. This particular report was based on the treatment of 41 patients who were observed for longer than 3 months. All of the patients were satisfied with the cosmetic result.     

Endoscopic glabellar approach to the anterior skull base: a technical note.

OBJECT: An endoscopic glabellar transethmoidal approach via a small nasional incision to the anterior skull base is reported as a minimally invasive neurosurgical technique. SURGICAL TECHNIQUE: A frontonasal craniotomy (2 x 2 cm in size) between the medial orbits is made via a nasional skin incision approximately 3-cm in length. An ethmoidectomy is performed in order to expose the skull base at the anterior cranial fossa. Anterior and posterior ethmoidal arteries, which provide blood-supply to the tumor, are interrupted during the ethmoidectomy. The tumor located at the anterior cranial fossa is removed under an endoscope. A rod-lens endoscope, which is 4-mm in diameter and 18-cm in length, is used. The dura mater is reconstructed with dural graft placement. The skull-base bone at the anterior cranial fossa is reconstructed with autogenous bone or a piece of titanium mesh. The ethmoidectomy site is filled with abdominal fat graft material. The craniotomy bone flap is secured with titanium microplates and screws. Two demonstrative patients are reported. The benefits of the minimally invasiveness of this surgical technique have been observed in patient recovery. CONCLUSION: An endoscopic glabellar transethmoidal approach to the anterior cranial fossa via a small nasional incision is reported with two patients with olfactory groove meningiomas.     

Efficacy of a new instrument for dural defect repair in anterior skull base reconstruction: a technical note

Background

The anterior skull base is a deep and narrow area, which makes dural repair technically challenging. The goal of this study was to demonstrate the efficacy of a new instrument for anterior skull base dural repair.

Methods

Ten patients underwent surgery via the transbasal approach, combined with either a transfacial or a transnasal endoscopic resection. The dural repair was performed prior to tumor resection, and the new instrument was used to suture the fascia lata in an underlay fashion. The repaired dural defect was then covered with a pericranial flap.

Results

The follow-up period ranged from 2 to 18 months, with an average follow-up time of 8.7 months. During this period, none of the patients experienced cerebrospinal fluid leakage, meningitis, tension pneumocephalus, abscess formation, or flap necrosis.

Conclusions

Our findings suggest that the use of this instrument combined with the technique of suturing the fascia lata in an underlay fashion and covering it with a pericranial flap, may be an effective alternative approach to anterior skull base reconstruction.     

Avoidance of postoperative epistaxis and anosmia in endonasal endoscopic skull base surgery: a technical note

Background

Most endoscopic transsphenoidal approaches jeopardize the sphenopalatine artery and septal olfactory strip (SOS), increasing the risk of postoperative anosmia and epistaxis while precluding the ability to raise pedicled nasoseptal flaps (NSF). We describe a bilateral “rescue flap” technique that preserves the mucosa containing the nasal-septal vascular pedicles and the SOS. This approach can reduce the risk of postoperative complications, including epistaxis and anosmia.

Methods

A retrospective analysis was conducted of all patients who underwent endoscopic transsphenoidal surgery with preservation of both sphenopalatine vascular pedicles and SOS. In a recent subset of patients, olfactory assessment was performed.

Results

Of 174 consecutive operations performed in 161 patients, bilateral preservation of the sphenopalatine vascular pedicle and SOS was achieved in 139 (80 %) operations, including 31 (22 %) with prior transsphenoidal surgery. Of the remaining 35 operations, 18 had a planned formal NSF and 17 had prior surgery or extensive lesions precluding use of this technique. Of pituitary adenomas, RCCs or sellar arachnoid cysts, 118 (94 %) underwent this approach, including 91 % of patients who had prior surgery. Preoperative olfaction function was maintained in 97 % of patients that were tested. None of the patients had postoperative arterial epistaxis.

Conclusion

Preservation of bilateral sphenopalatine vascular pedicles and the SOS is feasible in over 90 % of patients undergoing endonasal endoscopic surgery for pituitary adenomas and RCCs. This approach, while not hindering exposure or limiting instrument maneuverability, preserves the nasoseptal vasculature for future NSF use if needed and appears to minimize the risks of postoperative arterial epistaxis and anosmia.     

An automated robotic approach with redundant navigation for minimal invasive extended transsphenoidal skull base surgery.

BACKGROUND: The aim of this work was to determine the feasibility of a robotic-assisted and fully automated approach to the sphenoid sinus. An image-guided robotic system was designed to address potential human errors in performing transsphenoidal sinus surgery by combining the reproducible accuracy of a robotic system with standard computer navigation. METHODS: A six-degrees of freedom robotic assistance system and an opto-electrical navigation system were combined for image-guided assistance with redundantly controlled robotics. Newly designed endoscopic instruments for robotic surgery have been developed and are described. Telemanipulatory, as well as fully automated procedures, were tested on cadaveric heads as part of a preclinical trial. RESULTS: A fully automated sphenoidotomy as well as a telemanipulatory sphenoidectomy were performed successfully on cadaveric heads. Intraoperative performance, accuracy assessment studies, as well as possible sources of stereotactic offsets are described. The mean measured robotic reproducibility accuracy was 0.056 mm (range: 0.02 - 0.14 mm) and the mean overall navigated robotic accuracy, including all transformation and registration errors was 1.53 mm (range: 1.13 - 1.89 mm) respectively. CONCLUSION: A system for robot-guided surgery in combination with redundant navigational control was developed. It allows highly accurate maneuvers, performed either in a telemanipulation mode as master-slave system or in a fully automated fashion. A sphenoidectomy on cadaveric heads was performed in both telemanipulation and fully automated modes. The overall intraoperative accuracy was in the range of the resolution of the CT images and stereotactic offsets were caused mainly due to deflections of the endoscopic operating instrument.     

Adaptation of a hexapod-based robotic system for extended endoscope-assisted transsphenoidal skull base surgery.

OBJECTIVE: To adapt a hexapod-based robotic system for use in extended endoscope-assisted transsphenoidal skull base surgery. METHODS: A robotic system (Evolution 1, Universal Robot Systems, Schwerin, Germany) based on a hexapod design with an attached seventh axis is used as instrument holder. The instrument interface is operated via a joystick control. An endoscope is applied to the instrument interface, which is tracked by a navigation system (Stealth, Medtronic, USA). RESULTS: The instrument holder was modified so that it could be applied in transsphenoidal surgery. Furthermore, translation and pivoting movements of the system were implemented, also a quick change between microscope and robotic-controlled endoscope was made possible. After extensive phantom testing two patients with large invasive pituitary adenomas were operated on using the robotic endoscope assistance during transsphenoidal surgery. The robotic assistance allowed the use of two additional instruments under endoscopic view. For example, drilling, suctioning, application of punches, as well as microsurgical tumor removal could be performed under endoscopic view. CONCLUSION: A robotic system could be adapted for use in endoscope-assisted transsphenoidal skull base surgery allowing simultaneous use of two instruments under endoscopic view. This opens new possibilities to extend transsphenoidal skull base surgery.     

Use of modified pericranial flaps in anterior skull base reconstruction: technical note

Proper reconstruction of the cranial base is imperative in preventing cerebrospinal fluid leakage and in the protection of vascular elements. Living pericranial flaps are often key elements in such reconstruction; however, trauma, previous surgery, or pathologic involvement can result in the loss of important parts of the pericranium. Techniques for utilizing pericranial flaps despite defects in the pericranium are described and case examples are given to illustrate these techniques.     

Increased safety in robotic paranasal sinus and skull base surgery with redundant navigation and automated registration

We present an advanced version of our robotic setup for paranasal sinus surgery that was developed at the Department of Otorhinolaryngology, Head and Neck Surgery in Erlangen, Germany. The system was interconnected with a redundant navigation system for increasing intraoperative safety while performing telemanipulatory as well as fully automated maneuvers.In contrast to the previous "all in one" version, we built a modular three component setup. The basic feature of the computer navigation system is the "CAPPA ENT" station. The system references by automatically detecting a referencing frame mounted on a non-invasive upper jaw mouthpiece. Software components of both systems, navigation and robotics were combined on one user interface. Accuracy as well as clinical applicability studies were carried out. For better surveillance and increased safety, we decided to evaluate the robots reproducibility errors and overall stereotactic accuracy by means of redundant navigational control on a phantom model for paranasal sinus and skull base surgery. Multiple measurements from 14 CT-markers were taken representing different surgical approaches.A modular setup was designed and was deemed feasible in its size and weight dimensions as well as its maneuvrability for application in a routine operating room environment. The navigational feedback is integrated in real time in the robots user interface. In case of blocked visibility to the Dynamic Referencing Frame the robot powers down and activates the force torque sensor, thus softening all articulating joints. We found only adequate accuracies in pinpointing a specific CT-marker both in telemanipulatory and fully automated maneuvers. No significant offsets were observed evaluating accuracies for different surgical approaches.By using redundant navigation feedback, we were able to add another safety feature, the "loss of control" function, which shuts down any robotic action. However, no increase of the absolute accuracy was observed by adding this feature. We conclude that redundant navigational control does not make the robot more accurate, but it adds a potent safety feature to the system.     

A multi‐modality tracking,navigation and calibration for a flexible robotic drill system for total hip arthroplasty

Background

This paper presents a novel multi‐modality tracking and navigation system that provides a unique capability to guild a flexible drill tip inside the bone with accurate curved tunnelling.

Methods

As the flexible drill tip cannot be tracked optically inside the bone, this research focuses on developing a hybrid tracking and navigation system for tracking a flexible drill tip by using both optical and kinematic tracking. The tracking information is used to guide the THA (total hip arthroplasty) procedure, providing a real‐time virtual model of the flexible drill.

Results

The flexible and steerable drill tip system is then tested on total hip arthroplasty followed by evaluation of the positioning and orientation of femoral stem placement by femoral milling.

Conclusions

Based on this study, we conclude that the tracking and navigation system is able to guide the flexible drill to mill inside femoral canal.     

Integrated PET/CT system for staging and surveillance of skull base tumors

BACKGROUND: The utility of preoperative and postoperative whole body integrated positron emission tomography-computed tomography (PET-CT) scanning for staging and follow-up in patients with skull base tumors is undetermined. METHODS: We prospectively evaluated PET-CT findings in 47 patients using 57 scans. Most (35/47, 75%) had anterior skull base tumors and the majority (74%) had advanced-stage (III-IV) disease. RESULTS: The scans showed high sensitivity for detection of various types of malignant tumors and provided 39 items of additional information, changing the clinical staging and management of 11 patients (23%). Recurrence of primary tumors was detected in 8 patients, positive regional (neck) metastases in 3, and distant metastases in 3. The positive uptake was due to osteoradionecrosis in 2 other patients. The sensitivity of PET-CT was 0.77 and the specificity was 0.81 (0.83 positive predictive value and 0.76 negative predictive value). CONCLUSIONS: PET-CT provides accurate data on anatomy, tumor staging, and early disease recurrence in the skull base.     

Interstitial brachytherapy for skull base tumors

1. Irrespective of the histology, all tumors responded to 125I permanent BT. 2. There were no intra- or postprocedural complications, making this modality extremely safe. 3. There were no acute or late complications attributable to continuous LDR radiation with 125I permanent BT. 4. The dose distribution can be tailored to fit the tumor shape by seed placement at the desired location and by selecting the seed strength. 5. Unlike any other radiation therapy procedure, with SBT, the placement of the 125I seed or seeds is verifiable at each step of the procedure on the CT screen, making the treatment more accurate. 6. The procedure is performed under local anesthesia, and the patient is observed overnight at the most, making it safe and cost-effective. 7. Most skull base tumors are located close to the brain, cranial nerves, or blood vessels. Tolerance of these vital structures to high doses of radiation when given continuously at a LDR makes this treatment method safe.