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Biomedical subjects

H Walser

Publications and source records attributed to H Walser.

17 recordsLinked to original sources
PubMed1989

[Neurological gait changes in old age: basic principles, senile gait].

Gait abnormalities and falls often occur in the elderly, and it is often difficult for the practitioner to distinguish between a specific disease causing disordered gait and gradual changes due to "normal" involution. Based on the biomechanics and the neural control mechanisms of normal adult gait, characteristics of the "senile gait" are described. The senile gait abnormality is regarded as a clinical entity ascribed to age alone and its many cerebellar, extrapyramidal and cerebrofrontal changes, all of which may give rise to disordered central programming of upright stance and gait. The need for a careful evaluation of the elderly patient's station and gait is stressed.

Aged↗
PubMed1989

Effects of the benzodiazepine receptor antagonist flumazenil in hepatic encephalopathy in humans.

If increased gamma-aminobutyric acid (GABA)-mediated neurotransmission contributes to the mediation of hepatic encephalopathy, it may be possible to induce ameliorations of the syndrome by pharmacologically antagonizing a component of the GABA/benzodiazepine receptor complex. To test this possibility we administered the benzodiazepine receptor antagonist flumazenil by intravenous injection to 14 patients with hepatic encephalopathy complicating cirrhosis. Flumazenil administration induced variable and transient, but distinct, improvements of the mental status in 71% of the patients. The degree of encephalopathy improved from stage IV to stage II in 4 patients and from stage IV to stage III in 2 patients. The mental status of all patients with less advanced encephalopathy (3 with stage III, 1 with stage II) also improved, but these responses were clinically less impressive. The arousal effect occurred within minutes after the injection and lasted for 1 to 2 h. Furthermore, it was associated with a significant increase of the mean electroencephalographic frequency from 4.2 to 5.2 cycle/s. Of the 8 patients who were ultimately discharged from the hospital, 7 had responded to flumazenil. No patient who died within 48 h of receiving flumazenil had shown any arousal effect. These findings strongly favor a prominent pathogenetic role of increased GABAergic tone in hepatic encephalopathy in humans and suggest that a positive response to flumazenil might be of prognostic value in predicting short-term survival in encephalopathic patients with liver disease.

Adult↗
PubMed1986

Somatosensory evoked potentials in comatose patients: correlation with outcome and neuropathological findings.

Subcortical and early cortical somatosensory evoked potentials (SEPs) were recorded in 63 comatose patients and classified into five salient SEP grades, which were defined as follows: grade 1, normal SEP; grade 2, SEPs with a clearly recognizable scalp component N20, normal central conduction time but clearly distorted wave N20-P25; grade 3, SEPs with a still recognizable N20 but delayed central conduction time and severely altered wave N20-P25; grade 4, SEPs with absence of N20 but with a more or less recognizable P15; grade 5, SEPs with absence of both N20 and P15. When these five patterns were compared with outcome, it was found that bilaterally normal SEPs or only unilaterally distorted SEPs were generally followed by good outcomes. Bilaterally altered SEPs (grade 2 or 3) were indicative of reduced chances of full recovery. The great majority of patients showing either grade 4 or 5 SEPs died within a few days after the recording session. In 31 patients, it was found post mortem that grade-2 SEPs reflected cortical brain damage, whereas grade-3 SEPs correlated well with subcortical lesions. In post-traumatic patients, this SEP pattern corresponded to diffuse subcortical shearing lesions. Patients with grade 4 or 5 SEPs were found to have severe brain oedema giving rise to transtentorial herniation, which was combined with secondary midbrain haemorrhage and tonsillar herniation in all patients with bilateral grade-5 SEPs.

Adolescent↗
PubMed1986

[Automatic quantification of SEP for continuous patient monitoring].

Parameters presently used to analyse evoked potentials such as amplitude and latency are based on well defined single components, the recognition of which may become arbitrary in severely altered responses. Furthermore, they ignore changes also present in the remainder of an evoked potential wave form. Hence, they are ill suited for monitoring comatose patients or patients during high risk surgery. Alternatively, crosscorrelation analysis may be employed yielding two parameters by comparing the SEP of the patient with a reference response: R, the correlation coefficient, a numerical measure of similarity of the two responses in terms of overall configuration and tau, indicating the time displacement of the main common components of the two signals. A "grand average" evoked potential (SEP) composed of the responses of age and sex matched healthy subjects or in perioperative monitoring the patient's own preoperative response might be used as a reference. By help of continuous averaging of the SEP these two parameters may be determined in real time allowing a more dynamic way of monitoring than by sequential averaging individual responses.

Adult↗
PubMed1985

Early cortical median nerve somatosensory evoked potentials. Prognostic value in anoxic coma.

Subcortical and early cortical median nerve somatosensory evoked potentials (SEPs) were examined in 26 patients in hypoxic coma. The amplitude ratio between the negative slope of the scalp response and the following positive trough was determined. The latency difference between the major negative component recorded from the upper neck, N14, and the initial negative potential from the scalp, N20, was also measured. The mean of these parameters in both hemispheres was referred to as mean central conduction time (MCCT) and mean amplitude ratio (MAR). There was a significant difference in MAR in patients with a bilaterally recordable scalp response between those with a good and those with a bad outcome, but no difference in MCCT. Comparison of SEP findings with postmortem examinations suggests that a reduced MAR may yield an estimate of cortical damage in hypoxic coma.

Adult↗
PubMed1985

Non-convulsive status epilepticus after abrupt withdrawal of hypnotic-sedative drugs.

Four patients with severe addiction to sedative-hypnotics and with acute withdrawal symptoms of these drugs are described. They developed latent confusional states with characteristic EEG patterns (bilateral slow and sharp waves of high amplitude). Following small doses of benzodiazepines the EEG became normal together with a reduction in the clinical symptoms. It is suggested that the confusional states were of an epileptic nature.

Adult↗
PubMed1984

[Basilar migraine].

Basilar migraine is a well defined condition which is easily identified by a characteristic clinical picture such as headache associated with visual, cerebellar and brainstem symptoms. Occasionally, severe disturbances of consciousness may occur which blur this otherwise unequivocal clinical condition. Hence, diagnosis may be difficult. CT-scan, electroencephalography and lumbar puncture are then necessary in order to rule out more severe disorders. Treatment of this condition corresponds to the therapy of more common types of migraine. There is, however, no rationale for the administration of drugs conventionally used for migraine prophylaxis in patients with severe disturbances of consciousness, though treatment of brain edema with steroids may be helpful or occasionally even necessary.

Adolescent↗
PubMed1983

[Evaluation of coma using evoked brain potentials].

Subcortical sensory evoked potentials are of growing importance in assessing brain damage in comatose patients. First, they are not susceptible to sedative and narcotic drugs; second, the investigation can easily be performed in the intensive care unit; and third, off-line results are immediately available. Subcortical somatosensory evoked potentials (SEP) proved to be more reliable in assessing brain function than brainstem auditory evoked potentials (BAEP). Our own experience with this method is illustrated by several case reports.

Adult↗
PubMed1983

[Prognosis of severe craniocerebral trauma using neurophysiologic parameters].

40 patients in acute posttraumatic coma were assessed with help of 3 electrophysiological methods: short latency somatosensory evoked potentials (SEPs), brainstem auditory evoked potentials (BAEPs) and EEG, the results of which were compared with clinical outcome 3 months after the head injury (Fisher's exact probability test). SEPs proved to be the most reliable method for prognostic evaluation of these patients (p less than 0.001), followed by the EEG (p less than 0.002), the prognostic relevance of which, however, is limited by the use of narcotic drugs (barbiturates). BAEPs are less useful for the evaluation of these patients (p less than 0.01), which may be due to traumatic lesions of the cochlea, or even more often, to blood clots in the external ear canal, leading to conducting hearing loss. Conversely, the short axons of the auditory structures of the brainstem appear to be less susceptible to shearing forces of the primary mechanical impact, than the comparatively widely extended thalamocortical connections of the afferent somatosensory system.

Adolescent↗
PubMed1982

Auditory brain stem responses in patients with posterior fossa tumors.

Twenty patients suffering from space-occupying lesions of the posterior fossa were investigated with the help of brain stem auditory evoked potentials. The results were compared with the findings of computerized tomography (CT) and with the operative findings. In large cerebellopontine angle tumors, there was severe attenuation of all components ipsilateral to the lesion, which may or may not include wave I. In patients with intrinsic pontine tumors, severe degradation of the components subsequent to wave III was found. In cerebellar tumors, caudal distortion of the brain stem seems to cause an increase of the interpeak separation of III-V, whereas rostral compression did not alter the responses. No consistent pattern appears to be recorded in extrinsic brain stem tumors. In only 2 of 8 patients in whom postoperative observations were made did the postoperative responses parallel the overall clinical course of the early postoperative period.

Adolescent↗
PubMed1981

[Prognostic value of EEG in acute posttraumatic coma (author's transl)].

To evaluate the prognostic power of a single EEG-record, the recordings of 50 patients with posttraumatic coma performed within 48 hours after the injury were compared with the outcome after 6 months. A 5-point scale comprising 2 EEG-patterns being notorious for their dismal prognostic significance (suppression bursts, alpha-coma) and changes of vigilance were used as a mean of visual assessment of the recordings. In 24 out of the 28 patients with a bad outcome, the EEG had shown the patterns of category I, II and III (suppression bursts, alpha coma, no changes of vigilance). Of the 22 patients with a good outcome, the EEG had been classified as IV or V (clearly discernible changes of vigilance, sleep patterns). Further findings of particular dismal prognostic significance were focal epileptic discharges, as 9 out of the 11 patients with this EEG pattern had not survived the posttraumatic coma for more than 6 months.

Adolescent↗
PubMed1979

[Recurring loss of conciousness with middle brain symptoms in migraine].

A 49-year-old woman subject to frequent migraine attacks since childhood was seen for repeated episodes of confusion followed by loss of consciousness lasting for several hours. EEG during the acute stages showed marked slowing with bifrontal monorhythmic delta waves. After each episode, both the clinical and EEG findings subsided within hours. A similar course is described in a man who died at the age of 69 after preterminal mental deterioration. Autopsy showed evidence of bilateral damage to the hippocampal regions, apparently due to frequent impairment of perfusion in the last years of life. Atherosclerotic changes were within the normal range for his age. In both cases, the ischemic episodes are interpreted as consequences of constriction of the basilar artery, and it is assumed that the underlying mechanism is at least akin to that of migraine.

Aged↗