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H Wilhelm

Publications and source records attributed to H Wilhelm.

At least 55 records · Page 3Linked to original sources
PubMed1998

Mathematical procedures in data recording and processing of pupillary fatigue waves.

Spontaneous pupillary behaviour in darkness provides information about a subject's level of vigilance. To establish infrared video pupillography (IVP) as a reliable and objective test in the detection and quantification of daytime sleepiness, the definition of numerical parameters is an important precondition characterising spontaneous pupil behaviour adequately for further statistical procedures. The correct measurement of the pupil size, even if the lid or eyelashes are occluding the pupil, is of particular concern when testing vigilance. In this case many edge points of the pupil are detected and a fitting procedure is described that fits these edge points to a circle and excludes outliers. The first step of data preparation consists of a mathematical artefact management consisting of blink detection and elimination, followed by interpolation. Second, a fast Fourier transformation is carried out for frequencies from 0.0 to 0.8 Hz for each time segment of 82 s. Results are given in absolute and relative power of each frequency band per time segment and mean values over the entire record of 11 min. Third, the changes of the mean pupillary diameter per data window against time are shown graphically. An additional parameter referring to the pupil's tendency to instability, the pupillary unrest index (PUI), is defined by cumulative changes in pupil size based on mean values of consecutive data sequences. These mathematical procedures provide a high level of quality in both data collection and evaluation of IVP as an objective test of vigilance. In a pilot study, the pupillary behaviour of two groups were measured. One group rated themselves as alert (ten men), the other group as sleepy (12 men). The power and PUI were compared using the Mann-Whitney U-test. Both parameters show significant differences between the two groups.

Data Interpretation, Statistical↗
PubMed1998

[Pneumocysts juxta-articular to the ilial bone and the sacral bone].

PURPOSE: The purpose of the study was to detect and safely diagnose pneumatocysts by means of computed tomography. METHODS: From September 1995 to May 1996 computed tomography of the pelvis was performed in six patients for various indications. A slice thickness of 8 mm was employed for all studies. One patient had undergone surgery for hyperparathyroidism nine years previously. Attenuation values within the coincidentally diagnosed pneumatocysts were obtained. RESULTS: We found a total of 14 pneumatocysts juxtaarticular to the sacroiliac joint. Three patients demonstrated a bilateral intraarticular vacuum phenomenon, yet a joint communication was not found. The lesions did not coincide with inflammation, tumour or trauma. CONCLUSION: Pneumatocysts are benign bone lesions associated with arthrotic changes of the sacroiliac joint. Computed tomography is the modality of choice for the diagnosis of pneumatocysts.

Aged↗
PubMed1998

[Objective assessment of visual field defects using multifocal electroretinography].

BACKGROUND: Multifocal electroretinography allows simultaneous recording of 61 focal electroretinographic signals from the retina of the posterior pole. The function of the outer retinal layers can be mapped for a visual field of 30.5 degrees radius. We herein describe the topography of such potentials in patients with hemianopic and concentric visual field defects. SUBJECTS AND METHODS: Six patients with visual field defects caused by chorioretinal and central visual pathways diseases were examined using multifocal ERG. RESULTS: In 30 normal volunteers in the entire 30 degrees visual field clear signals were obtained. In the patients with visual field defects caused by retinal diseases in areas with reduced light sensitivity diminished electroretinographical activity was found. In contrast, in patients with bitemporal hemianopsia due to a chiasmal lesion no correlation between visual field and magnitude of focal ERGs was seen. CONCLUSIONS: In retinal disorders defects in multifocal ERG presented the similar pattern as scotomata in perimetry. The patient with visual field defects due to disturbances in the chiasma exhibited a normal ERG-topography. In patients with visual field defects multifocal ERG supported differentiation of the location of the lesion.

Adult↗
PubMed1998

[Optic neuropathy after erythema infectiosum].

BACKGROUND: Optic neuropathies can not always easily be classified as neuritis or ischemic disease. CASE REPORT: A 39 year old woman suffered from unilateral optic neuropathy 9 days after the acute onset of a general disease with erythema and joint swellings. The optic disc swelling and visual fields resembled an anterior ischemic optic neuropathy, however, a marked improvement was achieved by steroid treatment. The general disease proved to be erythema infectiosum. CONCLUSIONS: Erythema infectiosum as a frequent children's disease causes very rarely central nervous involvement, optic neuropathy has not been reported yet. In cases of atypical optic neuropathies search for an underlying systemic disease is of value.

Adult↗
PubMed1997

Source of cerebral microembolic signals in occlusion of the internal carotid artery.

BACKGROUND AND PURPOSE: There are several possible sources of cerebral embolic ischaemia distal to an occlusion of the internal carotid artery (ICA). Our aim was to identify the source of microembolic signals in the ipsilateral middle cerebral artery (MCA) by taking simultaneous bitemporal transcranial Doppler ultrasound recordings of the ipsilateral MCA and the contralateral ACA to find the route of potential microembolic material to MCA. SUBJECTS AND METHODS: The study group consisted of 38 patients with an occlusion of the ICA. With extracranial duplex sonography (ACUSON 128 XP; 7 MHz), performed by an experienced sonographer, the echo intensity and echo structure of the occluded ICA in the extracranial part (proximal) were classified as homogeneous or inhomogeneous. In addition, affected segments of the ipsilateral and contralateral carotid artery with arteriosclerotic vessel walls were compared. Microembolic signals were recorded with transcranial Doppler (TCD) monitoring. The microemboli counts in the MCA and ACA were added to the sum scores. RESULTS: The number of affected segments of the carotid artery on the ipsilateral (the bifurcation, the external or common carotid artery) and contralateral side of occluded ICA were equally distributed. In ipsilateral MCA 3.1, 7.1 microemboli (average mean, SD) with a range of between 0 and 34 were counted, in the contralateral ACA 0.3, 0.6 (range of between 0 and 2). Regression analysis confirmed the non-predictability of the microemboli variance on the ipsilateral side of the occlusion from the variance on the contralateral side (multiple r: 0.024). We found no significant correlation between the echo intensity or echo structure of the occluded artery and an increased rate of microemboli in the ipsilateral MCA. CONCLUSIONS: Our results indicate a predominantly ipsilateral source for cerebral microemboli in ICA occlusion. The rate of cerebral microembolic signals was not influenced by the echo structure and echo intensity of the occluded ICA.

Adult↗
PubMed1997

Side effects from increased doses of carbamazepine on neuropsychological and posturographic parameters of humans.

Patients taking anticonvulsant drugs display a broad spectrum of side-effects. Particularly, in the beginning of treatment and with increasing doses of carbamazepine, side effects such as dizziness, ataxia, drowsiness and reduction of alertness occur, which improve some days after the dose has reached a stable level. Our aim was to find objective parameters for grading these side effects and to differentiate between neurophysiological and neuropsychological side effects of carbamazepine in a clinical situation. Twenty-two patients with trigeminal neuralgia were included for a follow-up study with increasing carbamazepine doses (0 mg to 600 mg). The effect of carbamazepine on postural stability was quantified by posturography. Different neuropsychological tests to study cognitive effects of carbamazepine were performed. The composite equilibrium score showed a significant reduction of postural stability with increasing doses of carbamazepine. In sensory analysis the somatosensory ratio was significantly influenced by increased doses of carbamazepine during the study. Mean reaction time of tonic alertness and physical alertness varied significantly with different doses of carbamazepine. There was a significant influence in patients attention during trail making tests and divided attention tests with increase in carbamazepine. In conclusion our observations show that the rate of change of carbamazepine doses is an important determinant of cognitive and motor functions in the phase of increasing doses.

Adult↗
PubMed1997

[Relation between relative afferent pupillary defect and suprathreshold automated perimetry].

UNLABELLED: The purpose of this study was to test for correlation between relative afferent pupillary defect (RAPD) and visual acuity, central differential light threshold and visual field defect measured by suprasthreshold automated grid perimetry. METHODS: In 98 patients with optic neuropathies of different origin (inflammatory, ischemic, or compressive) in addition to a standard ophthalmological examination, static perimetry of the 30 degrees visual field with a dense grid of test spots, including measurement of the central differential light sensitivity, was done by means of the Tübingen Automated Perimeter. RAPD was tested using the swinging flashlight test quantified with neutral density filters. RESULTS: Visual acuity and central differential light sensitivity correlated only weakly with the RAPD. The visual field showed a better correlation (coeff. of corr. for all patients 0.58, for patients with optic neuritis 0.64. for patients with AION 0.53 and for patients with compressive neuropathies 0.84). One test spot not seen in perimetry corresponded to an RAPD of about 0.01 log-units. CONCLUSIONS: The results confirm those from previous studies obtained by threshold perimetry. The RAPD is a good parameter for the severity of an optic nerve lesion, especially of compressive origin.

Adult↗
PubMed1996

Ormond's disease or aortic aneurysm? Case reports.

This paper presents three case reports as a basis for discussing the differential diagnosis of retroperitoneal processes and for describing the possibilities and limitations of diagnostic imaging procedures. A definitive differentiation is not possible by CT and MRI alone, but always requires histologic confirmation. Nevertheless, imaging procedures are indispensable for assessing the extent of a lesion and for follow-up. On the basis of the cases presented here and reports in the literature, it can be hypothesized that benign retroperitoneal fibrosis is caused by a chronic inflammatory or autoimmune response of the vessels since the vast majority of cases are associated with pronounced wall abnormalities of the abdominal aorta.

Aged↗
PubMed1996

[Mobilization of intraocular foreign bodies by magnetic resonance tomography].

A 49-year-old patient suffered from a binocular perforating trauma with metal foreign bodies in 1974. During an MRI examination in 1992 for a lumbar spine herniation a metal foreign body was mobilised from the deeper vitreal and retinal area, now causing optical disturbances freely floating in the anterior vitreous. Refusing an operation, the patient, an electrical engineer, tried himself to remove the foreign body out of the optical axis by exposing his head to the electro-magnetic field of an induction coil (pulsed magnetic induction B at t0 of 0.26 Tesla). The foreign body was split into multiple small parts no longer disturbing the patient. To early detect a siderosis regular ophthalmological controls including ERG are necessary. This example stresses that even small intraocular metal foreign bodies are a contraindication for the usually applied field strength of MRI examinations.

Electromagnetic Fields↗
PubMed1996

Multi-layered perceptron as a model for the pupillary pathway.

Derived from models of neural networks, a model for the pupillary pathway is introduced that can easily be handled computationally and analytically. To model the binocular pupillary reactions we use a feed-forward network, namely, a multi-layered perception. It is possible to calculate the pupillary reactions analytically as a function of the light stimuli of the retinal hemifields, on the one hand, and the set of neural couplings between the neural layers, on the other. Several lesions, e.g., lesions of the intercalated neurons between the afferent and efferent pupillary pathways, can be simulated within the model and the corresponding pupillary reactions such as anisocoria or relative afferent pupillary defects (RAPD) can be calculated analytically. Due to its neural network structure the model described herein can easily be extended to much more complex pupillary pathways while remaining calculable computationally and analytically.

Humans↗
PubMed1996

Interaction of the indirectly acting topical sympathomimetics cocaine and pholedrine.

In suspected Horner's syndrome, cocaine eye drops are applied to verify the diagnosis. Subsequent application of hydroxyamphetamine or pholedrine eye drops allows localization of the site of the interruption in the oculosympathetic pathway. In the present study the influence of cocaine on subsequent pholedrine testing was examined. Cocaine 5% and pholedrine 5% eye drops were applied to eight (72-h interval only six) normal volunteers with light-colored irides. The ages of the subjects ranged from 23 to 40 years. Eye drops were applied to the same eye at varying intervals of up to 72 h, with the cocaine being given between 8:30 and 9:30 a.m. Pupil diameters were recorded by means of a frame-grabber card in a personal computer and were subsequently measured before and at 50-60 min after each drug application in 1.7 cd/m2 ambient light. In the absence of pretreatment with cocaine, pholedrine changed the mean pupil diameter from 6.89 to 8.57 mm. At 12 h after cocaine pretreatment the pupil remained dilated. Pholedrine dilated the pupil further, from 7.69 to 8.61 mm. When cocaine was given 24 h before pholedrine, the pupil dilated from 6.75 to 8.25 mm; at 48 h after cocaine application, pholedrine dilated the pupil from 6.14 to 8.20 mm; and at 72 h after cocaine pretreatment, pholedrine dilated the pupil from 5.74 to 8.00 mm. As compared with the mean diameter of the untreated contralateral pupil, the pholedrine-induced dilation amounted to 2.32 mm in the absence of cocaine pretreatment, 1.04 mm at 12 h after cocaine application, 1.29 mm at 24 h after cocaine administration, 1.89 mm at 48 h after cocaine pretreatment, and 2.18 mm at 72 h after cocaine application. The residual cocaine effect interfered with the mean pupil dilation produced by pholedrin for at least 48 h. To ensure that the sensitivity of the pholedrine test is maximal, the examiner should delay its use for more than 48 h after the cocaine test.

Administration, Topical↗
PubMed1996

[The pupil and retrogeniculate visual pathway. Overview].

Classically, the pathway serving the pupillary light reflex is considered to be a simple reflex arc consisting of the retinal ganglion cells, intercalated neurons in the midbrain, the oculomotor nerve and short ciliary nerves. Investigations in patients with lesions of the postgeniculate visual pathways showed that the pupillary pathway is more complex than previously assumed. The retrogeniculate visual pathway is also involved in the pupillary light reaction.

Animals↗
PubMed1996

[Pupillography for objective vigilance assessment. Methodological problems and possible solutions].

To measure vigilance disorders in healthy normals or in patients (narcolepsy, sleep apnea syndrome) is difficult, time-consuming and hardly objective with present methods. Recording and analysis of spontaneous pupillary behaviour in darkness by infrared video pupillography is an objective and time-saving method to measure daytime sleepiness. However, certain external conditions must be satisfied (avoid light, noise, stress) to get reliable results. Spontaneous pupillary oscillations are recorded in darkness over 10 min and data are analyzed by fast Fourier transformation, with additional calculation of the mean pupillary diameter for each time segment (approx. 1 min). While in the alert normal, pupil remains dilated during the measurement in darkness and oscillates with an amplitude below 0.3 mm and a frequency about 1 Hz, there are characteristic changes in fatigue: (1) low-frequency components dominate the spontaneous pupillary oscillations, with an amplitude reaching several millimeters, and (2) pupil diameter decreases with time. Infrared video pupillography could play a role as a screening method and therapy control for hypersonic patients (most frequent: sleep apnea syndrome) with excessive daytime sleepiness. An objective, time-saving method like infrared video pupillography would be useful in sleep medicine and psychiatry when testing the level of vigilance, and in psychology or industrial medicine as well, providing informations about acute vigilance problems in healthy normals.

Adult↗
PubMed1996

[Pupillography as an objective attention test].

Infrared video pupillography (IVP) allows continuous recording of spontaneous pupillary oscillations in darkness which change characteristically with fatigue. Pupil size in darkness is age-related, has its maximum in the second decade and subsequently decreases during life time. Normally, the pupil oscillates in darkness with a frequency of about 1 Hz and amplitudes of less than 0.3 mm. Excessive daytime sleepiness causes instability of this pupillary behaviour which is constant in alert normals, and so called fatigue waves appear with an amplitude reaching several millimeters. The frequency profile is dominated by slow frequencies below 0.5 Hz, while average pupil size decreases continuously with time. As IVP is an objective and time-saving method it could become an important supplement to test procedures used in sleep medicine and sleep research to measure daytime sleepiness.

Adult↗