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Biomedical subjects

R Benecke

Publications and source records attributed to R Benecke.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effects of riluzole on cortical excitability in patients with amyotrophic lateral sclerosis.

Using transcranial magnetic stimulation, the effect of riluzole (RLZ) on cortical excitability was studied in patients with amyotrophic lateral sclerosis (ALS). Paired-pulse inhibition (PPI) and paired-pulse facilitation (PPF) were reduced. RLZ partially restored deficient PPI in the first of 4 consecutive 3-month periods of testing, but left PPF unchanged. These findings substantiate the view that attenuation of glutamate-related excitotoxicity is an important factor contributing to the beneficial effect of RLZ in ALS.

Adult↗
PubMed2000

Cutaneomotor integration in humans is somatotopically organized at various levels of the nervous system and is task dependent.

Integration of tactile afferent signals with motor commands is crucial for the performance of purposeful movements such as during manipulation of an object in the hand. To study the somatotopic organization of sensorimotor integration we applied electrical peripheral conditioning stimuli to a digit located near (homotopic stimulation) or distant from (heterotopic stimulation) relaxed or isometrically contracted intrinsic hand muscles at variable time intervals prior to transcranial magnetic stimulation (TMS). Cutaneous stimulation has previously been shown to modulate the amplitude of the motor evoked potential (MEP) and to shorten the duration of the silent period (SP) evoked by TMS. In relaxed target muscles the time-dependent modulation of TMS-evoked motor responses by homotopic conditioning stimulation differed from modulation by heterotopic stimulation. Similar differences in the modulation pattern evoked by homotopic and heterotopic conditioning stimulation were observed for two distinct target muscles of the hand (abductor digiti minimi, abductor pollicis brevis muscle). Differences in modulation were maximal when the conditioning stimulation was applied 25-30 ms and 150-200 ms prior to TMS. Comparison of the modulation of the amplitudes of MEPs evoked by transcranial electrical stimulation (TES) and the modulation of those evoked by TMS suggests that differences between homotopic and heterotopic stimulation originate subcortically at 25- to 30-ms and, at least partially, cortically at 150- to 200-ms interstimulus intervals. In isometrically contracted intrinsic hand muscles the degree to which the SP was shortened reflected the location and the timing of the conditioning stimulus. Shortening was maximal when the conditioning stimulus was applied nearest to the contracted target muscle and 20 ms prior to the test stimulus. In contrast to the SP duration, the MEP size in voluntarily contracted target muscles was unaffected by the location of the conditioning stimulus. The somatotopic gradient of SP shortening was abolished when the two target muscles were simultaneously activated isometrically. Together, our findings suggest that somatotopy of input-output relationships is implemented at both a spinal and a cortical level in the human central nervous system and may also depend on the motor task involved.

Adult↗
PubMed2000

Alpha-synuclein accumulation in a case of neurodegeneration with brain iron accumulation type 1 (NBIA-1, formerly Hallervorden-Spatz syndrome) with widespread cortical and brainstem-type Lewy bodies.

We studied a 27-year-old woman who died after a 6-year history of progressive dementia, dystonia, ataxia, apraxia, spasticity, choreoathetosis, visual and auditory hallucinations, and optic atrophy. Magnetic resonance imaging showed decreased intensity in the globus pallidus, substantia nigra, and dentate nuclei in T2-weighted images, supporting the clinical diagnosis of neurodegeneration with brain iron accumulation type 1 (NBIA-1; formerly known as Hallervorden-Spatz syndrome). At autopsy the brain showed mild frontotemporal atrophy and discoloration of the globus pallidus and the substantia nigra pars reticularis. Histologically, features typical of NBIA-1 were found including widespread axonal spheroids and large deposits of iron pigment in the discolored regions. Additionally, excessive numbers of Lewy bodies (LBs) were found throughout all examined brain stem and cortical regions. LBs of both types, as well as Lewy neurites in this case of NBIA-1, were strongly labeled by antibodies against alpha-synuclein. These findings give further evidence that accumulation of alpha-synuclein is generally associated with LB formation, i.e., in Parkinson's disease, dementia with Lewy bodies and NBIA-1. The case presented here is particularly notable for its high number of LBs in all areas of the cerebral cortex.

Adult↗
PubMed2000

Induction of plasticity in the human motor cortex by paired associative stimulation.

Current models of motor cortical plasticity, developed in studies on experimental animals, emphasize the importance of the conjoint activity of somatosensory afferents and intrinsic motor cortical circuits. The hypothesis that an enduring change in excitability in the cortical output circuitry can be induced in the human motor cortex by a paired-stimulation protocol was tested. Low-frequency median nerve stimulation was paired with transcranial magnetic stimulation (TMS) over the optimal cranial site for stimulating the abductor pollicis brevis muscle (APB). This protocol induced an increase in the amplitudes of the motor evoked potentials (MEPs) in the resting APB as well as a prolongation of the silent period measured in the precontracted APB following TMS; amplitudes of MEPs measured in voluntary contraction remained unchanged. Experiments testing the excitability of spinal motoneurons using F-wave studies and electrical stimulation of the brainstem suggested that the site of the plastic changes was within the motor cortex. The increases in resting amplitudes and silent period duration were conditionally dependent on the timing between the afferent and the magnetic stimulation in that they were present when events elicited by afferent and magnetic stimulation were synchronous at the level of the motor cortex. Plasticity induced by paired stimulation evolved rapidly (within 30 min), was persistent (minimum duration 30-60 min) yet reversible, and was topographically specific. This combination of features and the similarity to properties of induced enduring changes in synaptic efficacy, as elucidated in animal studies, leads us to propose that the induced plasticity may represent a signature of associative long-term potentiation of cortical synapses or closely related neuronal mechanisms in the human cortex.

Adult↗
PubMed2000

A randomized, double-blind, placebo-controlled, dose-ranging study to compare the efficacy and safety of three doses of botulinum toxin type A (Dysport) with placebo in upper limb spasticity after stroke.

BACKGROUND AND PURPOSE: We sought to define an effective and safe dose of botulinum toxin type A (Dysport) for the treatment of upper limb muscle spasticity due to stroke. METHODS: This was a prospective, randomized, double-blind, placebo-controlled, dose-ranging study. Patients received either a placebo or 1 of 3 doses of Dysport (500, 1000, 1500 U) into 5 muscles of the affected arm. Efficacy was assessed periodically by the Modified Ashworth Scale and a battery of functional outcome measures. RESULTS: Eighty-three patients were recruited, and 82 completed the study. The 4 study groups were comparable at baseline with respect to their demographic characteristics and severity of spasticity. All doses of Dysport studied showed a significant reduction from baseline of muscle tone compared with placebo. However, the effect on functional disability was not statistically significant and was best at a dose of 1000 U. There were no statistically significant differences between the groups in the incidence of adverse events. CONCLUSIONS: The present study suggests that treatment with Dysport reduces muscle tone in patients with poststroke upper limb spasticity. Treatment was effective at doses of Dysport of 500, 1000, and 1500 U. The optimal dose for treatment of patients with residual voluntary movements in the upper limb appears to be 1000 U. Dysport is safe in the doses used in this study.

Arm↗
PubMed1999

Differential effects on motorcortical inhibition induced by blockade of GABA uptake in humans.

1. Blockade of uptake carriers of gamma-aminobutyric acid (GABA) has been shown to modulate inhibition in cortical slices of experimental animals, although little is known about this mechanism in vivo and, in particular, in humans. 2. The effects of blockade of GABA uptake were studied using transcranial magnetic stimulation (TMS) in humans. In eight healthy volunteers several measures of cortical excitation and inhibition were obtained before and approximately 2 h after ingestion of 5-15 mg of tiagabine (TGB). 3. After TGB ingestion, the duration of the TMS-induced silent period observable in the electromyogram of the voluntarily contracted target muscle was prolonged. Similarly, paired-pulse inhibition of the motor-evoked potential (MEP), as tested by delivering two magnetic shocks of equal suprathreshold intensities at 160 ms interstimulus interval (ISI), was more pronounced. In apparent contradistinction, paired-pulse inhibition of the MEPs produced by a subthreshold conditioning stimulus delivered 3 ms prior to a suprathreshold stimulus was reduced. Paired-pulse facilitation elicited by the same double-shock protocol at an ISI of 10 ms was increased. 4. The prolongation of the GABAB receptor-mediated component of the inhibitory postsynaptic potential observed with TGB in in vitro studies probably underlies the increase in cortical silent period duration. The reduction of the paired-pulse inhibition at 3 ms, in turn, probably reflects inhibition of GABAA receptor-mediated inhibition via presynaptic GABAB receptors. 5. These data provide in vivo evidence of differential modulation of cortical inhibition by blockade of GABA uptake. Presynaptic GABA autoreceptors may be involved in modulating cortical inhibition in the human motor cortex.

Adult↗
PubMed1999

Borrelia burgdorferi central nervous system infection presenting as an organic schizophrenialike disorder.

BACKGROUND: We report on a 42-year-old female patient who presented with a schizophreniform disorder and complete relief of symptoms after specific therapy. METHODS: Cerebrospinal fluid and magnetic resonance imaging findings led to the diagnosis of Lyme disease. RESULTS: To our knowledge this is the first reported case with an exclusive psychiatric manifestation of Lyme disease. CONCLUSIONS: In case of first manifestation of psychotic disorder, although neurological symptoms are lacking, Lyme disease should be considered and be excluded by cerebrospinal fluid analysis.

Adult↗
PubMed1999

Stimulation of peripheral nerves using a novel magnetic coil.

Magnetic nerve stimulation (MNS) using a novel figure-8 magnetic coil was compared with conventional electric nerve stimulation (ENS) in normal subjects and in patients with disorders of the peripheral nervous system. In contrast to previously tested coils, the virtual cathode of the novel coil was independent of the geometrical or electric conditions of the stimulated tissue. Maximal compound muscle action potentials (CMAPs) were elicited by MNS in all motor nerves tested. The slopes of the recruitment curves of ENS were steeper than those of MNS, indicating a comparatively lower maximal stimulation intensity and a higher intensity resolution of the magnetic stimulator. In four patients with entrapment syndromes at the ulnar groove, motor conduction velocities and amplitudes were similar for MNS and ENS across the affected nerve segment. However, in two patients with chronic inflammatory demyelinating polyneuropathy (CIDP), CMAPs were slightly smaller following MNS. This new technique is a promising step toward the ultimate goal of replacing ENS with MNS.

Adult↗
PubMed1999

[Marchiafava-Bignami syndrome. Extrapontine myelinolysis in chronic alcoholism].

Until now, the pathogenesis of Marchiafava-Bignami disease, an extrapontine myelinolysis, is unknown. Accept an abuse of alcohol for many years additional metabolic and vascular disturbances are supposed. The early performance of magnetic resonance imaging in patients with a sudden encephalopathy and history of alcoholism is essential for an assessment of the diagnosis. The bilateral lack of transcallosal inhibition--a parameter for the integrity of the transcallosal connections between motor cortices--is the consequence of the axonal degeneration of transcallosal fibers. Clinical and neuroradiological features of three patients with extrapontine myelinolysis are reported and possible etiologies of the complex disease are discussed. In two cases a severe alcohol abuse was present with the typical picture of the Marchiafava-Bignami disease. In a third patient an intoxication with methanol was present with a similar clinical picture. Although severe neurological disturbances were initially apparent in the patients, during the follow-up there was a significant amelioration of the clinical course under a high-dose vitamin B supplementation.

Adult↗
PubMed1999

Task-dependent modulation of inhibitory actions within the primary motor cortex.

In 11 healthy subjects motor-evoked potentials (MEPs) and silent periods (SPs) were measured in the right first dorsal interosseus (FDI) and abductor pollicis brevis muscles (APB): (1) when transcranial magnetic cortex stimulation (TMS) was applied at tonic isometric contraction of 20% of maximum force, (2) when TMS was applied during tactile exploration of a small object in the hand, (3) when TMS was applied during visually guided goal-directed isometric ramp and hold finger flexion movements, and (4) when at tonic isometric contraction peripheral electrical stimulation (PES) of the median nerve was delivered at various intervals between PES and TMS. Of the natural motor tasks, duration of SPs of small hand muscles was longest during tactile exploration (APB 205+/-42 ms; FDI 213+/-47 ms). SP duration at tonic isometric contraction amounted to 172+/-35 ms in APB and 178+/-31 ms in FDI, respectively. SP duration in FDI was shortest when elicited during visually guided isometric finger movements (159+/-15 ms). At tonic isometric contraction, SP was shortened when PES was applied at latencies -30 to +70 ms in conjunction with TMS. The latter effect was most pronounced when PES was applied 20 ms before TMS. PES-induced effects increased with increasing stimulation strength up to a saturation level which appeared at the transition to painful stimulation strengths. Both isolated stimulation of muscle afferents and of low-threshold cutaneous afferents shortened SP duration. However, PES of the contralateral median nerve had no effect on SPs. Amplitudes of MEPs did not change significantly in any condition. Inhibitory control of motor output circuitries seems to be distinctly modulated by peripheral somatosensory and visual afferent information. We conclude that somatosensory information has privileged access to inhibitory interneuronal circuits within the primary motor cortex.

Adult↗
PubMed1999

Long-term treatment of cervical dystonia with botulinum toxin A: efficacy, safety, and antibody frequency. German Dystonia Study Group.

Data from 616 patients suffering from idiopathic cervical dystonia were analyzed to determine the efficacy and safety of treatment with botulinum neurotoxin type A (BoNT/A). Since the specific purpose of this study was to determine the long-term effects of this treatment, the analysis focused specifically on the patients (n = 303) having received six or more injections. Statistical analysis of a standardized documentation showed sustained significant benefit as measured by a disease severity score independent of the type of cervical dystonia. Furthermore, pronounced individual differences were found in response to this treatment although initial clinical scores and doses of BoNT/A were similar. There was no indication of previously unknown adverse events, the only risk being the development of serum antibodies against the toxin. As in previous studies on short-term effects of BoNT/A treatment, the most frequent adverse event was dysphagia, which occurred on average 9.7 days after injection and lasted on average 3.5 weeks. While secondary nonresponse was seen in approx. 5% of patients, antibody tests revealed neutralizing serum antibodies in only 2%. On the basis of the present data, therapy of cervical dystonia with BoNT/A seems to be safe and yields good stable results even after 5 years of treatment.

Adolescent↗
PubMed1999

Demyelination and axonal degeneration in corpus callosum assessed by analysis of transcallosally mediated inhibition in multiple sclerosis.

OBJECTIVE: Following focal transcranial magnetic cortex stimulation (fTMS), inhibition of voluntary EMG activity in the ipsilateral first dorsal interosseus (FDI) muscle was studied, in order to assess the functional integrity of the corpus callosum in patients with multiple sclerosis (MS). METHODS AND RESULTS: Thirty-four patients suffering from definite MS and 12 healthy, age-matched normal subjects were examined. In mid-sagittal slices, 29 patients showed lesions within the truncus corporis callosi in T2-weighted MRI. In 20 patients, all areas (anterior, middle and posterior parts), in one both the anterior and posterior part, in 3 exclusively the anterior, in 4 the middle and in one the posterior area were affected. In 5 patients, lesions of corpus callosum were lacking. In normal subjects, fTMS elicited a transient inhibition (TI) of preactivated (50% of maximal force) isometric voluntary ipsilateral FDI muscle activity. Mean onset latencies of TI were 35.5+/-5.4 ms in right and 36.1+/-4.2 ms in left FDI. Mean duration of TI amounted to 23.0+/-8.4 ms for right and 24.6+/-8.4 ms for left FDI. In the MS group, TI latencies were significantly increased in 23 and TI durations in 16 cases, whereas a lack of TI was found in 5 patients bilaterally and in 6 unilaterally. In patients, mean onset latencies of TI were 40.4+/-13.8 ms in right and 43.3+/-14.4 ms in left FDI, TI duration amounted to 30.5+/-17.4 ms for right and 31.0+/-25.2 ms for left FDI. Increase of onset latencies and durations of TI were positively correlated with the summed area of lesions of corpus callosum in representative mid-sagittal MRI slices. Significant correlations between TI onset latencies and duration on the one hand, and central motor conduction latencies along corticospinal tracts (CML) on the other hand, were not found. CONCLUSION: The present investigation indicates that measurement of TI elicited by fTMS seems to be a sensitive method for an assessment of demyelination and axonal degeneration within corpus callosum in MS patients.

Adult↗
PubMed1999

Phenotypic variability of the DYT1 mutation in German dystonia patients.

Primary dystonia is a clinically and genetically heterogeneous movement disorder characterized by sustained involuntary muscle contractions causing repetitive movements and/or abnormal postures. Recently, the gene locus (DYT1) and mutation responsible for a substantial number of cases suffering from early-onset primary dystonia was described. Here we report 2 German families and 1 sporadic patient with early-onset dystonia due to the DYT1 mutation in order to illustrate the variability of clinical manifestation within this molecularly defined entity. We demonstrate that writer's cramp or focal cervical dystonia is a clinical presentation of DYT1 as well as generalized dystonia.

Adolescent↗