K Witt

Publications (10)35.22 Total impact

• Article: Neuropsychological consequences of endarterectomy and endovascular angioplasty with stent placement for treatment of symptomatic carotid stenosis

  K. Witt, K. Börsch, C. Daniels, K. Walluscheck, K. Alfke, O. Jansen, N. Czech, G. Deuschl, R. Stingele
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  ABSTRACT: Background and purpose Previous studies compared carotid endarterectomy (CEA) and carotid artery stent placement (CAS) for treatment of symptomatic carotid artery stenosis. Whereas most previous studies showed both treatment modalities to be associated with a comparable risk of periprocedural cerebrovascular complications, these previous studies have shown significantly more microemboli and significantly more lesions in diffusion-weighted MR imaging after CAS compared to CEA. The clinical relevance of these differences remains unknown.We therefore compared the neuropsychological consequences of CAS and CEA and additionally measured the S100β protein, a marker of cerebral damage. Methods A total of 48 patients with symptomatic carotid artery stenosis greater than 70 % (according to ECST criteria) were enrolled and 45 patients participated in the follow-up. The patients were randomly assigned for CEA (24 patients) or CAS (21 patients). S100β protein values were evaluated 2 hours before the procedure, as well as one and two hours thereafter. Patients were assessed before treatment, and again 6 and 30 days after treatment using a comprehensive neuropsychological test battery. Results Patients of the CAS and the CEA groups did not significantly differ in terms of age, gender, education, degree of carotid artery stenosis, cerebrovascular symptoms and vascular risk factors. Following previously used criteria, a cognitive change in patients was assumed to have occurred when there was a decline of more than one standard deviation in two or more tests assessing various cognitive domains. Six days and 30 days after the treatment both groups showed a comparable number of patients with cognitive changes compared to baseline. There were no significant differences in S100β protein values. Conclusion These results provide some reassurance that CAS is not associated with greater cognitive deterioration than CEA is.
  Journal of Neurology 04/2012; 254(11):1524-1532. · 3.47 Impact Factor
• Article: [Frontotemporal dementias.]

  K Witt, G Deuschl, T Bartsch
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  ABSTRACT: Frontotemporal dementias (FTD) account for only 5-7% of all dementia aetiologies. However, FTD is one common form of dementia in the presenile period with a symptom onset between an age of 45 and 65 years. FTD are clinically classified into a group of rare genetic variants, the behavioural variant, primary progressive aphasias and a variant including motor neuron symptoms (FTD-MNS). In recent years the pathobiological characteristics of some FTD variants was clarified, demonstrating a pathological accumulation of TAR-DNA binding protein 43 (TDP-43) as a common pathological substrate. The revised diagnostic criteria of the behavioural variant of the FTD require at least three of six clinically discriminating features (disinhibition, apathy, loss of sympathy, perseverative behaviours, hyperorality and dysexecutive neuropsychological profile). The primary progressive aphasias are classified in a nonfluent/agrammatic variant, a logopenic variant and a semantic variant according to clinical and imaging features. Movement disorders and more precisely a Parkinsonian syndrome can be part of the FTD spectrum. Some clinical features overlap the clinical diagnosis of a progressive supranuclear paralysis and the corticobasal ganglionic degeneration. A causal therapy does not exist and medical treatment is directed at the patient's key symptoms. Different agents such as serotonin reuptake inhibitors, tricyclic antidepressants, atypical neuroleptics, carbamazepine, valproate, lamotrigine and when indicated also acetylcholinesterase inhibitors are potentially helpful. All together, theses medical treatments have a low level of evidence. Non-pharmacological therapies such as physiotherapy, occupational therapy, speech therapy and disease-specific education of the patient and their relatives are important to ensure a safe residential environment and daily routine.
  Der Nervenarzt 02/2012; · 0.68 Impact Factor
• Article: Effect of controlled-release levodopa on the microstructure of sleep in Parkinson's disease.

  S Wailke, J Herzog, K Witt, G Deuschl, J Volkmann
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  ABSTRACT: Dopamine is an important neurotransmitter in the regulation of the sleep-wake cycle, and parkinsonian patients suffer from prominent sleep abnormalities. Hence, the question arises whether the disrupted sleep pattern in Parkinson's disease (PD) is responsive to dopaminergic treatment. Thirty-two patients (18 women, 45-82 years old; mean 61 ± 8 years) with dopamine-responsive, akinetic-rigid PD, not taking neuroleptic medication or suffering from dementia were randomized into two groups. Both groups had to withhold their usual dopaminergic medication after noon. At bedtime, one group received 200 mg controlled-release (CR) levodopa/carbidopa, whilst the other group spent the night in the 'off'-state. Polysomnographic recordings were obtained in all patients and 16 age-matched, healthy controls. Compared to healthy controls, patients with PD suffered from significantly decreased total sleep time, REM sleep and slow wave sleep (SWS), whilst the time spent awake was increased. The administration of levodopa/carbidopa CR had no impact on any of these variables. Levodopa/carbidopa CR has previously been found effective for treating night-time akinesia, but according to this study, it has no impact on the altered sleep structure in PD.
  European Journal of Neurology 04/2011; 18(4):590-6. · 3.69 Impact Factor
• Article: Sleep consolidates the effector-independent representation of a motor skill.

  K Witt, N Margraf, C Bieber, J Born, G Deuschl
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  ABSTRACT: During off-line consolidation a motor skill becomes less vulnerable to interference (stabilisation) and improves in performance (enhancement). Here we examined whether off-line consolidation contributes to the process of generalisation in the extrinsic and intrinsic coordinate frame in the motor domain. Participants trained with the left hand a sequential finger tapping task that has proved sensitive to off-line consolidation. Generalisation was tested by the ability to transfer the original sequence (extrinsic transformation) or the mirror sequence (intrinsic transformation) to the right hand, and this was compared with performance on a new sequence not learned before. To determine acute effects on generalisation, transfer was assessed immediately after training of the left hand. To study the effects of off-line consolidation participants were tested after an interval of daytime (training at 8 am and retrieval test on the transfer sequences at 8 pm) or after an interval of night-time sleep (training at 8 pm and retrieval test on the transfer sequences at 8 am). Acutely, training of the left hand induced significant transfer effects to the right hand for the extrinsic transformation of the sequence, but there was no advantage for the intrinsic transformation. After a period of daytime wakefulness the transfer from the left to the right hand for the extrinsic sequence transformation had vanished and, again, there was no transfer effect for the intrinsic transformation of the sequence. By contrast, nocturnal sleep saved the initial transfer effect for the extrinsic sequence transformation. The intrinsic sequence transformation was not affected by sleep. Our results show that an effector-independent representation in an extrinsic co-ordinate frame of a skill develops soon after initial training. Sleep has the capacity to consolidate this transfer and, in this way, contributes to the generalisation of a motor skill.
  Neuroscience 11/2010; 171(1):227-34. · 3.38 Impact Factor
• Source

  Available from: Christian Gaser

  Article: Voxel-based morphometry shows no decreases in cerebellar gray matter volume in essential tremor.

  C Daniels, M Peller, S Wolff, K Alfke, K Witt, C Gaser, O Jansen, H R Siebner, G Deuschl
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  ABSTRACT: To investigate cerebellar gray matter volume in patients with essential tremor (ET). We used voxel-based morphometry (VBM) based on high-resolution T1-weighted MRI to compare gray and white matter density between 27 patients with ET and 27 age- and sex-matched healthy control subjects. Fourteen patients had only postural tremor, whereas 13 patients showed additional intention tremor. VBM failed to demonstrate regional decreases in gray and white matter volume in patients with ET. There was, however, an expansion in gray matter depending on the type of tremor. Compared with age-matched control groups, patients with intention tremor showed a relative expansion of gray matter bilaterally in the region of the temporoparietal junction and the right middle occipital cortex. The lack of a consistent decrease in gray and white matter density argues against a progressive neurodegenerative process in essential tremor that leads to a substantial decrease in cerebellar gray matter volume. Patients with predominant intention tremor show a relative expansion of gray matter areas involved in higher order visuospatial processing, which might represent a long-term result of adaptive reorganization compensating the higher demands on the visuospatial control of skilled movements in case of trembling.
  Neurology 11/2006; 67(8):1452-6. · 8.31 Impact Factor
• Article: Rate dependency of the human cortical network subserving executive functions during generation of random number series--a functional magnetic resonance imaging study.

  C Daniels, K Witt, S Wolff, O Jansen, G Deuschl
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  ABSTRACT: In a random number generation (RNG) task subjects are instructed to generate the numbers 1-10 in a random fashion. RNG performance is assumed to involve executive functions, as it requires controlled response generation and suppression of habitual responses. To investigate cerebral structures involved in RNG associated executive functions we investigated functional magnetic resonance imaging in eight healthy subjects while performing an RNG task at two different response rates (1 and 2 Hz). During the 1 Hz condition an activation was detected bilaterally in the dorsolateral prefrontal cortex (BA 9/46), the lateral premotor cortex (BA 6), the anterior cingulate (BA 32), the inferior and superior parietal cortex (BA 7/40) and the cerebellar hemispheres. In the 2 Hz condition behavioural data showed higher counting tendencies reflecting poorer executive control. In parallel, a homogenous diminution of the activity in the involved cortical areas was obtained. This finding would support the theory of a cortical network involved in executive functions consisting of distinct brain regions working together rather than a distinct fronto-cortical functional localisation.
  Neuroscience Letters 08/2003; 345(1):25-8. · 2.11 Impact Factor
• Article: Typical features of cerebellar ataxic gait.

  H Stolze, S Klebe, G Petersen, J Raethjen, R Wenzelburger, K Witt, G Deuschl
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  ABSTRACT: Although gait disturbance is one of the most pronounced and disabling symptoms in cerebellar disease (CD), quantitative studies on this topic are rare. To characterise the typical clinical features of cerebellar gait and to analyse ataxia quantitatively. Twelve patients with various cerebellar disorders were compared with 12 age matched controls. Gait was analysed on a motor driven treadmill using a three dimensional system. A tandem gait paradigm was used to quantify gait ataxia. For normal locomotion, a significantly reduced step frequency with a prolonged stance and double limb support duration was found in patients with CD. All gait measurements were highly variable in CD. Most importantly, balance related gait variables such as step width and foot rotation angles were increased in CD, indicating the need for stability during locomotion. The tandem gait paradigm showed typical features of cerebellar ataxia such as dysmetria, hypometria, hypermetria, and inappropriate timing of foot placement. Typical features of gait in CD are reduced cadence with increased balance related variables and an almost normal range of motion (with increased variability) in the joints of the lower extremity. The tandem gait paradigm accentuates all the features of gait ataxia and is the most sensitive clinical test.
  Journal of Neurology Neurosurgery &amp Psychiatry 10/2002; 73(3):310-2. · 4.76 Impact Factor
• Article: Dissociation of habit-learning in Parkinson's and cerebellar disease.

  K Witt, A Nuhsman, G Deuschl
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  ABSTRACT: Damage to the medial-temporal region is known to result in declarative (explicit) memory deficits but nondeclarative (implicit) memory is largely unaffected by such lesions. Earlier studies have shown that some forms of implicit learning depend on cerebellar circuits but remain preserved following affections of the basal ganglia circuits. It is unknown which forms of implicit learning persist in patients with cerebellar pathology but are affected after basal ganglia lesions. Therefore, we determined if a test sensitive for habit-learning (probabilistic classification task) resulted in normal values for patients with cerebellar disease but resulted in affected results in patients with Parkinson's disease (PD). To this end, 23 patients with PD, 16 patients with familial or idiopathic cerebellar degeneration (CD), and 20 controls were tested for habit-learning. There was no impairment of patients with CD for the early learning period but there was abnormal learning in the PD group. For a later learning period, the patients with the PD showed improved performance. We conclude that the probabilistic learning task is an implicit, nonmotor learning task which is sensitive for basal ganglia pathology but remains unaffected in the case of cerebellar pathology. Such a test may be of special interest for the detection and possible neurobehavioral treatment of cognitive and motor deficits.
  Journal of Cognitive Neuroscience 05/2002; 14(3):493-9. · 5.18 Impact Factor
• Article: Intact artificial grammar learning in patients with cerebellar degeneration and advanced Parkinson's disease.

  K Witt, A Nühsman, G Deuschl
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  ABSTRACT: In an artificial grammar learning task, subjects were asked to memorise short lists of letter strings formed according to complex rules for letter order. After an interval they were unexpectedly asked to discriminate new grammatical strings from strings which used the same letters but violated the sequential constraints of the grammar. Artificial grammar learning can be mastered successfully by amnesic patients and is considered to be an implicit learning task independent of declarative learning and memory mechanisms. In this study, 10 patients with cerebellar degeneration (CD), 21 Parkinson's disease (PD) and 15 control subjects were tested on artificial grammar learning. Additionally PD patients with advanced disease were examined under adequate medication and dopaminergic withdrawal. All patient groups showed intact artificial grammar learning. Neither cerebellar damage nor basal ganglia dysfunction nor dopaminergic medication impairs or affects artificial grammar learning. Although the patients showed significant executive dysfunction, implicit learning remains intact. The conclusion is that cerebellar and basal ganglia circuits play no essential part in this kind of implicit learning. The results suggest that artificial grammar learning is a cortically mediated function comparable to the mechanism of visual priming.
  Neuropsychologia 02/2002; 40(9):1534-40. · 3.64 Impact Factor
• Article: Intact artificial grammar learning in patients with cerebellar degeneration and advanced Parkinson’s disease

  K Witt, A Nühsman, G Deuschl
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  ABSTRACT: In an artificial grammar learning task, subjects were asked to memorise short lists of letter strings formed according to complex rules for letter order. After an interval they were unexpectedly asked to discriminate new grammatical strings from strings which used the same letters but violated the sequential constraints of the grammar. Artificial grammar learning can be mastered successfully by amnesic patients and is considered to be an implicit learning task independent of declarative learning and memory mechanisms. In this study, 10 patients with cerebellar degeneration (CD), 21 Parkinson’s disease (PD) and 15 control subjects were tested on artificial grammar learning. Additionally PD patients with advanced disease were examined under adequate medication and dopaminergic withdrawal. All patient groups showed intact artificial grammar learning. Neither cerebellar damage nor basal ganglia dysfunction nor dopaminergic medication impairs or affects artificial grammar learning. Although the patients showed significant executive dysfunction, implicit learning remains intact. The conclusion is that cerebellar and basal ganglia circuits play no essential part in this kind of implicit learning. The results suggest that artificial grammar learning is a cortically mediated function comparable to the mechanism of visual priming.
  Neuropsychologia.