[Treatment options in traumatic epidural hematomas]

The authors report 118 consecutive cases of patients with traumatic extradural hematoma (EDH) which were analyzed according to different clinical parameters and treatment modalities. Patients, treated for EDH between 1992 and 1998 in our department were distributed into 5 treatment groups depending on their clinical and neuroradiological findings on admission and during the hospitalization. Group I consisted of 75 patients (64%) who required immediate surgical evacuation of the hematoma after admission. Group II included 12 patients (10%) with initially conservative treatment despite visible EDH on the first CT-scan, which had to be operated on in the course because of neurological deterioration or increase of hematoma size. The 14 patients (12%) forming group III developed an acute EDH after the initial CT-scan revealed no extradural blood; 7 patients (6%) out of group IV showed a chronic EDH (delay trauma/diagnosis > 72 h), which required operative evacuation. All 10 patients (8%) comprising group V were treated conservatively. In each group the following parameters were analyzed: patient age, size and location of hematoma, trauma mechanism, additional intracranial lesions or skull fractures, intraoperative findings and neurostatus on admittance and during the hospitalization. The decision for non-operative treatment of EDH and the timing of a delayed intervention has to be made individually in each case in dependence of parameters like patient age, hematoma-size and -location and neurological status and course. Chronic EDH should be operated immediately, as well as hematomas presenting with an increase in size. Delayed developing EDH imply worse outcome and make adequate surveillance of high-risk patients mandatory.

Movement artefacts and MR BOLD signal increase during different paradigms for mapping the sensorimotor cortex

BACKGROUND

The authors evaluated the impact of motion artefacts on presurgical mapping of the sensorimotor cortex with functional magnetic resonance imaging (fMRI). Different mapping paradigms were compared with regard to the frequency of motion artefacts and the resulting signal increase.

METHOD

94 surgical candidates with mass lesions near the central region were investigated using BOLD(1)-contrast T2(*) weighted multislice multi-echo EPI gradient echo sequences on a 1,5 T Philips Gyroscan. Three functional paradigms were performed: a) repetitive self-paced clenching of the hand to a fist (68 runs); b) repetitive finger-to-thumb opposition (46 runs); c) sensory stimulation by repetitive brushing of the palm (15 runs). Task-related haemodynamic changes were identified by statistical analysis with the Kolmogorov-Smirnov-test. MR signal increase in percent was calculated for each of the paradigms. Motion artefacts were rated on a scale from 1 to 3.

FINDINGS

Severe motion artefacts occurred in 8 hand clenching runs and in 2 finger opposition runs. Artefacts were more pronounced in hand clenching than in finger opposition. There were no motion artefacts in any of the sensory stimulation runs. Concerning the percent MR signal change there was no significant difference between hand clenching and finger opposition (T-test: p>0,5) but a highly significant difference (p<0,0001) between both motor tasks and the sensory paradigm (hand clenching: 2.68+/-0.75; finger opposition: 2.76+/-0.79; sensory stimulation: 1.72+/-0.65).

INTERPRETATION

Sensory stimulation causes by far less artefacts than motor paradigms but it also has to be considered less sensitive as it produces a smaller MR signal increase. Therefore in presurgical evaluation sensory stimulation should be kept in reserve for cases in whom motion artefacts are very likely to occur, i.e. patients with severe forms of paresis.

Error analysis in cranial neuronavigation

Neuronavigation systems are now an important component of many modern neurosurgical treatment strategies. Their support facilities intraoperative orientation and makes neurosurgical operations more precise and less traumatic. Computer-aided neurosurgery is definitively not a temporary fashionable phenomenon, the concept of neuronavigation is here to stay. This report summarizes a ten-years-long experience and presents an error analysis of 108 failures (12.4 %) in a total of 874 image-guided cranial neurosurgical procedures with an arm-linked (mechanical) system and two different infrared-light emitting (optical) systems. The application of neuronavigation incurs multiple reasons for pitfalls because of the complex man-machine interface. Principally, we have to differentiate two types of errors: "machine made errors" due to soft- or hardware failure and "man made errors" generally, due to inadequate handling of the navigation system. The error analysis demonstrated that the so-called human interface plays the main role causing a high error rate.

[Background and first results about methodological characteristics of the Aachen Life Quality Inventory]

Health-related quality of life has become an important criterion for assessing disease impact and treatment outcome. Therefore, we developed a questionnaire called Aachen Life Quality Inventory (ALQI) for the use in neurosurgical patients with brain damage. The ALQI is derived from the German version of the Sickness Impact Profile (SIP). The 117 items are formulated on a concrete behavioral level covering the following dimensions of health-related quality of life: 1. activation; 2. mobility; 3. house-work; 4. social contact; 5. family relations; 6. ambulation; 7. work; 8. free-time activities; 9. autonomy; 10. communication; 11. cognitive capacity. As in the SIP, a summary score of total impairment (ALQI Total score), a summary score covering the psycho-social dimension (ALQI Psycho-social score) and a summary score covering aspects of physical functioning (ALQI Physical score) can be calculated. The ALQI consists of a self-rating and a parallel proxy-rating version. The ALQI was validated and psychometrically verified using the data of as yet 231 neurosurgical patients with brain damage of mixed etiology (subarachnoid hemorrhage, closed-head injury, benign brain tumors). Internal consistency (Cronbach's Alpha) ranged from.68 to.91 for the subscales, while it was.97 for the whole instrument,.94 for the psycho-social and.93 for the physical score. The internal consistency for the subscales of the proxy-rating version of the ALQI ranged between.77 and.92, while it was.97 for the whole inventory and.94 for the psycho-social and the physical scores, respectively. Examination of construct validity revealed substantial correlations with a wide range of relevant neurological, neurosurgical and neuropsychological parameters. Beyond other findings, substantial associations emerged with several neuropsychological tests (r =.30 to r =.50), the Glasgow Outcome Scale (r =.39; p <.00) and in patients after subarachnoid hemorrhage with the Hunt& Hess grading (r =.28; p <.001). According to these results, the ALQI promises to become a valid and reliable means for assessing quality of life in patients with brain damage. Nevertheless, further analyses using larger patient samples and with particular emphasis on the investigation of the retest-reliability and the prognostic validity are called for in the future.

Activation in primary and secondary motor areas in patients with CNS neoplasms and weakness

OBJECTIVE

To demonstrate whether cortical activation within different cortical motor regions in neurosurgical patients varies with the degree of paresis induced by mass lesions near the central region.

METHODS

A total of 110 patients with brain tumors infiltrating the central region and with varying degrees of paresis were investigated employing fMRI during the performance of hand motor tasks. The percent signal change between rest and activation was calculated for four cortical regions: primary motor cortex (M1), supplementary motor area, premotor area, and superior parietal lobule.

RESULTS

Significant decreases in activation with increasing degrees of paresis were found in M1, whereas significant increases in activation were noted in secondary motor areas that were not affected by the tumor.

CONCLUSIONS

The signal loss in areas adjacent to tumor tissue may relate either to tumor-induced changes in cerebral hemodynamics or to a direct loss of cortical neurons resulting in a lesser degree of hemodynamic changes after motor activation. The increase in activation within secondary motor areas with increasing degrees of paresis supports the growing evidence of a practice- and lesion-dependent reorganization of the cortical motor system and the ability of the brain to modulate its excitatory output according to external demands.

Follow-up of extended pterional orbital decompression in severe Graves' ophthalmopathy

BACKGROUND

Compressive optic neuropathy (CON) with visual loss is, apart from corneal exposure and disfigurating proptosis, the most serious clinical sign encountered in Graves' ophthalmopathy. However, numerous different approaches and operative techniques have been proposed for orbital decompression, with varying results and side effects. The purpose of the present study was to analyze peri-operative data and long-term results in patients with severe thyroid-related orbitopathy, treated by extended pterional orbital decompression, comparing its effectiveness to other procedures.

METHOD

An extended pterional orbital decompression was performed in 42 consecutive patients (59 orbits) with severe thyroid-associated ophthalmopathy after failure of medical and radiation therapy during an 11-year period. Pre- and postoperative examination included visual acuity, Hertel exophthalmometry, ocular motility, visual fields (Goldmann perimetry) and notification of complications. Long-term evaluation was carried out on average at 11 months postoperatively (range 5-26 months).

FINDINGS

Visual acuity improved rapidly from a preoperative average of 0.53 +/- 0.33 (range, 0-1) to 0.77 +/- 0.31 (range, 0-1) postoperatively (p<0.001). Worsening was not seen. An average reduction of proptosis of 3.79 +/- 2.32 mm (range, 0.5-8 mm) was achieved with a mean preoperative Hertel measurement of 24.7 +/- 3.93 mm (range, 15-33 mm) (p<0.001). Double vision and restriction of eye motility was present in 76.3% of patients preoperatively and improved in 63% of patients (p<0.001). No new onsets of not already pre-existing double vision was seen. Complications included two cases of permanent palsy of the frontal branch of the facial nerve.

INTERPRETATION

The extended pterional orbital decompression improved vision and decreased proptosis and restriction of extra-ocular movements in patients with severe sight-threatening and disfiguring cases of Graves' orbitopathy and is still an effective and low-risk alternative to other non-neurosurgical operative techniques. Especially new developing postdecompression strabismus can be successfully avoided.

Microvascular decompression of a developmental venous anomaly in the cerebellopontine angle causing trigeminal neuralgia

We describe an apparently unique case of a patient with a trigeminal neuralgia caused by compression of the trigeminal nerve during its course by the draining vein of a developmental venous anomaly in the cerebellopontine angle. Typical symptoms of trigeminal neuralgia disappeared completely after microvascular decompression of the nerve. Neuroradiological findings, as well as particularities of this case are described and therapeutic options are discussed.

Diagnostic and therapeutic management of spinal arachnoid cysts

BACKGROUND

The wide variety of intraspinal cystic lesions necessitates different elaborate diagnostic procedures to choose the right therapeutic management in symptomatic patients. Based on the case reports of seven patients with symptomatic spinal arachnoid cysts we discuss the aetiology, diagnostic procedures and therapeutic management of extra- and intradural spinal cysts.

METHOD

All patients underwent MRI, Myelography and CT-Myelography during diagnostic evaluation. During surgery the cyst was resected and the communication between the cyst and the subarachnoid space was closed.

FINDINGS

Two patients were identified with intradural, five with extradural spinal arachnoid cysts. Postoperative outcome was favourable in those patients without preoperative cord damage.

INTERPRETATION

MRI is the diagnostic procedure of first choice because of its potential to demonstrate the exact localisation, extent and relationship of the arachnoid cyst to the spinal cord. Cord atrophy secondary to compression can be visualised and used for prediction of neurological outcome. Myelography and CT-Myelography (CTM) are still of diagnostic value since they might demonstrate the communication between the subarachnoid space and the cyst, which is important for surgical planning. The aim of surgical treatment is neural decompression and prevention of refilling of the cyst which is best accomplished by complete resection of the cyst and closure of the communication between cyst and subarachnoid space.

Metabolic and electrophysiological validation of functional MRI

OBJECTIVES

Although functional MRI is widely used for preoperative planning and intraoperative neuronavigation, its accuracy to depict the site of neuronal activity is not exactly known. Experience with methods that may validate fMRI data and the results obtained when coregistering fMRI with different preoperative and intraoperative mapping modalities including metabolically based (18)F-fluorodeoxyglucose PET, electrophysiologcally based transcranial magnetic stimulation (TMS), and direct electrical cortical stimulation (DECS) are described.

METHODS

Fifty patients were included. PET was performed in 30, TMS in 10, and DECS in 41 patients. After coregistration using a frameless stereotactic system, results were grouped into overlapping (<1 cm distance), neighbouring (<2 cm), or contradictory (>2 cm).

RESULTS

Comparing fMRI with PET, 18 overlapping, seven neighbouring, and one contradictory result were obtained. In four patients no comparison was possible (because of motion artefacts, low signal to noise ratio, and unusual high tumour metabolism in PET). The comparison of TMS and fMRI showed seven overlapping and three neighbouring results. In three patients no DECS results could be obtained. Of the remaining 38 patients, fMRI hand motor tasks were compared with DECS results of the upper limb muscles in 36 patients, and fMRI foot motor tasks were compared with DECS results of the lower limb on 13 occasions. Of those 49 studies, overlapping results were obtained in 31 patients, and neighbouring in 14. On four occasions fMRI did not show functional information (because of motion artefacts and low signal to noise).

CONCLUSIONS

All validation techniques have intrinsic limitations that restrict their spatial resolution. However, of 50 investigated patients, there was only one in whom results contradictory to fMRI were obtained. Although it is not thought that fMRI can replace the intraoperatively updated functional information (DECS), it is concluded that fMRI is an important adjunct in the preoperative assessment of patients with tumours in the vicinity of the central region.

Navigated transcranial magnetic stimulation for presurgical planning--correlation with functional MRI

PURPOSE

This paper describes the potential of navigated transcranial magnetic stimulation to map the motor cortex in patients with mass lesions near the primary motor cortex by comparing the results of this technique to those of functional MRI.

MATERIAL AND METHODS

Ten patients with mass lesions near the central sulcus were studied preoperatively using a figure-of-eight transcranial magnetic stimulator attached to a neuronavigation system to allow for direct visualization of the stimulated brain region. Subsequently, in all patients a blood oxygenation level dependent 2D multislice multishot T2*-weighted gradient echo EPI sequence on a 1.5 T Philips Gyroscan during motor activation was performed. Results of both methods were coregistered and compared.

RESULTS

The distances between the peak parenchymal fMRI activation and the cortical area where TMS elicited the maximum MEPs ranged between 0 and 1.2 cm (mean 0.6 cm, SD 0.4 cm).

CONCLUSION

We conclude that navigated TMS is a reliable alternative for localizing the motor-related areas in the human brain preoperatively and therefore may be a useful adjunct or, in selected patients, even a helpful alternative to functional MRI.

Influence of intraventricular hemorrhage on outcome after rupture of intracranial aneurysm

This study was performed to analyze the effect of intraventricular hemorrhage (IVH) on 14-day mortality, outcome at 6 months, and the occurrence of chronic hydrocephalus in patients with aneurysmal subarachnoid hemorrhage. Clinical grade of subarachnoid hemorrhage and the distribution of extravasated blood were evaluated in 219 patients with ruptured aneurysms. Computed tomographic scans performed within 72 h of hemorrhage were analyzed to determine the severity of intraventricular and subarachnoid hemorrhage and the volume of intracerebral hematomas. Outcome at 6 months was assessed using the Glasgow Outcome Scale. Intraventricular hemorrhage extension occurred in 109 of the 219 patients studied. Fourteen-day mortality increased from 7.3% in patients without IVH to 14.1% in those with moderate IVH (IVH score 1-6) and to 41.7% in those with more severe IVH (IVH score > 6). The corresponding figures for unfavorable outcome at 6 months are 19.8%, 30.5%, and 66.7%, respectively. According to logistic regression analyses, the severity of IVH was an independent predictor of mortality and functional outcome. The clinical outcome after aneurysm rupture is at least in part determined by the severity of IVH. Knowledge of the effect of IVH may help guide physicians in the care of patients with aneurysmal bleeding.

Virtual MRI endoscopy: detection of anomalies of the ventricular anatomy and its possible role as a presurgical planning tool for endoscopic third ventriculostomy

BACKGROUND

Many anatomical anomalies have the potential to impair the efficacy of endoscopic third ventriculostomy (ETV) and increase the surgical morbidity. By virtual magnetic resonance imaging (MRI) endoscopy, the real endoscopic view into the ventricular system can be simulated. It was the objective of the present study to investigate if this simulation is sensitive enough to detect anatomical anomalies of the ventricular system.

METHOD

In 18 hydrocephalic patients, first neuronavigationally guided ETV, then virtual MRI endoscopy were performed. This study design allowed for selection of a path for virtual MRI endoscopy, which was identical to that used during surgery, making the real and the virtual view on anatomical structures of the ventricular system highly comparable. It was investigated whether the intra-operatively identified anatomical anomalies could likewise be depicted on virtual MR endoscopic images.

FINDINGS

Seven anatomical variants (not enlarged interventricular foramen n=2, atrophic corpus callosum and split fornical bodies n=1, narrow retroclival space n=1, prominent basilar tip n=1, opaque and thick/atypically declining third ventricular floor n=2) were encountered in 5 of the 18 patients during surgery. The five variants of the non-membraneous structures were identified by virtual MRI endoscopy (sensitivity 71%), whereas the anatomical variants of the third ventricular floor were missed. Both the normal as well as the variant third ventricular floor could not be visualised and appeared as a defect. Through this artefact, the anatomy of the major vessels in the interpeduncular cistern could be assessed.

INTERPRETATION

The sensitivity of virtual MRI endoscopy for detection of anatomical variants of the ventricular system is low. Its potential usefulness as a presurgical planning tool inspite of this low sensitivity rate is discussed.

Functional and diffusion-weighted magnetic resonance images of space-occupying lesions affecting the motor system: imaging the motor cortex and pyramidal tracts

OBJECT

During neurosurgical interventions, preservation of subcortical axons is as important as preservation of cortical neurons. The goal of this study was to assess the combined use of functional (f) and diffusion-weighted (DW) magnetic resonance (MR) imaging to assist in the preservation of the structure and function of the motor system.

METHODS

The authors evaluated the combination of fMR imaging and DW MR imaging to detect cortical motor areas with their corresponding pyramidal tracts in 12 healthy volunteers and in 10 consecutive patients with various space-occupying lesions affecting the central motor system. Activation within the primary motor cortex (M1) and white matter bundles originating from this cortical region was demonstrated in 21 of the 22 individuals examined. Additional activation was exhibited along the course of white matter tracts at the level of the pons and. in the contralateral hemisphere, in the M1. Fiber tract displacement was visualized in all patients in white matter that had appeared normal on routine T1- and T2-weighted MR images.

CONCLUSIONS

The combination of DW MR and fMR imaging allows visualization of the origin, direction, and functionality of large white matter tracts. This will prove helpful for imaging structural connectivity within the brain during functional imaging. Moreover, local relationships of cerebral tumors that encroach upon M1 and subcortical fiber tracts can be defined. This promises to decrease patient morbidity and to broaden the clinical applications of functional imaging.

Dural arteriovenous fistulae at the foramen magnum

Spinal dural arteriovenous fistulae (DAVF) affect predominantly levels of the lower thoracic and lumbar segments; only 13 cases have been reported of DAVF at the foramen magnum. We present three surgically treated patients with DAVF at the foramen magnum. In none of our three patients could the site of the arteriovenous fistula be suspected from the clinical presentation. The clinical course varied from acutely developing signs and symptoms to a 10-year history of very slowly progressing symptoms. After neuroradiological diagnosis the patients were operated on direct microsurgical disconnection of the arteriovenous shunt via an enlargement of the foramen magnum and a hemilaminectomy of C1. DAVF at the foramen magnum may thus present with slowly to acutely progressing clinical symptoms and signs. Spinal angiographic examination should include the level of the foramen magnum if standard spinal angiography of thoracic, lumbar, and sacral segments is negative in suspected spinal DAVF since the nidus of the shunt can be situated remote from the level of neurological disorder. DAVF at the foramen magnum can be treated very effectively and with minimal surgical trauma by direct microsurgical disconnection of the shunt. This surgical procedure is indicated if embolization with glue is not possible or is unsuccessful.

The role of intraoperative magnetic resonance imaging for the detection of hemorrhagic complications during surgery for intracerebral lesions an experimental approach

BACKGROUND

Intraoperative magnetic resonance imaging (MRI) for guided biopsy or microsurgical resection of intracranial lesions is gaining broader acceptance. It is not known whether intraoperative MRI has the potential to detect hemorrhagic complications of these surgical procedures, because scientific research has so far focussed on the signal characteristics of less acute clots. It is the objective of this experimental study to investigate whether MRI can visualise intracerebral blood within minutes after its occurrence.

METHODS

In 26 pigs, a frontal hematoma was produced by injecting autologous blood. Twenty pigs underwent MRI 30 minutes after injection, and 6 pigs within the first 10 minutes. MRI scans were performed on a 1.5T system. T1-weighted spin echo (SE), T2-weighted turbo spin echo (TSE), T2-weighted fluid attenuated inversion recovery (FLAIR), and T2-weighted gradient echo (GE) images were acquired. Depending on the differences of the signal intensities of the hematoma and the surrounding brain, the detectability of the hematoma was rated as good, fair, or poor.

RESULTS

None of the induced hematomas were rated to be clearly visible on T1-weighted sequences. Six of the 26 hematomas (23%) were easily detectable on FLAIR sequences, 18 hematomas (69%) on T2-weighted TSE sequences, and 23 hematomas (88%) on the T2-weighted GE sequences.

CONCLUSION

Extravasated blood can be identified with a high reliability within minutes after its occurrence on MRI provided that T2-weighted GE sequences are used for imaging. In conclusion, intraoperative MRI is not only of value for guidance of neurosurgical procedures, but also for immediate detection of hemorrhagic complications.

Is the head position during preoperative image data acquisition essential for the accuracy of navigated brain tumor surgery?

OBJECTIVE

To analyze the influence of head positioning during preoperative image data acquisition on intraoperative accuracy of modern neuronavigation systems.

MATERIAL AND METHODS

All measurements were performed preoperatively before opening the head. In 24 patients, preoperative MR image data acquisition was performed twice on a 0.5 T scanner using a contrast-enhanced T1-weighted sequence; first in the neutral head position, and thereafter in the surgical head position for pterional craniotomy. For both data sets, the Sylvian fissure, the central sulcus, and the superior and inferior temporal sulci were depicted on the patient's scalp using the frameless neuronavigation system EasyGuide Neurotrade mark. At the beginning of surgery, with the head fixed in a Mayfield clamp and an articulated instrument holder being used for fixation of the navigation system's pointer, the distances of 10 correlating points of the sulci for the two data sets were measured. To evaluate the accuracy of the navigation system in this experimental set-up, a phantom study was also performed.

RESULTS

The phantom study revealed a mean inaccuracy of 1.6 mm (range 0.1-2.3 mm, standard deviation 0.6 mm). The patient study revealed a mean inaccuracy of 1.8 mm (range 0.4-2.8 mm, standard deviation 0.5 mm).

CONCLUSIONS

The data suggest that the positioning of the patient's head during preoperative imaging plays no relevant role in intraoperative accuracy of neuronavigation. However, further studies and a larger number of patients with various pathologies in different regions of the brain are necessary to obtain a better understanding of the problem of brain shift in neuronavigation due to patient positioning alone, and to avoid procedure-related operative morbidity.

In vivo 3D visualization of normal pyramidal tracts in human subjects using diffusion weighted magnetic resonance imaging and a neuronavigation system

We describe the potential of anisotropic diffusion weighted imaging to visualize the course of large cerebral fiber tracts. Five healthy volunteers were investigated at a field strength of 1.5 Tesla, employing a spin-echo diffusion weighted sequence with gradient sensitivity in six non-collinear directions to visualize the course of the pyramidal tracts. The pyramidal tracts were segmented and reconstructed for three-dimensional visualization. Reconstruction results together with a fusioned high resolution 3D T1 weighted image data set were available in a customized neuronavigation system. Origination in the primary motor cortex, convergence in the centrum semiovale, the posterior limb of the internal capsule, the cerebral peduncles, the splitting at the level of the pons, and the pyramidal decussation were identified in all subjects. Fiber tract maps might have the prospect of guiding neurosurgical interventions, especially when being linked to a neuronavigation system. Other potential applications include the demonstration of the anatomical substrate of functional connectivity in the human brain.

Three-dimensional visualization of the pyramidal tract in a neuronavigation system during brain tumor surgery: first experiences and technical note

OBJECTIVE

To integrate spatial three-dimensional information concerning the pyramidal tracts into a customized system for frameless neuronavigation during brain tumor surgery.

METHODS

Four consecutive patients with intracranial tumors in eloquent areas underwent diffusion-weighted and anatomic magnetic resonance imaging studies within 48 hours before surgery. Diffusion-weighted datasets were merged with anatomic data for navigation purposes. The pyramidal tracts were segmented and reconstructed for three-dimensional visualization. The reconstruction results, together with the fused-image dataset, were available during surgery in the environment of a customized neuronavigation system.

RESULTS

In all four patients, the combination of reconstructed data and fused images was a helpful additional source of information concerning the tumor seat and topographical interaction with the pyramidal tract. In two patients, intraoperative motor cortex stimulation verified the tumor seat with regard to the precentral gyrus.

CONCLUSION

Diffusion-weighted magnetic resonance imaging allows individual estimation of large fiber tracts applicable as important information in intraoperative neuronavigation and in planning brain tumor resection. A three-dimensional representation of fibers associated with the pyramidal tract during brain tumor surgery is feasible with the presented technique and is a helpful adjunct for the neurosurgeon. The main drawbacks include the length of time required for the segmentation procedure, the lack of direct intraoperative control of the pyramidal tract position, and brain shift. However, mapping of large fiber tracts and its intraoperative use for neuronavigation have the potential to increase the safety of neurosurgical procedures and to reduce surgical morbidity.

Intravascular ultrasound Doppler measurement of blood flow velocity

BACKGROUND AND PURPOSE

The authors investigated the feasibility and accuracy of intravascular Doppler sonography (IVDS) with a newly developed microprobe.

METHODS

The known method to determine blood flow velocity by transcutaneous Doppler sonography was transferred to an intravascular usable Doppler probe. With the improved technique, a microprobe measuring 0.3 mm in diameter can be advanced through a 5F catheter used in routine diagnostic angiography to perform intravascular Doppler sonography. In a first step, the conditions for application and measurement were studied in a flow tube model and were transferred in a second step to patients undergoing routine angiography and patients with arterial stenoses.

RESULTS

Measurements with nondegassed liquids showed a high intensive acoustic signal, but no echo effect could be recorded in degassed liquids. IVDS of healthy vessels in 40 patients showed the same typical flow pulse curve as seen in transcutaneous measurements. The optimal position of the microprobe with respect to the contact of the vessel wall, the diastolic and systolic phase, and the distance to the tip of the catheter could be evaluated. In 95.6% of the 40 patients with healthy vessels, IVDS was successful. Fourteen patients with arterial stenotic diseases were investigated before and after percutaneous transluminal angioplasty, and the results of these investigations correlated well with the angiographical results.

CONCLUSIONS

For percutaneously directly reachable vessels, the transcutaneous Doppler sonography is the choice for easy noninvasive and inexpensive measurement of blood flow velocity. However, for vessels that are difficult or impossible to reach percutaneously, intravascular measurement is a valid procedure.

Functional MRI for presurgical planning: problems, artefacts, and solution strategies

OBJECTIVES

Presurgical mapping of motor function is a widely used clinical application of functional (f) MRI, employing the blood oxygenation level dependent contrast. The aim of this study was to report on 3 years experience of 194 fMRI studies on the representation of motor function in 103 patients and to describe the problems and artefacts that were typically present.

METHODS

An evaluation was carried out to determine whether the patients' age, type or location of the tumourous lesion, severity of the paresis, or the tasks used during the investigation have an effect on artefacts of fMRI studies and how these artefacts are best overcome.

RESULTS

Functional MRI identified the motor regions in 85% of all investigated paradigms. In 11% of the investigated patients no information at all on functional localisation was obtained. A draining vein within the central sulcus was present in all patients that showed activation within the parenchyma of the precentral gyrus but also in three patients in whom no parenchymal activation was present. Head movement artefacts were the most frequent cause for fMRI failure, followed by low signal to noise ratio. Motion artefacts were correlated with the degree of paresis and with the functional task. Tasks involving more proximal muscles led to significantly more motion artefacts when compared with tasks that primarily involved distal muscles. Mean MR signal change during task performance was 2.5%.

CONCLUSIONS

Most of the artefacts of functional MRI can be reliably detected and at least in part be reduced or eliminated with the help of mathematical algorithms, appropriate pulse sequences and tasks, and-probably most important-by evaluating the fMRI raw data-that is, the MR signal time courses.

Virtual pointer projection of the central sulcus to the outside of the skull using frameless neuronavigation -- accuracy and applications

BACKGROUND

The purpose of this prospective study was to localize the central sulcus by frameless neuronavigation and to project this anatomical structure to the outside of the skull on the skin. This method was analyzed in respect to its practicability, accuracy, and potential applications.

METHOD

In 27 patients investigated (28 unaffected hemispheres), the central sulcus was virtually projected to the outside of the skull using frameless neuronavigation and a virtual pointer elongation of 15 or 20 mm. The following parameters were measured on the scalp: 1. the distance between the bregma and the midline junction of the central sulcus, and 2. the angle between the central sulcus and the midline. These dada were compared with measurements based on the original axial MR images of these patients. Finally, a laboratory phantom study was designed in analogy to a patient's examination for estimation of the overall accuracy of the neuronavigation system in the experimental setup used in this study.

FINDINGS

Virtual pointer projection of the central sulcus to the outside of the skull using frameless neuronavigation was found to be easily possible. The distance between the bregma and the midline junction of the central sulcus amounted to a mean of 55 mm on the left and 56 mm on the right. The angle between the central sulcus and the midline reached a mean of 63 degrees on the left and 60 degrees on the right. These data confirmed results of other studies with no frameless neuronavigation devices. The phantom study revealed a mean overall inaccuracy of 0.9 mm at a virtual pointer elongation of 15 mm. At a virtual pointer elongation of 20 mm, the mean overall inaccuracy of our study was 1.1 mm. These results correspond to the inaccuracy of frame based stereotaxy.

INTERPRETATION

It is easily possible, valid, and reliable to virtually project the central sulcus to the outside of the skull with an acceptably low inaccuracy using frameless neuronavigation. This is important for research studies that correlate and integrate different functional imaging methods with the aid of frameless neuronavigation.

Coil embolization of an incidental posterior cerebral artery aneurysm after initial OA-PCA bypass surgery

Aneurysms of the posterior cerebral artery (PCA) are rare and imply a variety of treatment modalities. We present a case of an incidental, nonruptured posterior cerebral artery aneurysm, which was successfully occluded by coil embolization after a bypass between the occipital artery and the distal posterior cerebral artery was created. MR imaging in a neurologically normal 26-year-old man, performed in the course of a work-up for nonrelated symptoms, incidentally revealed a partially thrombosed and calcified aneurysm of the left posterior cerebral artery (P2 segment). This was confirmed by angiography. Due to aneurysm configuration and localization in the asymptomatic patient, primary clipping or endovascular occlusion was considered to be too hazardous. Four weeks after successful microvascular connection of the left occipital artery to the distal posterior cerebral artery, the PCA was occluded at the level of the aneurysm with a detachable coil. The patient remained asymptomatic, without visual field defects. The above presented combined microvascular (bypass) and endovascular (coil embolization) treatment with excellent result should be considered as alternative in patients with nonruptured, asymptomatic P2 aneurysms, which are high risk for primary clipping or endovascular occlusion.

Microsurgical treatment of spontaneous and non-spontaneous spinal epidural haematomas: neurological outcome in relation to aetiology

BACKGROUND

This retrospective study evaluated the neurological outcome of 26 patients with spontaneous and non-spontaneous spinal epidural haematoma (SEH) who underwent microsurgical clot removal. It was the objective of the present study to investigate whether the aetiology of the SEH has an influence on the neurological outcome.

METHODS

The medical records and radiological investigations of 26 patients with SEH were re-examined, and the latency between symptom onset and operation, and the size of the haematoma were determined. Motor and sensory function had been evaluated before surgery and 90 days after discharge.

FINDINGS

Fourteen patients with non-spontaneous SEH and 12 patients with spontaneous SEH were identified. After surgery, neurological deficits improved in 9 of the patients with spontaneous (75%) and in 13 of the patients with non-spontaneous SEH (93%). In cases of spontaneous SEH, the median latency between symptom onset and operation was longer (72 hrs vs 7 hrs) and the median extent of the haematoma was larger (3.5 vs 2 spinal segments), than in the non-spontaneous cases.

INTERPRETATION

Neurological outcome seems to be related to the aetiology of the SEH. Better outcome was observed in patients with surgically treated non-spontaneous SEH. Two explanations for this finding are worth considering. First, patients with non-spontaneous SEH usually are already under medical surveillance and can undergo medullary decompression more rapidly. Second, the compression of the spinal cord is possibly less severe in non-spontaneous SEH because of their smaller size.

Health-related quality of life after aneurysmal subarachnoid hemorrhage: impacts of bleeding severity, computerized tomography findings, surgery, vasospasm, and neurological grade

OBJECT

Based on the results of earlier studies it is agreed that the significance of aneurysm location and surgery for neuropsychological impairments after subarachnoid hemorrhage (SAH) is secondary to the effects of the bleeding itself. Therefore, the present study was performed to evaluate whether bleeding, acute clinical course, and surgery have persistent effects on health-related quality of life (QOL) after SAH.

METHODS

A series of 116 patients was examined for 4 to 5 years (mean 52.2 months) after aneurysmal SAH by means of a QOL questionnaire. Eighty-six patients (74.1%) had undergone surgery early (< or = 72 hours post-SAH). There were 77 women (66.4%) and 39 men (33.6%) in the study group, and the mean age of the patients was 50.3+/-13.3 years (range 30-69 years). Patients who had undergone surgery for a left-sided middle cerebral artery (MCA) aneurysm complained of significantly more impairments in social contact, communication, and cognition than those treated for a right-sided MCA aneurysm. No other effects of aneurysm location (including the anterior communicating artery) emerged. Multiple aneurysms, intraoperative aneurysm rupture, and partial resection of the gyrus rectus had no adverse effects on later daily life. Only temporary clipping was associated with increased complaints in some QOL areas. Disturbances of the circulation of cerebrospinal fluid and the presence of intraventricular hemorrhage led to more impairments in daily life. Specific effects of the anatomical pattern of the bleeding could be identified, but no adverse effects of vasospasm were found. Multivariate analyses revealed, in particular, that patient age and admission neurological status (Hunt and Hess grade) are substantial predictors of the psychosocial sequelae of SAH.

CONCLUSIONS

In contrast to the mild effects of aneurysm surgery, patient's age, initial neurological state on admission, and the bleeding pattern substantially influence late QOL after SAH.