Cost-effectiveness of stereotactic vacuum-assisted biopsy for nonpalpable breast lesions

PURPOSE

To examine the potential cost-savings of stereotactic vacuum-assisted biopsy (SVAB) over open surgical biopsy (OSB) in diagnosis of nonpalpable lesions on mammography and to estimate the cost-saving effect on lesions at different levels of malignant probability.

METHODS

This retrospective study was approved by our Institutional Review Board. We retrospectively reviewed 276 (33.8 %) SVAB and 541 (66.2 %) OSB medical records at a medical center. Direct costs included patients' self-paid and national health insurance claim charges. Indirect costs were calculated using sick days, average salary, and age-adjusted employment rate. One-way and two-way sensitivity analyses were conducted. Lesion classification was determined by the assessment categories of Breast Imaging Reporting and Data System (BI-RADS), 4th or 5th editions.

RESULTS

SVAB decreased the direct cost by $90.3 (10.1 %) per diagnosis. The indirect cost was decreased by $560.2 (96.0 %). Overall, SVAB saved 43.9 % of resource utilization for each biopsy. Taking the cost of the subsequent malignant surgery into account, from the healthcare providers' perspective, SVAB was cost-effective if a lesion had less than 19 % likelihood of malignancy. From the societal perspective, SVAB reduced productivity loss for all the lesions. Based on the positive predictive value of the BI-RADS categories, SVAB was more suitable for the lesions of category 4A and category 3, resulting in greater savings in both medical and societal resources.

CONCLUSIONS

SVAB is a cost-effective diagnostic option for nonpalpable breast lesions. The cost-saving effect is greater for the lesions of category 4A and category 3.

Utility of Stereoelectroencephalography in Children with Dysembryoplastic Neuroepithelial Tumor and Cortical Malformation

BACKGROUND

Uncontrolled seizures in children can contribute to irreversible cognitive impairment and developmental delay, in addition to placing them at risk for sudden unexplained death in epileptic patients (SUDEP). Since its introduction at Saint Ann Hospital in Paris in the 1960s, stereoelectroencephalography (SEEG) is increasingly being utilized at epilepsy centers in the United States as an invasive tool to help localize the seizure focus in drug-resistant focal epilepsy.

INDICATIONS

Children with symptomatic epilepsy, commonly due to cortical dysplasia and dysembryoplastic neuroepithelial tumor (DNET), may benefit from SEEG investigation. The arrangement of SEEG electrodes is individually tailored based on the suspected location of the epileptogenic zone (EZ). The implanted depth electrodes are used to electrically stimulate the corresponding cortices to obtain information about the topography of eloquent cortex and EZ. Morbidity: Surgical morbidity in these children undergoing SEEG investigation is low, but not negligible. The number of electrodes directly correlates with the risk of intraoperative complication. Thus a risk and benefit analysis needs to be carefully considered for each patient. Neurodiagnostic technology: Both during and after the SEEG electrode implantation, the intraoperative monitoring and EEG technologists play a vital role in the successful monitoring of the patient.

CONCLUSION

SEEG is an important tool in the process of epilepsy surgery in children with symptomatic epilepsy, commonly due to cortical dysplasia and DNET.

Impact of stereotactic 11-g vacuum-assisted breast biopsy on cost of diagnosis in Austria

PURPOSE

To determine the frequency with which stereotactic 11-g vacuum-assisted breast biopsy (11-g SVAB) obviates an open surgical biopsy (OSB), to compare the costs of these two biopsy methods, and to estimate the potential cost savings attributable to 11-g SVAB in the diagnosis of suspicious breast lesions in patients in Austria.

MATERIALS AND METHODS

We retrospectively reviewed 318 consecutive breast lesions of BI-RADS categories IV and V (microcalcifications n=166; masses n=152) on which 11-g SVAB and OSB were performed. Cost savings were calculated using nationally allowed flat rates and patient charges. Costs were measured from a hospital and a socioeconomic perspective. Common clinical scenarios and sensitivity analyses assessed the extent of achievable cost savings.

RESULTS

11-g SVAB obviated the need for an OSB in 93 (29%) of 318 women. Overall cost savings per 11-g SVAB over OSB were € 242 per case from a hospital perspective, and € 422 per case from a socioeconomic perspective. The use of 11-g SVAB decreased the cost of diagnosis by 7% from a hospital perspective, and by 10% from a socioeconomic perspective.

CONCLUSION

In Austria, annual national savings of over 5 million Euro could be realized with the use of 11-g SVAB for the diagnosis of suspicious breast lesions. Although savings per case are modest, the national health care system realizes significant cost reduction as women benefit from a faster and less invasive approach to diagnosis.

Safety and efficacy of frameless and frame-based intracranial biopsy techniques

BACKGROUND

Frameless stereotaxy or neuronavigation has evolved into a feasible technology to acquire intracranial biopsies with good accuracy and little mortality. However, few studies have evaluated the diagnostic yield, morbidity, and mortality of this technique as compared to the established standard of frame-based stereotactic brain biopsy. We report our experience of a large number of procedures performed with one or other technique.

PATIENTS AND METHODS

We retrospectively assessed 465 consecutive biopsies done over a ten-year time span; Data from 391 biopsies (227 frame-based and 164 frameless) were available for analysis. Patient demographics, peri-operative characteristics, and histological diagnosis were reviewed and then information was analysed to identify factors associated with the biopsy not yielding a diagnosis and of it being followed by death.

RESULTS

On average, nine tissue samples were taken with either stereotaxy technique. Overall, the biopsy led to a diagnosis on 89.4% of occasions. No differences were found between the two biopsy procedures. In a multiple regression analysis, it was found that left-sided lesions were less likely to result in a non-diagnostic tissue sample (p = 0.023), and cerebellar lesions showed a high risk of negative histology (p = 0.006). Postoperative complications were seen after 12.1% of biopsies, including 15 symptomatic haemorrhages (3.8%). There was not a difference between the rates of complication after either a frame-based or a frameless biopsy. Overall, peri-operative complications (p = 0.030) and deep-seated lesions (p = 0.060) increased the risk of biopsy-related death. Symptomatic haemorrhages resulting in death (1.5% of all biopsies) were more frequently seen after biopsy of a fronto-temporally located lesion (p = 0.007) and in patients with a histologically confirmed lymphoma (p = 0.039).

CONCLUSIONS

The diagnostic yield, complication rates, and biopsy-related mortality did not differ between a frameless biopsy technique and the established frame-based technique. The site of the lesion and the occurrence of a peri-operative complication were associated with the likelihood of failure to achieve a diagnosis and with death after biopsy. We believe that using intraoperative frozen section or cytologic smear histology is essential during a stereotactic biopsy in order to increase the diagnostic yield and to limit the number of biopsy specimens that need to be taken.

Comparison of Frame-Based and Frameless Stereotactic Hematoma Puncture and Subsequent Fibrinolytic Therapy for the Treatment of Supratentorial Deep Seated Spontaneous Intracerebral Hemorrhage

OBJECTIVE

This study compared the technical implications and clinical outcome of patients treated for an intracerebral hemorrhage using two minimally invasive procedures: frame-based stereotactic hematoma aspiration and frameless navigation-guided hematoma aspiration followed by fibrinolysis.

METHODS

Thirty patients with a spontaneous supratentorial intracerebral hemorrhage, which was treated by a frame-based (n=15) and frameless (n=15) hematoma aspiration followed by subsequent fibrinolysis with urokinase, were retrospectively reviewed. The data for the two subsets of patients were analyzed with regard to hematoma reduction, Glasgow Coma Scale (GCS), and degree of weakness.

RESULTS

In the frame-based stereotactic hematoma aspiration group, the volume of the hematoma was 15.4-100.0 mL (mean: 40.7+/-24.4), the GCS upon admission was 4-15 (mean: 10.1+/-3.0), and the grade of weakness upon admission was 1-5 (mean: 2.1+/-0.9). On the other hand, in the frameless navigation-guided hematoma aspiration group, the hematoma volume was 15.2-62.0 mL (mean: 30.0+/-15.2), the GCS upon admission was 7-15 (mean: 13.0+/-2.4), and the grade of weakness upon admission was 1-4 (mean: 2.3+/-1.2). The drainage catheter was in place for a mean duration of 5.1+/-2.4 days (range: 1-12 days). In the frame-based group, the initial hematoma was reduced by -115-88.5% (mean: 52+/-31.5) immediately after surgery, and 90.5% (41-100%) of the initial volume 14 days after surgery. In the frameless group, the initial hematoma was reduced by 11.7-90.8% (mean 57.3+/-25.1) immediately after surgery and 95.8% (87.7-100%) 14 days after surgery. The GCS score and the degree of weakness were evaluated 14 days after surgery, and the Glasgow outcome scale (GOS) score was evaluated at discharge. There were no statistically significant differences between the two groups.

CONCLUSION

The frame-based group and the frameless group followed by fibrinolysis had similar outcomes, and both procedures effectively reduced the intracerebral hemorrhage volume within a short period of time. In addition, these procedures are simple, precise, safe, and brief with a very low rebleeding rate and mortality.

Unilateral pallidotomy versus bilateral subthalamic nucleus stimulation in Parkinson's disease: one year follow-up of a randomised observer-blind multi centre trial

BACKGROUND

To investigate whether STN stimulation is more efficacious than unilateral pallidotomy in advanced Parkinson's disease (PD) one year after surgery.

METHOD

Thirty-four patients with advanced PD were randomly assigned to unilateral pallidotomy or bilateral STN stimulation. Outcome measures were parkinsonian symptoms in off and on phases (UPDRS 3), dyskinesias, functional status, Parkinson's disease quality of life questionnaire, the effects on separate symptoms, timed tests, patient diaries, dopaminergic drugs changes, adverse effects, and global outcome scale. Patients were assessed before surgery, six months and one year after surgery. The primary outcome measure was the off phase UPDRS 3 at six months follow-up.

FINDINGS

The off phase UPDRS 3 score improved from 46.5 to 32 points in the pallidotomy patients and from 51.5 to 24 in the STN stimulation patients (p = 0.002). On phase UPDRS 3 and off phase Schwab and England functional scale improved significantly in favour of the STN stimulation patients. Dopaminergic drugs reduction was larger in the STN group although the difference between the treatment groups was not significant. One patient in each group had a major adverse effect.

CONCLUSIONS

Bilateral STN stimulation is more efficacious than unilateral pallidotomy in advanced PD up to one year after surgery.

Stereotactic biopsy of brain stem masses: decision analysis and literature review

BACKGROUND

Adult brain stem tumors are rare, and diverse pathology can be found in this location. Stereotactic biopsy of lesions in the brain stem has been performed since the 1960s with high diagnostic and low complication rates. Advances in imaging technology have raised questions regarding the utility of biopsy. We perform decision analysis to aid clinicians in their approach to management of adult brain stem lesions.

METHODS

A structured literature search revealed 20 publications with 457 patients who had undergone brain stem lesion biopsy. These publications were reviewed to determine diagnostic rates and the incidence of complications. Standard decision analytic techniques were applied to the case of a virtual adult patient with a lesion in the brain stem.

RESULTS

A 1-way sensitivity analysis revealed the likelihood that the preoperative diagnosis was correct and the rate at which incorrect treatment was based on faulty empirical diagnosis as the 2 factors with the greatest effects on patient outcome. The diagnostic rate and complication rate of biopsy, within the ranges reported in the literature, had lesser effects. A threshold analysis was constructed to compare outcomes from stereotactic biopsy vs empiric therapy for a brain stem lesion. The probability that the preoperative diagnosis is correct is plotted vs the probability that empirical treatment based on an incorrect diagnosis will have adverse effect.

CONCLUSIONS

Management of lesions in the adult brain stem requires careful consideration of multiple preoperative factors including clinical and radiographic diagnostic certainty, consequences of empiric therapy, and the surgeon's complication rate.

Contour and paired-point registration in a model for image-guided surgery

OBJECTIVES/HYPOTHESIS

This study assesses target registration error (TRE) of contour-based registration (CBR) and paired-point registration (PPR) for endoscopic sinus surgery.

STUDY DESIGN

The experimental registration model consisted of a replica of a human head (Sawbones #1345-27; Pacific Research Laboratories, Vashon, WA). Twelve surface fiducial markers were affixed to the simulated skin on the model, and titanium screws were placed in the regions of the anterior ethmoid (AE) and sphenoid face (SF). An axial computed tomography scan (1-mm slice thickness) was then obtained.

METHODS

Registration was then performed on the InstaTrak 3500 Plus (GE Surgical Navigation & Visualization, Lawrence, MA) with the standard PPR protocol with 12 points and CBR protocol with 500, 250, 125, 50, and 4 points. TRE was then calculated at the AE and SF targets.

RESULTS

Target registration error was significantly lower for paired-point registration compared with contour-based registration (AE, 0.5 mm vs. 1.5 mm, P < .0001; SF, 0.8 mm vs. 1.5 mm, P < .0001). Among contour-based registration protocols, target registration error at the sphenoid face was lowest with 50 points (1.5 mm, P < .02). At the anterior ethmoid, contour-based registration with 50 points produced a lower target registration error than contour-based registration with 125 points (1.5 vs. 1.8 mm, P < .01). Other target registration error values for CBR were similar at both regions. The target registration error interquartile range was lowest with CBR-125 at both regions.

CONCLUSIONS

Paired-point registration provided significantly lower target registration error. Contour-based registration with 125 points (and possibly as few as 50 points) produces clinically acceptable target registration error. This registration model elucidates important concepts about registration for surgical navigation for sinus surgery.

Prediction of the variance of stereological volume estimates from systematic sections using computer-intensive methods

The Cavalieri method is an unbiased estimator of the total volume of a body from its transectional areas on systematic sections. The coefficient of error (CE) of the Cavalieri estimator was predicted by a computer-intensive method. The method is based on polynomial regression of area values on section number and simulation of systematic sectioning. The measurement function is modelled as a quadratic polynomial, with an error term superimposed. The relative influence of the trend and the error component is estimated by techniques of analysis of variance. This predictor was compared with two established short-cut estimators of the CE based on transitive theory. First, all predictors were applied to data sets from six deterministic models with analytically known CE. For these models, the CE was best predicted by the older short-cut estimator and by the computer-intensive approach, if the measurement function had finite jumps. The best prediction was provided by the newer short-cut estimator when the measurement function was continuous. The predictors were also applied to published empirical datasets. The first data set consisted of 10 series of areas of systematically sectioned rat hearts with 10-13 items, the second data set consisted of 13 series of systematically sampled transectional areas of various biological structures with 38-90 items. On the whole, similar mean values for the predicted CE were obtained with the older short-cut estimator and the computer-intensive method. These ranged in the same order of magnitude as resampling estimates of the CE from the empirical data sets, which were used as a cross-check. The mean values according to the newer short-cut CE estimator ranged distinctly lower than the resampling estimates. However, for individual data sets, it happened that the closest prediction as compared to the cross-check value could be provided by any of the three methods. This finding is discussed in terms of the statistical variability of the resampling estimate itself.

Isotropic fractionator: a simple, rapid method for the quantification of total cell and neuron numbers in the brain

Stereological techniques that estimate cell numbers must be restricted to well defined structures of isotropic architecture and therefore do not apply to the whole brain or to large neural regions. We developed a novel, fast, and inexpensive method to quantify total numbers of neuronal and non-neuronal cells in the brain or any dissectable regions thereof. It consists of transforming highly anisotropic brain structures into homogeneous, isotropic suspensions of cell nuclei, which can be counted and identified immunocytochemically as neuronal or non-neuronal. Estimates of total cell, neuronal, and non-neuronal numbers can be obtained in 24 h and vary by <10% among animals. Because the estimates obtained are independent of brain volume, they can be used in comparative studies of brain-volume variation among species and in studies of phylogenesis, development, adult neurogenesis, and pathology. Applying this method to the adult rat brain, we show, for example, that it contains approximately 330 million cells, of which 200 million are neurons, and almost 70% of these are located in the cerebellum alone. Moreover, contrary to what is commonly assumed in the literature, we show that glial cells are not the majority in the rat brain.

Surgery for spontaneous intracerebral hemorrhage has greater remedial value than conservative therapy

BACKGROUND

The aim of this study was to compare the efficacy of surgery for spontaneous intracerebral hemorrhage with that of medical treatment, based on data from the Japan Stroke Registry Study.

METHODS

From 1999 to 2001, 1010 patients with spontaneous intracerebral hemorrhage were registered in the Japan Standard Stroke Registry Study from 45 stroke center hospitals in Japan. The National Institutes of Health Stroke Scale (NIHSS), Japan Stroke Scale (JSS), and modified Rankin Scale scores were used to compare severity and improvement in patients given surgical and medical treatment.

CONCLUSIONS

Surgically treated patients, especially those with cerebellar hemorrhage, had significantly greater improvement in NIHSS or JSS score compared with medically treated patients. Our findings indicated that the patients who underwent surgery appeared to have better outcomes. But, because the study was not randomized, this observation cannot be interpreted as indicating that surgery is advantageous.

Changing patterns in diagnosis and treatment of ductal carcinoma in situ of the breast

BACKGROUND

The increased incidence of ductal carcinoma in situ (DCIS) of the breast and the emergence of new diagnostic and therapeutic tools like mammographic screening, stereotactic core biopsy and reconstructive surgery prompted us to investigate how these developments influenced diagnosis and treatment.

METHODS

Clinical and pathological characteristics of 403 patients with DCIS consecutively treated at The Netherlands Cancer Institute between 1986 and 2002 were evaluated and the effect of introduction of mammographic screening, stereotactic core biopsy and reconstruction on diagnosis and treatment was studied.

RESULTS

Following the nationwide introduction of mammographic screening the number of non-symptomatic DCIS increased from 47 to 77%. Introduction of stereotactic core biopsy resulted in a rise of one-step procedures from 26 to 52%. Mastectomy rate did not change over time: 59% overall. However, reconstruction rate increased from 17 to 39%.

CONCLUSION

This study shows a steep rise in diagnosis of non-symptomatic DCIS after introduction of screening. Further, the introduction of pre-operative diagnosis by stereotactic core biopsy resulted in a decrease of multiple surgical procedures. Mastectomy, with increasing application of breast reconstructions, remains an important treatment modality in the management of DCIS despite advancements in detection and diagnosis.

Reliability of atlas-derived coordinates in deep brain stimulation

BACKGROUND

In deep brain stimulation the way to define and localize the optimal target for the individual patient is still under debate. The objective of our study was to investigate the reliability of atlas derived data by comparing them with direct targeting on MR images.

METHOD

We investigated 28 STN targets in 14 volunteers. The stereotactic coordinates of the dorso-lateral subthalamic nucleus (STN), were determined in 5 different ways for both STNs of each individual volunteer: 1. directly, on axial T2WI spin echo slices, 2. directly, on coronal T2WI spin echo slices and after fusion of data sets: 3. indirectly, on an axial atlas plate, 4. indirectly, on a coronal atlas plate, 5. indirectly, 12 mm lateral, 3 mm posterior and 3 mm inferior to mid-AC-PC.

FINDINGS

The differences between MRI derived targets on axial vs. coronal slices were not statistically significant. After detection of the atlas derived targets the resulting x-coordinates were found more lateral than after direct detection on both, axial and coronal T2-weighted images (p < 0.001). On axial images y-coordinates were located more anterior (p = 0.240) on atlas derived targets and more posterior when target localizations were compared on coronal slices (p < 0.001). z-Coordinates were more superior after atlas targeting compared to MRI targeting (p < 0.001). Differences up to 6.21 mm occurred.

CONCLUSIONS

Despite the limitations concerning image distortions and slice thickness, direct target planning on MRI, regarding our results, is more reliable than targeting solely based on atlas derived data. Only MRI gives us detailed information about the individual configurations of central structures in every single patient. However, targets, which are not detectable on MRI like the nucleus ventralis intermedius have to be planned using stereotactic atlas information. In these cases intra-operative micro-electrode recording might help to better define the target region.

Is the subthalamic nucleus hypointense on T2-weighted images? A correlation study using MR imaging and stereotactic atlas data

BACKGROUND AND PURPOSE

Although the subthalamic nucleus is the most frequently used target for surgical treatment of Parkinson's disease, the criteria on which it can be identified on T2-weighted images have never been clearly defined. This study was conducted to characterize the precise anatomic distribution of T2-weighted hyposignal in the subthalamic region and to correlate this hyposignal with iron content in the subthalamic nucleus.

METHODS

The T2-weighted MR imaging acquisitions of 15 patients with Parkinson's disease were fused with a digitized version of the Schaltenbrand and Wahren anatomic atlas. The MR signal intensity within the anatomic limits of the subthalamic nucleus was evaluated. An anatomic specimen obtained at autopsy was used to evaluate iron content.

RESULTS

In all patients, the subthalamic nucleus was hypointense on both sides in the anterior half of the nucleus. At more posterior levels of the nucleus, hypointensity was less frequently observed (20-80%). Hypointensity was never observed at the most posterior pole. Iron was present in the anteromedial part of the nucleus but absent at the most posterior levels.

CONCLUSION

The hypointense signal intensity located lateral to the red nucleus and dorsolateral to the substantia nigra correlates with the presence of iron and corresponds anatomically to the subthalamic nucleus. It can therefore be used as a landmark for electrode implantation in patients with Parkinson's disease. It should, however, be emphasized that although hypointensity was always present in the anterior half of the subthalamic nucleus, the posterior part of the nucleus was not visible in most cases.

[Optimization of microsurgical operation technique to insert auditory brainstem implants, taking into account the results of a morphometric study]

STATE OF THE ART

The surgical placement of auditory brainstem implants to stimulate the cochlear nuclear region in patients with acquired bilateral retrocochlear deafness allows limited restitution of hearing. However, there have been few studies on the topographical relations in the target region, particularly the floor of the IVth ventricle.

TOPIC OF THE STUDY

Is it possible to obtain more precise anatomical data in order to improve the surgical approaches and techniques for the placement of auditory brainstem implants? AIMS. To obtain a more precise topo- anatomical orientation in the target region for microsurgical lateral and midline approaches or a stereotactic operative strategy.

METHODS AND RESULTS

Landmarks for the placement of an auditory brainstem implant via the IVth ventricle were examined and measured in a series of formalin-fixed human brainstems ( n=28). These data, and knowledge of their variability, allow a more precise surgical lateral approach. It is essential to precisely localise the target region, as it can only be partly discerned under the microscope during an operation. For this reason, to date its precise localisation has been determined only electrophysiologically.

CONCLUSION

Exact target localisation improves safety. From an anatomical point of view the midline approach gives the chance to enlarge the indication spectrum for an implant. The anatomical data obtained here could also be integrated into a stereotactic surgical strategy.

Orbitofrontal epilepsy: electroclinical analysis of surgical cases and literature review

Clinical and electrographic data were reviewed on 2 of our patients with orbitofrontal epilepsy who were seizure free at 5-year follow-up, and on 2 similar patients from the literature. One of our patients was lesional, and the other was nonlesional. Interictal EEG discharges were lateralized to the side of invasively recorded orbitofrontal seizures in the nonlesional case. In this case, no clinical manifestations occurred until the orbitofrontal discharge had spread to the opposite orbitofrontal and both mesial temporal areas. Unresponsiveness or arrest of activity were the initial manifestations of complex partial seizures in both cases. The 2 cases from the literature with long-term seizure-free follow-up had little impairment of awareness and displayed vigorous motor automatisms. Interictal epileptiform activity was bifrontally synchronous in 1 case. Ipsilateral frontotemporal discharges were seen in both. Invasive ictal epileptiform activity appeared maximal in the ipsilateral orbitofrontal region in both patients. No consistent electrographic or clinical pattern characterized these 4 cases. Seizures of orbitofrontal origin may be characterized by either unresponsiveness associated with oroalimentary automatisms or limited alteration of awareness and associated with vigorous motor automatisms. Invasive monitoring of the orbitofrontal cortex should be considered in nonlesional cases with complex partial seizures that show nonlocalizing ictal patterns and interictal frontal or frontotemporal epileptiform discharges.

A Simple Method to Assess Accuracy of Deep Brain Stimulation Electrode Placement: Pre-Operative Stereotactic CT + Postoperative MR Image Fusion

OBJECTIVE

To describe a method for the measurement of the accuracy of deep brain stimulation (DBS) electrode placement with the use of image fusion technologies.

PATIENTS AND METHODS

Ten consecutive patients suffering from movement disorders underwent DBS electrode placement. Postoperative MR images were fused with the pre-operative stereotactic CT. The placement error in the anteroposterior, lateral and vertical planes was calculated.

RESULTS

The anteroposterior mean error +/- SD was 0.61 +/- 0.22 mm (range 0.2-0.9 mm). The lateral mean error +/- SD was 0.65 +/- 0.27 mm (range 0.2-2.2 mm). The vertical mean error +/- SD was 0.82 +/- 0.31 mm (range 0.3-1.6 mm).

CONCLUSIONS

This technique provides a simple and precise method for the evaluation of the accuracy of DBS electrode placement.

Surgery for Parkinson disease in the United States, 1996 to 2000: practice patterns, short-term outcomes, and hospital charges in a nationwide sample

Object. The surgical treatment of Parkinson disease (PD) has undergone a dramatic shift, from stereotactic ablative procedures toward deep brain stimulaion (DBS). The authors studied this process by investigating practice patterns, mortality and morbidity rates, and hospital charges as reflected in the records of a representative sample of US hospitals between 1996 and 2000.

Methods. The authors conducted a retrospective cohort study by using the Nationwide Inpatient Sample database; 1761 operations at 71 hospitals were studied. Projected to the US population, there were 1650 inpatient procedures performed for PD per year (pallidotomies, thalamotomies, and DBS), with no significant change in the annual number of procedures during the study period. The in-hospital mortality rate was 0.2%, discharge other than to home was 8.1%, and the rate of neurological complications was 1.8%, with no significant differences between procedures. In multivariate analyses, hospitals with larger annual caseloads had lower mortality rates (p = 0.002) and better outcomes at hospital discharge (p = 0.007).

Placement of deep brain stimulators comprised 0% of operations in 1996 and 88% in 2000. Factors predicting placement of these devices in analyses adjusted for year of surgery included younger age, Caucasian race, private insurance, residence in higher-income areas, hospital teaching status, and smaller annual hospital caseload. In multivariate analysis, total hospital charges were 2.2 times higher for DBS (median $36,000 compared with $12,000, p < 0.001), whereas charges were lower at higher-volume hospitals (p < 0.001).

Conclusions. Surgical treatment of PD in the US changed significantly between 1996 and 2000. Larger-volume hospitals had superior short-term outcomes and lower charges. Future studies should address long-term functional end points, cost/benefit comparisons, and inequities in access to care.

MRI-directed subthalamic nucleus surgery for Parkinson's disease

The subthalamic nucleus (STN) is now regarded as the optimal surgical target for the treatment of medically refractory idiopathic Parkinson's disease. In our center, a predominantly MRI-directed method has been developed for targeting the STN. The STN is localized on T2-weighted images from a 1.5-T MRI scanner. Long acquisition, high-resolution images are acquired in both the axial and coronal planes under strict stereotactic conditions with the patient under general anesthesia. The boundary of STN is co-registered in both planes to give optimal 3-dimensional target definition. Stereotactic coordinates of the dorsolateral STN are recorded and the trajectory is planned down the axis of the nucleus in the coronal plane. Initially, per-operative macrostimulation was used for adjustment at the target prior to unilateral subthalamotomy in 26 patients. Five patients were lost to follow-up. Assessments of the lesions in post-operative images confirmed successful localisation of the lesions within the dorsolateral STN in all of the remaining 21 cases. In a subsequent series of 19 patients treated by deep brain stimulation (DBS), unilateral in 1 patient and bilateral in 18, the STN was targeted using the same MRI-directed method, guide tubes and radio-opaque stylettes were implanted, and target verification was entirely MRI-based. Following implantation of the guide tubes and stylettes, assessments of the per-operative MRI images for the 37 STN targetings confirmed a mean target error, between the stylette and the desired target in the axial plane, of 0.3 mm mediolaterally (SD = 0.4) and 0.4 mm anteroposteriorly (SD = 0.4), with median errors of 0.5 mm. This study demonstrates that MRI-directed targeting of the STN through guide tubes is accurate, and allows direct verification and corrections as necessary. Cumulative frequencies predict that the majority of DBS electrodes placed in this manner will be within 0.5 mm of the planned target. Because physiological methods are not required, the whole procedure can be performed under general anesthesia. We feel that planning with reference to a standard atlas is unreliable and not significantly helped by the addition of microelectrode recording, the accuracy of which in the axial plane is dependent upon the distance between the recording trajectories, which is typically 2 mm.

Stereotactic management of craniopharyngiomas

Eleven patients with craniopharyngiomas underwent 13 stereotactic procedures (intracavitary irradiation, n = 7; radiosurgery, n = 6). Nine patients (82%) had recurrent tumors after prior surgery (median, 2 operations). The median patient age was 50 years (range, 6-63 years). At a median follow-up of 38 months (range, 24-102 months), no patient had progression of the treated tumor component. Two patients developed new cysts, so the actuarial 2- and 4-year progression-free survival rates were 91 and 73%, respectively. Visual function improved in 3 patients, remained stable in 6 patients, and worsened in 1 patient. Two patients (both without prior surgery) not having diabetes insipidus pre-operatively continued to have normal posterior pituitary function. Stereotactic techniques should be considered for patients with craniopharyngiomas, especially those who have failed prior surgical resection.

Deep brain stimulation for dystonia. Surgical technique

Stimulation electrodes are implanted under general anesthesia, without intra-operative electrophysiology or clinical testing, based only on stereotactic MRI and direct anatomical localization of the postero-ventro-basal GPi. We retrospectively analyzed the surgical procedure that has been designed and implemented in our center, using the Leksell G frame, for initiating deep brain stimulation in 65 dystonic patients. We report the surgical technique and the hardware and software complications. We recommend immediate postoperative stereotactic MRI under general anesthesia as a prerequisite to check the reliability of MR acquisition (magnet stability) and the exact localization of each electrode. This technique allowed us to reduce the duration of the operation to 4 h, including general anesthesia, frame fixation, MRI acquisition, implantation of two electrodes under radioscopic control, immediate postoperative stereotactic MRI and frame removal. Surgery-related morbidity was very low with a 0% hemorrhage rate and three delayed unilateral infections re-operated 6 months later. Hardware and software complications were rare. The advances in 3D-MR imaging permit the electrode implantation for deep brain stimulation without resorting to intraoperative localization techniques, which is especially helpful in children and for treating dystonia. The maximum follow-up period is 58 months (first case: November 1996). GPi stimulation has proven to be an effective treatment for most dystonic syndromes with particular efficacy in the disease due to the DYT1 mutation.

Safety and risk of microelectrode recording in surgery for movement disorders

There is an ongoing controversy about whether it is necessary to use microelectrode recording (MER) techniques in stereotactic surgery for Parkinson's disease and other movement disorders. This paper consists of a critical review of the published literature in order to analyze the value of MER in providing safe, efficient and accurate functional stereotactic surgery. Review of the literature revealed that MER techniques do not necessarily improve targeting accuracy or clinical results, compared to techniques using impedance monitoring and macrostimulation. In terms of safety for the patients, however, MER techniques are relatively safe, but non-Mer techniques, based on macrostimulation-guided surgery, are at least five times safer.

Surgery for Parkinson's disease: lack of reliable clinical trial evidence

There has been a striking resurgence of interest in surgery for Parkinson's disease (PD) with new targets identified and new procedures developed. This systematic review identified over 500 studies of surgery for PD published since 1990, including over 10 000 patients. However, the authors were unable to assess the value of PD surgery reliably because only seven randomised trials were identified including just 196 patients. Studies of surgery for PD have generally been of poor quality with too few patients, too short follow up, inappropriate choice of outcome measures, and lack of control groups. Much larger, randomised, controlled trials are needed to assess the longer term effects of surgery on patient rated quality of life and cost effectiveness.

Evaluating geometric accuracy of multi-platform stereotactic neuroimaging in radiosurgery

We used a spherical phantom to evaluate geometric accuracy in multi-platform stereotactic neuroimaging for radiosurgery. The phantom consisted of two plastic 16-cm-diameter hemispheres in which an exchangeable 8-cm plastic functional cube was incorporated. The functional cube contained cylinder and point targets. The targets were filled with a mixed aqueous solution of 2-mM copper sulfate and 300-mg/ml iodinated contrast medium and were visible on both MR and X-ray images. Two MR scanners and a biplane X-ray angio-suite were used to scan the phantom stereotactically in two sessions of the experiment. The angio-suite was equipped with digital subtraction and distortion-correction software. The resulting stereotactic images were transferred to a dose-planning computer for length measurement and coordinate determination of the targets. The mean errors of the measured cylinder length on distortion non-corrected X-ray stereotactic images were 0.24 +/- 0.14 and 0.73 +/- 0.10 mm, respectively, in the experiments; on distortion-corrected images 0.22 +/- 0.10 and 0.35 +/- 0.39 mm. They were 0.50 +/- 0.24, 0.25 +/- 0.19 and 0.49 +/- 0.34, 0.23 +/- 0.25 mm, respectively, of the two MR scanners. The mean errors of coordinate determination of point targets between the stereotactic MR and the distortion-corrected X-ray images were 0.70 +/- 0.18, 0.52 +/- 0.22 and 0.76 +/- 0.25, 0.40 +/- 0.10 mm, respectively, in the experiments. We found that the overall geometric errors of target delineation between stereotactic MR and X-ray images were in the submillimeter range. The current study validates the multi-platform and multi-facility stereotactic neuroimaging practice and ensures imaging accuracy in radiosurgery.

Nerve blocks in stereotactic neurosurgery

The advantage of performing preoperative nerve blocks of the supraorbital and occipital nerves facilitates frame fixation and the perioperative management of patients in stereotactic neurosurgery, resulting in better patient handling with reduced intraoperative medication and less monitoring by anesthesia personnel.

History of Chinese stereotactic and functional neurosurgery

Chinese stereotactic and functional neurosurgery started in 1963. Dr. Jian-Ping Xu did stereotactic surgery for Parkinson's disease with a small Cartesian coordinate stereotactic device which he designed. In 1983, the first Chinese Institute of Stereotactic and Functional Neurosurgery was established by Dr. Jian-Ping Xu and Dr. Ye-Han Wang in the Anhui Provincial Hospital in the city of Hefei. Since then, the Institute has hosted an annual National Workshop on Stereotactic and Functional Neurosurgery, where more than 80% of the functional neurosurgeons now practicing in China have been trained. In 1986, the Chinese Society of Stereotactic and Functional Neurosurgery was established, and the first issue of the Chinese Journal of Stereotactic and Functional Neurosurgery was published. With more than 35 years of development, stereotactic and functional neurosurgery has become a very important branch of surgery in China. More than 5,000 functional neurosurgery procedures and more than 8,000 stereotactic radiosurgery procedures are now performed annually.

Stereotactic neuroendoscopic management of hydrocephalus: a three-year follow-up and analysis of Malaysian children with aqueduct stenosis

The beneficial effects of stereotactic third ventriculostomy versus ventriculoperitoneal shunt were evaluated in 62 paediatric patients and analysed in relation to age, sex, clinical history, presence of meningomyelocele, magnetic resonance imaging measurements of hydrocephalus and third ventricle floor size. The third ventriculostomy were done on 50 patients using the Richard-Wolf Caemaert Endoscope and the Leksell Stereotactic Frame Model G. These patients were operated using the 4-French Fogarty catheter to open the base of the third ventricle. During the same period of study 12 paediatric patients with aqueduct stenosis who were managed by ventriculoperitoneal shunt were included. Both surgical procedures were compared. Statistically univariate analysis revealed that those patient with an age group of more than six months undergoing ventriculostomy had good outcome. Multivariate analysis revealed that past history of haemorrhage and/or meningitis were predictors of poor outcome. Sex, size of lumbar meningocele at birth, abnormal ventricular anatomy or narrow third ventricular floor size were non predictors of bad outcome in these patients. There was no difference in outcome in both the shunt or ventriculostomy group.

Sensitized Fos expression in subterritories of the rat medial prefrontal cortex and nucleus accumbens following amphetamine sensitization as revealed by stereology

Behavioral sensitization to the locomotor activating effects of amphetamine refers to the progressive, long lasting increase in locomotor activity that occurs with repeated injections. This phenomenon is thought to result from neuroadaptations occurring in the projection fields of mesocorticolimbic dopaminergic neurons. In the present study, we investigated the effects of amphetamine sensitization on Fos immunoreactivity (Fos-IR) in subterritories of the nucleus accumbens (core and shell) and medial prefrontal cortex (mPFC; dorsal and ventral) using stereology. Rats received five daily injections of amphetamine (1.5 mg/kg, i.p.) or saline. Behavioral sensitization was measured 48 h following the last injection, in response to a challenge injection of 1.5 mg/kg amphetamine. Sensitized rats showed a greater enhancement of locomotor activity upon drug challenge compared with their saline counterparts. Densities of Fos-positive nuclei were enhanced more in the dorsal than the ventral mPFC subterritory, whereas in the nucleus accumbens, densities of Fos-positive nuclei were increased more in the core than the shell of amphetamine-sensitized rats compared to controls. These results represent, to our knowledge, the first published report using stereological methods to quantify Fos-IR in the brain and suggest functional specialization of cortical and limbic regions in the expression of behavioral sensitization to amphetamine.

Altered spatial arrangement of layer V pyramidal cells in the mouse brain following prenatal low-dose X-irradiation. A stereological study using a novel three-dimensional analysis method to estimate the nearest neighbor distance distributions of cells in thick sections

Prenatal X-irradiation, even at doses <1 Gy, can induce spatial disarray of neurons in the brains of offspring, possibly due to disturbed neuronal migration. Here we analyze the effects of prenatal low-dose X-irradiation using a novel stereological method designed to investigate the three-dimensional (3D) spatial arrangement of neurons in thick sections. Pregnant mice were X-irradiated with 50 cGy on embryonic day 13 or were sham-irradiated. The right brain halves of their 180-day-old offspring were dissected into entire series of 150 microm thick frontal cryostat sections and stained with gallocyanin. Approximately 700 layer V pyramidal cells per animal were sampled in a systematic-random manner in the middle of the section's thickness. The x-y-z coordinates of these 'parent neurons' were recorded, as well as of all neighboring (up to 10) 'offspring neurons' close to each 'parent neuron'. From these data, the nearest neighbor distance (NND) distributions for layer V pyramidal cells were calculated. Using this novel 3D analysis method, we found that, in comparison to controls, prenatal X-irradiation had no effect on the total neuron number, but did cause a reduction in the mean volume of layer V by 26.5% and a more dispersed spatial arrangement of these neurons. Considering the recent literature, it seems reasonable to consider abnormal neuronal migration as the potential basic cause of this finding.

Magnitude of microelectrode refinement in pallidotomy and thalamotomy

The relative accuracy of starting point algorithms in microelectrode-guided stereotactic pallidotomy and thalamotomy was evaluated using postoperative magnetic resonance imaging (MRI) data. Multiplanar reformations were performed to align postoperative MRI in anterior-posterior, dorsal-ventral and mediolateral planes. Three-dimensional distance and direction from the pallidal and thalamic stereotactic starting points to the respective radiofrequency lesions were measured. Similar magnitude of microelectrode refinement in pallidotomy and thalamotomy suggested similar accuracy of algorithms used to set the stereotactic starting point. Fewer microelectrode-recording tracts were required to identify optimal lesioning sites in thalamotomy compared to pallidotomy. Lesions were consistently localized anterior and superior to the starting point and a refined starting point algorithm may reduce the number of microelectrode recording tracts.

Localisation of the subthalamic nucleus using Radionics Image Fusion and Stereoplan combined with field potential recording. A technical note

Subthalamic nucleus stimulation is an effective therapy for alleviating parkinsonian tremor, rigidity and bradykinesia. Although microelectrode recording is said to be essential for accurate targeting, this often prolongs the operation and the multiple recording tracts required may increase the incidence of complications, particularly haemorrhage. We describe a technique for implantation of deep brain electrodes in the subthalamic nucleus using MRI/CT fusion for anatomical localisation followed by bipolar recording of focal field potentials via the implanted stimulating electrode for neurophysiological confirmation of the stimulation site. The technique is effective, safe and requires much less time, and can be used as an alternative method to microelectrode recording.

Morbidity and mortality following pallidotomy in Parkinson's disease: a systematic review

OBJECTIVE

To study the frequency of morbidity and mortality associated with pallidotomy.

METHOD

The authors searched the MEDLINE electronic database for pallidotomy articles reported between January 1992 and December 2000. They selected studies by the following criteria: original clinical data, unequivocal description of morbidity and mortality, and unselected consecutive cases. The authors extracted the following data: number of patients, unilateral or bilateral procedures, age, localization technique, follow-up time, number of patients with adverse effects, number of patients with permanent adverse effects (>3 months), types of adverse effects, and mortality.

RESULTS

For unilateral pallidotomy, 12 prospective studies included 334 patients. Of these patients, 30.2% (95% CI, 25.3 to 35.2) had adverse effects, and 13.8% (95% CI, 10.1 to 17.5) had permanent adverse effects. A symptomatic infarction or hemorrhage occurred in 3.9% (95% CI, 2.1 to 6.6). The mortality rate was 1.2% (95% CI, 0.3 to 3.0). In the series with microelectrode recording, the frequency of adverse effects was 14.4% (95% CI, 4.7 to 24.1) higher and the frequency of stroke was 4.9% (95% CI, 1.4 to 8.4) higher. The most frequent adverse effects were problems with speech (11.1%) and facial paresis (8.4%). For bilateral pallidotomy, five historical cohort studies including 20 patients were available for review. Fourteen patients had an adverse effect, and the most frequent adverse effects were impairments of speech and cognition.

CONCLUSIONS

The risk of permanent adverse effects associated with unilateral pallidotomy was 13.8%. A symptomatic infarction or hemorrhage occurred in 3.9% of patients, and the associated mortality rate was 1.2%.

MRI volume measurements of hypointense objects. A phantom study using stereological methods

Volume estimates made from thick slabs overestimate the volume of a positive contrast particle in a translucent matrix and underestimate its volume if the particle has negative contrast and the matrix is opaque. For T2-weighted MRI high signal objects the bias can be corrected according to simple geometric models. For negative contrast or hypointense objects the magnitude of the bias is unknown and no corrections have yet been put forward. We wanted to determine the bias of MRI measurements of hypointense objects of known diameter surrounded by a positive contrast solution. One, 3 and 5 mm slices with three different contrast concentrations were obtained according to a stereological MRI protocol. Results were compared with the true object size to estimate the bias. A simple correction for the bias could not be developed due to interslice cross-talk. Cross-talk makes an object appear in more MRI slices than corresponding to its physical size and larger than the true diameter. For phantom measurements an empirical correction could be developed, but for measurements of non-ideal objects such as brain structures the validity of the correction would be unpredictable. Besides avoiding or reducing cross-talk, the best way to deal with this bias is to measure the object's maximal contrast from edge to edge, a solution which is not perfect.

Deep brain stimulation of the pedunculopontine region in the normal non-human primate

Lesions in the pedunculopontine nucleus (PPN) cause akinesia. The PPN degenerates in Parkinson's disease. Stimulation of the PPN region induces stepping movements in rats and cats. These findings suggest that the PPN may play an important role in akines ia and that stimulating it may alleviate akinesia.Therefore, we have stereotactically implanted a macroelectrode in the left PPN region in a normal macaque to investigate the effects of deep brain stimulation at different frequencies. Motor activity was recorded with an infra-red counter and behaviour videotaped. At frequencies above 45 Hz there was significantly more severe akinesia than at lower frequencies (paired t -test, n=15, P<0.005). At 100 Hz, there was gross impairment of postural control. At low frequencies (5-30 Hz), stimulation induced a 5-Hz tremor in the right arm. We conclude that stimulating the PPN region at high frequency causes akinesia, whereas low frequencies induce some positive motor effects.

Audit of neurophysiological recording during movement disorder surgery

Sixty-two cases of thalamic pallidal and subthalamic surgery in Dundee were audited to assess the influence of physiological localisation on the procedure. Methods included microelectrode recording, evoked potential and stimulation techniques. Although anatomical localisation is improving with modern techniques, the physiological information is still modifying the surgery in 67% of cases.

Stereotactic neurosurgical biopsy is an underutilized modality

The objective of this study was to ascertain if stereotactic neurosurgical biopsy (SNB) optimizes the therapy of undefined CNS masses. The design was of retrospective treatment and outcome analysis and the setting was a large general hospital. We studied a total of 141 patients with undefined, space-occupying CNS lesions detected between 1991-1997, with whom we used SNB to define the lesions. We sought to correlate empiric and histological diagnostics and their impact on medical management. The stereotactic biopsy produced a diagnostic yield for each patient. Management was altered in 57 cases (40%) due to histology and, of these, malignancy was found in 39. Morbidity was ten asymptomatic hemorrhages on post-biopsy CT scans and two cases of clinical deterioration. Our conclusions were that SNB produces high yield with low morbidity. In the community setting, a wide variety of diagnoses can be made with improvements in medical management. SNB should be employed to guide therapy of CNS lesions where complete excision is not possible or when diagnostic questions arise.

A computational model for tracking subsurface tissue deformation during stereotactic neurosurgery

Recent advances in the field of stereotactic neurosurgery have made it possible to coregister preoperative computed tomography (CT) and magnetic resonance (MR) images with instrument locations in the operating field. However, accounting for intraoperative movement of brain tissue remains a challenging problem. While intraoperative CT and MR scanners record concurrent tissue motion, there is motivation to develop methodologies which would be significantly lower in cost and more widely available. The approach we present is a computational model of brain tissue deformation that could be used in conjunction with a limited amount of concurrently obtained operative data to estimate subsurface tissue motion. Specifically, we report on the initial development of a finite element model of brain tissue adapted from consolidation theory. Validations of the computational mathematics in two and three dimensions are shown with errors of 1%-2% for the discretizations used. Experience with the computational strategy for estimating surgically induced brain tissue motion in vivo is also presented. While the predicted tissue displacements differ from measured values by about 15%, they suggest that exploiting a physics-based computational framework for updating preoperative imaging databases during the course of surgery has considerable merit. However, additional model and computational developments are needed before this approach can become a clinical reality.

Comparison of three methods of estimating confidence intervals for stereotactic error

When planning a stereotactic procedure, it is clinically valuable to know the spatial confidence intervals of a particular stereotactic technique. To do this, the aggregate error distribution of the stereotactic technique must first be estimated. In a frame-based stereotactic procedure, there is an imaging step and a treatment delivery step. If error is introduced independently at these steps, then the error of a stereotactic procedure may be computed from the error distributions of the component steps. Three computational methods of doing this were compared: parametric, convolution, and Monte Carlo. To test these methods, the error distributions of an imaging technique, a delivery technique, and the corresponding stereotactic imaging-plus-delivery system were measured empirically using a phantom, computed tomography, and the CRW stereotactic system. The three methods gave concordant estimates of mean aggregate error (respectively 2.71 +/- 1.52, 2.45 +/- 2.30, 2.51 +/- 2.34, and 2.47 +/- 2.31 mm for the empiric, convolution, Monte Carlo, and parametric methods). However, the estimates of the confidence intervals differed between the parametric and the nonparametric methods. In particular, the parametric method gave significantly higher estimates of the 99% spatial confidence interval (6.40 mm versus 5.41 mm and 5.38 mm for the convolution and Monte Carlo methods). Knowledge of the confidence intervals allows a neurosurgeon to determine a priori whether a particular stereotactic technique is likely to satisfy a clinically defined error budget, and thereby achieve clinical success.

Comparison of combined versus subdural or intracerebral electrodes alone in presurgical focus localization

PURPOSE

The yield of subdural versus intracerebral electrodes for ictal localization remains a point of controversy. We assessed the relative sensitivity of these two types of electrodes per case.

METHODS

Eighty-three intracranial recordings obtained from 82 patients were retrospectively reviewed to establish which type of electrode performed best in which patients and which seizure types.

RESULTS

Sixty (73%) of 82 patients had temporal lobe seizure onsets, eight frontal, nine widespread or multifocal/multilobar or both, whereas in five, seizure onset was not localized. Exclusive use of intracerebral electrodes would have been sufficient for accurate localization of the seizure-onset zone in all 35 patients with strictly mesial temporal seizure onsets. In only 20 (57%) of these 35 patients, the same decision would have been reached with exclusive use of subdural electrodes. In widespread neocortical and mesial temporal seizures (n = 25), yield of both electrode types was at about the same level, but neither was sufficient to identify the zone of ictal onset on its own. In frontal or multilobar seizures (n = 22), yield of subdural electrodes was slightly better then that of the intracerebral electrodes, but was not sufficient in all cases.

CONCLUSIONS

This study indicates that, depending on the characteristics of the seizure disorder, exclusive use of either intracerebral or subdural electrodes may easily result in erroneous diagnosis because of insufficient sampling of the brain. These findings are in contrast with other studies emphasizing the high yield of reliable EEG findings in evaluations with a single type of electrode and corroborate the results of one of our previous studies.

Adaptations of the Talairach technique to the evolution of medical imaging

We present an integrated imaging system which enables CT and MRI data to blend with angiographic or ventriculographic films obtained by teleradiography and digitized. From all the data fed to the calculator, orthogonal, frontal, lateral, simple or double-obliquity trajectories can be determined easily and rapidly.

Motor and sensory mapping of the frontal and occipital lobes

In patients with intractable epilepsy, surgical resections are performed with the primary goal of improving seizure control. The risk is that the resections may also remove tissues crucial for normal activities. The goal of surgical planning is therefore to determine as accurately as possible the regions of seizure onset and the regions controlling important functions, so that one can determine what to remove and what to leave in place. Clinical functional localization has been performed using cortical stimulation for over half a century, using both intraoperative and extraoperative methods. Signal averaging also has been widely used. More recently, techniques based on analysis of EEG in the frequency domain have shown promise. The methods appear to accurately indicate the function of the region assessed but do not necessarily predict functional consequences of resection. We review these methods, their indications, and the results obtained by their use.

Accuracy of stereotactic core-needle breast biopsy in atypical ductal hyperplasia

BACKGROUND

The histologic diagnosis of atypical ductal hyperplasia (ADH) has been reported as having a high rate of malignancy, either ductal carcinoma in situ (DCIS) or invasive ductal carcinoma (IDC). We reviewed our surgical group's experience with stereotactic core-needle biopsies (SCNB), specifically looking at the follow-up of ADH.

METHODS

From November 1994 through July 1997 our group performed 539 SCNB. Twenty-one patients (4%) were diagnosed as ADH. Eighteen patients had subsequent wire-localized excisional biopsies. Three patients were followed up mammographically. One patient refused follow-up.

RESULTS

Of the 18 patients who underwent excisional biopsies, 2 patients were found to have DCIS and 1 patient had lobular carcinoma in-situ. There were no cases of IDC.

CONCLUSION

Our results show a much lower incidence of malignancy in cases of ADH found on SCNB than has been previously reported. While the standard of care is still to follow up ADH found on SCNB with excisional biopsy, more data may justify following up certain subsets of patients.

Detection and mapping of abnormal brain structure with a probabilistic atlas of cortical surfaces

PURPOSE

We have devised, implemented, and tested a technique for creating a comprehensive probabilistic atlas of the human cerebral cortex, based on high-dimensional fluid transformations. The goal of the atlas is to detect and quantify subtle and distributed patterns of deviation from normal cortical anatomy, in a 3D brain image from any given subject.

METHOD

Given a 3D MR image of a new subject, a high-resolution surface representation of the cerebral cortex is automatically extracted. The algorithm then calculates a set of high-dimensional volumetric maps, fluidly deforming this surface into structural correspondence with other cortical surfaces, selected one by one from an anatomic image database. The family of volumetric warps so constructed encodes statistical properties of local anatomical variation across the cortical surface. Additional strategies are developed to fluidly deform the sulcal patterns of different subjects into structural correspondence. A probability space of random transformations, based on the theory of anisotropic Gaussian random fields, is then used to encode information on complex variations in gyral and sulcal topography from one individual to another. A complete system of 256(2) probability density functions is computed to reflect the observed variability in stereotaxic space of the points whose correspondences are found by the warping algorithm. Confidence limits in stereotaxic space are determined for cortical surface points in the new subject's brain.

RESULTS

Color-coded probability maps are generated, which highlight and quantify regional patterns of deformity in the anatomy of new subjects. These maps indicate locally the probability of each anatomic point being as unusually situated, given the distributions of corresponding points in the scans of normal subjects. 3D MRI volumes are analyzed, from subjects with clinically determined Alzheimer disease and age-matched normal subjects.

CONCLUSION

Applications of the random fluid-based probabilistic atlas include the transfer of multisubject 3D functional, vascular, and histologic maps onto a single anatomic template, the mapping of 3D atlases onto the scans of new subjects, and the rapid detection, quantification, and mapping of local shape changes in 3D medical images in disease and during normal or abnormal growth and development.

Curvature-based nonfiducial registration for the Frameless Stereotactic Operating Microscope

The Frameless Stereotactic Operating Microscope permits information from CT and MRI scans to be displayed in the operating microscope in the proper scale and perspective without using a mechanical frame in the process, when the microscope is positioned over the surgical field. This registration is currently done using fiducials that must be present when the imaging scans are taken. A new technique, based on the theory of curvatures, has been developed as an alternative to the use of fiducials for the registration of a patient's head position during surgery with diagnostic images from CT or MRI. Surface curvatures are estimated from a trace of points of the surface of the skin, obtained from both the diagnostic images and an intraoperative nonimaging ultrasonic rangefinder. The point traces need not be identical or evenly spaced. Plots of the resulting curvature fields are compared visually and the alignment determined. Phantom testing, using a human skull, has resulted in a median alignment error of 1.95 mm. Testing using a human subject with clinically obtained data has resulted in alignment errors on the order of 7 mm.

Statistical prediction of the optimal site for thalamotomy in parkinsonian tremor

Stereotactic lesions in the thalamus for treatment of parkinsonian tremor are often made at the location where neurons fire at approximately tremor frequency (tremor cells). Some of these cells show a large amount of activity at tremor frequency and are significantly correlated with electromyographic activity (EMG) during tremor. Our analysis of cellular location identifies a cluster of neurons showing activity characterized both by concentration of power at tremor frequency and by significant correlation with EMG. In a retrospective analysis of results in 15 patients, lesions placed within 2 mm of the center of this cluster were uniformly effective in relieving tremor. Therefore, a small lesion targeting this cluster is effective in treatment of parkinsonian tremor.

[The role of stereotactic radiography in nonpalpable breast lesions. The authors' own experience]

Stereotaxis is a well-known technique allowing fine-needle aspiration cytology and preoperative localization of the nonpalpable breast lesions seen on mammograms, permitting early diagnosis and easy surgical ablation. The authors report on their experience (126 cases) with stereotactic aspiration (85 cases) and preoperative localization (41 cases) of nonpalpable lesions. The technique allowed to hit the lesion in 115/126 cases (91.3%). Cytology showed 24 cases of cancer and 38 benign lesions (3 of them were false negatives); in 8 cases cytology was suspect (7 cancers and 1 sclerosing adenosis) and in 15 inadequate (17.7%). Sensitivity and specificity were confirmed by histology or follow-up (6 months + 6 months); sensitivity was 91.2% and specificity 97.2% (excluding inadequate cases). The 41 needle localizers were useful to detect 37 malignancies. Fifty-one lesions were biopsied: 37 of them were malignant and 14 benign (benign/malignant ratio = 0.38/1).