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Biomedical subjects

J Dichgans

Publications and source records attributed to J Dichgans.

At least 325 records · Page 18Linked to original sources
PubMed1980

Ischaemic neuropathy of the lumbosacral plexus following intragluteal injection.

A lesion of the lumbo sacral plexus may result from an inadvertent intra-arterial injection of vasotoxic drugs into one of the gluteal arteries. Symptoms and follow-up of three cases are reported. The neuropathy is attributed to a toxic endarteritis with retrograde propagation of spasm and thrombosis. Swelling an bluish discoloration of the buttocks ("embolia cutis medicamentosa") as well as an impaired circulation in the homolateral leg are associated with the neurological syndrome in fully developed cases and makes possible a correct diagnosis.

Adult↗
PubMed1979

Quantitative analysis of stance in late cortical cerebellar atrophy of the anterior lobe and other forms of cerebellar ataxia.

(1) Methods have been developed to measure, analyse and document postural sway. The main parameters studied were: average sway amplitude; length of the sway path per unit time; sway direction and sway position histograms; and the frequency spectra of the antero-posterior and lateral sway components. (2) Postural ataxia was quantitatively studied in three groups of patients with cerebellar lesions: (a) late atrophy of the anterior lobe, (b) tumours of the cerebellar hemisphere and (c) tumours within the vestibulo-cerebellum. Characteristic differences were found. (3) Patients with anterior lobe lesion show a specific 3 Hz postural tremor in the antero-posterior direction. The tremor can be evoked by sudden destabilization in incipient cases. Less characteristic and smaller in amplitude is a mainly lateral sway component with an average frequency of 0.5 Hz. This is also seen in cases with spinal ataxia. Visual stabilization of posture is frequently preserved. Its amount does not correlate with general instability of posture. Tremor and characteristically exaggerated intersegmental responses between head, trunk, hips and legs are interpreted as the consequence of hyper-excitability of postural reflexes in these patients. (4) Patients with lesions of the hemispheres show only slight postural instability without directional preference. Their sway parameters with eyes open are within the 2 sigma range of normals and there is no significant difference from normals in these parameters even when the eyes are closed. Therefore these patients cannot be distinguished from normals by means of their platform recordings. (5) Two patients with posterior vermal and flocculo-nodular lesions were very unstable without preferred axis or frequency of instability. In contrast to the anterior lobe group the instability was characterized by the absence of intersegmental movements.

Adult↗
PubMed1979

Simultaneous clinical manifestation of subependymoma of the fourth ventricle in identical twins. Case report.

At the age of 22 years, identical twin brothers simultaneously developed symptoms of intracranial pressure. Radiological investigation revealed cerebellar midline tumors with occlusive hydrocephalus of the third and lateral ventricles. At operation, subependymomas with identical histological features were found in the fourth ventricle in both twins. This is the first report of subependymomas in identical twins. The clinical data suggest that this tumor type is of maldevelopmental origin.

Adult↗
PubMed1978

The Pulfrich spatial frequency phenomenon: a psychophysical method competitive to visual evoked potentials in the diagnosis of multiple sclerosis.

The results of a study in which visual evoked responses (VERs) and a modified Pulfrich method were compared showed that both methods are very effective for the diagnosis of multiple sclerosis. With VERs, 97% of the multiple sclerosis cases were diagnosed correctly, while the corresponding value for the Pulfrich method was 93%. In contrast to VERs, the Pulfrich method allows only measurement of latency differences between the two visual pathways. This method involves measuring the speed required to cause a shift in the apparent depth location of a large, moving, striped pattern observed with a neutral density filter over one eye. A pathological transmission time was inferred when the patients observed a shift in the depth of the moving pattern either without any filter at all or with a filter whose attentuation was no more than 0.2 log units. A further criterion for pathology was a difference of more than 10% between the two eyes in the retinal speed required for a depth displacement using a 1.5 log unit filter. This test requires about 15 minutes, and can be carried out by a technical assistant.

Adult↗
PubMed1978

[Neurological and EEG-follow-up studies in head-injured adults: criteria for the clinical diagnosis concussion and contusion (author's transl)].

A stystematic neurological and electroencephalographical follow-up study in 344 head injured adults gave the following results: 1. 52% of all the hospitalized (mostly primarily amnesic) patients had a cerebral contusion. A contusion was assumed in cases with focal neurological signs (13%), amnesias of more than 8 hours (16%) and/or EEG-abnormalities lasting for more than 24 hours (49%). 2. Traumatic EEG-abnormalities were general slowing (43%) and foci (32%). In 40% of the cases with general slowing the slowing (greater than or equal to 1.5/sec) was within the alpha-frequency band and could only retrospectively be assed. 3. The EEG was invariably abnormal in cases with an amnesia exceeding 8 hours. If the amnesia exceeded 1 hour abnormalities were found in 73%. 4. Among the patients with contusion 6.5% had no amnesia, 48% less than 30 minutes and only 30% an amnesia for more than 8 hours. In 75% of the patients with concussion amnesia lasted less than one hour. 5. Skull fractures were mostly combined with contusion (74%). 6. Impaired drive, reduced ability to concentrate, memory deficits, headache and dizziness were significantly more frequent 6 months after contusion than after concussion. 7. 21% of the patients with traumatic dizziness (44%) had a labyrinthine contusion. 8. Among the contusions diagnosed with the aid of EEG recordings 58% would have been missed after exclusive neurological examination and 82% after application of the classical criteria used by surgeons and general practitioners.

Adolescent↗
PubMed1977

Direction-specific optokinetic modulation of monosynaptic hind limb reflexes in cats.

The excitability of hindlimb extensor and flexor motoneurons is tonically modulated by animal tilt and a large visual stimulus rotating about the animal's line of sight. This direction-specific modulation is opposite for extensor and flexor motoneurons and opposite for optokinetic and vestibular stimuli, thus combining to a functionally significant pattern of postural reflexes.

Animals↗
PubMed1977

[Similarities and differences after head injuries in children and adults (author's transl)].

The results of a systematic neurological and electro-encephalographical follow-up study in 344 head injured adults and 116 children were compared. The results show that posttraumatic EEG abnormalities lasting more than 24 hours, are equally frequent in children (53%) and in adults (49%). Mostly short lasting neurological signs of focal tissue damage are however significantly more frequent in children (30% vs. 13% and EEG-abnormalities (foci and general slowing) are on the average more pronounced. The recovery of EEG abnormalities follows the same pattern as in adults, occurs however faster among children. In both groups the normalization of general slowing precedes that of focal abnormalities only in 25% of the cases. Amnesias on the average last shorter in infants. Their duration seems of lesser significance for the judgement of the severity of the trauma in children than in adults. 6 months after the trauma children complain less frequently about headache, dizziness, or impaired memory and diminished ability to concentrate; emotional lability and impairement of drive, however, are more frequent than in adults. The results indicate an equal diagnostic and prognostic importance of systematic EEG studies (within 2 days, after 1 week and 6 month after the trauma) in both groups.

Adolescent↗
PubMed1977

[Oculomotor disturbances as cerebellar symptoms in pontine angle tumors. Contralateral diminution of optokinetic nystagmus as early sign of floccular lesions (author's transl)].

Spontaneous eye movements and responses to visual and vestibular stimuli were recorded in 30 patients with pontine angle tumors (26 neurinomas, 2 meningeomas, 1 chosteatoma, 1 angioma). Pre- and postoperative recordings in most cases showed a bilateral dimunition of horizontal optokinetic nystagmus (OKN) that prevailed towards the side contralateral to the tumor. This is explained by a homolateral floccular lesion and cannot be the consequence of spontaneous nystagmus or asymmetrical gaze nystagmus. The predominance of a homolateral OKN-diminution often described in the literature was found in advanced cases or post-operatively as a sign of pontine reticular formation damage. The neighbourhood of the flocculus to the VIIIth nerve and animal experiments with floccular lesions causing a contralateral OKN diminution support out explanation. Additional arguments for damage of cerebellar oculomotor functions are the predominance of cogwheeled smooth pursuit and the occasional observation of hypermetric saccades, both toward the side of the tumor. Patients with very large tumors finally develop a complete disruption of OKN toward the homolateral side together with concomitant gaze paralysis.

Adult↗
PubMed1976

[Visual stabilization of free stance in infants: a sign of maturity (author's transl)].

The development of the visual contribution to postural stabilization has been tested using a large visual display rotating around the stationary subject's line of sight. This, in the adult, causes a marked optokinetic postural reaction with a shift of the body center of gravity toward the direction of pattern motion. Scalings of the reactions in children between 6 months and 16 years revealed three phases of development: (1) 6--12-month-old-babies show none or very little optokinetic disturbance of their newly acquired ability to sit. With the development of upright stance and gait, optokinetic influences become increasingly important. (2) Children between the age of 2--5 show a marked dependence of postural stability on vision. In them, the disturbing optokinetic stimulus leads to a marked ipsilateral postural deviation or irresistible fall. (3) From 5 to 15 years of age, visual effects on postural balance slowly decrease to their final strength in adulthood--moderate head and body tilt--in response to the rotating stimulus. It is concluded that the optokinetic loop participates rather late in the multisensory process of postural stabilization. The calibration of the three main loops, visual, vestibular, and proprioceptive, seems to be sequential and mutually interactive. Optimal functioning requires the continuous evaluation of the reafferent sensory consequences of self-generated body movements. Optokinetic destabilization of stance requires the maturity of opto-vestibulo-spinal pathways. Its clinical applicability as a maturity test, however, sofar seems limited.

Adolescent↗
PubMed1976

Visual-vestibular interactions in the vestibular nuclei of the goldfish.

The responses of vestibular nuclei neurons of relaxed unanaesthetized goldfish have been examined with trapezoid velocity stimuli under three conditions. Responses to horizontal body rotation in the dark (pure vestibular stimulation) resemble those observed in vestibular nerve afferents. Optokinetic responses to exclusive visual surround-motion are also direction-specific and, in contrast to vestibular responses, exhibit a tonic response to constant velocity. They show three different response profiles, classified A,B or C, based on the neuron's discharge rate: either increasing, decreasing or remaining constant once surround motion is maintained at constant velocity. Following these dynamic effects, optokinetic responses have a maintained modulation of resting discharge until deceleration commences. The time constants associated with the dynamic effects vary between 1 and 11 seconds. Steady-state modulation of optokinetic responses shows a weak relation to stimulus velocities exceeding 10 deg/sec. Responses to body rotation in the light were found to linearly combine the weighted vestibular and optokinetic responses so that accurate velocity information is available for sensory and motor functions independent of the neuron's vestibular (I,II) or optokinetic (A,B,C) response type. The principle of this visual-vestibular interaction is discussed with respect to multisensory processing within the vestibular nuclei.

Action Potentials↗