Unilateral pallidotomy for Parkinson's disease: comparison of outcome in younger versus elderly patients.

We studied the effects of medial pallidotomy in the first 20 consecutive patients with Parkinson's disease (PD) undergoing this MRI/electrophysiologically guided procedure at our institution. The mean age of patients was 65.5 years (median 66.5) and none suffered any serious complications. Pallidotomy significantly improved motor function in both "on" and "off" states as measured by Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and timed tests (Purdue pegboard and counter tapping) in the arm contralateral to surgery 3 months postoperatively. Patients also improved in terms of activities of daily living, reflected by improved UPDRS activity of daily living and complications of therapy scoring and reduced levodopa-induced dyskinesias; six of 11 patients who could not walk in an "off" state prior to surgery could do so postoperatively. The total UPDRS score improved by 22% from preoperative values. The aforementioned improvements occurred similarly in patients greater than (n = 11) or less than 65 years (n = 9) at surgery. Neuropsychological measures indicated that although the majority of cognitive function remains unchanged in right-handed PD patients following dominant (left) hemisphere pallidotomy, mild specific declines in word generation are present. The findings of this study suggest that unilateral pallidotomy is safe and associated with improved motor functioning in elderly as well as younger PD patients experiencing significant disability despite optimal medical therapy.

Quantitative analysis of a noninvasive stereotactic image registration technique.

Our group has developed and tested a noninvasive image registration technique that does not require a special imaging study following the application of a head frame or radiological markers on the patient. This registration method involves performing automatic alignment between segmented scalp reconstructions from CT or MRI fitted with are surfaces traced with the Regulus Navigator. This paper will present a quantitative analysis of this technique compared to other stereotactic and image-guided registration techniques. This noninvasive surface alignment technique has been found to be a viable, quick and accurate method of performing image-guided registration.

Stereotactic ventrolateral thalamotomy: is ventriculography necessary?

In the computed tomography/magnetic resonance imaging (CT/MRI) era, the need for ventriculography to perform ventrolateral thalamotomy accurately has been debated. We retrospectively compared CT/MRI-derived coordinates for ventrolateral thalamotomy with the final lesion coordinates that were determined by ventriculography and microelectrode recording in 74 thalamotomies performed from 1984 to 1994. The median three-dimensional distance between the CT/MRI-derived loci and the ventriculography/microelectrode loci was 4.7 mm (range, 1.0-11.7 mm). The techniques correlated least along the Y axis (median, -0.3 mm; range, -8.2 to 8.0 mm). Correlation along the X axis was most consistent (median, 0.5 mm; range, -4.2 to 5.0 mm). Since 1990, the CT/MRI-derived coordinates have been generated by a multimodality correlative imaging technique (MCIT). A comparison of thalamotomies performed with and without the MCIT revealed a significant improvement in the correlation of CT/MRI- and ventriculography/microelectrode-derived coordinates when the MCIT was employed. The greatest improvement was noted along the Y axis where the median absolute difference was reduced from 4.0 to 1.8 mm (P = 0.0001). The result was a statistically significant reduction in the median three-dimensional distance from 5.6 to 3.7 mm (P = 0.0007). The authors conclude that thalamotomies can be safely and effectively performed without ventriculography when the MCIT is employed and supported by neurophysiological monitoring.

Three-dimensional display in the evaluation and performance of neurosurgery without a stereotactic frame: more than a pretty picture?

Display of three-dimensionally rendered images derived from radiological data sets is often suggested to be useful for surgical and radiation treatment planning in neurosurgery. Nevertheless, physicians will often note (off the record) that these rendered images are 'just a pretty picture' and are not clinically useful. This paper will discuss our three-dimensional rendering and quantitative analysis software and its primary use in evaluating and utilizing frameless stereotactic methodologies. A variety of concepts and techniques will be discussed. Specifically, a computer graphic and statistical-based technique will be presented that enables timely and measurable image registration between radiological image space and the coordinate system of computer-driven surgical devices in the operating room. This technique may be utilized to maintain a surgeon's orientation and to quantitatively and graphically monitor the position of probes and instruments in the surgical field. Three-dimensional quantitative results of phantom testing will be presented. Correlation to and validation against stereotactic imaging calculations using the compass stereotactic system will also be discussed. These computer graphic/statistical-based techniques are applicable for evaluating the accuracy of any frameless stereotactic device including, but not limited to robotic arms, spark gap, LED and magnetic field digitizers.

A new multimodality correlative imaging technique for VOP/VIM (VL) thalamotomy procedures.

This paper describes our experience at Mayo Clinic with a new technique for planning ventro-oralis posterior (VOP) ventral intermediate (ventrolateral) VIM (VL) thalamotomy procedures for selected patients with medically intractable tremor. This new method employs a multimodality correlative imaging technique for determining the lesion target point on MR images. At surgery, stereotactic frame settings for the final lesion target were ultimately determined by stereotactic ventriculography modified by neurophysiological recording. Acceptable correlation was found between the multimodality correlative imaging method and the actual target coordinates determined by ventriculography and semi-microelectrode recording.

Computer and imaging technology's impact on stereotactic neurosurgery. A 1987-1991 update.

Many improvements in computer and imaging technology have occurred since the last meeting of the American Society for Stereotactic and Functional Neurosurgery in 1987. These improvements are leading to a much wider acceptance of computerization and computer-assisted surgical procedures in the stereotactic neurosurgery field. This paper surveys the current fields of computer and imaging technology and its relationship and impact on the field of stereotactic neurosurgery during the period of 1987-1991. Forecasts about future developments are also discussed.

Evolution of contemporary instrumentation for computer-assisted stereotactic surgery.

This article discusses the evolution of our stereotactic system which evolved from the commercially available Todd-Wells stereotactic instrument. The Todd-Wells frame was originally designed for radiographically based, functional neurosurgical procedures. We modified it for computed tomography compatibility and later devised localization systems for magnetic resonance imaging and digital angiography. Based on the limitations in the original design applying to our own set of requirements, including tumor stereotaxis, we totally redesigned the system around the arc-quadrant principle of the original Todd-Wells instrument. While this intermediate system was being used in our surgical practice, further limitations were noted and corrected in the system we presently use. The present stereotactic frame is completely interactive with an operating room computer system.

The stereotaxic retractor in computer-assisted stereotaxic microsurgery. Technical note.

The authors describe a cylindrical retractor that is attached to a standard stereotaxic frame. This retractor provides a route for stereotaxic procedures and exposure of and a reference structure for the computer-assisted removal of deep-seated intracranial lesions defined stereotaxically by computerized tomography and magnetic resonance imaging.

Cerebral astrocytomas: histopathologic correlation of MR and CT contrast enhancement with stereotactic biopsy.

Gadolinium-labeled diethylenetriaminepentaacetic acid was used as a contrast agent for stereotactic magnetic resonance (MR) imaging in six selected patients with brain tumors who underwent stereotactic biopsy. Regions of contrast enhancement demonstrated by computed tomography (CT) and MR imaging in four of the six patients correlated with areas of malignant neovascularity and endothelial proliferation within solid tumor. Radiation necrosis produced contrast enhancement indistinguishable from that of recurrent neoplasm. Isolated tumor cells within intact white matter were identified in biopsy specimens obtained outside of regions that were depicted as abnormal by contrast material-enhanced CT, as well as by precontrast and postcontrast T1- and T2-weighted MR images.

Results of computed tomography-based computer-assisted stereotactic resection of metastatic intracranial tumors.

Forty-four patients underwent 45 computer-assisted stereotactic resections of intracranial metastases from various centrally located and deep-seated regions using methods described in this report and elsewhere. Gross total removal was achieved in all cases. There was no postoperative mortality (within 30 days). Postoperative neurological examinations revealed that: (a) of 26 who presented with preoperative neurological deficits, 13 were normal postoperatively, 7 were improved, 3 were unchanged, and 3 were worse; (b) 5 of 5 patients who had increased intracranial pressure preoperatively were normal postoperatively; and (c) 3 of 3 patients who had increased intracranial pressure and neurological deficit preoperatively were neurologically normal postoperatively. Nine of 10 patients who were neurologically normal preoperatively were normal postoperatively, and the other had transient upper extremity weakness after resection of a lesion in the contralateral motor strip. The 1-year survival in this group of patients was 62.5%. No local recurrence was noted in any patient. Computer-assisted stereotactic resection permits accurate localization of metastatic lesions and gross total resection from difficult locations with acceptable levels of morbidity.

Computer-assisted stereotactic biopsy of intracranial lesions in pediatric patients.

A computer-assisted stereotactic biopsy technique has been used in 30 patient (ages 5 months to 16 years) with intracranial lesions (supratentorial in 23 and infratentorial in 7). The computer program integrates stereotactically gathered imaging data and permits preoperative planning of a biopsy trajectory. Diagnostic tissue was obtained in 27 cases. In 2 cases, therapeutic interventions--third ventriculostomy and cyst aspiration--were accomplished at the time of the biopsy. There were no major complications related to the procedure; however, 2 patients had transient neurologic deficits. Computer-assisted stereotactic biopsy is a valuable diagnostic procedure in the pediatric patient with an intracranial lesion.

Computer-assisted stereotactic ventralis lateralis thalamotomy with microelectrode recording control in patients with Parkinson's disease.

Stereotactic ventralis lateralis thalamotomy can be performed in selected patients with medically intractable parkinsonian tremor and rigidity. New technology, including computed tomography-based stereotaxis and microelectrode recording techniques, provides a data base for precise localization of thalamic lesions tailored to each patient and thus reduces the risk associated with such a procedure. At our institution, 12 patients with medically intractable parkinsonian tremor have undergone this procedure; all experienced alleviation or cessation of the tremor and no permanent disabling neurologic sequelae.

Stereotactic histologic correlations of computed tomography- and magnetic resonance imaging-defined abnormalities in patients with glial neoplasms.

In 39 patients who harbored previously untreated astrocytomas (21 patients), oligoastrocytomas (9 patients), or oligodendrogliomas (9 patients), computed tomographic (CT) and magnetic resonance imaging (MRI) findings were correlated with stereotactic serial biopsy findings. The 39 patients were classified as having one of three types of tumor: type I (1 patient), which consisted only of circumscribed tumor tissue; type II (26 patients), which consisted of tumor tissue and isolated tumor cells; or type III (11 patients), which consisted of intact parenchyma infiltrated by isolated tumor cells. (In one patient, the biopsy sampling was inadequate for determining the type of tumor.) In high-grade lesions, tumor tissue was obtained from CT contrast-enhancing regions, and the area of enhancement accurately defined the tumor tissue volume. In low-grade lesions, tumor tissue was hypodense and indistinguishable from parenchyma infiltrated by isolated tumor cells on both CT and MRI. Isolated tumor cells usually extended as far as the prolongation of T2 on T2-weighted MRI of high-grade and low-grade tumors. CT and MRI detection of boundaries and stereotactic serial biopsies are necessary for the demarcation of glial neoplasms into tumor tissue and isolated tumor cell volumes as well as for the determination of the spatial extent of each component. This information is important for determining appropriate treatment.

Imaging-based stereotaxic serial biopsies in untreated intracranial glial neoplasms.

Forty patients with previously untreated intracranial glial neoplasms underwent stereotaxic serial biopsies assisted by computerized tomography (CT) and magnetic resonance imaging (MRI). Tumor volumes defined by computer reconstruction of contrast enhancement and low-attenuation boundaries on CT and T1 and T2 prolongation on MRI revealed that tumor volumes defined by T2-weighted MRI scans were larger than those defined by low-attenuation or contrast enhancement on CT scans. Histological analysis of 195 biopsy specimens obtained from various locations within the volumes defined by CT and MRI revealed that: contrast enhancement most often corresponded to tumor tissue without intervening parenchyma; hypodensity corresponded to parenchyma infiltrated by isolated tumor cells or in some instances to tumor tissue in low-grade gliomas or to simple edema; and isolated tumor cell infiltration extended at least as far as T2 prolongation on magnetic resonance images. This information may be useful in planning surgical procedures and radiation therapy in patients with intracranial glial neoplasms.

Magnetic resonance imaging-based computer-assisted stereotactic resection of the hippocampus and amygdala in patients with temporal lobe epilepsy.

In patients with medically intractable complex partial seizures of temporal lobe origin, stereotactic amygdalohippocampectomy can now provide excellent results. Target structures can be accurately identified and completely resected with use of a carbon dioxide laser. In a series of 18 patients who underwent this computer-interactive procedure, all experienced a cessation or dramatic reduction in frequency of seizure activity. Because the inferior optic radiations are disrupted with use of the posterolateral approach, nondisabling postoperative visual field deficits always ensue. In addition, two of our patients who underwent left-sided procedures had transient minor speech problems, perhaps attributable to postoperative swelling of the lateral temporal lobe. Patients in whom a surface electroencephalogram discloses a posterior temporal focus of seizure activity are candidates for stereotactic amygdalohippocampectomy.

Automated stereotactic positioning system.

An automated stereotactic machine has been interfaced to a surgical computer to complete a totally interactive surgical system capable of locating tumor volumes. Stepper motors, activated by the host computer, drive a three-dimensional slide to position the patient's head with respect to a fixed arc, locating the surgical target. Linear encoders on each axis create a closed-loop positioning system and a digital display for visual inspection of the slide's position. The 160-mm arc directs all instrumentation to its isocenter, regardless of the two angular settings, providing maximum freedom in selecting a safe trajectory to the target. Phantom test points compatible with computerized tomographic and magnetic resonance imaging were repeatedly scanned to determine the overall system accuracy, which approached 0.6 mm, depending on the spatial resolution of the image. This stereotactic device may be used to perform stereotactic laser craniotomies, biopsies, 192Ir implants for interstitial radiation, third ventriculostomies and functional procedures.

Computer-interactive stereotactic resection of deep-seated and centrally located intraaxial brain lesions.

The carbon dioxide laser has been incorporated into a computer-interactive stereotactic system for precision resection of deep-seated intraaxial neoplasma defined by stereotactic computed tomography and magnetic resonance imaging. One hundred and ninety-seven procedures were performed on 191 patients having deep-seated lesions. Postoperative results have been satisfactory as regards the postoperative condition of the patient in consideration of the completeness of tumor removal achieved.

Computer-assisted stereotactic biopsy of intracranial lesions.

The use of a computer program that allows the integration of stereotactically gathered CT, MRI and digital angiographic data in the planning of a biopsy trajectory is described. This system has been used to perform 447 stereotactic biopsies in 439 patients. Intracranial hemorrhages occurred in three patients; combined morbidity and mortality was less than 1%. Incorporation of angiographic data and visualization of the surgical trajectory enhances the safety and accuracy of stereotactic biopsy of intracranial lesions.

The impact of computer and imaging technology on stereotactic surgery.

Computers, particularly medical imaging techniques, have created a renaissance in stereotactic surgery. Human stereotaxis was primarily developed and performed beginning in the 1940s for functional disorders. Interest waned in the 1960s following the introduction of L-dopa until computer-based three-dimensionally precise tomographic modalities (specifically computed tomography) were introduced beginning in the mid-1970s as a routine diagnostic aid. New image-compatible hardware and instrumentation were introduced along with techniques and associated software for relating points and volumes appearing on these diagnostic images into stereotactic space. This paper reviews the computer and imaging technology that has led to this renaissance and discusses some of the important features of a computer-interactive stereotactic system.

The computer as a stereotactic surgical instrument.

We have developed methodology and stereotactic software for an operating room computer and imaging system. Patients undergo preoperative CT, MR and DSA imaging with their heads fixed in a stereotactic headholder. Localization systems attach to the headholder during the studies to create reference marks for computer transformation of points and volumes into three-dimensional stereotactic space. At the operating room computer console, the surgeon selects target points, avascular trajectories and tumour boundaries for volume reconstruction. Surgical approaches are simulated and target coordinates calculated. During surgery, the computer interactively monitors the position of stereotactically directed surgical instruments in relationship to the resident database along any viewing angle and conveniently superimposes the multiple data sources. We have found this system useful to provide rapid data acquisition and retrieval, accurate target point calculations, lesion volume reconstructions, and a convenient ability to reformat data from multiple sources in a manner useful to the surgeon and beneficial to the patient.