PubMed Health⌕ Search

Biomedical subjects

M J Aminoff

Publications and source records attributed to M J Aminoff.

At least 19 recordsLinked to original sources
PubMed1992

The basis and functional role of the late EMG activity in human forearm muscles following wrist displacement.

The present paper examines the hypothesis that the long latency EMG activity produced by muscle stretch is the result of long loop reflex pathways involved in the control of limb stiffness. We recorded the cerebral responses and late EMG activity in agonist and antagonist muscles following sudden stretch of the wrist extensor muscles under 4 experimental conditions in 11 subjects. In each experiment subjects held their right wrist extended isometrically against a constant force of 2.3 N and a trial was begun with a step increase in the force from 2.3 N to 18.4 N, to stretch the extensor muscle. In the first and second experiments the force change occurred unpredictably and subjects had to either oppose the perturbation (Unpredictable Oppose) or relax the forearm muscles once the increase in force was detected (Unpredictable Let-Go). In the third and fourth experiments the force change occurred predictably when subjects pressed a thumb switch with the left hand to cause it. As before, subjects were instructed to either oppose the perturbation (Predictable Oppose) or relax the forearm muscles (Predictable Let-Go). Responses were recorded from the flexor and extensor carpi radialis muscles and from the scalp. When the perturbing force occurred unpredictably, early latency EMG activity (the MI response) was seen in the stretched extensor muscle, and longer latency EMG activity was seen simultaneously in both extensor and flexor muscles. When the force change occurred predictably the late EMG activity was considerably attenuated, especially in the Predictable Let-Go condition. Cerebral responses similarly depended upon the predictability of the perturbation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Treatment of hemifacial spasm with botulinum toxin.

The effectiveness of botulinum toxin injections in 11 patients with hemifacial spasm was investigated in a prospective placebo-controlled blinded study. The patients were treated with four sets of injections to various facial muscles, selected by clinical evaluation. Three injections were with graded doses of toxin and one was with placebo. The order of injections was random and unknown to the patients. Results were scored both subjectively by patient assessment of symptoms and objectively by blinded review of videotapes made one month after each injection. Subjective improvement occurred after 79% of injections with botulinum toxin, regardless of dose of toxin. Only 1 patient improved after placebo. Objective improvement was seen after 84% of injections with botulinum toxin. No patient showed objective improvement after placebo injection. The most frequent side effect was facial weakness, seen after 97% of injections of botulinum toxin. Facial bruising (20%), diplopia (13%), ptosis (7%), and various other mild side effects were seen less frequently. Botulinum toxin appears to be an effective and safe method of therapy for hemifacial spasm.

Botulinum Toxins↗
PubMed1992

Effect of different high-pass filters on the long-latency event-related auditory evoked potentials in normal human subjects and individuals infected with the human immunodeficiency virus.

The effect of different high-pass filters on long-latency auditory evoked potentials was investigated in 25 subjects, 15 of whom were asymptomatic individuals seropositive for the human immunodeficiency virus (HIV) and 10 of whom were normal control subjects without known risk factors for HIV infection. High-pass filtering was done simultaneously at 0.25 Hz and 1.0 Hz, and cerebral responses to rare (2,000 Hz) and frequent (1,000 Hz) tones were recorded from Fpz, Cz, and Pz electrode placements and averaged separately. Using either filter, well-formed and reproducible responses were obtained, although the latencies of the N1, P2, N2, and P3 components of the response were slightly shorter when a 1.0 Hz filter was used. In addition, the appearance of the late response was modified in a manner suggesting that components of the ERP considerably slower than P3 were being attenuated by a 1.0-Hz filter. Although it could be argued that this makes the use of a 1.0-Hz filter setting preferable in the clinical setting, the variability and reproducibility of the ERP were comparable when either high-pass filter was used, and both resulted in similar findings in the HIV-infected individuals compared to normals.

Adult↗
PubMed1992

Evaluation of dementia by event-related potentials.

Event-related potentials depend on the context of the target stimulus and relate to the cognitive aspects of discriminating target from nontarget stimuli. For clinical purposes, they are elicited most commonly by auditory stimuli. They are influenced by advancing age and by alterations in mental function. They have been used to distinguish dementia from pseudodementia. More specifically, the P3 component of these potentials has a high sensitivity and specificity to dementia, and a prolongation in P3 latency is therefore helpful in establishing the diagnosis of dementia with confidence. Serial studies can provide a means of following changes in cognitive function over time. It may also be possible to distinguish between different types of dementia by the pattern of electrophysiologic abnormalities and in particular by which components of the event-related potentials are delayed.

Brain↗
PubMed1992

Clinical and EEG features of status epilepticus in comatose patients.

We retrospectively evaluated the clinical and EEG features of status epilepticus (SE) in 47 comatose adult patients in whom SE was suspected clinically or because the EEG revealed repetitive electrographic seizures or continuous spike-and-wave activity. Three groups of patients were identified. Group-1 patients (n = 33) had SE both clinically and on EEG. They usually had subtle, clonic movements restricted to the eyes, face, and upper extremities, and the EEG most commonly showed repetitive electrographic seizures or continuous spike-and-wave activity. Group-2 patients (n = 9) also had subtle motor manifestations of seizures, but the EEG was not that of SE, consisting of either irregular slowing with frequent spikes and sharp waves, an irregular mixed-frequency background with episodic accentuation, or diffuse slowing; one patient also had an intermittent burst-suppression pattern. The five patients in Group 3 lacked any clinical signs of seizures, but the EEG showed repetitive electrographic seizures or continuous spike-and-wave activity. There were no significant differences between groups in etiology of SE, response to therapy, or outcome, and there was no obvious relationship between the EEG findings and duration of SE. We conclude that recognition of SE in comatose patients may require both clinical and EEG evaluation since either approach by itself may fail to establish the diagnosis. Furthermore, the EEG findings in established SE do not necessarily progress through the series of defined stages suggested by some authors.

Adolescent↗
PubMed1992

Botulinum toxin therapy for limb dystonias.

We investigated the effectiveness of botulinum toxin in 17 patients with limb dystonias (10 with occupational cramps, three with idiopathic dystonia unrelated to activity, and two each with post-stroke and parkinsonian dystonia) in a placebo-controlled, blinded study. We identified affected muscles clinically and by recording the EMG from implanted wire electrodes at rest and during performance of tasks that precipitated abnormal postures. There were three injections given with graded doses of toxin (average doses, 5 to 10, 10 to 20, and 20 to 40 units per muscle) and one with placebo, in random order. Subjective improvement occurred after 53% of injections of botulinum toxin, and this was substantial in 24%. Only one patient (7%) improved after placebo injection. Subjective improvement occurred in 82% of patients with at least one dose of toxin, lasting for 1 to 4 months. Response rates were similar between clinical groups. Objective evaluation failed to demonstrate significant improvement following treatment with toxin compared with placebo. The major side effect was transient focal weakness after 53% of injections of toxin.

Adult↗
PubMed1992

Autonomic dysfunction in central nervous system disorders.

Dysautonomic symptoms are associated with many disorders of the central nervous system, in some of which the autonomic dysfunction is particularly conspicuous or the major cause of disability. New neuroimaging procedures and microneurographic techniques have helped to clarify the underlying pathophysiology and to distinguish or, classify disorders that are clinically similar. Recent studies also suggest that the autonomic nervous system is involved more frequently or extensively than previously thought in certain neurological conditions such as multiple sclerosis or human immunodeficiency virus (HIV) infection, and have helped to define the nature of its involvement in other disorders.

Autonomic Nervous System↗
PubMed1991

The nature of suprasegmental influences on the late reflex activity in human forearm muscles.

The earliest component of the late EMG response (M2) to sudden stretch of an isometrically contracting muscle is influenced by suprasegmental mechanism, but whether these are tonic, phasic, or both, is uncertain. We have therefore investigated the nature of these mechanisms by varying the predictability of the direction of perturbation of forearm muscles held isometrically against a constant flexor or extensor force of 2.3 N. We found that the M2 response did not change appreciably regardless of whether the direction of perturbation was known in advance or which hand was used by the subject. These findings suggest that any tonic supraspinal influence of the M2 response is of little significance compared to the importance of phasic mechanisms and provide support for the existence of a cerebral arc subserving this reflex component.

Adult↗
PubMed1991

Change in pattern of muscle activity following botulinum toxin injections for torticollis.

Twenty patients with torticollis had electromyographic studies of their neck muscles performed before and after a series of local injections of botulinum toxin. The pattern of muscle activity changed after the injections, and this effect persisted even after head position had returned to baseline. Patients who did not experience any clinical benefit from the injections also demonstrated a change in the pattern of muscle activity. These results suggest that the underlying abnormality in torticollis usually involves a general motor program for head position, rather than the activity of individual neck muscles.

Adult↗
PubMed1991

Clinical and electrodiagnostic features of X-linked recessive bulbospinal neuronopathy.

We describe four men from two kinships affected with X-linked recessive bulbospinal neuronopathy, and one sporadic case. All developed postural tremor, weakness, and fasciculations, with onset from age 25 to 39 years. Weakness began in the pelvic girdle or hands, with dysphagia or dysarthria occurring years later in two. Sensory symptoms were present in only one, who also had diabetes mellitus. In contrast, sural nerve action potentials were small or absent in all. Needle EMG showed widespread chronic partial denervation with reinnervation. The characteristic twitching of the chin produced by pursing of the lips consisted of repetitive or grouped motor unit discharges, rather than fasciculations. Broader awareness of the distinctive features of bulbospinal neuronopathy will probably increase the frequency of its recognition. Diagnosis is important for purposes of providing a prognosis for affected men and genetic counseling for affected families.

Action Potentials↗
PubMed1991

Segmentally specific somatosensory evoked potentials.

The recording of segmentally specific somatosensory evoked potentials (SEPs) is time-consuming and the findings have generally been clinically unhelpful. This article critically evaluates the role of these SEPs in patients with disorders of the spinal cord or nerve roots.

Electric Stimulation↗
PubMed1990

Detection of epileptiform activity by different noninvasive EEG methods in complex partial epilepsy.

The diagnostic utility of different noninvasive electrode placements for deriving the electroencephalogram and detecting interictal epileptiform discharges was compared. Anterior temporal and nasopharyngeal electrodes in combination with routine scalp electrodes detected over 97% of the spikes, whereas recording from only standard electrode placements detected 58%. Minisphenoidal and surface sphenoidal electrodes were generally not helpful. In some circumstances, however, the use of surface sphenoidal electrodes provided important confirmatory information. In no case did the minisphenoidal electrodes provide unique information, and their use seems unjustified, although the inclusion of other nonstandard electrodes in the recording montage is important to increase the yield.

Adolescent↗
PubMed1990

Long latency event-related potentials in patients infected with human immunodeficiency virus.

Long latency auditory evoked potentials were recorded in 55 homosexual men infected with human immunodeficiency virus (HIV). Forty-one of these patients were asymptomatic from the infection and 14 had clinical signs of illness. Nine of the symptomatic patients were demented and 8 (6 of whom were demented) met other diagnostic criteria for acquired immunodeficiency syndrome (AIDS). Cerebral responses were recorded from Fz, Cz, and Pz electrode placements referred to linked mastoids and averaged separately to rare (2,000 Hz) and frequent (1,000 Hz) tones presented in a pseudorandom sequence. Electroencephalography (EEG) was performed in 54 of the patients and magnetic resonance imaging (MRI) or computed tomography (CT) was done in 14 (13 of whom were symptomatic from the infection). The latency of N1, P2, N2, and P3 components was delayed in HIV-positive patients compared to normal and this was particularly so for the N1, N2, and P3 components. These changes were more marked in those patients who were symptomatic from their infection, especially in those who were demented. They were, however, present to a lesser degree even in asymptomatic (Class II) patients. Thus, 78% of the demented patients and 28% of nondemented patients had a delay in latency of at least one of the evoked potential components beyond the upper limit of our normal population. By contrast, the EEG was normal in all patients with asymptomatic HIV infection and most symptomatic patients, although 5 patients in this latter group had mild generalized slowing. MRI and CT findings were similarly nonspecific, particularly in the nondemented group.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1990

A comparison of magnetic and electrical stimulation of peripheral nerves.

We compared magnetic stimulation using different coil designs (2 rounded coils and a butterfly-prototype coil) with electrical stimulation of the median and ulnar nerves in 5 normal subjects. Using magnetic stimulation we were able to record technically satisfactory maximal sensory and motor responses only with the butterfly coil. Submaximal electrical stimuli preferentially activated sensory rather than motor axons, but submaximal magnetic stimuli did not. The onset latency, amplitude, area and duration of responses elicited electrically or magnetically with the butterfly coil during routine sensory and motor nerve conduction studies were similar, and motor and sensory conduction velocities were comparable when studied over long segments of nerve. However, the motor conduction velocities with magnetic and electrical stimulation differed by as much as 18 m/sec in the across-elbow segment of ulnar nerve. Thus, recent developments in magnetic stimulator design have improved the focality of the stimulus, but the present butterfly coil design cannot replace electrical stimulation for the detection of focal changes in nerve conduction velocity at common entrapment sites, such as in the across-elbow segment of the ulnar nerve.

Action Potentials↗
PubMed1990

A comparison of thermography and electromyography in the diagnosis of cervical radiculopathy.

We studied 20 asymptomatic control subjects and 14 patients with clinically unequivocal cervical radiculopathy to compare the diagnostic value of thermography with that of electromyography. We measured the average skin temperature of designated regions over the neck, shoulder, and upper extremities. We then compared the temperature between corresponding regions of the two limbs, and between fingers innervated by different roots in the same hand. Thermography was abnormal in 6 patients (43%), whereas electromyography was abnormal in 10 (71%). Thermographic abnormalities were seen only in the hands and fingers, and the pattern did not follow the dermatome of the clinically involved cervical root. When compared to electromyography, thermography provided no additional diagnostic information. Thus, thermography does not have an established role in the evaluation of patients with cervical radiculopathy.

Arm↗
PubMed1990

Evidence that the long-latency stretch responses of the human wrist extensor muscle involve a transcerebral pathway.

Ballistic wrist extensor movements were interrupted by a sudden perturbing force in two conditions, and subjects were asked either to compensate for ('oppose') the perturbation or to cease the extensor movement ('let-go') when the interruption occurred. In the first condition, the interruption occurred unexpectedly in some of the trials, whereas in the second it occurred on every trial. Responses were recorded from the flexor and extensor carpi radialis muscles, and from the scalp and cervical spine. Unexpected perturbing forces were associated with an early extensor EMG response (M1) and longer latency EMG responses in both flexor and extensor muscles. When the interruptions occurred in every trial, both the late EMG activity and the cerebral responses were markedly attenuated. The relation between expectation of perturbation and the occurrence or size of the late EMG activity indicates that this response is under supraspinal control. The potentials recorded over the cervical spine and scalp were, like the late EMG activity, influenced by the expectancy of interruption. These potentials persisted even when the potentials related to the mechanically elicited SEP were removed by subtraction of responses to anticipated interruptions from those to unanticipated interruptions. The earliest of these potentials preceded the late EMG activity by 30-50 ms. They were present when the late responses were present, absent when the late responses were absent, and became progressively smaller when the late responses became smaller, suggesting a tight coupling between these events and the late EMG events. These results indicate that cerebral activity, unrelated merely to mechanical stimulation, consistently precedes the late EMG activity, and thereby directly suggests that the long-latency response has a cerebral (possible cortical) pathway.

Adult↗