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Biomedical subjects

U Thoden

Publications and source records attributed to U Thoden.

At least 37 records · Page 2Linked to original sources
PubMed1984

Responses to corneal stimulation in vestibulospinal units of nucleus Deiters.

In precollicular decerebrated cats, the response patterns of antidromically identified vestibulospinal Deiters's neurons to stimulation of corneal receptors were investigated. These patterns were compared with the responses of the somatosensory receptors of the neck and limbs as well as with the vestibular input of the horizontal semicircular canals. Of the 162 antidromically driven Deiters's units, 23 were influenced, mainly bilaterally, from corneal receptors. Response latencies evoked by electrical stimulation of the cornea ranged from 6 to 16 ms (mean 12 ms). In 99 Deiters's cells, the influence from the limbs was examined: 51 revealed primarily an ipsilateral modulation from proximal joint receptors. Convergence with joint receptor input was found in 16 of the 18 corneally driven cells tested. Of the 115 cells tested, 15 neurons responded to neck rotation in the horizontal plane. A contribution from the lateral semicircular canals was found in 7 of the 101 examined Deiters's neurons. The connection of corneal receptors with the spinal motor system, via a vestibulospinal pathway, may mediate a nociceptive reflex protecting the eyes and the face.

Afferent Pathways↗
PubMed1983

Cervico-ocular responses (COR) during slow sinusoidal head movements in subjects with bilateral labyrinthine lesions.

Eye movements in five patients with chronic bilateral labyrinthine loss were tested with sinusoidal movements during cervico-ocular stimulation and active head movements (0.05, 0.1 and 0.2s-1; 20, 40, and 60 degrees) and were compared with healthy subjects. Consideration was given to saccadic activity and slow phase velocity of nystagmus and overall gaze shift. The cervico-ocular response was not altered in the patients. During active pendular head movements the saccadic activity and slow phase velocity of nystagmus were more reduced than the eye shifts. The phase relation of eye shifts was not changed. In our patients neck to eye responses did not compensate for the abolished vestibulo-ocular reflex.

Adolescent↗
PubMed1982

The effect of cervical and vestibular reflexes on eye movements in Huntington's chorea.

In 8 patients with manifest Huntington's Chorea vestibulo-ocular (VOR) and cervico-ocular (COR) reflexes were compared with eye movements during active head turnings. Seated patients were stimulated with their eyes closed by sinusoidal swings around the vertical axis at frequencies of 0.05, 0.1 and 0.2s-1 with amplitudes of 20, 40 and 60 degrees. 1) With all stimuli and in all patients a weak nystagmus was elicited in the direction of head movements, superimposed on larger slow eye deviations. 2) The averaged total saccadic amplitudes were smaller than in normals, increased with stimulus amplitudes and were smallest for COR, followed by VOR and active head movements. 3) The gain (peak velocity of slow phase of nystagmus to peak stimulus velocity) was only slightly below norm values and decreased with increasing stimulus frequency and amplitude. 4) The peak amplitudes of average slow eye deviations increased with stimulus amplitudes. In VOR they were comparable to norm values but were below them during COR and active head movements. 5) In normal subjects these slow eye deviations were compensatory to head movements in VOR but anticompensatory in COR and during active head movements. In choreic patients during COR and more often during active head movements these slow eye movements were compensatory for the head turning.

Adult↗
PubMed1982

Huntington's disease: alterations of visual and somatosensory cortical evoked potentials in patients and offspring.

In 13 patients suffering form Huntington's chorea (H.Ch.), VEPs and SEPs were investigated in comparison to 9 clinically inconspicuous offspring and normal adults. 1. The mean amplitude of VEP was reduced in choreatic patients and in four out of nine offspring. 2. Latencies of P100 in VEP were normal in all subjects. 3. The late components were reduced in amplitude and rather irregular in shape. 4. The latencies of SEPs were slightly prolonged, less marked in the early peaks and more pronounced in the later ones. 5. The late components after 70 to 100 msec were often attenuated or even absent. 6. The mean amplitude of the first two peaks was reduced. 7. Interhemispheric asymmetries were pronounced in three out of nine offspring.

Adult↗
PubMed1982

Visual evoked potentials by central foveal and checkerboard reversal stimulation in multiple sclerosis.

In 200 patients with suspected MS, the diagnostic value of VEP elicited by checkerboard reversal and central foveal stimulation was compared. No significant difference was evident, but both methods overlap. The more stable checkerboard reversal stimulation should be preferred as a diagnostic method. Only in suspected MS with normal checkerboard responses, additional foveal responses may give supplementary information. Normal VEPs cannot exclude a prior retrobulbar neuritis.

Diagnosis, Differential↗
PubMed1981

[Addiction-like behavior with continuous self-stimulation of the mediothalamic system (author's transl)].

In a patient with postamputation pain a continuous self-stimulation of the mediothalamic system by a chronic deep brain electrode induced a change in behavior, similar to addiction. At the same time various psychological tests (HAWIE, Benton, Hooper-VOT and concentration tests) were significantly disturbed. After interruption of the deep brain stimulation all induced psychic abnormalities normalized within a few days.

Adult↗
PubMed1981

Disturbance of eye movements in Huntington's chorea.

Eye movements were investigated in 14 patients with manifest Huntington's Chorea, 10 offspring and 10 normal subjects with electronystagmography (ENG) and during REM sleep. In choretic patients the following abnormalities were found: 1. Voluntary saccades were slowed in 10 of 14 patients and were more disturbed in the vertical than the horizontal direction. 2. Also, the velocity of the fast phase of optokinetic nystagmus was clearly reduced, especially in the vertical plane. 3. Horizontal, pendular pursuit movements are often superimposed by square wave opposite jerks. 4. Vestibular nystagmus was disturbed, too, especially in the fast phase. 5. During paradoxical sleep, rapid eye movements are less frequent. 6. In ten offspring, eight showed similar oculomotor disturbances.

Adult↗
PubMed1981

Vestibulo-ocular reflex (VOR), cervico-ocular reflex (COR) and its interaction in active head movements.

In normal adults the vestibulo-ocular reflex (VOR) and the cervico-ocular reflex (COR) were investigated during passive and active head or body movements, respectively. Sinusoidal rotations around the vertical axis of the body at frequencies of 0.05, 0.1, and 0.2s-1 and total amplitudes of 20 degrees, 40 degrees, 60 degrees, or 80 degrees were employed. The average eye deviations (Schlagfeld) during VOR were directed opposite to the direction of the head turning. During COR, however, slow eye deviations of higher amplitude were anticompensatory relative to the fixed head. During active head turnings the average eye deviations showed the same anticompensatory direction as in COR, but were still larger. The increased with stimulus amplitudes up to 60 degrees. At least a weak cervical nystagmus was elicited in all subjects, with its fast phases beating in the direction of the relative head movement. Its gain reached marked values up to 0.5, but only for peak stimulus velocities below 25%. The nystagmus gain during active head turnings was only slightly higher than during VOR. With higher stimulus velocities, large anticompensatory saccades appeared just before the change of stimulus direction; these are typical for active head movements, but were also found during COR.

Adult↗
PubMed1981

Visual evoked potentials (VEP) elicited by checkerboard versus foveal stimulation in multiple sclerosis. A clinical study in 235 patients.

In 235 patients with suspected multiple sclerosis (MS) the diagnostic value of visual evoked potentials (VEP) elicited by checkerboard and central foveal stimulation was compared. No significant difference was found. Both methods are supplementary in diagnostic value. Foveal stimulation may provide an additional diagnostic clue. Normal VEPs do not exclude a prior retrobulbar neuritis. Electronystagmography and examination of CSF are at least essential for the diagnosis of MS as VEPs. The combination of these methods increase the accuracy of diagnosis.

Adolescent↗
PubMed1981

Visual (VEP) and somatosensory (SSEP) evoked potentials in Huntington's chorea.

In 13 patients suffering from Huntington's chorea (H.Ch.) VEPs and SSEPs were investigated in comparison with 9 clinically unaffected offsprings and 40 normal adults. (1) The mean amplitude of VEPs was reduced in all patients and in 4 out of 9 offsprings. (2) Latencies of P100 in VEPs were normal in all subjects. (3) The late components were reduced in amplitude and rather irregular in shape. (4) The latencies of SSEPs were slightly prolonged, less marked in the early peaks and more pronounced in the later ones. (5) The late components after 70--100 msec were often attenuated or even absent. (6) The mean amplitude of P1/N2 was remarkably reduced. (7) Interhemispheric asymmetries were pronounced in 3 out of 9 offsprings.

Adult↗
PubMed1980

The late facilitation in H-reflex recovery cycles in different pyramidal lesions.

H-reflex amplitudes were recorded after stimulation of the tibial nerve and different electrical stimuli in 18 normal persons and 26 patients showing pyramidal spasticity (8 spastic spinal paralysis, 6 spastic hemiparesis, 12 spinal lesions). A just subthreshold stimulus of the tibial nerve facilitated the H-reflex in spastic patients slightly after about 300 ms (up to 113%), following an early strong facilitation (10 ms) and a longer lasting depression (20-200ms). Similar postinhibitory facilitation was obtained in spastic patients after ipsilateral stimulation of the plantar surface and after direct stimulation of the dorsal columns. Conditioning by contralateral stimuli of the posterior tibial nerve caused a slight late facilitation in both normal and spastic patients. This late facilitation did not correlate significantly with the severity of spasticity, but it was more pronounced in cerebral pyramidal lesions than in spinal ones. It is assumed that this postinhibitory facilitation is probably generated as a spinal rhythm, similar to the clonus, and that it is modulated from supraspinal structures.

Adolescent↗
PubMed1979

[An evaluation of methods of diagnosing central nervous system metastases (author's transl)].

In 50 cases of histologically identified metastases of the central nervous system it was found that in cases of breast cancer and malignant melanomas the diagnosis of the primary tumor is the key to the diagnosis of the metastasis; bronchial carcinomas are usually found upon diagnosis of cerebral metastases; angiography, color scintigraphy and the computer tomography have a false negative rate of 10--15%, in cerebrospinal fluid protein levels are often increased (64%), and tumor cells are found in 18%.

Adult↗
PubMed1979

[Cauda equina syndrome with total myelographic block (author's transl)].

Twenty-seven cases of complete subarachnoid block discovered through myelography are analysed with regard to the causes of obstruction, the neurologic symptoms, and the cerebrospinal fluid. The neurologic signs in cases of cauda equina compression, most often caused by massive disc protrusions (20 patients), vary considerably and rarely correspond to the gross myelographic findings. Bilateral neurologic symptoms of any degree with or without sphincter disturbance were observed in 21 among 27 cases and are signs of cauda compression. In contrast to cases of sciatica with unilateral root compression and radicular symptoms neurological symptoms are not reliable in revealing the site of the lesion in cases of massive central disc protrusions. Therefore radiculography (myelography of the cauda equina) is necessary for diagnosis. In addition to the well-known elevation of the spinal fluid protein and pleocytosis, the presence of neutrophile granulocytes is frequently found (11 of 20 cases) in cytological analysis.

Cauda Equina↗
PubMed1979

Medial thalamic permanent electrodes for pain control in man: an electrophysiological and clinical study.

In 7 patients with medial thalamic electrodes implanted for relief of chronic pain, clinical observations and electrophysiological recordings showed: (1) Clinically, paresthesia in the pain area and contralateral half of the body was reported as well as some unpleasant side effects. The EEG was not changed during medial thalamic stimulation. (2) Threshold for non-painful and painful perception of electrical stimuli were not significantly raised by contralateral medial thalamic stimulation. (3) After electrical median nerve stimulation, evoked thalamic potentials started after 17 msec. With ipsilateral stimulation the early components (up to 40 msec) showed longer latencies and the late components slightly shorter latencies as compared to the contralateral stimulation. (4) Median nerve evoked cortical SSEPs are not significantly changed either by a 500 msec lasting conditioning stimulation of the dorsal columns or by such stimulation of the medial thalamic structures. A facilitation at about 90 msec was found in the cortical SSEP after medial thalamic conditioning in only one of three patients tested. (5) Visual and auditory evoked potentials can be recorded in the medial thalamus as well.

Electric Stimulation Therapy↗