Development of the Arterial Supply of the Spinal Cord Tissue Based on Radioanatomical and Histological Studies in Cattle.

PURPOSE: Angiographic techniques have gained increasing importance in suspected vascular disease of the spinal cord. This demands an advanced understanding of spinal cord blood vessel anatomy and its embryologically founded broad spectrum of variations. The aim of this study was to improve knowledge on contentious issues concerning the development of spinal cord arterial supply in higher mammals and to offer visual information of high didactic value. METHODS: The prenatal development was examined in cattle, using multiplanar high-resolution microangiography of injected specimens and microscopic sections. The gestational ages of the 15 specimens were between the late embryonic and the early fetal period (5-11 weeks). Microangiography of the human spinal cord from an earlier published study were used to envisage an adult arterial vascularization pattern in higher mammals. RESULTS: Establishment of the unpaired anterior spinal artery (ASA) goes through two procedures of reconfiguration until achieving its final design. Regression of the primarily established anteromedian tract is observed in cattle fetuses of 9-10 weeks. Return to the ontogenetic disposition of bilateral symmetry and a burst of vascularization from all parts of the spinal meninges follow and include the anterior median fissure as a preferred vascular pathway. Large sulcal/central arteries longitudinally anastomosing between each other emerge on both sides of the midline. The embryological pattern of exclusive peripheral medullary supply must have been converted into a combined system of predominant central (centrifugal) supply of the enlargements before a final unpaired ASA can be reconstructed. CONCLUSION: Previous investigators focused on the early embryonic development of spinal cord arteries and missed the profound remodeling of the vascular architecture in the early fetal period.

Endovascular management of spinal vascular malformations.

Spinal vascular malformations are rare diseases with a wide variety of neurological presentations. In this article, arteriovenous malformations (both from the fistulous and glomerular type) and spinal dural arteriovenous fistulae are described and an overview about their imaging features on magnetic resonance imaging (MRI) and digital subtraction angiography is given. Clinical differential diagnoses, the neurological symptomatology and the potential therapeutic approaches of these diseases which vary depending on the underlying pathology are given. Although MRI constitutes the diagnostic modality of first choice in suspected spinal vascular malformation, a definite diagnosis of the disease and therefore the choice of suited therapeutic approach rests on selective spinal angiography. Treatment in symptomatic patients offers an improvement in the prognosis. In most spinal vascular malformations, the endovascular approach is the method of first choice; in selected cases, a combined or surgical therapy may be considered.

Spinal glomus-type arteriovenous malformations: microsurgical treatment in 20 cases.

OBJECT: Glomus-type spinal arteriovenous malformations (AVMs) are rare. In the literature only small series and anecdotal reports can be found, and there are no prospective series elucidating the natural course or the superiority of 1 treatment regimen over another (such as surgery versus embolization versus conservative treatment). Microsurgical treatment of spinal AVMs often seems difficult because many lesions are not anatomically suitable for primary microsurgical occlusion and are therefore treated with first-line neuroradiological interventions or not at all. METHODS: Between 1989 and 2005, 20 patients with glomus-type AVMs underwent microsurgical treatment at 2 major neurosurgical centers in Germany. The history of symptoms in these patients ranged from 2 days to 11 years. Four patients presented with subarachnoid hemorrhage, 2 with intramedullary hematoma, 4 with paresthesia or pain, and 10 with clinical signs of myelopathy. Seven patients underwent partial embolization prior to microsurgery. The authors only operated on AVMs accessible from a dorsal or dorsolateral approach. Neurological status was assessed with the McCormick classification scheme. Follow-up data were obtained from outpatient records. Three patients were interviewed over the telephone and 4 patients were not available for follow-up evaluation. RESULTS: Surgery was performed via a laminectomy in 14 and hemilaminectomy in 6 patients. The microsurgical technique used consisted of retrograde dissection of the AVM from the venous side in most cases. Four (20%) of 20 patients showed worsening of neurological symptoms to a worse McCormick grade, probably caused by suspected venous stasis directly after surgery, however only 1 patient (5%) suffered permanent deterioration after surgery. In 14 patients postoperative angiography proved complete occlusion in 11 patients, including the presence of a remnant requiring a second operation with complete occlusion thereafter in 1 patient. In 3 patients occlusion was incomplete: a small residual AVM remained in 1 patient, and a discrete feeding vessel without a vein was evident in 2 patients. CONCLUSIONS: Spinal cord AVMs are rare. If embolization is not possible, surgery may be indicated in selected cases. Spinal AVMs behave differently after incomplete occlusion either surgically or with embolization. A postoperative reduction in symptoms is frequent despite the presence of small remnants, and the risk of neurological deficits seems relatively low even in residual AVMs. Therefore, treatment need not necessarily aim at complete occlusion if that would be associated with an unacceptably high risk of neurological deficits.

Imaging in spinal vascular disease.

Spinal vascular diseases are rare and constitute only 1% to 2% of all vascular neurologic pathologies. In this article, the following vascular pathologies of the spine are described: spinal arterial infarcts, spinal cavernomas, and arteriovenous malformations (including perimedullary fistulae and glomerular arterivenous malformations), and spinal dural arteriovenous fistulae. This article gives an overview about their imaging features on MRI, MR angiography, and digital subtraction angiography. Clinical differential diagnoses, the neurologic symptomatology, and the potential therapeutic approaches of these diseases, which might vary depending on the underlying pathologic condition, are given.

The hyperdense posterior cerebral artery sign: a computed tomography marker of acute ischemia in the posterior cerebral artery territory.

BACKGROUND AND PURPOSE: In the anterior circulation, the hyperdense middle cerebral artery (MCA) sign is a well-established marker for early ischemia. Similarly, the hyperdense basilar artery sign or the MCA "dot" sign may be a diagnostic clue for basilar artery or distal MCA branch thrombosis. The purpose of this study was to define the hyperdense posterior cerebral artery (PCA) sign and determine its incidence, diagnostic value, and reliability as a marker for ischemia in the territory of the PCA. METHODS: Cranial computed tomographies (CCTs) of 48 patients with proven acute ischemia (<12 hours) in the PCA territory were compared by 3 independent and blinded readers to the CCTs of 86 age-matched patients without PCA infarction. Using follow-up imaging, the correlation of the hyperdense PCA (HPCA) with infarct size, thalamic infarction, and bleeding were investigated. RESULTS: An HPCA was found in 35.4% of all patients with PCA infarction, typically within the ambient cistern, with a specificity of 95.4%. The thalamus was affected significantly more often (P=0.009) and the size of the infarct was significantly more often large than medium (P=0.018) or small (P<0.001) when an HPCA was present. Hemorrhagic transformation tended to occur more often when the HPCA was present. CONCLUSIONS: An HPCA was detected in more than one third of all patients with PCA ischemia, suiting the incidence of the hyperdense MCA. Based on our results, this sign may not only be helpful in the early diagnosis of PCA infarction but might also act as a prognostic marker in acute PCA territory ischemic stroke.

Spinal epidural arteriovenous fistula with perimedullary drainage. Case report and pathomechanical considerations.

The classic angiographically demonstrated features of spinal dural arteriovenous fistulas are shunts of radiculomeningeal branches with radicular veins draining exclusively in the direction of perimedullary veins and thereby causing venous congestion. These shunts are located at the point where the radicular vein passes the dura mater. Spinal epidural arteriovenous shunts, however, normally do not drain into the perimedullary veins and are, therefore, asymptomatic, presumably because of a postulated reflux-impeding mechanism between the dural sleeves. The authors report on a patient in whom an epidural arteriovenous shunt showed delayed retrograde drainage into perimedullary veins, leading to the classic clinical (and magnetic resonance imaging-based) findings of venous congestion. Intraoperatively the angiographically established diagnosis was confirmed. Coagulation of both the epidural shunt zone and the radicular vein resulted in complete obliteration of the fistula, as confirmed on repeated angiography. This rare type of fistula should stimulate considerations on the role of valvelike mechanisms normally impeding retrograde flow from the epidural plexus to perimedullary veins and suggest that, in certain pathological circumstances, epidural fistulas can drain retrogradely into perimedullary veins as an infrequent variant of spinal arteriovenous shunts.

Spinal dural arteriovenous fistula associated with a spinal perimedullary fistula: case report.

Among spinal cord vascular malformations, dural arteriovenous fistulas (DAVFs) must be distinguished from intradural malformations. The concurrence of both is extremely rare. The authors report the case of a 35-year-old man who suffered from progressive myelopathy and who harbored both a DAVF and an intradural perimedullary fistula. During surgery, both fistulas were identified, confirmed, and subsequently obliterated. The fistulas were located at two levels directly adjacent to each other. Although the incidence of concurrent spinal DAVFs is presumed to be approximately 2%, the combination of a dural and an intradural fistula is exceedingly rare; only two other cases have been reported in the literature. One can speculate whether the alteration in venous drainage caused by the (presumably congenital) perimedullary fistula could possibly promote the production of a second dural fistula due to elevated pressure with concomitant venous stagnation and subsequent thrombosis. The authors conclude that despite the rarity of dual pathological entities, the clinician should be aware of the possibility of the concurrence of more than one spinal fistula in the same patient.

Memory-related hippocampal dysfunction in poly-drug ecstasy (3,4-methylenedioxymethamphetamine) users.

RATIONALE: 3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is neurotoxic in animal studies and its use has been associated with cognitive impairments in humans. OBJECTIVE: To study hippocampal activation during the retrieval from episodic memory in polyvalent users of ecstasy. METHODS: Twelve polyvalent ecstasy users and twelve matched controls were examined by means of functional magnetic resonance imaging (fMRI) while they retrieved face-profession associations from episodic memory. RESULTS: Ecstasy users had a normal structural MRI scan without focal brain lesions or anatomical abnormalities. They exhibited equal retrieval accuracy during memory retrieval to that of the matched controls. Yet, their retrieval-related activity was lower and more spatially restricted in the left anterior hippocampus than that of the controls. CONCLUSIONS: These results provide evidence for abnormal hippocampal functioning in MDMA users even at the presence of normal memory performance. This finding may be linked to MDMA-induced neurotoxicity and suggests that diminished hippocampal activation during memory retrieval might be a more sensitive or earlier index of MDMA-related neurotoxicity than neuropsychological performance.

Functional outcome after surgical treatment of spontaneous and nonspontaneous spinal subdural hematomas.

OBJECT: Because of the rarity of spinal subdural hematomas (SDHs), the literature offers scarce estimates of the outcome and predictive factors in patients suffering from these lesions. In addition, single-institution surgical series are still lacking. Therefore, the authors retrospectively evaluated the early and long-term functional outcomes measured in eight patients with spontaneous and nonspontaneous spinal SDHs in whom the clot had been evacuated. METHODS: The patients' charts were evaluated for origin of the lesion, risk factors, and neurological deficits at symptom onset and at 28 days after extirpation of the spinal SDH. Long-term clinical outcome (Barthel Index [BI]) was evaluated by administering a telephone questionnaire to the patient or a relative. Only one patient with a spontaneous spinal SDH was identified. Four patients were undergoing anticoagulant therapy, and three patients had undergone a previous anesthetic/diagnostic spinal procedure. Twenty-eight days postoperatively, neurological deficits improved in six of eight patients; however, in two of the six patients, the improvement did not allow the patients to become independent again. In two patients, surgery did not affect the complete sensorimotor deficits. In the long-term survivors (median 45 months) a median BI of 55 was achieved. The latency between symptom onset and surgery did not correlate with functional outcome in this series. The preoperative neurological condition and location of the hematoma correlated positively with early and long-term functional outcome. CONCLUSIONS: To the best of their knowledge, the present study is the largest single-institutional study of patients with surgically treated spinal SDHs. Despite some postoperative improvement of sensorimotor deficits in most patients, the prognosis is poor because 50% of the patients remain dependent. Their outcome was determined by the preoperative sensorimotor function and spinal level of the spinal SDH.

Neural mechanisms of working memory in ecstasy (MDMA) users who continue or discontinue ecstasy and amphetamine use: evidence from an 18-month longitudinal functional magnetic resonance imaging study.

BACKGROUND: Working memory processing in ecstasy (3,4-methylenedioxymethamphetamine) users is associated with neural alterations as measured by functional magnetic resonance imaging. Here, we examined whether cortical activation patterns change after prolonged periods of continued use or abstinence from ecstasy and amphetamine. METHODS: We used an n-back task and functional magnetic resonance imaging in 17 ecstasy users at baseline (t(1)) and after 18 months (t(2)). Based on the reported drug use at t(2) we separated subjects with continued ecstasy and amphetamine use from subjects reporting abstinence during the follow-up period (n = 9 and n = 8, respectively). RESULTS: At baseline both groups had similar task performance and similar cortical activation patterns. Task performance remained unchanged in both groups. Furthermore, there were no detectable functional magnetic resonance imaging signal changes from t(1) to t(2) in the follow-up abstinent group. However, the continuing users showed a dose-dependent increased parietal activation for the 2-back task after the follow-up period. CONCLUSIONS: Our data suggest that ecstasy use, particularly in high doses, is associated with greater parietal activation during working memory performance. An altered activation pattern might appear before changes in cognitive performance become apparent and, hence, may reflect an early stage of neuronal injury from the neurotoxic drug ecstasy.

Cerebral activation in abstinent ecstasy (MDMA) users during a working memory task: a functional magnetic resonance imaging (fMRI) study.

The popular recreational drug ecstasy (3,4-methylenedioxymethamphetamine=MDMA and related congeners) is neurotoxic upon central serotonergic systems in animal studies. So far, the most convincing evidence for neurotoxicity-related functional deficits in humans derives from neurocognitive studies demonstrating dose-related long-term learning and memory problems in ecstasy users. In our study we used functional magnetic resonance imaging (fMRI) and a working memory task to investigate cerebral activation in eleven heavy, but currently abstinent MDMA users and two equally sized groups of moderate users and non-users. There were no significant group differences in working memory performance and no differences in cortical activation patterns for a conservative level of significance. However, for a more liberal statistical criterion, both user groups showed stronger activations than controls in right parietal cortex. Furthermore, heavy users had a weaker blood oxygenation level-dependent (BOLD) response than moderate users and controls in frontal and temporal areas. Our results may indicate subtle altered brain functioning associated with prior MDMA use, although alternative interpretations of these group differences must be considered.

Neural correlates of working memory in pure and polyvalent ecstasy (MDMA) users.

Poor cognitive performance in ecstasy (3,4-methylenedioxymethamphetamine; MDMA) users has been related to the well-recognized neurotoxic effects of the drug upon central serotonergic and possibly also dopaminergic systems. However, concomitant use of other drugs has been a critical confound in most investigations. In this study we used an n-back task and fMRI to investigate working memory performance and related cerebral activation in eight, currently abstinent pure MDMA users and two matched groups of polyvalent MDMA users and non-users. Pure MDMA users presented lower activations than controls and/or polyvalent users, most notably in inferior temporal regions, the angular gyrus and the striate cortex, whereas polyvalent users did not differ from controls. Our results suggest that altered brain activation patterns during cognitive processing in ecstasy users may be mainly associated with prior MDMA use. Concomitant use of other drugs may modify this effect.

Frame-based and frameless stereotactic hematoma puncture and subsequent fibrinolytic therapy for the treatment of spontaneous intracerebral hemorrhage.

OBJECTIVES: Comparison of two minimally invasive procedures for the treatment of intracerebral hemorrhage and subsequent lysis with regard to technical implications and clinical outcome of the patients. METHODS: Retrospective analysis of 126 patients with spontaneous supratentorial intracerebral hemorrhage treated by frame-based (n=53) or frameless (n=75) hematoma aspiration and subsequent fibrinolysis with recombinant tissue plasminogen activator (rt-PA). Data were analysed for the whole group as well as for the two subsets of patients with regard to hematoma reduction, procedure-related complications, and the early and long term clinical outcome of the patients. Functional outcome was rated using the Glasgow Outcome Scale (GOS) and Barthel-Index (median follow-up 178 weeks). The prognostic impact of patient related covariates on the GOS was analysed using logistic regression analysis. RESULTS: 49 out of 126 patients (38.9 %) died, 25 of them in the early postoperative period. Only 22/126 (17.5 %) had a favorable long term outcome (GOS >3). Age > 65 years was significantly (p<0.03, OR 3.6) associated with a higher risk for an unfavorable long term outcome (GOS < or = 3). Treatment had no impact on outcome. Both techniques were highly effective in reducing the intracerebral blood volume by 75.8+/-21.4% of the initial hematoma volume in frame-based and 64.8+/-25.4 % in frameless stereotaxy within 2 days of rt-PA-therapy. Malpositioning of the catheter occurred more often in the frameless group (21.3% vs. 9.4 % in the frame-based procedure) without gaining statistical significance. CONCLUSIONS: Frame-based and frameless stereotactic hematoma aspirations with subsequent fibrinolysis are effective in volume reduction of intracerebral hemorrhage with comparable clinical outcome. The frameless procedure is associated with a higher risk for malpositioning of the catheter. Despite effective hematoma reduction with both techniques, the percentage of patients with a good clinical outcome remained limited especially in the elder subpopulation.

Motor representation in patients rapidly recovering after stroke: a functional magnetic resonance imaging and transcranial magnetic stimulation study.

OBJECTIVE: Neuroimaging studies have suggested an evolution of the brain activation pattern in the course of motor recovery after stroke. Initially poor motor performance is correlated with an recruitment of the uninjured hemisphere that continuously vanished until a nearly normal (contralateral) activation pattern is achieved and motor performance is good. Here we were interested in the early brain activation pattern in patients who showed a good and rapid recovery after stroke. METHODS: Ten patients with first-ever ischemic stroke affecting motor areas had to perform self-paced simple or more complex movements with the affected or the unaffected hand during functional magnetic resonance imaging (fMRI). The location and number of activated voxels above threshold were determined. To study possible changes in the cortical motor output map the amplitude of the motor evoked potentials (MEP) and the extent of the excitable area were determined using transcranial magnetic stimulation (TMS). RESULTS: The pattern of activation observed with movements of the affected and the unaffected hand was similar. In the simple motor task significant (P<0.05) increases were found in the primary motor cortex ipsilateral to the movement, the supplementary motor area and the cerebellar hemisphere contralateral to the movement during performance with the affected hand compared to movements with the unaffected hand. When comparing simple with more complex movements performed with either the affected or the unaffected hand, a further tendency to increased activation in motor areas was observed. The amplitude of MEPs obtained from the affected hemisphere was smaller and the extent of cortical output maps was decreased compared to the unaffected hemisphere; but none of the patients showed MEPs at the affected hand when the ipsilateral unaffected motor cortex was stimulated. CONCLUSIONS: Despite a rapid and nearly complete motor recovery the brain activation pattern was associated with increased activity in (bilateral) motor areas as revealed with fMRI. TMS revealed impaired motor output properties, but failed to demonstrate ipsilateral motor pathways. Successful recovery in our patients may therefore rely on the increased bilateral activation of existing motor networks spared by the injury.

Proton magnetic resonance spectroscopy in ecstasy (MDMA) users.

The popular recreational drug 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) has well-recognized neurotoxic effects upon central serotonergic systems in animal studies. In humans, the use of MDMA has been linked to cognitive problems, particularly to deficits in long-term memory and learning. Recent studies with proton magnetic resonance spectroscopy (1H MRS) have reported relatively low levels of the neuronal marker N-acetylaspartate (NAA) in MDMA users, however, these results have been ambiguous. Moreover, the only available 1H MRS study of the hippocampus reported normal findings in a small sample of five MDMA users. In the present study, we compared 13 polyvalent ecstasy users with 13 matched controls. We found no differences between the NAA/creatine/phosphocreatine (Cr) ratios of users and controls in neocortical regions, and only a tendency towards lower NAA/Cr ratios in the left hippocampus of MDMA users. Thus, compared with cognitive deficits, 1H MRS appears to be a less sensitive marker of potential neurotoxic damage in ecstasy users.

Time-of-flight-, phase contrast and contrast enhanced magnetic resonance angiography for pre-interventional determination of aneurysm size, configuration, and neck morphology in an aneurysm model in rabbits.

We describe three different magnetic resonance (MR)-angiography techniques to evaluate aneurysm size, configuration, and neck morphology of experimentally created aneurysms in a rabbit model. In five New Zealand White rabbits an aneurysm was created by endovascular occlusion of the right common carotid artery (CCA) using a pliable balloon and subsequent endoluminal incubation of elastase within the proximal CCA above the balloon and distal ligation of the vessel. In all animals, time-of-flight (TOF), phase contrast and contrast enhanced (CE) MR angiographies (MRA) were performed and compared to conventional digital subtraction angiography results. We found, that aneurysms are best visualized employing CE MRA, however, neck morphology was also found to demonstrate interpretable results when evaluating the axial source data of the TOF MRA. The animal model we used can be employed for testing endovascular devices such as new coil material, or covered stents. The described MRA techniques might then be helpful for pre-interventional planning and maybe even for the follow-up of the thus treated aneurysms.

Clinical hypnosis modulates functional magnetic resonance imaging signal intensities and pain perception in a thermal stimulation paradigm.

OBJECTIVE: This study was designed to describe regional changes in blood oxygenation level dependent signals in functional magnetic resonance images (fMRI) elicited by thermal pain in hypnotized subjects. These signals approximately identify the neural correlates of the applied stimulation to identify neuroanatomic structures involved in the putative effects of clinical hypnosis on pain perception. METHODS: After determination of the heat pain threshold of 12 healthy volunteers, fMRI scans were performed at 1.5 Tesla by using echoplanar imaging technique during repeated painful heat stimuli. Activation of brain regions in response to thermal pain during hypnosis (using a fixation and command technique of hypnosis) was compared with responses without hypnosis. RESULTS: With hypnosis, less activation in the primary sensory cortex, the middle cingulate gyrus, precuneus, and the visual cortex was found. An increased activation was seen in the anterior basal ganglia and the left anterior cingulate cortex. There was no difference in activation within the right anterior cingulate gyrus in our fMRI studies. No activation was seen within the brainstem and thalamus under either condition. CONCLUSION: Our observations indicate that clinical hypnosis may prevent nociceptive inputs from reaching the higher cortical structures responsible for pain perception. Whether the effects of hypnosis can be explained by increased activation of the left anterior cingulate cortex and the basal ganglia as part of a possible inhibitory pathway on pain perception remains speculative given the limitations of our study design.

Preoperative mapping of cortical motor function: prospective comparison of functional magnetic resonance imaging and [15O]-H2O-positron emission tomography in the same co-ordinate system.

BACKGROUND: Two of the most widely accepted approaches to map eloquent cortical areas preoperatively are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). As yet, no study has compared these two modalities within the same frame of reference in tumour patients. AIM: We employed [15O]-H2O-PET and fMRI in patients undergoing presurgical evaluation and compared the results with those obtained by direct electrical cortical stimulation (DECS). METHODS: Twenty-five patients with tumours of different aetiology near the central region were investigated. fMRI and PET were processed using the same methods, i.e. statistical parametric mapping (SPM) without anatomical normalization, and transformed into the same frame of reference. RESULTS: fMRI activity was found in more cranial and lateral sections, i.e. closer to the brain surface, in comparison with PET, which demonstrated parenchymal activation. The mean localization difference between fMRI and PET was 8.1 +/- 4.6 mm (range, 2-18 mm). fMRI and [15O]-H2O-PET could reliably identify the central sulcus, as demonstrated by DECS. CONCLUSIONS: fMRI and [15O]-H2O-PET demonstrate comparable results and are sensitive and reliable tools to map the central region, especially in cases of infiltrating brain tumours. However, fMRI is more prone to artefacts, such as the visualization of draining veins, which may explain the more cranial and lateral activation visualized by fMRI, whereas PET depicts capillary perfusion changes and therefore shows activation closer to the parenchyma.

Preoperative assessment of motor cortex and pyramidal tracts in central cavernoma employing functional and diffusion-weighted magnetic resonance imaging.

BACKGROUND: Functional MRI (fMRI) combines anatomic with functional information and has therefore been widely used for preoperative planning of patients with mass lesions affecting functionally important brain regions. However, the courses of functionally important fiber tracts are not visualized. We therefore propose to combine fMRI with diffusion-weighted MRI (DWI) that allows visualization of large fiber tracts and to implement this data in a neuronavigation system. METHODS: DWI was successfully performed at a field strength of 1.5 Tesla, employing a spin-echo sequence with gradient sensitivity in six noncollinear directions to visualize the course of the pyramidal tracts, and was combined with echo-planar T2* fMRI during a hand motor task in a patient with central cavernoma. RESULTS: Fusion of both data sets allowed visualization of the displacement of both the primary sensorimotor area (M1) and its large descending fiber tracts. Intraoperatively, these data were used to aid in neuronavigation. Confirmation was obtained by intraoperative electrical stimulation. Postoperative MRI revealed an undisrupted pyramidal tract in the neurologically intact patient. CONCLUSION: The combination of fMRI with DWI allows for assessment of functionally important cortical areas and additional visualization of large fiber tracts. Information about the orientation of fiber tracts in normal appearing white matter in patients with tumors within the cortical motor system cannot be obtained by other functional or conventional imaging methods and is vital for reducing operative morbidity as the information about functional cortex. This technique might, therefore, have the prospect of guiding neurosurgical interventions, especially when linked to a neuronavigation system.

Intraoperative three-dimensional visualization of the pyramidal tract in a neuronavigation system (PTV) reliably predicts true position of principal motor pathways.

BACKGROUND: This prospective study employs anisotropic diffusion-weighted (ADW) magnetic resonance imaging for the integration of individual spatial information concerning the principal motor pathways into the operating room during microneurosurgery in the central region. We hypothesize that the three-dimensional (3-D) visualization of the pyramidal tract position (PTV) in a neuronavigation system based on ADW provides valid information concerning the position and extension of the principal motor pathways. METHODS: A total of 13 consecutive patients with lesions adjacent to the pyramidal tracts and the central region underwent microneurosurgery with the help of pyramidal tract visualization (PTV). An ADW sequence obtained preoperatively was fused to an anatomic navigation sequence. The 3-D reconstructions of the precentral gyrus (PG), the pyramidal tract, and the tumor were available in a customized neuronavigation system during surgery. Intraoperatively the PG was identified on the basis of the aforementioned data. Electric motorcortex stimulation (CS) was used to directly verify the PG location and indirectly the fiber tract position. RESULTS: In 11 cases (92%) the prediction of the principal motor pathways' position was correct. In one case of a meningioma, according to PTV, the tumor was falsely localized postcentrally. In the case of a precentral cavernoma, no motor response could be elicited by cortical stimulation. CONCLUSION: Intraoperative PTV on the basis of ADW provides the neurosurgeon with reliable information concerning the position of the principal motor pathways during intracranial procedures as proved with intraoperative electrophysiological testing. The technique has the potential to reduce operative morbidity. PTV is straightforward and can be adapted to other customized neuronavigation devices.