Biomedical subjects

Martin Südmeyer

Publications and source records attributed to Martin Südmeyer.

8 recordsLinked to original sources

PubMed2006

Frequency-dependent reciprocal modulation of verbal fluency and motor functions in subthalamic deep brain stimulation.

BACKGROUND: High-frequency deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor functions in those with Parkinson disease but may worsen frontal functions such as verbal fluency (VF). In contrast, low-frequency DBS leads to deterioration of motor functions. It is not known whether low-frequency STN DBS also has an effect on frontal functions. OBJECTIVE: To examine whether low-frequency STN DBS in contrast to high-frequency STN DBS has a positive effect on frontal functions on the basis of VF test results. DESIGN: A double-blind randomized crossover experiment to compare performance in 4 VF subtests and motor performance at 10 Hz, 130 Hz, and no stimulation. SETTING: University hospitals in Düsseldorf and Cologne, Germany. PATIENTS: Twelve patients with Parkinson disease 3 months or more after bilateral electrode implantation into the STN. MAIN OUTCOME MEASURE: Mean number of words in VF at different stimulation frequencies. RESULTS: The VF was significantly better at 10 Hz (48.3 words) compared with 130 Hz and showed a nonsignificant trend toward worsening at 130 Hz (42.3 words) compared with no stimulation (43.8 words). These results were consistent across all subtests. CONCLUSIONS: The study provides evidence of a beneficial effect of low-frequency (10 Hz) STN DBS on VF, which may be caused by activating neural pathways projecting to the frontal cortex. In addition, the study reproduces the negative effect of therapeutic high-frequency STN DBS on VF. The study results provide evidence for a frequency-dependent modulation of cognitive circuits involving the STN.

Aged↗

PubMed2006

Synchronized brain network underlying postural tremor in Wilson's disease.

Common neurological manifestation of Wilson's disease (WD) is a postural tremor of the upper extremities. Recently, the primary sensorimotor cortex (S1/M1) has been shown to be involved in WD postural tremor generation. However, neuropathological changes in WD are mostly observed in subcortical structures. We therefore aimed to investigate whether S1/M1 may be functionally interconnected with other brain areas. In five WD patients, we used magnetoencephalography and surface electromyography (EMG) to record simultaneously cerebral neuronal activity and muscular activity during sustained posture of the right forearm. As demonstrated previously, the strongest coupling to tremor EMG was observed in the contralateral S1/M1. This area was taken as reference in order to identify and localize cerebro-cerebral coherence at tremor frequency and its first harmonic. The analysis revealed significant coherence within an oscillatory network including S1/M1, higher cortical motor areas (premotor cortex, PM; supplementary motor area, SMA), posterior parietal cortex (PPC) and thalamus contralateral as well as the cerebellum ipsilateral to the tremor forearm. Flow of information was mainly of bidirectional nature. Taken together, our results indicate that WD postural tremor is generated within a synchronized cerebello-thalamo-cortical network, comprising S1/M1, higher cortical motor areas (SMA, PM), and PPC.

Adult↗

PubMed2006

Wilson's disease tremor is associated with magnetic resonance imaging lesions in basal ganglia structures.

Wilson's disease (WD) is an inherited disorder of copper metabolism yielding marked motor deficits, including a severely disabling tremor. As a structural correlate of the disease, a variety of cerebral abnormalities has been revealed. However, the relationship between motor deficits and cerebral lesions has remained largely unknown. Here, we investigated correlation between WD tremor and cerebral magnetic resonance imaging (MRI) findings. Cerebral MRI abnormalities in 6 symptomatic WD patients were compared to findings in 6 asymptomatic WD patients and 10 healthy controls. All patients were treated with long-term copper chelating therapy. Motor symptoms including tremor were determined by Unified Parkinson's Disease Rating Scale Part III (UPDRS-III). MRI findings in symptomatic WD patients revealed significant symmetric T2*-weighted hypointense signal alterations of globus pallidus, head of the caudate nucleus, and substantia nigra. In contrast, MRI of asymptomatic WD patients did not differ from healthy controls. Correlation analysis revealed a significant positive correlation between MRI basal ganglia lesions and UPDRS action tremor score. Our results demonstrate for the first time that Wilson's disease tremor is associated with lesions of the globus pallidus, the head of the caudate nucleus, and the substantia nigra.

Adult↗

PubMed2006

Coupling between cerebellar hemispheres: behavioural, anatomic, and functional data.

Although the cerebellum has been related to emotional, cognitive, and sensory processes, its outstanding significance for motor behaviour has attracted a vast variety of studies. Specifically, the role of cerebellar activity for appropriate movement timing has been investigated intensively. Behavioural studies, particularly of patients following cerebellar lesions, gave rise to the hypothesis that each hand is controlled by separate timing mechanisms most likely localized within lateral portions of each cerebellar hemisphere. Reduced timing variability during simultaneous bimanual tasks implies that both timing signals are integrated prior to movement execution, probably by information transfer between both cerebellar hemispheres. However, this raises the question for functional and anatomic fundamentals of such an integration process. The present article reviews behavioural, functional, and anatomic data to shed light on possible interactions between both cerebellar hemispheres during the execution of timed motor behaviour.

Animals↗

PubMed2005

The oscillatory network of simple repetitive bimanual movements.

Bimanual synchronization relies on the precisely coordinated interplay of both hands. It is assumed that during temporal bimanual coordination, timing signals controlling each hand might be integrated. Although a specific role of the cerebellum for this integration process has been suggested, its neural foundations are still poorly understood. Since dynamic interactions between spatially distributed neural activity are reflected in oscillatory neural coupling, the aim of the present study was to characterize the dynamic interplay between participating brain structures. More specifically, the study aimed at investigating whether any evidence for the integration of bilateral cerebellar hemispheres could be found. Seven right-handed subjects synchronized bimanual index finger-taps to a regular pacing signal. We recorded continuous neuromagnetic activity using a 122-channel whole-head neuromagnetometer and surface EMGs of the first dorsal interosseus (FDI) muscle of both hands. Coherence analysis revealed that an oscillatory network coupling at 8-12 Hz subserves task execution. The constituents are bilateral primary sensorimotor and premotor areas, posterior-parietal and primary auditory cortex, thalamus and cerebellum. Coupling occurred at different cortical and subcortical levels within and between both hemispheres. Coupling between primary sensorimotor and premotor areas was observed directly and indirectly via the thalamus. Coupling direction suggests that information was integrated within the left premotor cortex corroborating a specific role of the left premotor cortex for motor control in right-handers. Most importantly, our data indicate strong coupling between both cerebellar hemispheres substantiating the hypothesis that cerebellar signals might be integrated during task execution.

Adult↗

PubMed2005

Heterogeneous patterns of lymphatic drainage to sentinel lymph nodes by primary melanoma from different anatomic sites.

UNLABELLED: We want to define the patterns of lymphatic drainage for primary melanoma to sentinel lymph nodes (SLNs) based on a large lymphoscintigraphic database. Preoperative lymphoscintigraphy was used to identify and classify SLN drainage basins and patterns of drainage. METHODS: Lymphoscintigraphy using intradermally administered technetium-99m labeled sulfur colloid was performed on 400 consecutive patients with malignant melanoma to define lymphatic drainage channels and draining SLN basins before surgery. Primary tumor sites consisted of head and neck, upper extremity, trunk, and lower extremity. Different types of drainage patterns were classified and correlated with different anatomic sites. RESULTS: SLN(s) were identified in over 98% of the patients, whereas lymphatic drainage channels were successfully identified in 90% of the patients. Drainage from the primary site to a single SLN through a single lymphatic channel (type IA) was seen in 186 of 400 patients (47%) as the most common type. In patients with a single SLN within a single basin (type I-V), the percentage of patients with primary lesions in the head and neck, upper extremity, trunk, and lower extremity regions were 61%, 79%, 55%, and 78%, respectively. In cases of multiple lymphatic channels (type VI-VII), the percentages of patients with primary lesions in the head and neck, upper extremity, trunk, and lower extremity regions were 24%, 8%, 36%, and 19%, respectively. CONCLUSION: Various drainage patterns were noted from primary melanomas in different anatomic sites. Preoperative lymphoscintigraphy is important in establishing the SLN basins for harvesting the SLN(s).

Humans↗

PubMed2004

CT-guided lymphoscintigraphy in patients with squamous cell carcinoma of the head and neck: a feasibility study.

Accurate knowledge of lymphatic drainage facilitates planning of surgery for patients with squamous cell carcinoma of the head and neck. The aim of this study was to evaluate the feasibility of a new injection technique for lymph node detection in patients with squamous cell carcinoma of the hypopharynx and larynx, in whom simple peritumoural injection is hampered by the tumour localisation. Computed tomography (CT)-guided lymphoscintigraphy was performed in a total of 13 patients with squamous cell carcinoma of the hypopharynx and larynx who could not be injected by simple visual inspection. In a first step, contrast medium-enhanced axial 5-mm-thick CT slices of the neck were obtained. After tumour localisation on these CT images, 1-2 ml contrast medium and, in the event of appropriate distribution, subsequently 50 MBq technetium-99m colloid were injected at one to three peritumoural sites under CT guidance. Peritumoural tracer distribution was controlled by thin-slice CT. Subsequently, planar scintigrams from anterior, right and left lateral views were obtained. In all patients, peritumoural colloid application was feasible, as shown on control CT scans. Post injection, neither severe nor minor complications were noted. The patients complained of only low pain sensations with an average score of 1.8 on a pain scale from 0 to 10. Lymphatic drainage was identified in nine of the 13 patients, with a total of 14 detected lymph nodes. In six patients, ipsilateral sentinel lymph nodes were visualised; bilateral sentinel lymph nodes were identified in one patient and contralateral lymphatic drainage was observed in two patients. CT-guided lymphoscintigraphy is a feasible and minimally invasive diagnostic tool for sentinel lymph node detection in patients with squamous cell carcinoma of the hypopharynx and the larynx. In contrast to endoscopic colloid injection under general anaesthesia, this technique seems to be a well-tolerated method for lymphatic mapping prior to surgical procedures.

Adult↗

PubMed2004

Postural tremor in Wilson's disease: a magnetoencephalographic study.

The following study included 5 Wilson's disease (WD) patients showing a right-sided postural forearm tremor (4-6 Hz) and addressed the question of whether the primary motor cortex (M1) is involved in tremor generation. Using a 122-channel whole-head neuromagnetometer and surface electromyogram (EMG), we investigated cerebromuscular coupling. Postural tremor was observed in a sustained 45-degree posture of the right-sided forearm. Data were analyzed using dynamic imaging of coherent sources (DICS), revealing cerebromuscular coupling between EMG and cerebral activity. Coherent sources were superimposed on individual high-resolution T1-weighted magnetic resonance images (MRI). Phase lags between EMG and cerebral areas showing strongest coherence were determined by means of a Hilbert transform of both signals. In all patients, postural tremor was associated with strong coherence between tremor EMG and activity in contralateral primary sensorimotor cortex (S1/M1) at tremor or double tremor frequency. Phase lag values between S1/M1 activity and EMG revealed efferent and afferent components in the corticomuscular coupling. Taken together, our results indicate that postural tremor in WD is mediated through a pathological oscillatory drive from the primary motor cortex.

Adult↗