Amir Samii

International Neuroscience Institute Hannover, Hanover, Lower Saxony, Germany

Are you Amir Samii?

Claim your profile

Publications (107)281.45 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the last decade, several studies have investigated the neuroplastic changes induced by long-term musical training. Here we investigated structural brain differences in expert pianists compared to non-musician controls, as well as the effect of the age of onset (AoO) of piano playing. Differences with non-musicians and the effect of sensitive periods in musicians have been studied previously, but importantly, this is the first time in which the age of onset of music-training was assessed in a group of musicians playing the same instrument, while controlling for the amount of practice. We recruited a homogeneous group of expert pianists who differed in their AoO but not in their lifetime or present amount of training, and compared them to an age-matched group of non-musicians. A subset of the pianists also completed a scale-playing task in order to control for performance skill level differences. Voxel-Based Morphometry analysis was used to examine gray-matter differences at the whole-brain level. Pianists showed greater gray matter (GM) volume in bilateral putamen (extending also to hippocampus and amygdala), right thalamus, bilateral lingual gyri and left superior temporal gyrus, but a GM volume shrinkage in the right supramarginal, right superior temporal and right postcentral gyri, when compared to non-musician controls. These results reveal a complex pattern of plastic effects due to sustained musical training: a network involved in reinforcement learning showed increased GM volume, while areas related to sensorimotor control, auditory processing and score-reading presented a reduction in the volume of GM. Behaviorally, early-onset pianists showed higher temporal precision in their piano performance than late-onset pianists, especially in the left hand. Furthermore, early onset of piano playing was associated with smaller GM volume in the right putamen and better piano performance (mainly in the left hand). Our results therefore reveal for the first time in a single large dataset of healthy pianists the link between onset of musical practice, behavioral performance, and putaminal gray matter structure. In summary, skill-related plastic adaptations may include decreases and increases in GM volume, dependent on an optimization of the system caused by an early start of musical training. We believe our findings enrich the plasticity discourse and shed light on the neural basis of expert skill acquisition.
    Full-text · Article · Nov 2015 · NeuroImage
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study is to analyze the quantitative DTI parameters of the CST in patients suffering from subcortical gliomas affecting the CST using generally available navigation software. A retrospective study was conducted on 22 subjects with diagnosis of primary cerebral glioma and preoperative motor deficits. Exclusion criteria were: involvement of motor cortex, lesion involving both hemispheres, previous surgical treatment. All patients were studied using magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) sequences. Volume, fractional anisotropy (FA) and mean diffusivity value (MD) of the entire CSTs were estimated. Moreover, distance from midline, diameters, FA and MD were calculated on axial images at the point of minimal distance between tumor and CST. Statistical analysis was performed. There was a statistically significant difference of CST volume between affected and non-affected hemispheres (p<0.01). Mean overall/local FA, overall/local MD and sagittal diameter of CST were also significantly different between the two sides (p<0.05). Correlation tests resulted positive between the shift of CST and overall/local MD. Moreover there is significance between CST volume of tumor hemisphere and preoperative duration of motor deficits (p<0.05). The present study has demonstrated for the first time a significant difference of DTI based quantitative parameters of the CST between a tumor affected and a non-affected hemisphere in patients with a corresponding motor deficit. This preliminary data suggests a correlation between DTI based integrity of CST and its function. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Sep 2015 · Clinical Neurology and Neurosurgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background and importance: Local biological drug delivery in the brain is an innovative field of medicine that developed rapidly in recent years. Our report illustrates a unique case of de novo development of a cerebral arteriovenous malformation (AVM) after implantation of genetically modified allogeneic mesenchymal stem cells in the brain. Clinical presentation: A 50-year-old man was included in a prospective clinical study (study ID number CM GLP-1/01, 2007-004516-31) investigating a novel neuroprotective approach in stroke patients to prevent perihematomal neuronal damage. In this study, alginate microcapsules containing genetically modified allogeneic mesenchymal stem cells producing the neuroprotective glucagon-like peptide-1 (GLP-1) were implanted. Three years later, the patient presented with aphasia and a focal seizure due to a new left frontal intracerebral hemorrhage. Angiography revealed a de novo left frontal AVM. Conclusion: The development of an AVM within a period of 3 years after implantation of the glucagon-like peptide-1-secreting mesenchymal stem cells suggests a possible relationship. This case exemplifies that further investigations are necessary to assess the safety of genetically modified cell lines for local biological drug delivery in the brain. Abbreviations: ALK1, activin-like kinase 1AVM, arteriovenous malformationENG, endoglin; GLP-1, glucagon-like peptide-1GLP-1R, glucagon-like peptide-1 receptorMSC, mesenchymal stem cell.
    No preview · Article · Sep 2015 · Neurosurgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: Since the use of computed tomography and magnetic resonance imaging, colloid cysts (CCs) are discovered more frequently and subsequently their true incidence exceeds the numbers previously estimated. In 1986, the first familial case was reported in two identical twin brothers. To date, a total of 17 of these cases have been reported, all differing in the pattern of affected family members. Here, we describe a unique presentation of a familial case and review the relevant literature on CCs and their natural history to improve our understanding of these cases. Familial CC can present in various patterns, sizes, and forms. A genetic factor is likely to be responsible in these cases, and further research is warranted to clarify this phenomenon.
    No preview · Article · Aug 2015 · Surgical Neurology International
  • [Show abstract] [Hide abstract]
    ABSTRACT: Peritumoral edema (PTE) in skull base meningiomas correlates to the absence of an arachnoid plane and difference in outcome. In vestibular schwannomas (VS), PTE and its significance for microsurgery and outcome have never been systematically evaluated. To evaluate whether PTE correlates with tumor characteristics, the presence of an arachnoid plane, and outcome. A retrospective study of the institutional database. PTE was evaluated on fluid-attenuated inversion recovery magnetic resonance images. Preoperative patient data and intraoperative tumor features (presence of tumor pseudocapsule, vascularity, degree of adhesion/invasion of the arachnoid) were noted. Outcome measures were completeness of removal, neurological outcome, and complication rate. These parameters in patients with PTE (group A) were correlated to those in matched series without edema (group B). Thirty patients presented with PTE (5%). The mean VS size was 3.4 cm. No major differences in the degree of adhesion or presence of an arachnoid plane were found. VS with PTE were more frequently hypervascular (26.7% in group A vs 6.7% in group B). The presence of PTE in VS was not related to surgical radicality. VS with PTE had worse early postoperative facial nerve function, but at 12 months, there was no major difference. VS with PTE were prone to cause postoperative hemorrhages in the tumor bed. PTE in VS does not correlate with the degree of tumor adhesion and the presence of an arachnoid dissection plane. The radicality of tumor removal and long-term functional outcome in patients with and without PTE was similar. VS with PTE are more vascular and prone to cause postoperative hemorrhages. Therefore, meticulous hemostasis is advisable. FLAIR-MRI, fluid-attenuated inversion recovery magnetic resonance imagePTE, Peritumoral edemaVS, vestibular schwannomas.
    No preview · Article · Apr 2015 · Neurosurgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by muscular atrophy, spasticity, and bulbar signs caused by loss of upper and lower motor neurons. Evidence suggests that ALS additionally affects other brain areas including premotor cortex and supplementary motor area. Here, we studied movement execution and inhibition in ALS patients using a stop-signal paradigm and functional magnetic resonance imaging. Seventeen ALS patients and 17 age-matched healthy controls performed a stop-signal task that required responding with a button press to a right- or left-pointing black arrow (go-stimuli). In stop-trials, a red arrow (stop-stimulus) was presented shortly after the black arrow indicating to withhold the prepared movement. Patients had by trend higher reaction times in go-trials but did not differ significantly in their inhibition performance. Patients showed stronger inhibition-related activity in inferior, superior, and middle frontal gyri as well as in putamen and pallidum. Error-related activity, conversely, was found to be stronger in healthy controls, particularly in the insula bilaterally. Patients also showed increased activity in the motor cortex during button presses. The results provide evidence for altered prefrontal and subcortical networks underlying motor execution, motor inhibition, and error monitoring in ALS. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    No preview · Article · Apr 2015 · Human Brain Mapping
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the introduction of intraoperative and postoperative pneumatic compression additionally to the use of compression stockings, low molecular weight heparin-LMWH and early mobilization, a retrospective study in cranial neurosurgery using intraoperative MRI was performed. A retrospective analysis of 207 neurosurgical patients using intraoperative MRI was performed. A group of 86 patients was treated with the additional use of intraoperative and postoperative pneumatic compression until mobilization out of bed. One hundred twenty-one patients were treated without the use of additional pneumatic compression. Postoperatively the patients were screened for deep venous thrombosis by ultrasound and pulmonary embolism by CT-scan if suspicious. Statistical analysis was performed. The development of deep venous thrombosis was reduced from 9.9% to 3.5% in our patients with the additional use of intraoperative and postoperative pneumatic compression. That is a 64.6% relative risk reduction to develop deep venous thrombosis with the use of intraoperative and postoperative pneumatic compression. An additional 52% relative risk reduction was found for the chance of developing pulmonary embolism. In the 15 patients with detected deep venous thrombosis, the OR-time was more than 100min longer than in the 192 patients without detected deep venous thrombosis. The difference between both groups was significant. This study demonstrates the benefit of pneumatic compression with a risk reduction for the development of thromboembolic complications. OR-time is another risk factor that attributes to a significant risk for the development of thromboembolic complications. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Mar 2015 · Clinical Neurology and Neurosurgery
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sinus histiocytosis (Rosai-Dorfman disease) with massive lymphadenopathy is a rare nonneoplastic and nonlangerhans cell proliferation disorder of the histiocytes. Extranodal location with or without lymphadenopathy occurs in about 40 % of the cases. Intracranial location is rare in children often mimicking meningiomas. The parasphenoidal region is more frequently involved though intraxial or intraventricular locations were described as well. Rarely, the surgical treatment allows the complete excision of the lesion; however, in symptomatic cases, partial resections of the tumor allow to counteract its mass effect. Long survivals are possible, even without radiotherapy or chemotherapy, due to the frequent spontaneous benign evolution of the lesions. A 2-year-10-month-old girl presented with high fever and vomiting. One year ago, she had a period of muscular weakness in both legs that recovered completely. MRI of the brain revealed an axial enhancing lesion with ventricular spreading mainly to the left occipital horn and bilateral frontal periventricular infiltration. After steroid therapy, all the symptoms recovered. Partial removal of the occipital intraventricular lesion was performed and the diagnosis of Rosai-Dorfman disease was established and confirmed by the reference center. At the latest follow-up (16 months), the girl is without any neurological symptoms and without any treatment.
    Full-text · Article · Feb 2015 · Child s Nervous System
  • Souvik Kar · Amir Samii · Helmut Bertalanffy
    [Show abstract] [Hide abstract]
    ABSTRACT: Cerebral cavernous malformations (CCM) are common vascular malformation of the brain and are associated with abnormal angiogenesis. Although the exact etiology and the underlying molecular mechanism are still under investigation, recent advances in the identification of the mutations in three genes and their interactions with different signaling pathways have shed light on our understanding of CCM pathogenesis. The phosphatidylinositol 3-kinase (PI3K)/Akt pathway is known to play a major role in angiogenesis. Studies have shown that the phosphatase and tensin homologue deleted on chromosome ten (PTEN), a tumor suppressor, is an antagonist regulator of the PI3K/Akt pathway and mediates angiogenesis by activating vascular endothelial growth factor (VEGF) expression. Here, we provide an update literature review on the current knowledge of the PTEN/PI3K/Akt/VEGF signaling in angiogenesis, more importantly in CCM pathogenesis. In addition to reviewing the current literatures, this article will also focus on the structural domain of the three CCM proteins and their interacting partners. Understanding the biology of these proteins with respect to their signaling counterpart will help to guide future research towards new therapeutic targets applicable for CCM treatment.
    No preview · Article · Nov 2014 · Neurosurgical Review
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective The operative management of cystic vestibular schwannoma is more challenging. In the study we focus on the peculiarity of cystic vestibular schwannoma in terms of management and outcome. We evaluated a homogenous series of consecutive patients with cystic vestibular schwannomas, operated with similar technique and via the same surgical approach Methods The patients with vestibular schwannoma, who were operated at our center from 2000 to 2012, were retrospectively analyzed. Those having cystic vestibular schwannomas, recognized with the presence of cystic components both on the preoperative MRI images and intraoperatively, were included. Thirty seven consecutive patients matched the inclusive criteria. The whole pool of solid vestibular schwannomas with similar tumor extension was used as a control group. The facial nerve outcome is reported early after surgery and after one year follow up. Facial nerve palsy GI-III according to House-Brackmann grading system was considered favorable outcome. Facial nerve palsy GIV-VI was considered unfavorable. The surgical morbidity in the two groups were compared. A special point of interest was the correlation between the cyst pattern and outcome. Results Cystic vestibular schwannomas are associated with a worse early facial nerve outcome (unfavorable in 37.8% in cystic vestibular schwannoma compared to 17.5% in the solid variant). After one year follow-up, 8.1% of the cystic variant had unfavorable facial nerve outcome. Meanwhile 6.2% of the solid variant had unfavorable outcome. There was no statistically significant difference between both groups regarding the long term facial nerve outcome. The cystic variant had a higher postoperative morbidity rates especially hemorrhage (8.1%) in comparison to solid vestibular schwannoma of the same extension(1.7%).Hydrocephalus without significant hematoma is also significantly higher in the cystic type than the solid variant. Medially located thin walled cyst are related to worse facial nerve outcome. Conclusion Surgery of cystic vestibular schwannomas is associated with a higher morbidity rate and facial nerve dysfunction in comparison to the solid variant. Special attention is required during facial dissection allow functional preservation especially with tumors with medially located thin walled cysts. Meticulous hemostasis is also required to avoid postoperative hematoma. Close postoperative care is mandatory for early detection and prompt management of possible postoperative complications.
    No preview · Article · Jul 2014 · World Neurosurgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: The extent of resection in cerebral gliomas is considered to be of critical importance to increase patient's overall survival. For this purpose, advanced imaging techniques such as DTI based tractography are important to depict the relation between white matter fibers and tumor. The use of this tool combined with intraoperative high-field MRI (iopMRI) opens the possibility to update this information during surgery. Our aim is to verify fiber-tracking reliability using direct electrical subcortical stimulation (DES) during glioma surgery in the iopMRI environment. Method: We report preliminary results of 5 consecutive patients treated at our institute for gliomas located near the CST using iopMRI (1.5 T). The patients were preoperatively studied using an MR protocol including DTI. After every intraoperative imaging control the CST was reconstructed using the navigation software (Brainlab) to obtain updated images with the exact relation of the CST to the residual lesion and/or resection cavity. DES was performed with a bipolar electrode at 50Hz right after the image update under the guidance of the updated navigation system. This allowed to precisely document the position the bipolar electrode tip in relation to the resection cavity and the DTI tractography based CST. Results: The cases included 4 GBM and one low grade glioma. All patients suffered preoperatively from motor deficits. The tumors were in close proximity to the CST causing displacement and morphological changes compared to the healthy side. DES resulted in positive motor responses in four cases at the location of the DTI-based reconstruction of the CST. All of these 4 patients experienced a progressive improvement of the preoperative motor weakness, starting at the immediate postoperative course. DTI tractography also displayed a normalization of CST anatomy in terms of position and volume related to the neurological improvements after tumor removal. In one case, DES with an intensity of 3-12 mA showed no positive motor response, however, DTI tractography demonstrated an anatomically accurate location of CST adjacent to the resection border. This DTI based information was respected and no further resection towards the CST was performed. After surgery the preoperative motor weakness was improved significantly. The volume of resection was more than 95% in all cases. Conclusions: These preliminary results indicate that the iop-DTI based location of the CST correlates with DES evoked positive motor responses.
    No preview · Conference Paper · May 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Music can elicit strong emotions and can be remembered in connection with these emotions even decades later. Yet, the brain correlates of episodic memory for highly emotional music compared with less emotional music have not been examined. We therefore used fMRI to investigate brain structures activated by emotional processing of short excerpts of film music successfully retrieved from episodic long-term memory. Methods: Eighteen non-musicians volunteers were exposed to 60 structurally similar pieces of film music of 10 s length with high arousal ratings and either less positive or very positive valence ratings. Two similar sets of 30 pieces were created. Each of these was presented to half of the participants during the encoding session outside of the scanner, while all stimuli were used during the second recognition session inside the MRI-scanner. During fMRI each stimulation period (10 s) was followed by a 20 s resting period during which participants pressed either the “old” or the “new” button to indicate whether they had heard the piece before. Results: Musical stimuli vs. silence activated the bilateral superior temporal gyrus, right insula, right middle frontal gyrus, bilateral medial frontal gyrus and the left anterior cerebellum. Old pieces led to activation in the left medial dorsal thalamus and left midbrain compared to new pieces. For recognized vs. not recognized old pieces a focused activation in the right inferior frontal gyrus and the left cerebellum was found. Positive pieces activated the left medial frontal gyrus, the left precuneus, the right superior frontal gyrus, the left posterior cingulate, the bilateral middle temporal gyrus, and the left thalamus compared to less positive pieces. Conclusion: Specific brain networks related to memory retrieval and emotional processing of symphonic film music were identified. The results imply that the valence of a music piece is important for memory performance and is recognized very fast.
    Full-text · Article · Feb 2014 · Frontiers in Psychology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Object: An extensive craniopharyngioma is a tumor that extends into multiple compartments (subarachnoid spaces) and attains a size larger than 4 cm. A wide spectrum of approaches and strategies has been used for resection of such craniopharyngiomas. In this report the authors focused on the feasibility and efficacy of microsurgical resection of extensive craniopharyngiomas using a frontolateral approach. Methods: A retrospective analysis was performed on 16 patients with extensive craniopharyngiomas who underwent operations using a frontolateral approach at one institution. The preoperative and postoperative clinical and radiological data, as well as the operative videos, were reviewed. The main focus of the review was the extent of radical tumor removal, early postoperative outcome, and approach-related complications. Results: Gross-total resection of craniopharyngioma was achieved in 14 (87.5%) of 16 cases. Early after surgery (within 3 months), 1 patient showed improvement in hormonal status, while in the remaining 15 patients it worsened. No major neurological morbidity was observed. Two patients experienced temporary psychotic disorders. Visual function improved in 6 patients and remained unchanged in 9. One patient experienced a new bitemporal hemianopsia. Three patients with features of short-term memory disturbances at presentation did show improvement after surgery. There were no deaths or significant approach-related morbidity in this patient series. Only 1 patient required revision surgery for a CSF leak. Conclusions: The safe and simple frontolateral approach provides adequate access even to extensive craniopharyngiomas and enables their complete removal with a reasonable morbidity and approach-related complication rate.
    Full-text · Article · Nov 2013 · Journal of Neurosurgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: Intraoperative magnetic resonance imaging (iopMRI) actually has an important role in the surgery of brain tumors, especially gliomas and pituitary adenomas. The aim of our work was to describe the advantages and drawbacks of this tool for the surgical treatment of cervical intramedullary gliomas. We describe two explicative cases including the setup, positioning, and the complete workflow of the surgical approach with intraoperative imaging. Even if the configuration of iopMRI equipment was originally designed for cranial surgery, we have demonstrated the feasibility of cervical intramedullary glioma resection with the aid of high-field iopMRI. This tool was extremely useful to evaluate the extent of tumor removal and to obtain a higher resection rate, but still need some enhancement in the configuration of the headrest coil and surgical table to allow better patient positioning.
    No preview · Article · Nov 2013 · Neurosurgical Review
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Speech comprehension relies on auditory as well as visual information, and is enhanced in healthy subjects, when audiovisual information is present. Patients with schizophrenia have been reported to have problems regarding this audiovisual integration process, but little is known about which underlying neural processes are altered. Functional magnetic resonance imaging was performed in 15 schizophrenia patients and 15 healthy controls to study functional connectivity of Brocás area by means of a beta series correlation method during perception of audiovisually presented bisyllabic German nouns, in which audio and video either matched or did not match. Brocás area of schizophrenia patients showed stronger connectivity with supplementary motor cortex for incongruent trials whereas healthy controls connectivity was stronger for congruent trials. The right posterior superior temporal sulcus (RpSTS) area showed differences in connectivity for congruent and incongruent trials in healthy controls in contrast to schizophrenia patients where the connectivity was similar for both conditions. These smaller differences in connectivity in schizophrenia patients suggest a less adaptive processing of audiovisually congruent and incongruent speech. The findings imply that audiovisual integration problems in schizophrenia are associated with maladaptive connectivity of Broca's and RpSTS area in particular when confronted with incongruent stimuli. Results are discussed in light of recent audio visual speech perception models.
    Full-text · Article · Aug 2013 · Neuroscience
  • Source

    Full-text · Article · Jul 2013 · Clinical neurology and neurosurgery
  • [Show abstract] [Hide abstract]
    ABSTRACT: Image-guided neurosurgery, endoscopic-assisted neurosurgery and the keyhole approach are three important parts of minimally invasive neurosurgery and have played a significant role in treating skull base lesions. This study aimed to investigate the potential usefulness of coupling of the endoscope with the far lateral keyhole approach and image guidance at the ventral craniocervical junction in a cadaver model. We simulated far lateral keyhole approach bilaterally in five cadaveric head specimens (10 cranial hemispheres). Computed tomography-based image guidance was used for intraoperative navigation and for quantitative measurements. Skull base structures were observed using both an operating microscope and a rigid endoscope. The jugular tubercle and one-third of the occipital condyle were then drilled, and all specimens were observed under the microscope again. We measured and compared the exposure of the petroclivus area provided by the endoscope and by the operating microscope. Statistical analysis was performed by analysis of variance followed by the Student-Newman-Keuls test. With endoscope assistance and image guidance, it was possible to observe the deep ventral craniocervical junction structures through three nerve gaps (among facial-acoustical nerves and the lower cranial nerves) and structures normally obstructed by the jugular tubercle and occipital condyle in the far lateral keyhole approach. The surgical area exposed in the petroclival region was significantly improved using the 0° endoscope (1147.80 mm(2)) compared with the operating microscope ((756.28 ± 50.73) mm(2)). The far lateral retrocondylar keyhole approach, using both 0° and 30° endoscopes, provided an exposure area ((1147.80 ± 159.57) mm(2) and (1409.94 ± 155.18) mm(2), respectively) greater than that of the far lateral transcondylar transtubercular keyhole approach ((1066.26 ± 165.06) mm(2)) (P < 0.05). With the aid of the endoscope and image guidance, it is possible to approach the ventral craniocervical junction with the far lateral keyhole approach. The use of an angled-lens endoscope can significantly improve the exposure of the petroclival region without drilling the jugular tubercle and occipital condyle.
    No preview · Article · May 2013 · Chinese medical journal
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND:: Surgery of lesions of the petrous apex involving the inframeatal/infralabyrinthine area is challenging and related to high risk of complications. Various extensive skull base approaches have been utilized. OBJECTIVE:: To present and evaluate our experience with a new hearing preserving extension of the retrosigmoid approach to the inframeatal/infralabyrinthine area. METHODS:: The approach was used in three patients harboring lesions in the petrous apex with variable extension in the inframeatal/infralabyrinthine region. The surgical accessibility of the lesions offered by the approach, the completeness of tumor removal, and the outcome, in particular the functional outcome and complication rate, were assessed. RESULTS:: The tumor could be resected from the target area in all cases. No approach-related complications occurred. Serviceable hearing and normal facial nerve functions were preserved in all cases. CONCLUSION:: Our initial experience with the retrosigmoid inframeatal approach showed that it provides sufficient access to the area and offers the possibility of complete tumor removal. It allows for hearing and facial nerve functional preservation. The approach is safe and related to a very low complication rate.
    Full-text · Article · Jan 2013 · Neurosurgery
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Parkinson's disease has been found to impair comprehension of complex sentences. Here we follow up on earlier findings that sentences describing two successive events in the form of "Before B, A" are understood worse by Parkinson patients than sentences in the form of "After A, B". Before-initial sentences express events in an order inconsistent with their actual order of occurrence and therefore require additional computations during comprehension. In a behavioral study we tested whether 28 German Parkinson patients reading 'before'- and 'after'-initial sentences correctly understood the sequence of events. A second functional magnetic resonance imaging study investigated 16 different patients who read sentences while in the scanner. The behavioral study revealed that 'before' sentences were misunderstood with regard to the temporal sequence of events in 53% (controls 6.5%). The imaging study demonstrated a functional network of the caudate nucleus, middle frontal gyrus, medial superior frontal gyrus, parietal lobule and inferior temporal gyrus. This network was dynamically modulated for 'before' compared to 'after' sentences in healthy controls but not in Parkinson patients. The current results suggest that the additional computations required for 'before' sentences are supported by a network with the caudate nucleus as a central element. This network was compromised in Parkinson patients. We propose that dysfunction of the caudate nucleus networks underlies Parkinson patients' difficulty in dealing with complex sentence structures.
    Full-text · Article · May 2012 · Neuropsychologia
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Writer's cramp (WC) is characterized by excessive cocontractions of agonist and antagonist hand and forearm muscles during writing. Changes in functional magnetic resonance imaging activation patterns in such conditions can be ambiguous as they might either reflect some aspect of the primary pathophysiological mechanism or, alternatively, may be the result of adaptive actions during task execution. To circumvent this problem, we examined WC patients during rest, i.e., without a task, using independent component analysis (ICA) applied to the blood oxygen level-dependent time series. Functionally connected brain networks during rest were defined by ICA to assess differences between WC patients (n = 16) and healthy controls (n = 16). Analysis was carried out using FMRIB's Software Library. Two functional networks showed between-group differences, the sensorimotor network and the default-mode network. In WC patients, the connectivity was reduced in the left postcentral area and increased in basal ganglia in contrast to healthy controls. These changes were not reversed after treatment with botulinum toxin. In line with other studies, the results show a dysfunction in cortico-subcortical circuits in WC involving somatosensory cortex, areas interfacing the sensory and motor systems, and putamen contralateral to symptomatic hand.
    Full-text · Article · Apr 2012 · Human Brain Mapping

Publication Stats

2k Citations
281.45 Total Impact Points

Institutions

  • 2006-2015
    • International Neuroscience Institute Hannover
      Hanover, Lower Saxony, Germany
    • Universitätsklinikum Tübingen
      • Department of Neurosurgery
      Tübingen, Baden-Württemberg, Germany
  • 2005-2015
    • International Neuroscience Institute
      Hanover, Lower Saxony, Germany
    • The Jikei University School of Medicine
      • Department of Neurosurgery
      Edo, Tokyo, Japan
  • 2008-2010
    • Hannover Medical School
      Hanover, Lower Saxony, Germany
  • 2003-2009
    • Insight Institute of Neurosurgery and Neuroscience
      Flint, Michigan, United States
    • Stanford University
      Palo Alto, California, United States
    • Children's Hospital of Michigan
      Detroit, Michigan, United States
  • 2000
    • Humboldt-Universität zu Berlin
      Berlín, Berlin, Germany
  • 1999
    • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center
      Torrance, California, United States