Biomedical subjects

Armin Thron

Publications and source records attributed to Armin Thron.

At least 19 recordsLinked to original sources

PubMed2006

An fMRI approach to particularize the frontoparietal network for visuomotor action monitoring: Detection of incongruence between test subjects' actions and resulting perceptions.

Contemporary theories of motor control assume that motor actions underlie a supervisory control system which utilizes reafferent sensory feedbacks of actions for comparison with the original motor programs. The functional network of visuomotor action monitoring is considered to include inferior parietal, lateral and medial prefrontal cortices. To study both sustained monitoring for visuomotor incongruence and the actual detection of incongruence, we used a hybrid fMRI epoch-/event-related design. The basic experimental task was a continuous motor task, comprising a simple racing game. Within certain blocks of this task, incongruence was artificially generated by intermittent takeover of control over the car by the computer. Fifteen male subjects were instructed to monitor for incongruence between their own and the observed actions in order to abstain from their own action whenever the computer took over control. As a result of both sustained monitoring and actual detection of visuomotor incongruence, the rostral inferior parietal lobule displayed a BOLD signal increase. In contrast, the prefrontal cortex (PFC) exhibited two different activation patterns. Dorsolateral (BA 9/46) and medial/cingulate (BA 8, BA 32) areas of the PFC displayed a greater increase of activation in sustained monitoring, while ventrolateral PFC showed greater event-related activation for the actual detection of visuomotor incongruence. Our results suggest that the rostral inferior parietal lobule is specifically involved in the reafferent comparison of the test subjects' own actions and visually perceived actions. Different activation patterns of the PFC may reflect different frontoparietal networks for sustained action monitoring and actual detection of reafferent incongruence.

Adult↗

PubMed2006

Long-term histological and scanning electron microscopy results of endovascular and operative treatments of experimentally induced aneurysms in the rabbit.

OBJECTIVE: Treatment strategies of cerebral aneurysms include surgical clipping and endovascular therapies. To determine the long-term results of these therapeutic strategies, the vessel wall reaction close to the former aneurysm was studied according to the assumption that an intact endothelial layer over the former aneurysm neck constitutes complete vessel wall reconstruction and stable aneurysm obliteration. METHODS: Aneurysms were created in 40 rabbits by intraluminal elastase incubation of the common carotid artery. Five animals each were assigned to the following groups: untreated, porous stents, polyurethane covered stentgrafts, porous stents with subsequent coiling. Ten animals were treated with coils alone, 10 with clips. After 6 months, angiography, histology, and scanning electron microscopy was performed. RESULTS: Porous stents did not obliterate the aneurysm, whereas stentgrafts did; in-stent stenosis of up to 60% was present because of neointimal multilayer proliferation. After coiling, the aneurysm dome was occluded with fibrinous and collagenous material, whereas the aneurysm neck was not covered by an endothelial lining. Coil loops lay bare within the vessel, with fresh thrombus material on their surface. After clipping, a thin layer of endothelial lining bridging the two attached vessel walls was present, thereby completely obliterating the aneurysm and reconstructing the vessel wall. CONCLUSION: This study demonstrates complete and stable aneurysm obliteration with vessel wall reconstruction after clipping, a sufficient obliteration of the aneurysm dome using endovascular techniques, but a failed healing response of the aneurysm neck that might correlate to its associated higher risk of rebleed. Whether or not this is counterbalanced by the better immediate outcome after endovascular treatment remains a matter of debate.

Animals↗

PubMed2006

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.

Adult↗

PubMed2006

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.

Aged↗

PubMed2005

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.

Adult↗

PubMed2005

Prospective demonstration of short-term motor plasticity following acquired central pareses.

The effect of newly acquired central pareses on functional MRI (fMRI) signal pattern is not known, since up to now all investigated patients were examined while they already experienced the motor weakness. We describe the first prospective and controlled study demonstrating the impact of new, acquired central pareses on fMRI motor activation pattern. Six patients suffering from a new central paresis after resection of a brain tumor infiltrating the central region were prospectively compared with a control group of five patients without postoperative paresis and a group of six healthy, age-matched controls who were investigated at two time points. fMRI signal was postoperatively analyzed during the performance of hand motor tasks and compared to the preoperative fMRI results. The relative signal change between rest and activation was evaluated for five cortical regions: the primary motor cortex (M1) and the ipsilateral primary motor cortex (M1i), the supplementary motor area (SMA), the premotor area (PMA), and the superior parietal lobule (SPL). In the patients with new postoperative central pareses, significant (P = 0.0313) decreases in fMRI activation were found in M1, whereas significant (P = 0.0313) increases were found in SMA and PMA. For M1i and SPL, there was a signal increase on average as well, but it failed to reach significance (P = 0.1250). In both control groups, no significant changes between both examinations were seen. Even though the number of investigated patients is too small to draw definite conclusions, our results support the concept of short-term motor plasticity being mediated by redundant systems that may take over function after damage of the primary motor cortex. The findings potentially also reflect increased functional demands imposed upon the motor network subsequent to a loss of dexterity.

Adult↗

PubMed2005

Effects of long-term practice and task complexity in musicians and nonmusicians performing simple and complex motor tasks: implications for cortical motor organization.

Motor practice induces plastic changes within the cortical motor system. Whereas rapidly evolving changes of cortical motor representations were the subject of a number of recent studies, effects of long-term practice on the motor system are so far poorly understood. In the present study pianists and nonmusicians were investigated using functional magnetic resonance imaging. Both groups performed simple and complex movement sequences on a keyboard with the right hand, the tasks requiring different levels of ordinal complexity. The aim of this study was to characterize motor representations related to sequence complexity and to long-term motor practice. In nonmusicians, complex motor sequences showed higher fMRI activations of the presupplementary motor area (pre-SMA) and the rostral part of the dorsal premotor cortex (PMd) compared to simple motor sequences, whereas musicians showed no differential activations. These results may reflect the higher level of visuomotor integration required in the complex task in nonmusicians, whereas in musicians this rostral premotor network was employed during both tasks. Comparison of subject groups revealed increased activation of a more caudal premotor network in nonmusicians comprising the caudal part of the PMd and the supplementary motor area. This supports recent results suggesting a specialization within PMd. Furthermore, we conclude that plasticity due to long-term practice mainly occurs in caudal motor areas directly related to motor execution. The slowly evolving changes in M1 during motor skill learning may extend to adjacent areas, leading to more effective motor representations in pianists.

Adult↗

PubMed2005

The neural correlate of very-long-term picture priming.

Repetition priming denotes a behavioural change caused by prior exposure to a stimulus. The effect is known to last for weeks. This study addresses the underlying neural mechanisms for very-long-term picture priming by using event-related functional magnetic resonance imaging complemented by a behavioural paradigm. Previous functional imaging studies with shorter retention intervals have shown that priming is associated with changes in the activity of both the occipital and posterior temporal cortex. In this study we compared retention intervals of 1 day and 6 weeks after initial exposure to a picture stimulus. Priming-related decreases in cortical activity in posterior extrastriate and dorsal left inferior frontal areas were found only for the shorter retention interval. In contrast, fMRI activation in the inferior posterior temporal and anterior left inferior frontal cortex was reduced following priming for both retention intervals. In the behavioural paradigm, the priming effect was stable over time. We conclude that the left inferior frontal and inferior posterior temporal cortex play a key role in the very-long-term priming effect.

Adult↗

PubMed2005

Treatment of experimentally induced aneurysms with stents.

OBJECTIVE: Although Guglielmi detachable coil systems have been widely accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents, stent grafts, or implantation of coils after stent placement constitute emerging techniques in endovascular treatment. The aim of the present study was to use an animal model to investigate these different approaches to treat cerebral aneurysms with regard to the rate of closure and the histopathological changes within the aneurysm cavity and the parent vessel after stent placement. METHODS: We created aneurysms in 30 rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. Ten animals were treated with porous stents alone, 10 animals with stent grafts (covered stents), and 10 animals with stents and additional coiling via the interstices of the stent, which enabled dense packing of the coils. Five animals in each group were observed for 1 month and the other animals for 3 months. Histological analyses were performed, including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration. RESULTS: Covered stents led to a complete and stable aneurysm occlusion with only minimal proliferative carrier vessel wall changes. One covered stent was completely occluded with old thrombus, and the other 9 remained patent. Porous stents occluded two of five aneurysms in the 1-month follow-up group and four of five after 3 months. However, progressive sprouting of neointima inside the carrier vessel that resulted in a stenosis of up to 40% was present. In the Stent + Coil group, one aneurysm showed recanalization after 1 month, and three of five aneurysms were recanalized after 3 months after coil compaction. Moreover, in-stent stenosis of up to 30% was present. CONCLUSION: This study demonstrates the possible shortcomings and problems of emerging stent techniques to treat intracerebral aneurysms, shows where technical advances have to be made, and describes in which cases of aneurysm morphology caution has to be exercised when considering an endovascular approach using stents.

Aneurysm↗

PubMed2005

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.

Adult↗

PubMed2004

Spinal vascular malformations.

Spinal vascular malformations are rare diseases that consist of true inborn cavernomas and arteriovenous malformations (including perimedullary fistulae, glomerular and juvenile AVMs) and presumably acquired dural arteriovenous fistulae. This review article gives an overview of the imaging features both on MRI and angiography, the differential diagnoses, the clinical symptomatology and the potential therapeutic approaches to these diseases. It is concluded that MRI is the diagnostic modality of first choice in suspected spinal vascular malformation and should be complemented by selective spinal angiography. Treatment in symptomatic patients offers an improvement in the prognosis, but should be performed in specialized centers. Patients with spinal cord cavernomas and perimedullary fistulae type I are surgical candidates. Dural arteriovenous fistulae can either be operated upon or can be treated by an endovascular approach, the former being a simple, quick and secure approach to obliterate the fistula, while the latter is technically demanding. In spinal arteriovenous malformations, the endovascular approach is the method of first choice; in selected cases, a combined therapy might be sensible.

Angiography↗

PubMed2004

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.

Adult↗

PubMed2004

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.

Adult↗

PubMed2004

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.

Aged↗

PubMed2004

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.

Adult↗

PubMed2003

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.

Adult↗

PubMed2003

A refined method for creating saccular aneurysms in the rabbit.

We describe a refined animal model of human intracerebral aneurysms for testing endovascular devices for interventional neuroradiological procedures. Saccular aneurysms resulting from a stump of the right common carotid artery (CCA) were created in 15 New Zealand White rabbits by intraluminal incubation of elastase that was applied to the CCA after distal ligation of the CCA and proximal occlusion of the vessel using a pliable balloon. Subsequently a microcatheter was advanced to a position cranial to the balloon and the elastase was infused under fluoroscopic guidance to avoid retrograde flow to the trachea via aberrant vessels. Contrast-enhanced (CE) MRA at 1.5 T and conventional digital subtraction angiography was performed to test for aneurysm size, morphology and neck anatomy. In all 15 animals aneurysms resulted from the stump of the right CCA, ranging in size from 2.0 to 9.9 mm (mean 6.3 mm) in craniocaudal direction, 1.0 to 5.5 mm (mean 3.8 mm) in mediolateral direction and 1.0 to 3.8 mm (mean 2.4 mm) in neck diameter. Aneurysm morphology could be adequately demonstrated using CE MRA. On histological evaluation a loss of the internal elastic lamina was noted. The described method represents an easy, reliable, and reproducible method of aneurysm creation in the rabbit in an area of high shear stress. These aneurysms can be used for testing new endovascular devices for embolization of intracranial aneurysms.

Angiography, Digital Subtraction↗

PubMed2003

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.

Adult↗