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Biomedical subjects

Konrad J Werhahn

Publications and source records attributed to Konrad J Werhahn.

13 recordsLinked to original sources
PubMed2006

Antiepileptic drug use in nursing home residents: a cross-sectional, regional study.

The use of antiepileptic drugs (AED), their primary indication, comorbid conditions, and concomitant medications were collected from 565 nursing homes (NH) residents of six NH located around the city of Mainz, Germany representing 5.05% of all NH residents in the area. Data were collected from the electronic pharmacy files and by reviewing all available medical records. Average age was 82.2 +/- 2.4 years, 85.5% were women. Of 565 NH residents 28 (4.96%) received AED therapy, of which in 17 (63%) AED were prescribed for a seizure-related diagnosis. In 76.5% seizure types were unspecified and a distinction in focal and generalized epilepsy was made in only 23.5% of patients. Three patients never had epileptic seizures and in four residents the reason for AED use was unclear. AEDs most frequently prescribed were carbamazepine (37.1%), valproic acid (25.9%), and phenytoin (14.8%). Five patients received benzodiazepines (18.5%), newer generation AED were used in only four (14.8%) cases. Residents on average took n = 5.6 +/- 3.3 other drugs. Opportunities exist for health care professionals to improve the medical management of nursing facility residents receiving AEDs.

Aged↗
PubMed2006

Contralateral hand anesthesia transiently improves poststroke sensory deficits.

OBJECTIVE: To test a possible strategy to alleviate somatosensory deficits after stroke. METHODS: Here, we applied ischemic nerve block to the intact hand of patients with chronic stroke, which in healthy subjects elicits improvements in sensibility of the other hand. RESULTS: We found that sensibility in the affected hand improved with intact hand anesthesia, but not with intact foot anesthesia or no anesthesia. INTERPRETATION: We conclude that reduction of sensory input from the intact hand leads to site-specific improvements in tactile discriminative skills in the affected hand after the period of anesthesia, a potentially relevant finding in designing neurorehabilitative interventions.

Adult↗
PubMed2006

Decreased dopamine D2/D3-receptor binding in temporal lobe epilepsy: an [18F]fallypride PET study.

PURPOSE: Although animal data are suggestive, evidence for an alteration of the extrastriatal dopaminergic system in human focal epilepsy is missing. METHODS: To quantify D2/D3-receptor density, we studied seven patients with temporal lobe epilepsy (TLE) and nine age-matched controls with positron emission tomography (PET) by using the high-affinity dopamine D2/D3-receptor ligand [18F]Fallypride ([18F]FP) suitable for imaging extrastriatal binding. TLE was defined by interictal and ictal video-EEG, magnetic resonance imaging (MRI), and [18F]fluorodeoxyglucose ([18F]FDG)-PET and was due to hippocampal sclerosis (HS), based on histology in all patients. Primary analysis was based on regions of interest (ROIs) defined on individual MRIs. For each patient, binding potential (BP) was calculated by using the simplified reference tissue model, and the epileptogenic was compared with the unaffected hemisphere in each ROI. To confirm the results, an additional voxel-based group analysis was performed by using statistical parametric mapping. RESULTS: Compared with controls, [18F]FP BP was significantly decreased in the epileptogenic temporal lobe in all patients. On ROI analysis, this reduction was evident in areas surrounding the seizure-onset zone at the pole (-34.2%) and lateral aspects (-32.9%) of the temporal lobe. Although the hippocampus [18F]FDG uptake (-8.1%) and hippocampal MR volume (-35.1%) were significantly reduced, no significant decrease of [18F]FP BP was found. Reduction of [18F]FP BP did not correlate with hippocampal atrophy. CONCLUSIONS: D2/D3-receptor binding is reduced at the pole and in lateral aspects of the epileptogenic temporal lobe in patients with mesial TLE and HS. This area might correspond to "the irritative zone," indicating that D2/D3 receptors might play a specific role in the pathophysiology of mesial TLE.

Adult↗
PubMed2004

Influence of somatosensory input on motor function in patients with chronic stroke.

In healthy volunteers, reduction of somatosensory input from one hand leads to rapid performance improvements in the other hand. Thus, it is possible that reduction of somatosensory input from the healthy hand can influence motor function in the paretic hand of chronic stroke patients with unilateral hand weakness. To test this hypothesis, we had 13 chronic stroke patients perform motor tasks with the paretic hand and arm during cutaneous anesthesia of the healthy hand and healthy foot in separate sessions. Performance of a finger tapping task, but not a wrist flexion task, improved significantly with anesthesia of the hand, but not the foot. This effect progressed with the duration of anesthesia and correlated with baseline motor function. We conclude that cutaneous anesthesia of the healthy hand elicits transient site-specific improvements in motor performance of the moderately paretic hand in patients with chronic stroke, consistent with interhemispheric competition models of sensorimotor processing.

Adult↗
PubMed2004

Functional connectivity between somatosensory and visual cortex in early blind humans.

Crossmodal plasticity occurs when loss of input in one sensory modality leads to reorganization in brain representations of other sensory modalities. In congenital blindness the visual cortex becomes responsive to somatosensory input such as occurs during Braille reading. The route by which somatosensory information reaches the visual cortex is not known. Here, we used repetitive transcranial magnetic stimulation (rTMS) to probe the connection between primary somatosensory cortex (S1) and early visual cortex (V1 and neighboring areas), combining rTMS with positron emission tomography (PET). We applied stimulation over S1 in sighted, early blind and late blind individuals. Baseline regional cerebral blood flow in occipital cortex was highest in early blind and lowest in late blind individuals. Only the early blind group showed significant activation of early visual areas when rTMS was delivered over S1. This activation was significantly higher in early than in late blind, but not relative to sighted controls. These results are consistent with the hypothesis that tactile information may reach early visual areas in early blind humans through cortico-cortical pathways, possibly supporting enhanced tactile information processing.

Age of Onset↗
PubMed2003

Contribution of the ipsilateral motor cortex to recovery after chronic stroke.

It has been proposed that the intact (ipsilateral) motor cortex play a significant role mediating recovery of motor function in the paretic hand of chronic stroke patients, but this hypothesis has not been tested experimentally. Here, we evaluated the effects of transcranial magnetic stimulation (TMS) on motor performance of the paretic hand of chronic stroke patients and healthy controls. We hypothesized that, if activity in the intact hemisphere contributes to functional recovery, TMS should result in abnormal motor behavior in the paretic hand. We found that stimulation of the intact hemisphere resulted in delayed simple reaction times (RTs) in the contralateral healthy but not in the ipsilateral paretic hand, whereas stimulation of the lesioned hemisphere led to a marked delay in RT in the contralateral paretic hand but not in the ipsilateral healthy hand. RT delays in the paretic hand correlated well with functional recovery. Finger tapping in the paretic hand was affected by TMS of the lesioned but not the intact hemisphere. These results are consistent with the idea that recovered motor function in the paretic hand of chronic stroke patients relies predominantly on reorganized activity within motor areas of the affected hemisphere.

Adult↗
PubMed2002

Enhanced tactile spatial acuity and cortical processing during acute hand deafferentation.

Acute deafferentation of a limb results in bilateral cortical reorganization, but the behavioral consequences of this phenomenon are unknown. Here we found rapid improvements in tactile spatial acuity and changes in cortical processing for the left hand during cutaneous anesthesia of the right hand. The site-specific improvement in tactile spatial acuity may represent a behavioral compensatory gain.

Action Potentials↗
PubMed2002

Cortical excitability changes induced by deafferentation of the contralateral hemisphere.

Short-term deprivation of sensory input by ischaemic nerve block (INB) leads to functional reorganization in the deafferented motor cortex. Here, we show that INB also elicits functional changes in homotopic regions of the cortex contralateral to the deafferented one. We measured motor evoked potential (MEP) amplitudes elicited by transcranial magnetic stimulation (TMS) in small hand and biceps brachii muscles before, during and after INB of the right hand. INB increased excitability of the cortical representation of (i) the intact hand and (ii) body parts proximal to the deafferented hand (upper arm), in the absence of excitability changes in other body part representations such as thorax or leg muscles. This effect persisted throughout the entire period of deafferentation and returned to baseline values afterward. Motor responses to brainstem electrical stimulation remained unchanged during INB, indicating that the effect is probably of cortical origin. Lorazepam, a GABA(A) receptor agonist, blocked this increased excitability. Interhemispheric inhibition between hand muscles decreased during INB. After chronic deafferentation in amputees, MEP amplitudes and motor output curves in small hand muscles were depressed and motor thresholds were elevated compared with aged-matched controls. These results indicate that acute hand deafferentation can elicit a focal increase in excitability in the hand motor representation contralateral to the deafferented cortex that is influenced by transcallosal interactions and GABAergic transmission, and is balanced in the setting of chronic deafferentation.

Adult↗
PubMed2002

Focal epileptiform activity in the brain: detection with spike-related functional MR imaging--preliminary results.

The purpose of this study was to develop a spike-related functional magnetic resonance (MR) imaging method to detect epileptic brain activity. Correlations between simultaneous spike-related functional MR imaging and electroencephalographic (EEG) recordings were performed in 10 patients with focal epilepsy. Postprocessing techniques were implemented to eliminate contamination of the EEG recording from ballistocardiography and the echo-planar MR imaging sequence. A diagnostic EEG recording was achieved during functional MR imaging. Spike location correlated with the site of blood oxygen level-dependent signal increase. Spike-related functional MR imaging is a promising technique for detecting focal epileptic brain activity.

Adult↗
PubMed2002

Clinical features and EEG findings differentiating mesial from neocortical temporal lobe epilepsy.

We evaluated whether mesial temporal lobe epilepsy (MTE) and neocortical temporal lobe epilepsy (NTE) can be distinguished on electroclinical grounds. One hundred and twenty-two consecutive MTE (n = 86) and NTE (n = 36) patients were included in this prospective study. All patients underwent prolonged EEG-video monitoring and high resolution magnetic-resonance imaging (MRI). MTE was defined as epilepsy with purely mesial temporal lesion in the absence of extramesial temporal pathology, based on pre-operative MRI or post-operative histology. NTE was defined as neocortical temporal MRI lesions, depth recorded neocortical temporal seizure onset and lack of mesial temporal lesions on MRI or histology. One thousand two hundred and fourty-nine epileptic seizures were analyzed. Congenital malformation (NTE 19% versus MTE 3%, P < 0.01), nonspecific auras (NTE 25% versus MTE 8%, P < 0.001) and early clonic activity following automatisms (NTE 22% versus MTE 8%, P < 0.03) were more frequent in NTE. In contrast, a history of febrile seizures (MTE 29% versus NTE 3%, P < 0,001), abdominal auras (MTE 62% versus NTE 33%, P < 0.005) and contralateral hand dystonia (MTE 43% versus NTE 22%, P < 0.03) were more often documented in MTE. Interictal epileptiform discharges in MTE occurred predominantly (> 67%) over the ipsilateral mesial temporal regions (MTE 65% versus NTE 33%, P < 0.001). No MTE patient had lateral neocortical temporal spike predominance (NTE 22%, P < 0.001). Multiple logistic regression revealed that a history of febrile seizures, abdominal auras, contralateral dystonic posturing and predominance of ipsilateral mesial temporal spikes point to MTE, with an accuracy of 73% (PPV 81%, NPV 70%). Analyzing clinical and EEG features, particularly the distribution of interictal epileptiform discharges, helps to differentiate between MTE and NTE.

Adult↗