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Biomedical subjects

A H Lang

Publications and source records attributed to A H Lang.

At least 19 recordsLinked to original sources
PubMed1990

Transient asymmetries of steady-state visual evoked potentials in classic migraine.

Unilateral abnormalities in the regional cerebral blood flow (rCBF) and visual evoked potentials (VEPs) during the visual aura of classic migraine have been reported. On the other hand, there are only few observations suggesting unilateral abnormality of neural function during the headache-free period. An experiment is described in which the symmetries of steady state VEPs (SVEPs) are compared in healthy subjects and classic migraineurs in the headache-free interval. In the patients an increased number of strong short-lasting interhemispheric asymmetries was found. In the serial recordings performed, pathologic recordings were obtained intermittently, usually with complete normalisation in the following session. The incidence of abnormalities was relatively independent of the interval between the recording and attack, except for the next few hours. The findings may be related to instability of occipital cortical function in classic migraine.

Adult↗
PubMed1989

Difference of steady-state visual evoked potentials in classic and common migraine.

The present study was designed to find evidence for the neural hypothesis of migraine and to evaluate possible interictal differences in the two varieties of migraine by electrophysiological means. Steady-state visual evoked potentials (SVEPs) in response to sinusoidally modulated light were measured in 20 patients with classic migraine and compared with those of 30 common migraineurs and 49 reference subjects. SVEPs to stimuli at 10-24 Hz were recorded occipitally from a pair of midline electrodes and, in classic migraineurs and controls, additionally from left and right occipital areas. The response was processed by the Fast Fourier Transform and automatically analysed. The fundamental component of the midline response to medium frequency stimuli (16-22 Hz) appeared normal in patients with classic migraine, contrary to an augmented response in common migraineurs (ANOVA between groups, P = 0.006). In classic migraine the 2nd harmonic component was attenuated (P less than 0.01 at 18-20 Hz) and the amount of strong interhemispheric f1 asymmetries was increased in about half of the patients. The groups also diverged significantly in the SVEP dynamics during stimulation. The results support the hypothesis of a primary neural disorder in both types of migraine. Different sites and mechanisms of brain dysfunction in classic and common migraine are suggested. Hypothetical neuroanatomical correlates for the abnormalities are presented.

Adult↗
PubMed1985

[Pump-guided continuous subcutaneous opiate infusion for the treatment of the most severe pain].

The continuous subcutaneous infusion of opiate, a new approach to the alleviation of severe chronic pain, has been carried out using a pump system normally employed for the infusion of insulin. Relapses of pain can be controlled with bolus doses. This mode of application was compared with conventional therapy in 11 patients. All patients were free of pain during the continuous infusion, but none showed a satisfactory response during conventional treatment. The improved response under continuous opiate infusion was attained with much lower doses and thus with fewer side effects. The procedure is therefore highly effective and well tolerated.

Adult↗
PubMed1984

Steady-state visual evoked potentials during migraine prophylaxis by propranolol and femoxetine.

The amplitude of visual evoked potentials (VEPs) for flickering light has been reported to be increased in migraine. In the present study, we have examined whether the VEPs are attenuated when the clinical state of the patient improves during a double-blind experiment with propranolol and femoxetine. VEPs for sinusoidally-modulated light were measured by spectral analysis, and an index depicting the visual reaction type was calculated. The group mean VEP index closely followed the group mean attack frequency, but individual variance was considerable. The changes were most evident in VEPs elicited by stimuli of about 20 Hz. During the treatments, the VEP and headache were also significantly correlated among subjects. The results suggest a close relationship between the enlarged VEPs and the headache mechanisms.

Adult↗
PubMed1983

Acute effects of intravenously given alcohol on saccadic eye movements and subjective evaluations of intoxication.

Effects of intravenously given alcohol on eye movements were analysed in ten voluntary subjects. Each subject served as his/her own control. Good correlations were found between the changes in saccade variables and subjective evaluations of alertness, eye movement control and intoxication. Interindividually, the subjective evaluation of drunkenness correlates with the alcohol effect on saccade variables better than do the other subjective variables or blood or breath alcohol concentrations. A steady decrease of mean and maximum velocity and a steady increase in the duration of saccades was observed during the alcohol infusion. The latency of saccades also increased. There was, however, a slight decrease of latency due to alcohol 15 min after the start of infusion, suggesting a biphasic effect of alcohol on saccade latency.

Alcoholic Intoxication↗
PubMed1983

Vestibular neuronitis; a neurological and neurophysiological evaluation.

Neurological and neurophysiological findings were retrospectively reviewed in a group of 50 patients with vestibular neuronitis (VN). The onsets of VN were found to be clustered in the period from August to January. A preceding infection was reported by 36% of the patients. Neurological examinations did not reveal any other relevant signs than a spontaneous nystagmus during the acute phase. The results of routine laboratory tests and cerebrospinal fluid tests were within normal limits. EEG was recorded in 37 patients; 15 patients had a definitely abnormal EEG, with a slowing of the dominant occipital rhythm or more generalized diffuse slowing in 12 cases. 5 patients, 3 of them without slowing of the background activity, had a distinct focal disturbance of intermittent slow activity in the temporal region. In control recordings, an improvement was seen in the slowing of the background activity but not in the focal disturbances. Brainstem auditory evoked responses (BSER) were recorded in 12 patients, 5 of whom had abnormal responses. The seasonal clustering of VN onsets and the association of VN with overt infections further suggest its infectious pathogenesis. The observed EEG and BSER disturbances suggest a subclinical brainstem involvement in some cases of VN.

Adolescent↗
PubMed1983

Asymmetric function of peripheral nerves in children with cerebral palsy.

Nerve conduction velocities (NCVs) in both motor and sensory nerves as well as nerve action potentials (NAPs) of sensory nerves were measured bilaterally in 24 children with cerebral palsy. The NAP amplitude and both sensory and motor NCV were on the average higher on the intact or less affected side. The NCV side difference was still present after the temperature asymmetry of the limbs had been taken into account by calculating the temperature-corrected NCV values, and was statistically significant for motor NCV in N. peroneus and for sensory NCV in N. suralis; this could neither be explained on the basis of spasticity nor by the length difference of the extremities. No correlation of NCV asymmetry with the degree of atrophy seemed to exist.

Action Potentials↗
PubMed1983

Femoxetine - a new 5-HT uptake inhibitor - and propranolol in the prophylactic treatment of migraine.

The prophylactic effect of a 5-HT uptake inhibitor, femoxetine, was compared with that of propranolol in a double-blind crossover study of 6-months duration. 29 patients commenced the experiment. 3 subjects withdrew because of side effects and 2 because the program was inconvenient for them. In the 24 patients who continued the study to the end, the periods of propranolol (administered 160 mg daily) and of femoxetine (given 400 mg daily) differed significantly from each other with respect to the attack frequency and headache index. A significant reduction in the use of medication relieving attacks was observed during the propranolol treatment as compared with the pre-treatment period. The study showed that partial depletion of thrombocyte 5-HT uptake inhibitor did not lead to a marked improvement in headache, contrary to what might be expected on the grounds of the 5-HT hypothesis of migraine.

Adult↗
PubMed1982

Spectral analysis of visual potentials evoked by sine wave modulated light in migraine.

Visual evoked potentials to unstructured sine wave-modulated light were measured in 30 common migraine patients and 23 controls. The fundamental and the second harmonic components of the response were analysed separately in the frequency domain by power spectrum estimation. The absolute and relative powers of the fundamental component were significantly larger in the patients at 16-22 Hz stimulation both initially, in the onset phase, and later, in the steady-state phase, whereas those of the 2nd harmonic component were smaller in the later stages of stimulation. Significant difference occurred in the dynamics of the 2nd harmonic response between patients and controls. No significant difference was observed at 10 Hz stimulation.

Adult↗
PubMed1981

Dual influence of temperature on compound nerve action potential.

Compound neural action potentials (NAPs) were recorded from N. suralis and the digital nerves of N. medianus in man using the antidromic technique. The nerves were cooled either at the site of the recording ("local cooling") avoiding temperature change proximally, or between the stimulating and recording electrodes ("segmental cooling") avoiding temperature change at the recording site. Local cooling was followed by a pronounced increase in NAP amplitude and rise time without any change in the onset latency. The values of Q10 were identical for both amplitude and rise time changes. Segmental cooling caused a definite fall in the amplitude of NAP and a slight increase in its rise time. The practical consequences of the dual temperature effect on NAP are discussed.

Action Potentials↗
PubMed1981

Sensory neuropathy in rheumatoid arthritis: an electroneurographic study.

In a selected series of twenty-three RA patients, aged from 23 to 56 years, mean 41, the neurophysiological functions of six sensory nerves were measured and the results were correlated with clinical and laboratory data. Significant changes in the functions of one or more nerves were found in 10 patients, 2 of whom had no symptoms of clinical neuropathy. There was a highly significant correlation between neurophysiological symptoms and clinical neuropathy symptoms, although the combination of the clinical and electrophysiological findings was variable. On the other hand, there was no significant correlation between neurophysiological/neurological findings and clinical/laboratory data (age, sex, duration of disease, stage of disease, rheumatoid factor and erythrocyte sedimentation rate). Manifest or sub-clinical mono-neuropathies in n. medianus were found in 5 patients. In the light of these results it would seem in order to recommend the inclusion of an electro-neurophysiological examination of the medianus nerves of RA patients in routine diagnostic procedures.

Adult↗
PubMed1980

A two-channel method for sampling, averaging and quantifying motor unit potentials.

A method is described for sampling and averaging individual motor unit potentials (MUPs), which is based on an averaging technique using a special EMG electrode. The needle has two separate electrode surfaces, a conventional coaxial electrode at the tip and a single-fiber electrode opposite the bevel of the tip. With this method it is possible to extract individual MUPs even from interference activity during a moderate or even high muscular effort. The averaging of MPUs gives a good signal-to-noise ratio, which makes the quantification of MPUs precise. Late components are easily identified. Additionally during the collection of MPUs information of single-fiber characteristics (jitter, blocking and fiber density) is also acquired.

Electrodes↗
PubMed1979

Acute effects of alcohol on saccadic eye movements.

Four components of 20 degrees horizontal saccadic eye movements, i.e., latency, mean and maximum velocities, and duration were measured in 16 students under the influence of alcohol and also in a control situation. The experimental procedures were standardized and automated as much as possible. Latency (simple eye reaction time) was not influenced by alcohol in blood concentrations of 0.056--0.116%. Mean and maximum eye velocities decreased by about 9% and duration of saccades increased by 11%. The maximum changes occurred 90--120 min after the start of alcohol ingestion. The changes in velocities and durations correlated more closely with feelings of intoxication than with blood alcohol concentrations. There were great intra- and intersubject variations in reactions to alcohol. The close resemblance between the effects of certain psychotropic drugs, alcohol, fatigue, and decreased attention on eye movement control suggest that all these may act upon the same nervous structures in the brain stem.

Alcoholic Intoxication↗