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  • 1
    ISSN: 1432-1106
    Keywords: Long latency reflexes ; Transcranial stimulation ; Physiology ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The interaction of transcranial electric and magnetic brain stimulation with electrically elicited shortand long latency reflexes (LLR) of hand and fore-arm flexor muscles has been investigated in normal subjects. In the first paradigm, the motor potential evoked in thenar muscles by transcranial stimulation was conditioned by median nerve stimulation at various conditioning-test intervals. At short intervals (electric: 5–12.5 ms, magnetic: 0–7.5 ms) facilitation occurred that corresponded to the H-reflex and at longer intervals (electric: 25–40 ms, magnetic: 22.5–35 ms) there was a facilitation corresponding to the LLR. Electric and magnetic stimulation resulted in a similar degree of facilitation. A second paradigm investigated the facilitation of the forearm flexor H-reflex by a cutaneo-muscular LLR elicited by radial superficial nerve stimulation and transcranial stimulation used separately or together. When electric and magnetic brain stimulation were compared, magnetic brain stimulation was followed by significant extrafacilitation but electric stimulation was not. This result favours an interaction between the afferent volley eliciting the LLR and transcranial magnetic stimulation most likely at supraspinal level.
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  • 2
    ISSN: 1432-1106
    Keywords: Cutaneous reflexes ; Long-Latency reflexes ; Precision grip ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hand muscle reflexes following muscle stretch and electrical nerve stimulation show a typical pattern consisting of short- and long-latency reflexes. The present investigation was designed to test reflexes following pure cutaneous stimulation. Air puffs were delivered to the palmar tip and the nail bed of the first, second and fifth fingers during isotonic contraction of hand muscles. The EMGs from the thenar muscles, the first dorsal interosseous muscle and the hypothenar muscles were recorded. Reflexes were obtained in all muscles, with a typical configuration consisting of a short-latency excitatory component (cutaneous longlatency reflex I, cLLR I) and a second excitatory component (cutaneous long-latency reflex II, cLLR II), with an inhibitory component between them. The size of cLLR II differed depending on the area stimulated and the muscle recorded. We found the largest responses always in the muscle acting on the stimulated finger. The reflex size depended on the strength of air puff stimulation. Allowing small displacements of the fingers led to an additional increase in the size of the reflex. The pattern of reflexes was identical independent of whether the finger tip or the nail bed was stimulated, but the size of the reflexes was smaller following nail bed stimulation. Following blockade of the cutaneous nerve branches of the thumb with local anaesthetics, air puff stimulation of the thumb no longer elicited this reflex pattern. Hence, under our experimental conditions, cutaneous receptors were the only source of afferent input for these reflexes. The results suggest that these cutaneous reflexes are mainly dedicated to controlling the stimulated finger independent of whether the palmar tip or the nail bed is stimulated. A possible physiological function is the adapting of grip force during handling of delicate objects if a perturbation is applied either to the object or the hand.
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  • 3
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Bewegungsstörungen ; M. Parkinson ; Stereotaxie ; Tremor ; Hirnstimulation ; Key words Stereotactic surgery ; Parkinson’s disease ; Movement disorders ; Thalamotomy ; Pallidotomy ; Brain ; Stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Stereotactic surgery for movement disorders is currently undergoing a re-evaluation. A new understanding of the pathophysiology makes the surgical lesion a logical step for the aleviation of both hyperkinetic symptoms such as tremor and hypokinetic symptoms like bradykinesia. Advances in imaging and electrophysiological control render these procedures more accurate and safer. Indications are medically refractory, Parkinsonean tremor, essential tremor, cerebellar tremor, bradykinesia and L-Dopa induced dyskinesis. The standard procedure is ablative surgery, i.e. thalamotomy for tremors and pallidotomy for bradykinesia, dystonia and L-Dopa induced dyskinesias. Deep brain stimulation is a novel alternative for selected patients which is currently evaluated. Neural transplantation of autologus, fetal or genetically manipulated cell suspensions into the striatum for the time being is experimental.
    Notes: Zusammenfassung Die chirurgische, d.h. stereotaktische Behandlung von Bewegungsstörungen erfährt derzeit eine Neubewertung. Neue Einsichten in die Pathophysiologie der Bewegungsstörungen haben dazu geführt, daß der stereotaktische Eingriff als begründeter therapeutischer Schritt angesehen wird. Die Nebenwirkungen stereotaktischer Eingriffe sind durch neue operative Techniken, digitale Bildgebung und elektrophysiologische Kontrollen geringer geworden. Die hauptsächlichen Indikationen sind Parkinson-Tremor und Rigidität, essentieller Tremor und zerebellärer Tremor. Als etablierte Routinemethode wird die stereotaktische Elektrokoagulation im Thalamus für alle Tremorformen weiterhin bevorzugt. Für die Behandlung von Akinesie und Bradykinesie, besonders auch der Dopa-induzierten Hyperkinesien, gewinnt die Pallidotomie rasch wieder an Bedeutung. Die chronische Stimulation durch Implantation von Hirnelektroden ist in Einzelfällen indiziert. Die Transplantation autologer, fetaler oder gentechnisch manipulierter Zellen wird derzeit in ihrer Bedeutung für die Therapie untersucht.
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  • 4
    ISSN: 1433-8491
    Keywords: Extracerebral and Intracerebral Processes ; Different EEG Blocking while Eyes Open ; Blocking of α and Abnormal Waves ; Tumors and Haematomas of Cerebral Hemispheres ; Extra- und intracerebrale Prozesse ; Verschiedene EEG-Blockierung durch Augenöffnen ; Blockierung von Alpha- und Deltawellen ; Tumoren und Hämatome der Großhirnhemisphären
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei einer Gruppe von 45 Patienten mit einem durch Operation oder Sektion gesicherten extra oder intracerebralen raumfordernden Prozeß wird das Verhalten der physiologischen und pathologischen Aktivität im EEG bei Ableitung mit offenen Augen untersucht. Es ließ sich zeigen, daß bei extraoerebralen Prozessen (Meningiom, Sub- und Epiduralhämatom) im Gegensatz zu den intracerebralen Tumoren sowohl die Alphatätigkeit wie auch die pathologische Aktivität über der betroffenen Hemisphäre durch Augenöffnen blockiert werden. Die pathophysiologischen Aspekte werden diskutiert. Außerdem wird auf die Bedeutung der Befunde für die EEG-Praxis als einfaches differentialdiagnostisches Kriterium bei extra- und intracerebralen Prozessen hingewiesen.
    Notes: Summary The blocking reaction of the EEG was investigated in 45 patients with intracranial extra- and intracerebral space occupying processes. It was shown, that in 15 out of 17 cases with an extracerebral process (meningeoma, sub- and epidural haematoma) the δ as well as the α activity over the affected hemisphere were blocked by opening the eyes. In contrast the δ activity on the affected side was blocked in only 3 out of 28 cases with intracerebral tumors (gliomas) during eyes open. Besides some interesting patho-physiological aspects of this observation, the statistical differences between the two groups are a useful, though limited EEG-criterion for differentiating between extra- and intracerebral space-occupying processes.
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  • 5
    ISSN: 1619-1560
    Keywords: carbon dioxide ; sympathetic activity ; humans ; cardiovascular regulation ; autonomic failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In vivo studies selectively assessing preganglionic and central autonomic nervous system activity in patients with autonomic failure have so far been limited to testing pituitary function. In animal experiments carbon dioxide (CO2) selectively stimulates central sympathetic nuclei in the ventrolateral medulla and preganglionic sympathetic neurons in the cervical trunk. This central stimulation seems to overrule less pronounced peripheral vasodilatatory effects. This study addressed the question of whether hypercapnea is a suitable challenge procedure to test preganglionic and central autonomic activity in healthy subjects and in patients with autonomic failure of preganglionic and central origin. Seven patients with multiple system atrophy (MSA) and 30 age-matched healthy volunteers underwent a protocol including a Valsalva manoeuvre (VM) under normo- and hypercapnic conditions and exposure to hypercapnea under supine resting conditions. Blood pressure (BP), heart rate (HR) and end-tidal CO2 partial pressure were measured continuously and non-invasively. In normal controls hypercapnea induced significantly higher BP values in phases II, IIe, III and IV of the VM compared to the normocapnic VM and a significant increase in BP during steady-state supine exposure compared to normocapnic baseline. HR increased significantly only after 40 s of steady-state hypercapnea during the latter challenge. In patients with MSA and autonomic failure, in whom a predominantly preganglionic lesion of the autonomic nervous system is established, no significant effects of hypercapnea on the cardiovascular parameters were found. Although this non-invasive challenge procedure cannot differentiate between pre- and postganglionic autonomic failure, exposure to hypercapnea enables the investigation of efferent autonomic activity to vasoconstrictors generated from autonomic centres in the brainstem and cervical trunk.
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  • 6
    ISSN: 1619-1560
    Keywords: postural tachycardia syndrome ; autonomic testing ; quality of life
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The postural tachycardia syndrome (POTS) is characterized by excessive tachycardia only in upright position without evidence of a cardiac or metabolic disease in combination with orthostatic symptoms like dizziness, lightheadedness or syncope but without relevant falls in blood pressure. The cause is unknown. A specific diagnostic marker has not been found so far. Eighteen patients with typical symptoms of POTS were examined. They underwent standard autonomic function tests with continuous measurement of heart rate (HR) and blood pressure. All fulfilled the inclusion criteria of pathologically increased HR activation during passive tiltor standing over 90 seconds. The upper limits of normal were based on data from 137 healthy volunteers between 18 and 85 years of age. Actively standing up induced more POTS-typical HR increases and lead to more consistent results than passive tilt. HR responses during Valsalva manoeuvre and deep breathing were normal in all except one patient each, indicating that assessment of HR during these tests does not contribute to the diagnosis of POTS. Frequency of symptoms reducing overall well-being and the degree of impairment of life quality by symptoms typical of POTS were measured with a self-assessment scale. The majority of patients reported a permanent reduction of overall wellbeing and a relevant impairment of life quality due to dizziness, tachycardia, and syncopes. This underlines the importance of considering POTS as a differential diagnosis of orthostatic syndromes and the necessity of treating it adequately.
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  • 7
    ISSN: 1619-1560
    Keywords: autonomic testing ; normal ranges ; sex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In 137 healthy volunreers between 18 and 85 years of age, blood pressure (BP) and heart rate (HR) were measured continuously with the Finapres device during active change of posture (ACP), i.e. standing upright, passive tilt (PT, i.e. head-up tilt), Valsalva manoeuvre (VM), deep brearhing (DB), isometric muscle exercise (IME) and a mental arithmetic task (MA). Mean HR activation was attenuated with increasing age in all manoeuvres, but was unrelated to sex. In non-orthostatic challenge procedures like MA and IME mean BP increases were independent of age and sex, despite lower increases in HR in the elderly. This points to a preserved sympathetic efferent activity. Following a forced fall in BP during ACP, PT and VM, the initial responses and maintenance values of BP showed a significant age-related decrease. This finding was strongly related to lower BP values in males compared with females, which became more pronounced with increasing age. Further studies to investigate age-related changes in the activation of the various components of the cardiovascular regulation need to consider the mode of activation of the autonomic nervous system and sex as factors of influence. Normal ranges, and also some new points in time not previously measurable, were calculated for all standard autonomic tests based on the continuous measurement of BP and HR. The minimum length of time necessary to assess the cardiovascular responses during ACP and PT was found to be 60 s. The upper time limits for reaching maximum activation during IME and MA were 3.5 min and 1 min, respectively. Age had a relevant influence on the lower limits of normal of all HR parameters and of some BP measurements during PT, ACP and VM. Sex was found to have no relevant impact on normal ranges. Over 65 years of age the normal values for HR activation during VM and DB hardly exceeded baseline values. The possibility of increasing the sensitivity of detection of autonomic dysfunction by measuring BP continuously must be approached with caution, as sufficient sensitivity was only reached at the lower limits of normal during late phase II of the VM. The initial increase of HR after ACP and the BP values after 60 s standing time proved to be the parameters with the best sensitivity for detecting an affection of the regulation of HR and BP over the whole range of age.
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  • 8
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 9
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 10
    ISSN: 1432-2072
    Keywords: Caudate nucleus ; Hippocampus ; Serotonin ; Dopamine ; Chlorimipramine ; Fluvoxamine ; 6-Nitroquipazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Slices of rabbit hippocampus or caudate nucleus were incubated with [3H]-5-HT (0.1 µM, 60 min) or with [3H]-DA. In hippocampal tissue, the 5-HT uptake blockers chlorimipramine, fluvoxamine, and 6-nitroquipazine (0.1, 1, 10 µM) reduced the percentage content of [3H]-5-HT in a concentration dependent manner. The degree of inhibition of [3H]-5-HT content produced by the 5-HT uptake inhibitors was not affected by the MAO inhibitors pargyline or amezinium (which by themselves enhanced [3H] loading) or the catecholamine uptake inhibitor nomifensine (which by itself did not affect [3H] loading). In caudate nucleus tissue, however, the [3H]-5-HT accumulation was reduced only at the highest concentration of the 5-HT uptake blockers (10 µM). In the additional presence of the MAO inhibitors or nomifensine (which by themselves increased or diminished, respectively, the [3H] labelling) the 5-HT uptake inhibitors became more potent in reducing the percentage [3H]-5-HT accumulation of caudate nucleus slices. These results indicate (1) that a false labelling of [3H]-5-HT into dopaminergic terminals in the caudate nucleus can be prevented by nomifensine, (2) that the 5-HT uptake blockers seem to accumulate within the dopaminergic terminals, where they may display a MAO inhibitory property. The 5-HT uptake blockers were ineffective on the percentage tritium accumulation of caudate nucleus slices incubated with [3H]-DA, regardless of the presence of pargyline or nomifensine. Tritiated DA and deaminated [3H]-metabolites were separated in the superfusate of [3H]-DA-release experiments in caudate nucleus tissue. In the presence of 6-nitroquipazine the percentage efflux of unmetabolized [3H]-DA was significantly enhanced in a concentration and time dependent manner. In comparison to 6-nitroquipazine, fluvoxamine was less potent in that respect. 6-Nitroquipazine inhibited the electrically evoked [3H]-DA and [3H]-ACh release from caudate nucleus slices in a concentration dependent manner. The effects on [3H]-DA release were abolished in the presence of pargyline. The inhibition of [3H]-ACh release was significantly diminished by the D2-receptor antagonist domperidone. In conclusion, some 5-HT-related drugs may diminish the release of ACh from caudate nucleus slices via an enhanced dopaminergic transmission due to inhibition of MAO within the dopaminergic terminals.
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