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Biomedical subjects

J Dichgans

Publications and source records attributed to J Dichgans.

At least 307 records · Page 17Linked to original sources
PubMed1983

The significance of somatosensory evoked potentials for localization of unilateral lesions within the cerebral hemispheres.

Thirty patients with unilateral lesions of the cerebral hemisphere and clinical signs of an affected somatosensory system (mainly disturbances of kinesthesia and stereoesthesia) were investigated. SEP recordings were abnormal in 27. The degree of sensory loss (especially kinesthesia) correlated well with the SEP abnormalities in 26. These SEP abnormalities could be segregated into 4 groups (types 1-4). A type 1 SEP with pathological evoked potentials from P15 on (but a normal P13/14 complex with ear- or extracephalic reference recordings) correlated with lesions of the thalamus, the internal capsule, and the centrum semiovale. A type 2 SEP characterized by loss or severe attenuation of N20 and the following components was found in patients with lesions of the postcentral gyrus. A variant (type 2a) showed isolated loss of N20, but preserved subsequent components and may be due to lesions restricted to area 3b. A third pattern of SEP abnormality is characterized by a preserved primary cortical response and loss of all the subsequent potentials. It is assumed to correlate with lesions of the parietal association cortex. In only 1 case was a type 4 SEP found, with pathological features from N3 (N55) on, caused by an ischemic stroke in area 39. Loss of all evoked responses after P13/14, including P15, suggests a lesion between thalamus and centrum semiovale. Lesions located close to the postcentral cortex lead to a loss of N20 and a variable cut off of the rising negativity following P15. Preservation of the primary cortical complex and distortion or loss of the later components point to a parietal lesion. Severe disturbances of kinesthesia and stereognosia in patients with a normal primary cortical complex and isolated abnormality of the following potentials suggests that the adjacent association cortex may be important for the perception of this complex somatosensory information. Thus the neuronal activity underlying the primary cortical response does not suffice for perception of motion and for stereoesthesia.

Adult↗
PubMed1982

Stabilization of human posture during induced oscillations of the body.

Displacements of the center of foot pressure, the hip and the head were recorded in six subjects standing on a platform, sinusoidally tilting in pitch (anterior-posterior). Stimulus frequencies ranged between 0.01 and 1 Hz. Stimulus amplitudes were 2, 4 and 6 degrees. With eyes open the displacements were minimal at 0.3 Hz. With eyes closed, however, induced sway was maximal at this frequency. The apparent lack of visual stabilization at the lowest frequency (0.01 Hz) might be attributed to a subthreshold velocity of the retinal image motion induced by the swaying body. A similar absence of visual stabilization of 1 Hz is assumed to indicate the limit of the working range of visual stabilization of posture. Independent of stimulus amplitude a phase lead of about 90 degrees was found at 0.01 Hz. This decreased with increasing frequency up to a phase lag of 100 degrees at the highest frequency (1 Hz). Head stabilization was generally more effective than hip stabilization. EMG recordings from the leg muscles suggest that with eyes closed the center of force is mainly stabilized by leg muscle activity, while with eyes open this stabilization is best, when vision allows for stabilization of body posture by intersegmental movements between head, trunk and legs.

Biomechanical Phenomena↗
PubMed1982

Diagnosis of cerebral Whipple's disease by cerebrospinal fluid cytology.

In a case of Whipple's disease the diagnosis was made by careful cytologic evaluation of the cerebrospinal fluid (CSF), identifying "Sieracki cells". A basal granuloma invaded the hypothalamus, diencephalon, and rostral parts of the brainstem. An exploration in the initial stage led to misdiagnosis as a granular cell tumor. Diagnosis was then confirmed by intestinal biopsy.

Adult↗
PubMed1982

The significance of luminance on visual evoked potentials in diagnosis of MS.

In view of the fact that with psychophysical methods monocular luminance changes may increase the detection rate of pathological interocular-latency differences in MS patients, we studied the influence of stimulus luminance on the detection rate of MS using checkerboard visual evoked potentials. Decrements of stimulus luminance covering a range of three log units were unable to increase the detection rate of VEP. Regression coefficients of the luminance-latency functions did not differ in MS patients and normals. Contrary to the hypothesis tested, the diagnostic significance of VEP decreases with decreasing stimulus intensity.

Adult↗
PubMed1981

Functional anatomy of extracranial arteries in occlusive vascular diseases by direct continuous wave Doppler sonography.

Doppler sonography of supratrochlear and neck arteries permits a determination of the direction and speed of flow. By compression of distal branches, the external carotid artery can be recognized, the occipital artery can be distinguished from the vertebral, and the direction of flow in the supratrochlear artery can be ascertained regardless of the artery's coiling. Compression of the arm can reveal subclavian steal. In order to localize a stenosis the vessel is followed by the probe. The accuracy of Doppler sonography is approximately 96%, and while the method may miss the diagnosis of slight stenoses and ulcerations, it nevertheless appears to be superior to all other indirect, noninvasive techniques that are currently available.

Aged↗
PubMed1981

Delayed and enhanced long latency reflexes as the possible cause of postural tremor in late cerebellar atrophy.

The pathophysiology of postural tremor was studied in 7 patients with cortical cerebellar atrophy, and compared with the responses of 14 healthy control subjects to the same tests. Both tibial nerves were simultaneously and selectively stimulated in the fossa poplitea. EMG was recorded from agonist gastrocnemius muscles and from the antagonistic anterior tibial muscles. Displacement of the centre of foot pressure, inclination of trunk and head in the anteroposterior direction, and the ankle angle were also measured. Patients and controls both exhibit a synchronized discharge in the anterior tibial muscle (antagonist) with a latency of 120 ms to stimulus onset (tib1). Tib1 is shown to be a segmental stretch reflex elicited by the contraction of the gastrocnemius (agonist). A later, presumed long-loop response occurs after another 120 ms both in gastrocnemii and anterior tibial muscles in the normal subjects. This latency, and the amplitude of the late reflex, are increased in the patient group. The synchronization of delayed long-loop reflexes and a stretch response of the gastrocnemius in response to tib1 terminate the first cycle of the postural tremor which thereafter continues by way of the same mechanism generating a contraction of the anterior tibial muscle. Postural tremor can thus be synchronized by a single bilateral electrical stimulus and can even be elicited in incipient cases of the disease. With further progression of the cerebellar atrophy the dominant frequency of the postural tremor decreases along with an increase of long-loop latencies.

Atrophy↗
PubMed1981

Aftereffects of vestibular and optokinetic stimulation and their interaction.

In humans the influence of prior vestibular stimulation (3, 6, 9, 12, and 18 degrees/second2 for 10 seconds) and subsequent whole-field optokinetic stimulation (30, 60, 90, 120, and 180 degrees/second for 1 minute) or the presentation of a stationary pattern on after-nystagmus (AN) was studied. For comparison, pure vestibular and pure optokinetic stimuli also were employed. The presentation of a stationary pattern resulted in suppression of vestibular nystagmus, which recovered after the termination of fixation. Fixation during the period of AN I did not inhibit an AN II. During the combinations of vestibular and optokinetic stimuli when the elicited vestibular (VN) and optokinetic nystagmus (OKN) had the same direction, there was a weak AN I toward the direction of the preceding VN and OKN, and a strong AN II toward the opposite side. When VN had been opposite to the subsequent OKN, there was a strong AN I toward the direction of OKN; AN II toward the opposite direction was small or mostly absent. Thus, AN was always stronger into the direction opposite to the previously elicited VN, indicating that the vestibular afference is the predominant input to the VAN II-integrator.

Acceleration↗
PubMed1981

[Spontaneous oral dyskinesia. Successful treatment with tetrabenazine (author's transl)].

Tetrabenazine (50-150 mg/day) was a moderate to excellent efficacy in each of six patients with severe spontaneous oral dyskinesia. Slight akinesia, rigidity, and transient disorientation were occasional side effects that could easily be controlled and were tolerated by the patient in view of the lasting amelioration of this debilitating symptom. When tetrabenazine was administered for blepharospasm, only two of six cases showed partial improvement with more severe side effects.

Aged↗
PubMed1980

Some methods and parameters of body sway quantification and their neurological applications.

Methods and parameters are described to quantify body sway as measured by a force-transducing platform. Analogue data representing the coordinates of the body's center of force (COF) are fed into a digital computer. Th following parameters are then calculated and tested for their diagnostic significance: sway path (SP), mean amplitude of sway (MA), mean sway frequency (MF), their lateral and sagittal components, and the quotients sagittal/lateral of these as well as the sway area (SA) circumscribed by the COF. Quotients of eyes open/eyes closed for all these parameters determine the visual stabilization of posture. Sway position and sway direction histograms allow for a more detailed analysis of MA and SP. Despite considerable inter- and intraindividual variance of these parameters (in 28 normals), some of them seem of clinical significance not only for documentation and follow-up studies but also for differential diagnosis. In patients with cerebellar lesions (n = 12), SP and MA were up to 10 times larger with a marked antero-posterior instability, MF being above normal. Patients with labyrinthine lesions (n = 10) showed significant instability only with eyes closed, MF being slightly below normal.

Cerebellar Ataxia↗