Endoscope-assisted keyhole surgery via an eyebrow incision for removal of large meningiomas of the anterior and middle cranial fossa.

BACKGROUND: Conventional open surgery of large meningiomas has proven to be challenging even in experienced hands. Intense retraction and dissection around neurovascular structures increase morbidity and mortality. In the present study, we retrospectively analyzed the surgical technique, and outcome in 40 patients with large anterior cranial fossa meningiomas extending to the middle fossa. All patients were approached via a supraorbital mini craniotomy. METHODS: It is a retrospective study of 40 patients (12 males, 28 females) who underwent surgery for large anterior cranial fossa meningiomas (diameter >5 cm) extending to the middle fossa in four different neurosurgical centers within 6 years. Depending on the localization of the tumor, the skin incision was between 2.5 and 3 cm long and was made without shaving the patient's eyebrow hair. Subsequently, a keyhole craniotomy was performed of approximately 0.8×1.2-1.4 cm in diameter. Preoperative and postoperative clinical and radiological data were analyzed and discussed. RESULTS: Headache and psycho-organic syndrome were the most common presenting symptom in all patients. Presenting symptoms were associated with psychological changes in 23 cases, visual impairment in 19 patients, and anosmia in 17 patients. In overall, 36 of 40 patients (90%) showed a good outcome and returned at long-term follow-up to their previous occupations. The elderly patients returned to their daily routine. CONCLUSION: With the appropriate keyhole approach as a refinement of the classic keyhole craniotomy to a smaller key"burr"hole, and with use of modern and new designed equipment, it is possible to perform complete resection of large anterior and middle fossa meningiomas with the same safety, efficiency and with less complication rates as described in the literature for large meningiomas even performed with classic keyhole craniotomies.

Brain tumor classification on intraoperative contrast-enhanced ultrasound.

PURPOSE: Contrast-enhanced ultrasound (CEUS) imaging of tissue perfusion is based on microbubble echo detection. CEUS can visualize tumors based on local perfusion variations. The acquired video data are qualitatively interpreted by subjective visualization in clinical practice. An automated CEUS classifier was developed for intraoperative identification of tumor tissue and especially tumor borders. METHODS: Support vector machines (SVM) were trained using CEU data sets to differentiate tumor and non-tumor tissue in glioblastoma patients. The classification was based on features derived from model functions approximated to time courses for each pixel in the video data. Classification performance was evaluated with single and cross- patient training data sets. RESULTS: The minimum mean classification error (14.6 %) with single patient data set training was achieved by SVM training using a sigmoid combination of model function parameter sets. A comparison of different model functions showed that the minimum average classification error (17.4 %) in a cross-validation study with 13 patients was achieved with the sigmoid model using an automatic relevance detection kernel. CONCLUSION: CEUS-based classification map images derived from approximated model functions can be generated with moderate accuracy and have significant potential to support intraoperative decisions concerning glioblastoma tumor borders.

Visualization of small veins with susceptibility-weighted imaging for stereotactic trajectory planning in deep brain stimulation.

Intracerebral hemorrhage (ICH) is the most significant complication of Deep Brain Stimulation (DBS). To prevent ICH, stereotactic contrast enhanced T1-weighted images are used to visualize vessels as source of hemorrhage. Susceptibility-Weighted Imaging (SWI) is an MRI sequence with improved visualization of susceptibility differences between tissues, particularly sensitive for brain veins. The aim of this prospective study was to analyze the utility of SWI compared to contrast enhanced stereotactic T1-weighted images for trajectory planning of DBS. Preoperative SWI was performed in 33 patients undergoing DBS and was compared to the T1-weighted images. Vessels identified only with SWI in relation to the bilateral planned trajectory were analyzed. In all patients vessels were depicted on SWI only within the planned trajectory (range 1-4 vessels, for each trajectory, mean: 2.4). In 6 patients vessels were identified on SWI adjacent to the target (up to 5mm distal from target). In 11 patients SWI visualized additional cortical veins adjacent to the entry point of the trajectory. The apparent diameter of these vessels ranged between 0.8 and 2.1mm (mean: 1.2mm). Postoperative MRI was compared with preoperative SWI and revealed in two patients small (<3 mm) T2 hyperintense lesions along electrodes without correlation with visualized veins. SWI facilitates the visualization of small veins superior to T1-weighted images. However, cerebral veins within the trajectory were not found to be a significant source of ICH after DBS. Potential sources of ICH are mesencephal veins at the endpoint of electrodes which can cause fatal hemorrhage and are visualized with SWI reliably.

Endoscopic endonasal transsphenoidal approach for resection of a coexistent pituitary macroadenoma and a tuberculum sellae meningioma.

The coexistence of a pituitary macroadenoma and a tuberculum sellae meningioma is very rare. This article demonstrates the surgical technique of the simultaneous resection of a pituitary macroadenoma and a tuberculum sellae meningioma using an endoscopic, endonasal, biportal, transsphenoidal approach. A 36-year-old woman presented with frontal headache and extended visual field loss of the right eye. She underwent cranial magnetic resonance imaging (MRI) revealing a 2 × 2 × 2.5 mm contrast-enhancing intrasellar and suprasellar lesion with compression of the optic chiasma. The coexistence of a pituitary macroadenoma and meningioma was suggested. A biportal endoscopic endonasal transsphenoidal approach was performed to remove both lesions. The histological results confirmed the coexistence of the pituitary macroadenoma and meningioma, World Health Organization (WHO) grade I. The endoscopic, endonasal, transsphenoidal approach is a safe and reliable minimal invasive surgical alternative for resection of the intra-, supra- and parasellar lesions, avoiding additional craniotomy.

Optimal invasive key-hole neurosurgery with a miniaturized 3D chip on the tip: Microendoscopic device.

OBJECTIVE: The goal of the performed study was to evaluate the possibility of a three-dimensional endoscope to become a combined microscope-endoscope device in one. We analyzed the ergonomy of the device, the implementation into the surgical workflow, the image quality, and the future perspectives such devices could have for the next generation of neurosurgeons. MATERIALS AND METHODS: Within 6 months, 22 patients (10 male, 12 female, 20-65 age) underwent surgery in neuroaxis using the new 3D-microendoscope (ME). The new 3D-ME has (a) the ability to visualize the surgical field from out- to inside with all advantages offered by a microscope, and in the same moment, (b) its design is like a small diameter endoscope that allows stereoscopic views extracorporal, intracorporal, and panoramic "para-side" of the lesion. RESULTS: In general, transcranial 3D-"microendoscopy" was performed in all patients with high-resolution 3D quality. No severe complications were observed intra- or postoperatively. With the addition of depth perception, the anatomic structures were well seen and observed. CONCLUSION: The 3D-microendoscopy is a very promising surgical concept associated with new technological developments. The surgeon is able to switch to a modern visualization instrument reaching the most optimal surgical approach without compromising safety, effectiveness, and visual information.

The subthalamic nucleus at 3.0 Tesla: choice of optimal sequence and orientation for deep brain stimulation using a standard installation protocol: clinical article.

OBJECT: Reliable visualization of the subthalamic nucleus (STN) is indispensable for accurate placement of electrodes in deep brain stimulation (DBS) surgery for patients with Parkinson disease (PD). The aim of the study was to evaluate different promising new MRI methods at 3.0 T for preoperative visualization of the STN using a standard installation protocol. METHODS: Magnetic resonance imaging studies (T2-FLAIR, T1-MPRAGE, T2*-FLASH2D, T2-SPACE, and susceptibility-weighted imaging sequences) obtained in 9 healthy volunteers and in 1 patient with PD were acquired. Two neuroradiologists independently analyzed image quality and visualization of the STN using a 6-point scale. Interrater reliability, contrast-to-noise ratios, and signal-to-noise ratios for the STN were calculated. For illustration of the anatomical accuracy, coronal T2*-FLASH2D images were fused with the corresponding coronal section schema of the Schaltenbrand and Wahren stereotactic atlas. RESULTS: The STN was best and reliably visualized on T2*-FLASH2D imaging (in particular, the coronal view). No major artifacts in the STN were observed in any of the sequences. Susceptibility-weighted, T2-SPACE, and T2*-FLASH2D imaging provided significantly higher contrast-to-noise ratio values for the STN than standard T2-weighted imaging. Fusion of the coronal T2*-FLASH2D and the digitized coronal atlas view projected the STN clearly within the boundaries of the STN found in anatomical sections. CONCLUSIONS: For 3.0-T MRI, T2*-FLASH2D (particularly the coronal view) provides optimal delineation of the STN using a standard installation protocol.

The subthalamic nucleus at 7.0 Tesla: evaluation of sequence and orientation for deep-brain stimulation.

BACKGROUND: Deep-brain stimulation (DBS) of the subthalamic nucleus (STN) is an accepted neurosurgical technique for the treatment of medication-resistant Parkinson's disease and other neurological disorders. The accurate targeting of the STN is facilitated by precise and reliable identification in pre-stereotactic magnetic resonance imaging (MRI). The aim of the study was to compare and evaluate different promising MRI methods at 7.0 T for the pre-stereotactic visualisation of the STN METHODS: MRI (T2-turbo spin-echo [TSE], T1-gradient echo [GRE], fast low-angle shot [FLASH] two-dimensional [2D] T2* and susceptibility-weighted imaging [SWI]) was performed in nine healthy volunteers. Delineation and image quality for the STN were independently evaluated by two neuroradiologists using a six-point grading system. Inter-rater reliability, contrast-to-noise ratios (CNRs) and signal-to-noise ratios (SNRs) for the STN were calculated. For the anatomical validation, the coronal FLASH 2D T2* images were co-registered with a stereotactic atlas (Schaltenbrand-Wahren). RESULTS: The STN was clearly and reliably visualised in FLASH 2D T2* imaging (particularly coronal view), with a sharp delineation between the STN, the substantia nigra and the zona incerta. No major artefacts in the STN were observed in any of the sequences. FLASH 2D T2* and SWI images offered significantly higher CNR for the STN compared with T2-TSE. The co-registration of the coronal FLASH 2D T2* images with the stereotactic atlas affirmed the correct localisation of the STN in all cases. CONCLUSION: The STN is best and reliably visualised in FLASH 2D T2* imaging (particularly coronal orientation) at 7.0-T MRI.

Non-fusion rates in anterior cervical discectomy and implantation of empty polyetheretherketone cages.

STUDY DESIGN: A prospective analysis. OBJECTIVE: Our aim was to assess the radiographically detectable bony fusion in patients with anterior cervical discectomy (ACD) and polyetheretherketone (PEEK)-cage implantation without additional filling. Furthermore, clinical data of patients with and without fusion were compared. SUMMARY OF BACKGROUND DATA: PEEK-cage implantation is performed in cervical spinal surgery because of its benefits. However, fusion rates without filling of the cage have not been reported. METHODS: Patients selected for ACD with PEEK-cage implantation prospectively underwent plain radiography in anterior-posterior and lateral projections during the postoperative hospital stay and at follow-up. Furthermore, clinical status was evaluated using the Odom scale, the Short Form-36, the Visual Analog Scale (VAS) for arm and neck pain, and the cervical Oswestry score. Fusion status, migration, and subsidence of the PEEK cage were evaluated on the basis of the lateral radiographs. Fusion was confirmed by presence of continuous trabecular bone bridges in the disc space. To exclude an influence of the cage on the evaluation of fusion rates, fusion was evaluated in analogous fashion retrospectively in a control group. RESULTS: A total of 52 patients underwent ACD and interbody fusion. One-level surgery was performed in 44 patients and 2-level surgery in 8 patients. A total of 60 ACD and interbody fusions with a PEEK cage were analyzed. A majority of operations were at the C5/6 level (40 patients, 77%). Cage height was 4 mm in 32 cases, 5 mm in 23 cases, and 6 mm in 5 cases. Bony fusion was present at 43 treated levels (71.7%), whereas at 17 levels (28.3%) no fusion was found. Statistical analysis revealed no significant difference between the fusion and non-fusion groups regarding time to follow-up, implanted cage height. Short Form-36, cervical Oswestry score, VAS arm and neck, or Odom criteria. In the control group, ACD was performed in 29 patients (42 levels; 18 one-level and 12 two-level operations). Bony fusion was present at 30 levels (71.4%), whereas non-fusion was present at 12 treated levels (28.6%). Statistically analysis revealed no significant difference between the study group and the control group regarding time to follow-up or fusion rates. CONCLUSION: Implantation of empty PEEK cages after ACD shows an unexpectedly low rate effusion according to radiologic criteria, although no statistically significant difference could be observed clinically.

Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: retrospective study.

STUDY DESIGN: Retrospective, multicenter study of robotically-guided spinal implant insertions. Clinical acceptance of the implants was assessed by intraoperative radiograph, and when available, postoperative computed tomography (CT) scans were used to determine placement accuracy. OBJECTIVE: To verify the clinical acceptance and accuracy of robotically-guided spinal implants and compare to those of unguided free-hand procedures. SUMMARY OF BACKGROUND DATA: SpineAssist surgical robot has been used to guide implants and guide-wires to predefined locations in the spine. SpineAssist which, to the best of the authors' knowledge, is currently the sole robot providing surgical assistance in positioning tools in the spine, guided over 840 cases in 14 hospitals, between June 2005 and June 2009. METHODS: Clinical acceptance of 3271 pedicle screws and guide-wires inserted in 635 reported cases was assessed by intraoperative fluoroscopy, where placement accuracy of 646 pedicle screws inserted in 139 patients was measured using postoperative CT scans. RESULTS: Screw placements were found to be clinically acceptable in 98% of the cases when intraoperatively assessed by fluoroscopic images. Measurements derived from postoperative CT scans demonstrated that 98.3% of the screws fell within the safe zone, where 89.3% were completely within the pedicle and 9% breached the pedicle by up to 2 mm. The remaining 1.4% of the screws breached between 2 and 4 mm, while only 2 screws (0.3%) deviated by more than 4 mm from the pedicle wall. Neurologic deficits were observed in 4 cases yet, following revisions, no permanent nerve damage was encountered, in contrast to the 0.6% to 5% of neurologic damage reported in the literature. CONCLUSION: SpineAssist offers enhanced performance in spinal surgery when compared to free-hand surgeries, by increasing placement accuracy and reducing neurologic risks. In addition, 49% of the cases reported herein used a percutaneous approach, highlighting the contribution of SpineAssist in procedures without anatomic landmarks.

A healthy man with intractable hiccups.

We present a patient with intractable hiccups. Medical treatment decreased the frequency of the hiccups to only 5-10 per minute. After exclusion of gastrointestinal reasons for the hiccups, cranial MRI revealed a small lesion in the right rhomboid fossa, close to the vagal trigone. Microsurgical resection of the lesion was performed via a suboccipital median craniotomy. The histopathological diagnosis was a cavernoma. Promptly after surgery the patient was free of symptoms. Intractable hiccups can be associated with intracranial pathologies, including lesions in the brain stem, which we highlight with the presentation of this patient.

Far-distant metastases along the CSF pathway of glioblastoma multiforme during continuous low-dose chemotherapy with temozolomide and celecoxib.

Glioblastoma multiforme is the most common and most malignant primary brain tumour. Prognosis after diagnosis remains poor despite recent advances in adjuvant therapy. Treatment of choice is gross surgical resection and combined radio-chemotherapy with temozolomide as chemotherapeutic agent. Experimental continuous low-dose chemotherapy with temozolomide in combination with a cyclooxygenase-2 inhibitor has shown encouraging effects on progression-free survival and overall survival in patients, but leads to a high proportion of distant recurrences. Here, we describe extreme far-distant metastases along the neural axis of glioblastoma multiforme in four patients receiving metronomic antiangiogenic chemotherapy and review the literature to discuss possible mechanisms.

Toward registration of 3D ultrasound and CT images of the spine in clinical praxis: design and evaluation of a data acquisition protocol.

Recent work has demonstrated the accuracy and operational viability of an algorithm proposed by the authors that successfully registers 3-D ultrasound data with CT or MRI data. The successful application of this method to intraoperative navigation, however, depends critically on the quality of the acquired ultrasound data. This gives rise to two questions concerning the usability of the algorithm in clinical praxis. First, how can one guarantee high-quality, user-independent ultrasound registration data with this procedure? Second, can this approach work reliably in clinical practice, namely within the operating theater? To address both of these questions, we present an ultrasound data acquisition protocol that leads the user through the data acquisition process and also provides the criteria to adjust the relevant ultrasound parameters. We also evaluated criteria for the visual inspection of the suitability of the ultrasound data for the registration process. Results for this evaluation show that these visual criteria can be used to decide preoperatively if an ultrasound registration will be successful in a patient. The intraoperative evaluation of the protocol showed that high-quality registrations can be achieved under realistic conditions. This protocol and the visual inspection criteria, together with the ultrasound registration algorithm, provide a surgical team with a means of performing precise, cost-effective navigation in patients for whom a navigated intervention was previously impossible. We evaluated the proposed procedure in clinical practice.

Percutaneous placement of pedicle screws in the lumbar spine using a bone mounted miniature robotic system: first experiences and accuracy of screw placement.

STUDY DESIGN: A prospective analysis. OBJECTIVE: The idea of this study was to evaluate a new miniature robotic system providing passive guidance for pedicle screw placement at the lumbar spine. Special focus was laid on the postoperative accuracy of screw placement. SUMMARY AND BACKGROUND DATA: Recent technical developments lead to a minimization of pedicle screw fixation techniques. However, the use of navigational techniques is still under controversy. METHODS: Patients selected for a minimal invasive posterior lumbar interbody fusion received a spiral computer tomographic scan before surgery. The miniature hexapod robot was mounted to the spinous process and the system moves to the exact entry point according to the trajectory of the surgeon's preoperative plan. After minimal invasive screw placement all patients received routinely a postoperative spiral computer tomographic scan. Screws placed exactly within the pedicle were evaluated as group A, screws deviating <2 mm were evaluated as group B, > or =2 mm to <4 mm (group C); > or =4 mm to <6 mm (group D); and more than 6 mm (group E). RESULTS: Thirty-one patients received a PLIF with percutaneous posterior pedicle screw insertion using the bone mounted miniature robotic device. A total of 133 pedicle screws were placed. The majority of the screws were placed in L5 (58 screws; 43.6%). In axial plane, 91.7% of the screws were evaluated as group A and 6.8% were evaluated as group B. In longitudinal plane, 81.2% of the screws were evaluated as group A and 9.8% were evaluated as group B. In 1 screw (L5 right) the postoperative evaluation was done as group C (axial plane) and D (longitudinal plane). In 29/31 cases the integration of the miniature robotic system was successful. CONCLUSION: In our study the first clinical assessment of a new bone mounted robot system guiding percutaneous pedicle screw placement was done. A deviation <2 mm to the surgeon 's plan in 91.0% to 98.5% verifies the system's accuracy.

Successful resection of the recurrence of a cavernous malformation of the optic chiasm.

The case of a 33-year-old female who suffered from a recurrence of an intrachiasmatic cavernous malformation is presented. She had already undergone surgery in 1991 and 2001 and was admitted to our hospital with reduced vision in the right eye. After MRI, and diagnosis of recurrence of the cavernoma, a neurosurgical operation was performed using the pterional approach. The intraoperative situation was documented with micro photographs. The postoperative course was uneventful. The female described a minimal improvement of her vision. No postoperative complications were observed. To our knowledge, microsurgically complete extirpation of a recurrence of an intrachiasmatic cavernoma has not yet been reported in the literature.

In vitro flexibility of the cervical spine after ventral uncoforaminotomy. Laboratory investigation.

OBJECT: Degenerative spine disorders are, in the majority of cases, treated with ventral discectomy followed by fusion (also known as anterior cervical discectomy and fusion). Currently, nonfusion strategies are gaining broader acceptance. The introduction of cervical disc prosthetic devices was a natural consequence of this development. Jho proposed anterior uncoforaminotomy as an alternative motion-preserving procedure at the cervical spine. The clinical results in the literature are controversial, with one focus of disagreement being the impact of the procedure on stability. The aim of this study was to address the changes in spinal stability after uncoforaminotomy. METHODS: Six spinal motion segments derived from three fresh-frozen human cervical spine specimens (C2-7) were tested. The donors were two men whose ages at death were 59 and 80 years and one woman whose age was 80 years. Bone mineral density in C-3 ranged from 155 to 175 mg/cm3. The lower part of the segment was rigidly fixed in the spine tester, whereas the upper part was fixed in gimbals with integrated stepper motors. Pure moment loads of +/- 2.5 Nm were applied in flexion/extension, axial rotation, and lateral bending. For each specimen a load-deformation curve, the range of motion (ROM), and the neutral zone (NZ) for negative and positive directions of motion were calculated. Median, maximum, and minimum values were calculated for the six segments and normalized to the intact segment. Tests were done on the intact segment, after unilateral uncoforaminotomy, and after bilateral uncoforaminotomy. RESULTS: In lateral bending a strong increase in ROM and NZ was detectable after unilateral uncoforaminotomy on the right side. Overall, the ROM during flexion/extension was less influenced after uncoforaminotomy. The ROM and NZ during axial rotation to the left increased strongly after right unilateral uncoforaminotomy. Changes after bilateral uncoforaminotomy were marked during axial rotation to both sides. CONCLUSIONS: Following unilateral uncoforaminotomy, a significant alteration in mobility of the segment is found, especially during lateral bending and axial rotation. The resulting increase in mobility is less pronounced during flexion and least evident on extension. Further investigations of the natural course of disc degeneration and the impact on mobility after uncoforaminotomy are needed.

Individualized ventriculostomy in hydrocephalus: an intravital anatomical study.

BACKGROUND: Ventriculostomy is a common neuroendoscopic operation but one with disastrous complications in rare cases. AIMS: The aim of this study was to perform an intravital analysis of the configuration at the floor of the third ventricle as a possible basis for selection of the ventriculostomy site. MATERIALS AND METHODS: The study population consisted of 32 patients who underwent ventriculostomy for the treatment of hydrocephalus. Perforation of the floor of the third ventricle was carried out on an individual basis following evaluation of the anatomic situation. Video material and magnetic resonance images (MRI) were analyzed. RESULTS: A classification system including three major groups was developed using the inner distance of the mamillary bodies as the key criterion. It was defined as narrow for values between 0 and 1 mm (observed range: 0-0.5 mm), medium for values between 1.1 and 3.4 mm (range 1.1-3.4 mm) and large for values greater than 3.4 mm (range: 3.8-6.9 mm). Statistical analysis of MR and video measurements revealed a good correlation. The ventriculostomy site was rostral of the mamillary bodies in 23 of the patients (n=27) and slightly occipital in four. The ventriculostomy site was located more to the left in 22 patients and more to the right in five. CONCLUSION: As a conclusion the ventriculostomy site has to be chosen in each case following a careful review of all available information. A classification system for the anatomical variations as well as the exact size and site of ventriculostomy should be introduced.

A program of microsurgical training for young medical students: are younger students better?

In the European countries there is a lack of young doctors. This shortage limits the possibilities for recruiting skilled surgeons for the microsurgical disciplines. Complicating the situation is the fact that most students do not decide on their area of specialization until the late clinical semesters. The authors present a new program of microsurgical training that dispenses completely with animal training. In addition, a scoring system is presented that enables instructors to compare the microsurgical skills of different students for the purpose of further statistical analysis. This scoring system could be used for the evaluation of potential microsurgical candidates as well as for other purposes, e.g. scientific projects. A total of 36 students with an average age of 24.2 were trained, with good-to-excellent results. Microsurgical training of young students can be recommended. A point worth exploring in the future is whether there are different learning curves for different age groups.

Subsidence of the wing titanium cage after anterior cervical interbody fusion: 2-year follow-up study.

OBJECT: Cage subsidence occurs after anterior cervical discectomy and fusion (ACDF). The aim of this prospective study was to evaluate subsidence and total segmental height after implantation of a newly designed Wing titanium cage. Furthermore, alignment of the entire cervical spine was analyzed 2 years after surgery. METHODS: Fifty-four patients (26 women and 28 men) whose mean age was 48.3 years underwent ACDF. Follow-up examinations were performed at discharge and 6, 12, and 24 months postoperatively by an independent investigator. The clinical course was evaluated using the visual analog pain scale and the Prolo scales. Measurements of subsidence and total segmental height were conducted, and the alignment of the entire cervical spine was classified using two methods. In 54 patients 64 levels were fused. The patients noted a significant reduction of pain, and scores on both Prolo scales were significantly improved. At the 2-year follow-up examination, subsidence was present in 30 of the 67 fused segments. There was a statistically significant correlation between subsidence and the presence of posterior spondylosis at the initial surgery. Furthermore, there was a significant correlation between reduction of total segmental height and the presence of subsidence; however, subsidence did not prevent the development of a solid bone arthrodesis (fusion rate 98%) or have an adverse effect on the alignment of the cervical spine. CONCLUSIONS: Titanium Wing cage-augmented ACDF was associated with comparatively good long-term results. Subsidence was present but did not cause clinical complications. Furthermore, radiological studies demonstrated that the physiological alignment of the cervical spine was preserved and a solid bone arthrodesis was present at 2 years after surgery.

Vibrography during tumor neurosurgery.

OBJECTIVE: The aim of this study was to determine whether elastography, a sonographically based real-time strain imaging method for registering the elastic properties of tissue, can be used in brain tumor surgery. METHODS: A modification of classic elastography called vibrography was applied in these measurements with static compression replaced by low-frequency axial vibration. Twenty patients were examined with this technique during brain tumor surgery. A conventional sonographic system with a custom-designed radio frequency (RF) interface was used. The RF data were digitized with a 50-MHz, 12-bit peripheral component interconnect analog/digital converter for real-time or offline processing. Sonographic RF data were acquired with a 6.5-MHz endocavity curved array. A special applicator equipped with a stepping motor moved the ultrasonic probe and produced a low-frequency mechanical vibration of approximately 5 to 10 Hz with a vibration amplitude of 0.3 mm. RESULTS: Detection of tumors was possible in 18 of 20 cases. Brain tissue was normally color coded orange or red. Three major groups of tumors with different elastic properties relative to brain tissue could be differentiated. In 3 cases, the stiffness of the tumor was identical to that of brain tissue, but the tumors were surrounded by a thin yellow border. Six tumors displayed higher strain than brain, whereas 7 tumors exhibited lower strain than the surrounding cerebrum. Two patients could not be assigned clearly to either of these groups. CONCLUSIONS: These findings indicate that vibrography is a feasible imaging method for brain tumor surgery and may have numerous potential applications in neurosurgery if further improvements are made.