Treatment of degenerative cervical disc disease with uncoforaminotomy--intermediate clinical outcome

BACKGROUND

Anterior cervical uncoforaminotomy (uncoforaminotomy) is an operative method intended to preserve the functional motion segment of the cervical spine while removing the underlying pathology. Controversy exists concerning the patients best suited for this treatment modality. Furthermore, no long-term outcome analyses have been published.

METHODS

Between November 2002 and June 2004, 96 patients underwent single-level uncoforaminotomy in our neurosurgical department for the treatment of cervical radiculopathy. The patients were divided into three groups: A, soft disc; B, hard disc; C, hard and soft disc. Follow-up was performed 2 years after surgery. Clinical outcome was classified according to Odom et al. and to the cervical Oswestry and 11-point box scales for arm and neck pain.

RESULTS

Ninety patients (92%) underwent intermediate follow-up examinations at an average of 33 months after surgery. Forty-nine patients were in group A, 24 in group B, and 17 in group C. At discharge, 98% of those in group A, 96% in group B, and 94% in group C showed excellent or good results. In two patients revision surgery was performed within 4 weeks due to recurrent disc herniation. In one patient revision was carried out due to a subcutaneous hematoma. In group B one case of vertebral artery injury occurred. Additionally in one patient of this group revision surgery was performed due to inadequate decompression of the neural foramen. At follow-up 94% of the patients in group A, 89% in group B, and 87% in group C had excellent or good results. The scores on the cervical Oswestry scale and the 11-point-box scale showed no significant differences among the groups.

CONCLUSION

Uncoforaminotomy, especially in patients with soft-disc pathologies, is a good operative method for the treatment of radicular pain.

[Occult sacral meningocele--a diagnostic challenge]

Occult sacral meningoceles are a rare causative factor for neural claudication or radiculopathy. Facet joint cysts in the lumbar spine causing similar symptoms are much more frequent. We report the case of a patient with the radiological diagnosis of a facet joint cyst causing neural claudication. During surgery an occult sacral meningocele was diagnosed. In the literature there are only few cases reported. Hence, the findings and important differential diagnoses of cystic epidural lesions in the lumbar spine are discussed.

Computed tomographic angiography in the evaluation of clip placement for intracranial aneurysm

BACKGROUND

Computed tomographic angiography (CTA) has been shown to reliably detect aneurysms pre-operatively. The aim of this study was to compare the ability of post-operative CTA to detect aneurysmal remnants in connection with clip placement compared with digital subtraction angiography (DSA). Furthermore, special attention was paid to identifying factors influencing the image quality of CTA.

METHOD

Between January 2005 and January 2006 a total of 76 patients with intracranial aneurysms were treated in our department. Thirty-two patients with a total of 33 clipped aneurysm were included in this study. All patients underwent CTA and DSA after surgery. Two investigators, each blinded to the classifications of the other, assessed image quality and clip placement.

FINDINGS

In three patients aneurysmal remnants could be detected with CTA and DSA. One 2-mm aneurysmal remnant was not clearly identified on CTA; two small (<2-mm) aneurysmal remnants were definitely not seen on CTA. A single titanium clip was used for aneurysmal clipping in 26 patients, two clips were needed in six patients and one aneurysm required three clips being used. Overall, use of one titanium clip tended to result in better image quality. In addition, clip-gantry angles between 30 degrees and 60 degrees tended to yield better image quality.

CONCLUSION

Post-operatively, CTA can be recommended as a reliable non-invasive diagnostic tool only with optimal image quality and with this criterion up to 66% of the aneurysms can be evaluated. Titanium artefacts, especially in the important zone (<2 mm) around the clip in which small aneurysmal remnants can occur, can render adequate evaluation impossible. CTA image quality depends on the number of titanium clips used, but clip-gantry-angle does not significantly influence the image quality.

Deep venous thrombosis after lumbar disc surgery due to compression of the vena cava caused by a retroperitoneal haematoma

The case of a 46-year-old Arabian male complaining of low back pain due to congenital lumbar spinal canal stenosis with additional disc herniation is presented. Following CT scan and MRI, bilateral enlarged partial hemilaminectomy was performed in L5/S1 with removal of herniated disc material. Intraoperatively, no complication was encountered. In the postoperative course, the patient had persistent low back pain and developed deep venous thrombosis in the left leg. Phlebography revealed thrombosis in the deep veins of the left leg extending into the pelvic region. The source of this high obstruction of the venous outflow was a retroperitoneal haematoma, visible on CT scan, compressing the vena cava at the level of L5/S1, the most probable cause of which was accidental perforation of the anterior spinal ligament. This case demonstrates that injury to the retroperitoneal vessels during lumbar disc surgery can also present as deep venous thrombosis due to obstruction of venous outflow.

In vitro flexibility of the cervical spine after ventral uncoforaminotomy

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.

Current status of intraoperative real-time vibrography in neurosurgery

PURPOSE

Intracranial lesions are often characterized by different elasticities. The aim of the present study was to test the application of vibrography during brain tumor surgery.

MATERIALS AND METHODS

The real-time vibrography system consisted of a conventional ultrasound system (Siemens Sonoline Omnia) with a custom-designed RF interface and a 6.5-MHz endocavity curved array (Siemens 6.5EC10). The RF data were digitized using a 50-MHz, 12-bit PCI analog/digital (A/D) converter for real-time or offline processing. Static compression was replaced by low-frequency axial vibration of the probe. A special applicator equipped with a stepping motor moved the ultrasonic probe and produced a low frequency mechanical vibration of 5-10 Hz with a vibration amplitude of 0.3 mm and slight preliminary compression (total<1 mm). The maximum application time was 60 sec. A pneumatic holding device (Unitrac, Aesculap, Tuttlingen, Germany) was used.

RESULTS

Brain tissue is normally color coded between red and orange. In this study 41 out of 45 tumors could be detected via vibrography. Two tumors could not be detected with this imaging technique: a glioblastoma at a depth of 2 cm and a metastasis at a depth of 3 cm. Two additional tumors were not recognized because of technical problems. In 4 cases tumors with strain values identical to those in brain tissue (coded red or orange) but easily identified by a peripheral zone of high strain (yellow) were found. Tumors with strain values higher than those measured in brain tissue coded yellow and were softer than brain during surgical intervention. Higher strain was found in 23 tumors. Tumors with strain values lower than those in cerebral tissue were found to be harder during surgery and coded brown or black. Lower strain was found in 10 cases. Four tumors were inhomogeneous and could not be assigned to one of the above groups. Mortality was 0%, morbidity 2.3%. One patient displayed transient paresis of the lower extremity due to microsurgical difficulties during the approach. In one patient minimal bleeding of the cortical surface occurred in a frontobasal tumor; however, no postoperative deficits were noted.

CONCLUSION

Vibrography is a new low-risk technique for intraoperative imaging. In low-grade astrocytomas and oligodendrogliomas, this additional technique can be used to control resection. In other cortical and subcortical tumors (e. g. metastases), it can provide an impression of the intratumoral elasticities.

Feasibility of contrast-enhanced sonography during resection of cerebral tumours: initial results of a prospective study

The aim of this study was to adapt the ultrasonographical techniques developed for brain perfusion imaging to an intraoperative setting for topographic diagnosis of cerebral tumours. During surgery, the patients underwent contrast-enhanced ultrasonography (phase inversion harmonic imaging, bolus kinetic, fitted model function). Endocavity curved array (6.5EC10, 6.5 MHz) was used intraoperatively. The ultrasound contrast agent SonoVue (Bracco) was administered IV as a bolus injection. Off-line, time-intensity curves as well as perfusion maps were calculated and parameters such as peak intensity were locally extracted to characterise perfusion. Seven patients with brain tumours of different histologic types were subjected to contrast-enhanced ultrasonography during surgery. Tissue differentiation with contrast agent was superior to conventional B-mode ultrasound imaging. Intraoperative contrast-enhanced ultrasonography enabled visualisation of cerebral tumours in high spatial resolution.

Anterior Uncoforaminotomy in the Treatment of Recurrent Radiculopathy after Anterior Cervical Discectomy with Fusion

BACKGROUND

In patients after anterior cervical discectomy (ACD) with fusion newly developed retrospondylophytes or incomplete decompression of the nerve root can cause recurrent radicular pain. Anterior cervical uncoforaminotomy (uncoforaminotomy) is an operative method which removes the causative degenerative pathology at the level of the neural foramen leaving untouched the inserted graft at this level.

METHOD

Between February 2004 and April 2005, 7 patients underwent uncoforaminotomy after ACD with fusion for the treatment of recurrent cervical radiculopathy in our neurosurgical department. Prior to treatment patients received a computed tomography (CT) and a neurological examination. Anterior uncoforaminotomy was performed thereafter (for technical details see publication by Jho, 1996). A postoperative CT scan was done before discharge. Follow-up examination was performed eight weeks after surgery.

FINDINGS

Five patients underwent the operation at C5/6, one patient was operated at C6/7 and one patient had the operation at two levels (C5/6 and C6/7). At discharge six patients had excellent or good results.

CONCLUSION

Uncoforaminotomy is a good method for the treatment of newly acquired spondylotic spurs in the foramen or incomplete osseous decompression after ACD with fusion and recurrent radicular pain.

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.

Dynamic Cerebral Autoregulation in Patients with Ruptured and Unruptured Aneurysms after Induction of General Anesthesia

INTRODUCTION

Blood pressure management in patients undergoing surgery for clipping of aneurysms is demanding. More information about the ability of cerebral vessels to normally regulate cerebral blood flow may have a direct influence on the intraoperative management. In patients with subarachnoid hemorrhage (SAH) a disturbance of cerebral autoregulation has been reported and it correlated with the severity of the bleeding in these studies. The impairment of autoregulation was demonstrated using static measurements of cerebral pressure autoregulation. However, the dynamic component of the autoregulatory capacity seems to be of importance in the acute setting after SAH. The aim of this study was to evaluate dynamic pressure autoregulation in patients undergoing surgery for intracranial aneurysms.

PATIENTS/MATERIAL AND METHODS

36 patients with a mean age of 45 years were evaluated, 26 patients with acute SAH, 10 patients with unruptured aneurysms. Cerebral autoregulation in normocapnia was tested using thigh cuffs to alter arterial blood pressure and continuous registration of the blood flow velocities with transcranial Doppler sonography. After the induction of general anesthesia under normocapnia the autoregulatory index (ARI) was calculated (values between 0-9). Patient groups were compared using Wilcoxon- and Spearman's rank test.

RESULTS

The two patient groups were comparable with regard to gender, age, PaCO(2), blood flow velocities and blood pressure. In patients with SAH mean ARI was 3.1/3.3 (right/left side) compared to 4.7/4.6 (right/left side) in patients without SAH. The difference was statistically significant (Wilcoxon p = 0.0399). The degree of impairment of the autoregulatory capacity increased significantly (p = 0.006) with the severity of the SAH (Hunt&Hess and Fisher scale).

CONCLUSION

Dynamic pressure autoregulation is impaired in patients after SAH compared to patients without SAH and correlates with the severity of the SAH. We propose that autoregulation should be measured in all patients with SAH or that an impaired autoregulation should be taken into account in patients with SAH undergoing surgery in the acute phase.

Neurosurgical operations with the patient in sitting position: analysis of risk factors using transcranial Doppler sonography

BACKGROUND

One major risk factor of the sitting position for neurosurgery is air embolism, especially in patients with persistent foramen ovale (PFO). The first aim of this prospective study was to evaluate a bedside method for detecting PFO using transcranial Doppler sonography (TCD) with contrast medium. A second aim was to address intraoperative monitoring, patient positioning and the occurrence and clinical relevance of air embolism.

METHODS

Ninety patients with a mean age of 56.5 yr (range 14-81 yr) undergoing surgery in sitting position were investigated by TCD with contrast agent to detect functional PFO, that is PFO that can be provoked with a Valsalva manoeuvre. In patients in whom TCD was not possible, transcranial duplex sonography, duplex sonography of the carotid artery at the neck or transoesophageal ECG was performed.

RESULTS

In 26 patients PFO was detected. Thirteen of them presented a persistent PFO with high-intensity transient signal in both middle cerebral arteries without Valsalva manoeuvre. The intraoperative positioning in these patients was adapted to the risk for a paradoxical air embolism, although, after surgical recommendations, three patients with a persistent PFO underwent surgery in sitting position. Intraoperative air embolisms were seen in 8 of 80 patients in sitting or semi-sitting position with air aspirable through the central venous catheter.

CONCLUSION

To address the risk of a paradoxical air embolism, especially in patients undergoing surgery in sitting position, preoperative detection of PFO is advisable. If surgery is performed in seated PFO patients, additional monitoring and special care are warranted.

Analysis of Surgical Management of Calvarial Tumours and First Results of a Newly Designed Robotic Trepanation System

This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.

Schmerzreduktion nach Operation an der Halswirbelsäule

AIM

Surgery in cervical spine disease using titanium cages is a common procedure to reduce the pain and neurological deficits. This study was aimed to evaluate the results in pain reduction using the wing cage intraoperatively.

METHOD

In this prospective study demographic data were noted, whereas special emphasis was placed on pain, which was noted using a visual pain scale and the prolo score, neurological deficits and the causing pathology. Furthermore, questions about the use of analgesics and the duration of pain were asked. After operation with insertion of a wing cage instead of the disk, a neurological investigation 6, 12 and 24 months later was done to evaluate the postoperative status.

RESULTS

54 patients underwent a cervical discectomy in 64 segments as therapy for neck pain or a radiculopathy caused by osteochondrosis or disc disorder. Patients with brachialgia profited most from the operation. Less improvement was seen in cases of osteochondrosis or combined pathology.

CONCLUSION

Patients with pain caused by discs in the cervical spine, have better improvement than patients with other pathologies. This should be taken into account when choosing the mode of therapy.

3-Dimensional computed tomographic angiography for use of surgery planning in patients with intracranial aneurysms

BACKGROUND

After subarachnoid haemorrhage (SAH) diagnostic evaluation of the underlying cause is warranted since the rebleeding rate is high. The objective of the study was to answer the question, whether 3-Dimensional computed tomographic angiography (3D-CTA) is able to accurately determine the surgical indications in patients with intracranial aneurysms.

METHODS

After performing 3D-CTA the size of the aneurysm, direction of the aneurysmal dome, neck position and variants of the circle of Willis were analysed. Surgery was performed solely on CTA data in those cases, where the aneurysm was clearly visible. If the findings were negative or inconclusive, intra-arterial digital subtraction angiography (DSA) was also done.

FINDINGS

Between January 2001 and December 2002 100 patients (68 F, 32 M) were examined and 123 aneurysms (86 ruptured and 37 unruptured) were diagnosed. All patients received CTA preoperatively and in 27 patients selective DSA was additionally performed. Postoperatively in 34 patients the operative result was checked by DSA. A good correlation between CTA and the intra-operative findings was present in 92 of 100 patients. One aneurysm was not seen on CTA, but was on DSA. In four cases we could confirm DSA findings in CTA after re-evaluation of the data. In three cases neither CTA nor DSA clearly showed an aneurysm, but it was confirmed during surgery. A good correlation between CTA and DSA was found in 60 of 61 patients (98%). The correlation between CTA and intra-operative findings was good as expected in 92 patients, in 5 patients an aneurysm was detected on re-evaluation. Only one aneurysm could not be demonstrated by CTA but in DSA.

CONCLUSION

CTA is less invasive, less time consuming, cheaper and easier to demonstrate the essential information regarding the aneurysm than DSA. We therefore recommend that following a careful analysis most aneurysms - 92% - can be operated solely on CTA data.

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.

Accidential Dural Tears Occurring during Supratentorial Craniotomy - A Prospective Analysis of Predisposing Factors in 100 Patients

OBJECT

Accidental dural tears during craniotomy constitute a possible source of CSF leakage and wound infection. This can turn an elective procedure into a complicated and cost-intensive problem. Only a few studies have addressed the incidence of dural tears, but there have been many studies dealing with various techniques that can be employed to repair dural tears. The present study was carried out to analyze predisposing factors for dural tears during trepanation in order to optimize the design of a robot-assisted trepanation system.

PATIENTS

100 patients were analyzed prospectively. An evaluation sheet was designed to document size and location of the lesion and the craniotomy, the geometry and number of burr holes, and the auxiliary tools used during bone flap removal. Furthermore, the suspected histology was noted and anatomical facts, including cranial vault thickness and the presence of hyperostosis frontalis interna, were documented.

RESULTS

In 100 craniotomies performed, in the majority of cases (64 %), in order to gain access to intracerebral lesions, 30 dural tears were seen, involving both dural layers in 26 cases. There were 26 tears located under the margins of the craniotomy; the length was 0-3 cm in 18 patients (69 %). Significant predisposing factors were the thickness of the cranial vault and the presence of a hyperostosis frontalis. Furthermore, the location (frontal) and the diagnosis of an extracerebral pathology, including meningiomas, were significant factors for dural tears. Elderly patients and the use of the drill to complete the trepanation were also significant predisposing factors. Dural repair was done using suturing, in most of the cases combined with a free periostal flap. Central dural tears were integrated into the planned dural opening. A vascularized flap or muscle was used in the minority of cases. Postoperative cerebral fluid leakage was seen in two patients, wound infections in three.

CONCLUSIONS

Dural tears occurring during craniotomy cannot be prevented, when predisposing factors are taken into account. The absence of brain damage may due to two factors: 1) in elderly patients with hyperostosis, an additional atrophy of the brain is present; 2) extracerebral tumors, with their space-occupying growth, shift the underlying brain away from the calvaria. Considering the design of a robot-assisted trepanation system, the following conclusions seem possible: dural tears cannot be avoided because predisposing factors are overriding. For improved safety, additional, specialized instrumentation is required.

Application of a Newly Developed Visual Navigation System in Humans. First Results

A visual navigation system (VN) was developed which uses intraoperatively stored endoscopic images together with their specific 3D-address. A special calibration enables one to recalculate the distortion of the endoscopic images. Several modules (e. g., landmark tracking, virtual back-movement) are offered to the neurosurgeon. The system was tested in 12 human subjects during neuroendoscopic interventions and worked without problems in nearly all cases. The possibilities of digital image navigation can be used especially for control of instrument movement in case of red-out situations or blurred vision. Many further developments of the VN system are possible in order to increase the safety of neuroendoscopic interventions.

Vibrography: first experimental results in swine brains

OBJECT

The aim of this study was to determine whether vibrography, an ultrasound-based real-time strain imaging method for registering the elastic properties of tissue, is superior to conventional ultrasound imaging techniques for detecting low-contrast space-occupying lesions in brain tissue and for delineating the boundaries between such lesions and the surrounding tissue.

METHODS

As our experimental model we used swine brains taken from freshly slaughtered pigs. After injecting agarose into these brains at different depths, we compared both the conventional ultrasonographic images and the elastographic images of the region of interest with the corresponding anatomical brain sections.

RESULTS

In 83.6 % of the experiments, it was possible to detect the polymerized agarose in the brain tissue with vibrographic techniques. In 17 experiments agarose lesions which were not detectable by ultrasound were visualized via vibrography. Furthermore, statistical analysis revealed that elastography is a more precise tool than conventional ultrasound for determining lesion size.

CONCLUSION

These findings indicate that vibrography is a promising real-time imaging method with numerous potential applications in the field of neurosurgery. Visualization of the elastic properties provides the neurosurgeon with additional data on the lesion and the boundary between the lesion and the surrounding tissue.