Predictive value of hippocampal MR imaging-based high-dimensional mapping in mesial temporal epilepsy: preliminary findings.

BACKGROUND AND PURPOSE: We objectively assessed surface structural changes of the hippocampus in mesial temporal sclerosis (MTS) and assessed the ability of large-deformation high-dimensional mapping (HDM-LD) to demonstrate hippocampal surface symmetry and predict group classification of MTS in right and left MTS groups compared with control subjects. METHODS: Using eigenvector field analysis of HDM-LD segmentations of the hippocampus, we compared the symmetry of changes in the right and left MTS groups with a group of 15 matched controls. To assess the ability of HDM-LD to predict group classification, eigenvectors were selected by a logistic regression procedure when comparing the MTS group with control subjects. RESULTS: Multivariate analysis of variance on the coefficients from the first 9 eigenvectors accounted for 75% of the total variance between groups. The first 3 eigenvectors showed the largest differences between the control group and each of the MTS groups, but with eigenvector 2 showing the greatest difference in the MTS groups. Reconstruction of the hippocampal deformation vector fields due solely to eigenvector 2 shows symmetrical patterns in the right and left MTS groups. A "leave-one-out" (jackknife) procedure correctly predicted group classification in 14 of 15 (93.3%) left MTS subjects and all 15 right MTS subjects. CONCLUSION: Analysis of principal dimensions of hippocampal shape change suggests that MTS, after accounting for normal right-left asymmetries, affects the right and left hippocampal surface structure very symmetrically. Preliminary analysis using HDM-LD shows it can predict group classification of MTS and control hippocampi in this well-defined population of patients with MTS and mesial temporal lobe epilepsy (MTLE).

Triple-technique (MR imaging, single-photon emission CT, and CT) coregistration for image-guided surgical evaluation of patients with intractable epilepsy.

Ictal and interictal single-photon emission CT (SPECT) play an increasingly important role in the surgical evaluation of patients with epilepsy. We present a method of coregistration of MR, SPECT, and CT images to correlate structural data (MR imaging), blood flow changes (SPECT), and location of subdural electrodes (CT) for patients undergoing image-guided surgical treatment of epilepsy. MR-SPECT root mean square (rms) mismatch distances were 2.1 to 2.5 mm, and MR-CT rms mismatch distances were 1.0 to 4.5 mm. Coregistration assisted in image-guided placement of subdural electrodes and in surgical resection of the suspected epileptogenic focus.

Endoscopic coagulation of the choroid plexus using the Nd:YAG laser: initial experience and proposal for management.

Although most patients with hydrocephalus are treated effectively with ventriculoperitoneal shunts, a small group fails to respond to diversion procedures. In some patients within this group, hydrocephalus may be caused in part by the overproduction of the cerebrospinal fluid (CSF). In other patients, previous shunt infections may limit the ability of the peritoneum to absorb fluid, and patient response to a ventriculoperitoneal shunt may be improved by reducing CSF production. We discuss a case of a 29-month-old hydrocephalic infant with a ventriculoperitoneal shunt who had ascites. Computed tomography showed bilateral symmetrical enlargement of the choroid plexus. Repeated cultures of the CSF and shunt tubing were sterile, and the daily production of the CSF exceeded 1000 ml. Therapy with acetazolamide decreased the CSF output temporarily, but it was discontinued after serious electrolyte abnormalities occurred. The endoscopic coagulation of the choroid plexus with a neodymium:YAG laser transmitted through a flexible quartz fiber decreased CSF production effectively. This procedure may be useful in a variety of clinical conditions associated with hydrocephalus or with other intraventricular lesions.

Magnetic source imaging: a review of the Magnes system of biomagnetic technologies incorporated.

Magnetic source imaging (MSI) is a new, noninvasive technique for defining the relationship between brain function and structure on a patient-to-patient basis. It achieves this by combining detailed neurophysiological data derived from magnetoencephalography with high-quality neuroanatomical data derived via magnetic resonance imaging. By the use of mathematical models, the spatial locations of those neurons that generate neuromagnetic signals of interest are estimated and subsequently marked on spatially aligned magnetic resonance images. There are three prominent types of clinical MSI examinations. These are: 1) functional mapping examinations in which sensory and motor functions are localized; 2) examinations of interictal epileptiform activity; and 3) examinations of abnormal low-frequency magnetic activity, which has been found to be present in a wide range of pathophysiological conditions. Functional mapping provides useful information regarding the relationship between the cortical representation of eloquent function and the location of pathological lesions that may be surgically resectable. This application is of particular utility in cases of intracortical masses that distort and obscure the local neuroanatomy. By defining the primary sites of interictal epileptiform activity, MSI examinations are useful in the surgical planning for the implantation of depth electrodes and the planning of partial lobectomies. Abnormal low-frequency magnetic activity appears to be a neurophysiological correlate of ischemic penumbra associated with stroke, neoplasms, and vascular malformations. Abnormal low-frequency magnetic activity has also been found to be present in several other conditions, including head trauma and psychiatric dysfunction, although the exact pathophysiological mechanisms are presently unclear.(ABSTRACT TRUNCATED AT 250 WORDS)

Halo vest versus spinal fusion for cervical injury: evidence from an outcome study.

The indications for surgical fusion, as opposed to halo fixation, in the management of cervical spine injury are still unclear. At St. Louis University Medical Center a conservative protocol has been adopted to treat almost all cervical spine fractures with halo fixation. To determine what factors have contributed to failure of halo fixation, the records and radiographs of all patients with cervical spine injuries who were treated at that institution between 1984 and 1986 were reviewed. During this interval, 124 patients were treated, consisting of 93 men and 31 women between 6 and 94 years old. Of these, 15 (12%) had cervical fusion without preoperative halo device application. This group included eight patients with old injuries and delayed diagnosis, three with nonreducible locked facets, and four with miscellaneous indications. The remaining 109 patients were treated with halo vests. Four died before completing the 3-month standard treatment. Of those completing the treatment, 48 had C1-2 level injuries and 57 had C3-T1 level injuries. Sixteen patients (15%) failed their halo treatments and required surgical fusion: eight while still in halo fixation and eight after they had completed treatment with a halo device. Failure of halo treatment was indicated by recurrent dislocation in 13 patients and increased neurological deficit in three. Thirteen of the patients who failed treatment had C3-T1 injuries and three had C1-2 injuries. Of 27 patients with odontoid fractures, only two (7.4%) failed halo fixation. There were no failures in 11 patients with hangman's fractures. Of the 57 patients with C3-T1 injuries, 13 (23%) failed treatment, nine of whom had locked or "perched" facets. The factors causing failure of halo fixation were analyzed. The overall success rate was 85%, suggesting that the halo vest can be used to treat most patients with cervical spine injuries. Under certain circumstances (in the presence of old injuries, difficult reduction, or locked or "perched" facets), surgery may be indicated to avoid unnecessary delay in definitive management.

Temporoparietal craniopagus. Case report and review of the literature.

A case of craniopagus twins joined in the temporoparietal area is presented, along with a review of the literature on craniopagus. A large area of brain was shared between the neurologically normal infants, with defects in the scalp, skull, and dura. The twins were separated in a three-step procedure. First, areas of shared brain were divided and separated with silicone sheets. The second procedure consisted of the insertion of scalp expanders to allow primary skin closure. In the third procedure complete separation was performed which was complicated by severe hypotension in one infant that was due to dural sinus hemorrhage. Cerebrospinal fluid leak was the most difficult problem encountered in the postoperative period; this was treated with lumboperitoneal and ventriculoperitoneal shunts. After 2 years, one twin is neurologically normal; the other is severely developmentally delayed, possibly related to the severe hypotension experienced during the third procedure. A review of the literature on craniopagus is presented. Analysis of data in the literature suggests that the area involved in the craniopagus as well as the venous connections are closely related to survival following separation of craniopagus twins.

Variables affecting the accuracy of stereotactic localization using computerized tomography.

Stereotactic localization using computerized tomography (CT) is increasingly employed to guide neurosurgical procedures in crucial areas of the brain such as the brain stem. This technique allows the surgeon to resect a lesion in its entirety while sparing critical areas of the brain. Thus, the parameters used for scanning should be selected for maximum accuracy. While the small pixel size of CT scanners suggests a high degree of precision in localization, there have been few systematic studies of this accuracy. The authors have studied the amount of error in localization created by variables such as CT scan thickness, interscan spacing, size of lesion, and method of computation when using the Brown-Roberts-Wells (BRW) stereotactic system. Over 1000 CT scans were made of a phantom composed of spheres of differing diameter and location. The CT slice thickness was varied from 1.5 to 5.0 mm, and interscan spacing was varied from 0.5 to 3.0 mm. The coordinates of the center of the spheres were calculated independently using the laptop computer supplied with the unit and also by a stereotactic computer which automatically calculates the center of the fiducials. The actual BRW coordinates of the sphere center were obtained using the phantom base and were then compared to the computer-calculated coordinates to determine error in localization. Variables with a significant effect on error included the scan thickness, interscan spacing, and sphere size. The mean error decreased 23% as the scan thickness decreased from 5.0 to 1.5 mm and 45% as the interscan spacing decreased from 3.0 to 0.5 mm. Mean error was greatest for the smallest sphere sizes. The two computational methods did not differ in error. This study suggests that, for critical areas of the brain or for small lesions, a scan thickness of 1.5 mm and interscan spacing of 0.5 mm should be employed.

Spinal cord arteriovenous malformation with an associated lymphatic anomaly. Case report.

Spinal cord arteriovenous malformations (AVM's), like other vascular anomalies of the central nervous system, can be associated with similar vascular lesions of the skin and viscera. A 7-year-old girl, who presented with rapidly progressing paraplegia, was found to have a spinal cord AVM, cutaneous angioma, and a chylous malformation of the lymphatic system. She had previously undergone treatment for a posterior thoracic cutaneous angioma. At surgery, upon incision of the paravertebral muscle fascia, viscous pale fluid was encountered emanating from a foramen in the thoracic lamina. The spinal AVM was resected in spite of concern that the abnormality represented spinal osteomyelitis. Postoperatively, there was full return of function in the lower extremities, along with recurrent episodes of chylothorax, which slowly came under control with dietary manipulation. A review of the anatomy of the thoracic duct and nontraumatic causes of chylothorax is presented, and the association of cutaneous and central angiomas is discussed. Finally, the treatment of chylothorax is delineated.

Presurgical localization of functional cortex using magnetic source imaging.

The boundaries of somatosensory cortex were localized noninvasively by means of a large-array biomagnetometer in six patients with mass lesions in or near eloquent cortex. The results were used by neurosurgeons and neurologists in preoperative planning and for reference in the operating room. The magnetic source imaging (MSI) localizations from somatosensory evoked potentials were used to predict the pattern of phase reversals measurable intraoperatively on the cortical surface, providing a quantitative comparison between the two measures. The magnetic localizations were found to be predictive in all six cases, with the two sets of localizations falling within an 8-mm distance on average. Somatosensory localizations using MSI offer accuracy in localizing somatosensory cortex stereotactically and in depicting its relationship to lesions. Such data are valuable preoperatively in assessing the risks associated with a proposed surgical procedure and for optimizing subsequent minimum-risk surgical strategy.

Neurologic recovery associated with anterior decompression of spine fractures at the thoracolumbar junction (T12-L1).

Between 1981 and 1990, twenty-two patients with incomplete neurologic deficits after thoracolumbar junction fractures were treated by anterior decompression and stabilization. Two patients were unavailable for follow-up examination, eleven underwent spinal canal decompression within 48 hours of injury (Group A); and nine patients underwent surgical decompression in an average of 61 days after injury (Group B). Neurologic recovery was analyzed by a modified Frankel grading system, the ASIA motor point scale and conus medullaris function. Patients were followed for an average of 3.5 years (range, 6-92 months). No patients had any deterioration in neurologic function after surgery. Patients in Group A had a modified Frankel grade improvement with a median of two grades and a mean American Spine Injury Association motor point improvement of 21.1 +/- 4.1. Four of nine patients with conus medullaris deficits demonstrated complete functional bladder and bowel return postoperatively. Those patients in Group B had a modified Frankel grade improvement with a median of one grade and a mean ASIA motor point improvement of 7.6 +/- 1.7. None of the six patients with conus medullaris injuries showed complete improvement in bladder or bowel function postoperatively. The modified Frankel grade and ASIA motor point score improvements were significant when the two groups were compared (P less than 0.04 and P less than 0.01, respectively). In this series of patients, early anterior decompression for traumatic injuries at the thoracolumbar junction was associated with improved rates of neurologic recovery when compared to late decompression.

Image-guided surgical techniques for infections and trauma of the central nervous system.

The value of image-guided stereotactic systems is directly dependent on the ease and speed of their use. In the past, most stereotactic techniques were complicated and timely to set up; thus, they were used exclusively for either resecting neoplasms or for neurologic function. However, current systems equipped with advanced registration techniques are much simpler and faster to employ, and indications for their use are rapidly increasing. We describe an advanced image-guided navigation system and provide examples of its successful use in neurosurgical treatment of central nervous system infection and trauma.

Transcranial Doppler ultrasound following closed head injury: vasospasm or vasoparalysis?

Nine patients suffering closed head injury were studied using transcranial Doppler ultrasound recording of the basal cerebral arteries. On admission, six patients had Glasgow Coma Scores of 7 or less, while three had initial scores of 8-10. Eight of the nine patients (82%) developed abnormally high mean velocities (greater than or equal to 110 cm/s) in one or more vessels. The onset, duration, and amplitude of the altered flow velocities were somewhat different from those that are seen with vasospasm after aneurysmal subarachnoid hemorrhage, which tend to occur later. Cerebral angiography in one of the study patients confirmed the presence of vasospasm. Multivariate regression analysis showed a definite correlation between the velocities recorded, even when abnormally elevated, and concurrent pH and PCO2 measurements (p = 0.01, R2 = 0.23). Although these results suggest that the cerebral vasculature retains its vasoreactivity following head injury, arguing against vasoparalysis, inconsistencies found in some of the patients lead us to think that both vasospasm and vasoparalysis may occur following head trauma but that they may have different temporal profiles.

Cerebrospinal fluid endothelin-1 and endothelin-3 levels in normal and neurosurgical patients: a clinical study and literature review.

Endothelins are a family of structurally related, potent, long-lasting vasoconstrictor peptides. There are no established normal human levels of endothelin-1 or endothelin-3 in the cerebrospinal fluid. We measured cerebrospinal fluid endothelin-1 and endothelin-3 levels in five groups of patients: normal controls, patients with subarachnoid hemorrhage and cerebral vasospasm, patients with severe head injuries, patients undergoing temporal lobectomy for intractable epilepsy, and a patient with a gunshot injury to the thoracic spine. Endothelin-3 levels were significantly elevated in patients with subarachnoid hemorrhage and may participate in cerebral vasospasm and subsequent neurologic deterioration.

Separation of craniopagus twins utilizing tissue expanders.

An example of craniopagus Siamese twins is presented. The methods used in their separation using skin expanders and scalp flaps to achieve primary closure of the wounds with hair-bearing scalp are outlined. A detailed discussion of the planning and the mathematical considerations of these skin expanders and scalp flaps is included.

Therapeutic Intervention Scoring System used in the care of patients in pentobarbital-induced coma to determine nurse-patient ratios.

BACKGROUND: Critical care patients generally require extensive interventions, thereby consuming a large percentage of healthcare resources. Induced pentobarbital coma for the management of increased intracranial pressure is one such intervention, required to maintain patient stability. Quantification of these interventions, as well as the amount of nursing work required, has not been addressed in the literature. OBJECTIVE: To use the Therapeutic Intervention Scoring System to analyze and quantify how interventions affect nurse-patient ratios in the management of patients in pentobarbital coma for refractory increased intracranial pressure. METHODS: The medical records of patients with subarachnoid hemorrhage from aneurysmal rupture and subsequent increased intracranial pressure, in whom pentobarbital coma was salvage therapy, were reviewed retrospectively. The Therapeutic Intervention Scoring System was used to quantify the number of interventions required before, during, and after coma induction. The data were analyzed and daily Therapeutic Intervention Scoring System scores correlated with serum pentobarbital levels. Typically, a critical care nurse can manage a patient caseload of 40 to 50 Therapeutic Intervention Scoring System points. By quantifying the interventions, the score reflected the amount of care required to manage the patient in barbiturate coma. RESULTS: The intensity of interventions correlated with the level of coma, length of time in coma, and associated complications. CONCLUSIONS: The scores indicated the intensity of interventions used in pentobarbital coma and the use of resources. Nursing care and complications involved with this therapy were quantified and nurse-patient ratios were established.

The NeuroStation--a highly accurate, minimally invasive solution to frameless stereotactic neurosurgery.

The NeuroStation is an image-guided neurosurgery workstation designed to deliver frameless stereotaxy within an ergonomic, integrated surgical environment. Generally, stereotaxy can provide the neurosurgeon with important intra-operative localization information using diagnostic images such as computerized tomography (CT) or magnetic resonance imaging (MRI). To date, however, stereotaxy has not been widely accepted by neurosurgeons due to the procedural difficulties of incorporating conventional stereotaxy. The NeuroStation addresses the problems of conventional stereotaxy through the use of frameless stereotactic methods wherein state-of-the-art instrumentation and computer innovations allow: a) standard surgical instruments to be used as the localization device; b) multipoint registration methods in place of frame-based registration; and c) real-time interactive surgical localization. The NeuroStation can thus be transparently integrated into the neurosurgical procedure providing the neurosurgeon with image-guidance for surgical planning, biopsies, craniotomies, endoscopy, intra-operative ultrasound, radiation therapy, etc.

An accurate and ergonomic method of registration for image-guided neurosurgery.

We have developed a system for accurately and conveniently achieving surgical registration for image-guided neurosurgery, based on alignment and matching of patient forehead contours. The system consists of a contour digitizer that is used in the operating room to acquire patient contours, editing software for extracting contours from patient image data sets, and a contour-match algorithm for aligning the two contours and performing data set registration. Initial tests of the individual portions of the system have found each to be robust; we are in the process of refining the design of the optical digitizer in order to further automate the procedure as well as provide increased accuracy.

Frameless stereotactic ultrasonography: method and applications.

In stereotactic neurosurgery, computed tomography (CT) and magnetic resonance (MR) images are registered in a coordinate system defined with respect to the skull. By intraoperatively tracking the coordinate position of a surgical instrument, various displays can be formed which show the position of the instrument in the MR and/or CT images. However, the accuracy of this display varies because intracranial structures may shift or warp from their position prior to surgery. Ultrasonic imaging systems provide real-time images of the brain, but structures in these images are difficult to interpret because the images are based on ultrasonic echoes. A method has been developed for the real-time registration of these images. With this registration, software continuously updates a corresponding image constructed from the set of MR and/or CT images used for guidance. By developing this second view of the structures in the ultrasound image, the surgeon can easily interpret the ultrasound image, and it becomes possible to determine the extent of the intra-operative structure shift between the two images.

Comparison of Scientific Calipers and Computer-Enabled CT Review for the Measurement of Skull Base and Craniomaxillofacial Dimensions.

Traditionally, cadaveric studies and plain-film cephalometrics provided information about craniomaxillofacial proportions and measurements; however, advances in computer technology now permit software-based review of computed tomography (CT)-based models. Distances between standardized anatomic points were measured on five dried human skulls with standard scientific calipers (Geneva Gauge, Albany, NY) and through computer workstation (StealthStation 2.6.4, Medtronic Surgical Navigation Technology, Louisville, CO) review of corresponding CT scans. Differences in measurements between the caliper and CT model were not statistically significant for each parameter. Measurements obtained by computer workstation CT review of the cranial skull base are an accurate representation of actual bony anatomy. Such information has important implications for surgical planning and clinical research.