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Biomedical subjects

J Dichgans

Publications and source records attributed to J Dichgans.

At least 217 records · Page 12Linked to original sources
PubMed1993

Classical conditioning after cerebellar lesions in humans.

We explored classical conditioning in human subjects who had lesions in their cerebellar circuitry. Seven patients with damage to cerebellar structures and matched control subjects underwent simple delay tone-airpuff conditioning. Eyelid conditioned response (CR) acquisition was severely disrupted in the patient group, whereas autonomic CRs and slow cortical potentials developing between conditioned stimulus (CS) and the unconditioned stimulus (UCS) were unaffected. Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses.

Adult↗
PubMed1993

Hemodynamics in subclavian-steal syndrome: difficulties in their evaluation.

In a patient with subclavian-steal syndrome transcranial Doppler sonography detected transient retrograde basilar blood flow whereas routine angiography failed to document this condition. Thus, orthograde basilar blood flow at routine angiography does not rule out basilar steal. Presumably the forced injection of contrast media conceals less pronounced steal phenomena. Our exemplary case indicates that a subgroup of patients with vertebro-basilar symptoms concomitant with basilar flow abnormalities may benefit from invasive or semi-invasive treatment.

Angiography↗
PubMed1993

Magnetic resonance imaging in hereditary and idiopathic ataxia.

We used magnetic resonance imaging (MRI) to study brain and spinal cord morphology in hereditary and idiopathic ataxia. Our interest was in whether the classical neuropathologic categories--cerebellar cortical atrophy (CCA), olivopontocerebellar atrophy (OPCA), and spinal atrophy (SA)--could be identified in vivo and which clinical phenotype corresponded to which morphologic category. To this end, we measured the size of the cerebellar vermis, cerebellar hemispheres, fourth ventricle, middle cerebellar peduncles, basis pontis, medulla oblongata, and cervical spinal cord on T1-weighted images of 61 patients and 24 healthy controls. Five patients with Friedreich's ataxia (n = 7) and all with late-onset Friedreich's ataxia (n = 3) had SA without major involvement of the brainstem or cerebellum. Morphologic findings in patients with early-onset cerebellar ataxia with retained tendon reflexes (n = 11) were heterogeneous: six patients had MRI findings compatible with CCA, and two patients had a combination of SA and CCA. The three remaining patients had an atypical pattern of atrophy. Similarly, the morphologic changes in patients with autosomal-dominant cerebellar ataxia with additional noncerebellar symptoms (ADCA-I; n = 13) were nonuniform: atrophic changes typical for CCA, OPCA, or SA were each present in one case, four patients had a combination of OPCA and SA, and the remaining patients could not be assigned to one of the morphologic categories. In autosomal-dominant cerebellar ataxia with a pure cerebellar syndrome (ADCA-III; n = 6), all patients except one had CCA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Compartmentalized cerebellar functions upon the stabilization of body posture.

This paper reviews the features and topodiagnostical meaning of pathological body posture in cerebellar disorders and presents knowledge as to the physiology and pathophysiology of postural disturbances attributed to the cerebellum. Lesions of the spinocerebellar (upper vermal and intermediate) part of the anterior lobe lead to spontaneous anterior-posterior body sway, with a frequency of about 3 Hz with mild or absent ataxia of the upper limbs, but prominent ataxia of the lower limbs. The tremor is provoked by eye closure and by body displacement. Increased gain and poor cerebellar control of the duration and gain of stabilizing reflexes may be the mechanisms of this oscillation. Lesions of the lower (vestibulocerebellar) vermis cause postural ataxia of the head and trunk while sitting, standing, and walking. Postural ataxia is omnidirectional, sometimes of excessive amplitude and contains frequency components below 1 Hz. Dysmetria of the upper and lower limbs is not prominent. Visual stabilization is less than in the other groups of cerebellar patients. Lesions of the cerebellar hemispheres alone, do not cause an increase of postural sway. Lesions of spinocerebellar afferents (Friedreich's disease) lead to a low frequency large amplitude lateral sway with the most of its power below 1.1 Hz. Visual stabilization is preserved. Latencies of early and late EMG responses to sudden displacements are normal in patients with cerebellar disorders. The cerebellum is, therefore, unlikely to be the primary generator of these reflexive responses. On the other hand, the temporal composition of the orderly time sequence of a complex motor program--be it a voluntary act or its postural balancing--is deranged in cerebellar lesions. It is hypothesized that the cerebellum helps to coordinate the timing not only within but also between the single components involved in each subunit of a complex movement in three-dimensional space and that is scales the size and duration of each muscular action. The cerebellum possibly specifies the cortical movement command and sends it back to the motor cortex. The basic structure of a motor program, however, does not seem to be generated within the cerebellum.

Cerebellar Diseases↗
PubMed1992

The coordination of posture and voluntary movement in patients with cerebellar dysfunction.

Postural adjustments associated with the task of rising on tiptoes were investigated in a reaction time paradigm in 10 normal subjects and 18 patients with cerebellar disorders. Cerebellar dysfunction was due to either degenerative cerebellar disease, tumor, or ischemia. Displacements of the center of foot pressure (CFP) were recorded. The task, accomplished by the triceps surae muscle (executional activity, mean latency of 411 ms), is mechanically effective only if the center of gravity has been shifted forward in advance. To this effect, a phasic burst of preparatory EMG activity in the tibialis anterior normally occurs at a mean latency of 163 ms, shifting the center of gravity forward. Shortly thereafter, activity of the quadriceps femoris (175 ms) extends the knee and aids the forward shift of the center of gravity. Different aspects of this motor sequence were disturbed in individual patients: Latencies of preparatory and executional activity were uncorrelated in 15 of the 18 patients. Executional (n = 16) or preparatory (n = 13) EMG activity was tonic instead of phasic. Latencies of either preparatory or executional EMG activities or both were prolonged (n = 10). The time interval between motor preparation and execution was increased (n = 9). The trial-to-trial variability of biomechanical parameters and EMG latency was increased. Preparatory EMG activity in the quadriceps was entirely missing (n = 9), resulting in knee bending at the unsuccessful attempt to rise on tiptoes. Patients who were most severely affected had no preparatory activity at all (n = 2), and therefore were unable to perform the task.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Pathophysiology of cerebellar ataxia.

Human and animal experiments performed recently have resulted in a more detailed understanding of limb movement and body posture disorders associated with cerebellar dysfunction. The delay in movement initiation can be explained by a delay in onset of phasic motor cortex neural discharge owing to decreased input from the cerebellar hemispheres. Disorders of movement termination (dysmetria), which can occur for movements at proximal and distal joints, result from disturbances of the timing and intensity of antagonist electromyographic (EMG) activity necessary to break the movement. Disorders in velocity and acceleration of limb movements result from muscular activity that is smaller in amplitude and more prolonged. The cerebellum is important for control of constant force but not for generation of maximal force. Dysdiadochokinesia is explained by a combination of the above mentioned mechanisms. During complex movements in three-dimensional space, the cerebellum contributes to timing between single components of a movement, scales the size of muscular action, and coordinates the sequence of agonists and antagonists. The basic structure of motor programs is not generated in the cerebellum. Hypotonia can be observed only in acute cerebellar lesions. Cerebellar tremor appears to result from a central mechanism, but is modulated or provoked through increased long-loop EMG responses. The common assumption that cerebellar ataxia of stance does not improve with visual feedback is true only of vestibulocerebellar lesions, not for ataxia resulting from atrophy of the anterior lobe of the cerebellum.

Cerebellar Ataxia↗
PubMed1992

Neurophysiological evaluation of sensorimotor functions of the leg: comparison of evoked cortical potentials following electrical and mechanical stimulation, long-latency muscle responses, and transcranial magnetic stimulation.

Twenty-two patients with localized lesions of the central nervous system (unilateral cerebral ischaemia, cervical myelopathy, spinal tumour, familial spastic paraplegia) underwent neurophysiological evaluation of sensorimotor deficits of the leg. Functional methods using muscle stretch as stimulus, i.e. long-latency muscle responses and cortical potentials evoked by dorsiflection of the foot, were compared with transcranial magnetic stimulation and somatosensory evoked cortical potentials following electrical stimulation of the posterior tibial nerve. The functional neurophysiological methods yielded no diagnostic superiority with respect to the procedures using artificial (i.e. magnetic and electrical) stimulation. However, in most cases of missing compound motor action potentials following transcranial magnetic stimulation or missing electrically evoked cortical potentials, the long-latency muscle responses still allowed quantitative assessment of sensorimotor function.

Adult↗
PubMed1992

Tonic pupil, areflexia, and segmental anhidrosis: two additional cases of Ross syndrome and review of the literature.

Two patients are described with the triad of tonic pupil, hyporeflexia and segmental anhidrosis (Ross syndrome). Only 18 cases of this syndrome have been reported in the literature so far. While tonic pupil and reduced sweating can be attributed to the affection of postganglionic cholinergic parasympathetic and sympathetic fibres projecting to the iris and sweat glands, respectively, the pathogenesis of diminished or lost tendon jerks remains obscure. To identify the characteristic clinical features, the previous cases of Ross syndrome are reviewed. Recent evidence of subclinical disturbances of sweating in most patients with Adie's syndrome, i.e. tonic pupil and areflexia, casts doubt on the nosological concept of Ross syndrome as a distinct clinical entity.

Adult↗
PubMed1992

Ganglioside antibodies: a lack of diagnostic specificity and clinical utility?

Serum IgG and IgM antibodies to gangliosides GM1, GM2, GM3, AGM1, GD1a, GD1b and GT1b were determined in 210 patients with different degenerative and inflammatory disorders including motor neuron diseases, peripheral radiculopathies and neuropathies, multiple sclerosis and neuroborreliosis. No single disorder was associated specifically with ganglioside antibodies. No characteristic patterns of ganglioside antibodies were observed in any disease category. However, 32% of all patients had pathological antibody titres to at least one ganglioside. Four patients had pathological IgG and IgM titres for all gangliosides evaluated. They suffered from systemic lupus erythematosus [2], neuroborreliosis and schizophrenia, respectively. The results of this study indicate that the introduction of ganglioside antibody determination as a differential diagnostic test in clinical neurology is only helpful in a few patients with typical lower motor neuron syndromes.

Biomarkers↗
PubMed1992

Automatic-voluntary dissociation: an unusual facial paresis in a patient with probable multiple sclerosis.

A patient with multiple sclerosis is described who presented with a unilateral loss of voluntary function of his lower face muscles. However, in an emotional situation, there was strong involuntary innervation of these muscles: automatic-voluntary dissociation. The subcortical afferents to the facial motor nucleus are discussed. It is hypothesized that cortical disinhibition of midbrain nuclei underlies the accentuated involuntary innervation.

Adult↗
PubMed1992

Three-dimensional properties of human pursuit eye movements.

For any given location and velocity of a point target, there are infinitely many different eye velocities that the pursuit system could use to track the target perfectly. Three-dimensional recordings of eye position and velocity in 8 normal human subjects showed that the system chooses the unique tracking velocity that keeps eye position vectors (a particular mathematical representation of three-dimensional eye orientation) confined to a single plane, i.e. pursuit obeys Listing's law. One advantage of this strategy over other possible ones, such as choosing the smallest eye velocity compatible with perfect tracking, is that it permits continuous pursuit without accumulation of ocular torsion. For nonpoint targets, there is at most one eye velocity compatible with perfect retinal image stabilisation, and the optimal velocity may not fit Listing's law; we observed small but consistent deviations from the law during pursuit of rotating line targets.

Adult↗
PubMed1992

Immunological abnormalities in the tears of multiple sclerosis patients.

IgG and IgM concentrations in tears of multiple sclerosis patients (n = 38) are increased compared to normal controls (n = 23). The occurrence of oligoclonal tear IgG bands (7.9%)--as determined by immunoblotting--did not differ between groups. Our findings suggest an altered reactivity of the secretory immune system in MS patients, but did not differ from findings in patients with eye affections or wearing hard contact lenses.

Adult↗
PubMed1992

[Diagnosis and therapy of meningosis neoplastica].

Metastatic leptomeningeal disease occurs in 5-30% of patients with breast or lung cancer, malignant melanoma, non-Hodgkin's lymphoma, leukemia and primary malignant brain tumors. Intrathecal chemotherapy with methotrexate, cytarabine, or thiotepa combined with irradiation of the site of major involvement increases overall median survival from 1-2 months to 2-7 months. Clinical outcome is limited by progression of systemic or CNS disease and by the neurotoxic side effects of therapy, i.e. leukoencephalopathy. New immunotherapeutic strategies of intrathecal treatment may be effective and less toxic, but are not yet sufficiently defined and available. This review covers the current diagnostic and therapeutic features of metastatic leptomeningeal disease. Pragmatic therapeutic recommendations, based on available clinical knowledge are given with special consideration of the side effects of therapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Influence of an acoustic preparatory signal on postural reflexes of the distal leg muscles in humans.

In standing subjects the sudden displacement of a platform toe-up evokes a stabilizing postural response of the anterior tibial muscle (long-latency reflex). A preparatory signal (acoustic warning stimulus) preceding the postural perturbation by 1 s results in a significant decrease in latency of this long-latency response. There is no parallel modulation of the afferent cortical input in terms of evoked cerebral potentials following platform tilts toe-up nor of efferent cortico-spinal functions as evaluated by means of transcranial magnetic stimulation. Conceivable underlying mechanisms include faster intraspinal and/or intracortical processing of afferent input or switching to a shorter spinal reflex pathway.

Acoustic Stimulation↗
PubMed1991

Cerebrospinal fluid interleukins, immunoglobulins, and fibronectin in neuroborreliosis.

Intrathecal synthesis of IgM and IgG, oligoclonal immunoglobulin bands, and the levels of fibronectin, soluble interleukin 2 receptor, interleukin 6, and tumor necrosis factor alpha were investigated with the use of enzyme-linked immunosorbent assay in 46 paired cerebrospinal fluid and serum samples from 32 patients with meningopolyradiculoneuritis due to Borrelia burgdorferi (Lyme borreliosis stage 2). Cerebrospinal fluid and serum interleukin 6, although not specific for neuroborreliosis, were good indicators of disease activity, while the serum soluble interleukin 2 receptor level was only mildly elevated. Tumor necrosis factor alpha was never detected in cerebrospinal fluid or serum specimens, and cerebrospinal fluid IgM, IgM index, and cerebrospinal fluid IgM/cerebrospinal fluid IgG ratios were significantly higher than in all other neuroimmunologic disorders evaluated and may be valuable diagnostic indicators for neuroborreliosis. The estimation of intrathecally synthesized IgG and IgM fractions for the differential diagnosis of neuroimmunologic disorders did not add to IgG and IgM index calculations.

Antibody Formation↗
PubMed1991

Selective impairment of smooth-pursuit eye movements due to an ischemic lesion of the basal pons.

Voluntary and reflex-like eye movements were measured in a patient with an ischemic lesion of the right basal pons. Ipsilateral smooth-pursuit eye movements were predominantly impaired and interrupted by saccades. This profound smooth-pursuit deficit contrasted with only minor abnormalities of visually guided saccades and the vestibulo-ocular reflex. A selective disturbance of smooth-pursuit eye movements due to a lesion of the basal pons in this patient concurs with recent work in monkeys suggesting that smooth-pursuit eye movements are mediated by a parietooccipito-ponto-cerebellar pathway.

Brain Ischemia↗
PubMed1991

Direction and amplitude precuing has no effect on automatic posture responses.

Automatic postural responses of leg muscles to the sudden displacement of standing support were investigated under four different conditions of information given to subjects in advance. Results from three groups of subjects were compared: 6 normal subjects, 10 patients with cerebellar disease, and 9 patients with Parkinson's disease. Specifically, each subject was provided with visual information about the direction and/or the amplitude of an upcoming platform tilt. For the control situation no advance information on the characteristics of platform tilt was provided. Neither the latencies nor the integrals of postural EMG-responses showed alterations with advance information. In contrast, in a control experiment in which 3 normal subjects had to perform large or small forward or backward voluntary movements of the body around the ankle joint, shorter onset-latencies of leg muscle EMG responses were observed with increasing complexity of the advance information. These results suggest that, unlike voluntary movements, postural responses to rapid surface tilts do not benefit from advance visual information on direction or amplitude of a postural disturbance.

Adult↗