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Biomedical subjects

R L Rodnitzky

Publications and source records attributed to R L Rodnitzky.

At least 37 records · Page 2Linked to original sources
PubMed1991

Neuroleptic malignant syndrome in Parkinson's disease after withdrawal or alteration of dopaminergic therapy.

Neuroleptic malignant syndrome is characterized by altered consciousness, fever, extrapyramidal signs, autonomic instability, elevated creatine kinase level, and leukocytosis. Although originally described in patients receiving neuroleptic drugs, this syndrome may also occur in patients with Parkinson's disease during withdrawal or reduction of levodopa therapy or other dopaminergic drug therapy. We have encountered three cases of neuroleptic malignant syndrome related to withdrawal of levodopa therapy. These cases illustrate the variety of circumstances in which alteration of therapy with dopaminergic drugs can cause this syndrome and the relative unfamiliarity of the neuroleptic malignant syndrome-levodopa relationship among physicians who do not treat large numbers of patients with Parkinson's disease. An understanding of the role of brain dopamine in the pathogenesis of neuroleptic malignant syndrome and an appreciation of the great variety of drugs whose manipulation can result in this potentially fatal syndrome will aid its proper and timely recognition, especially when the offending pharmacologic manipulation does not involve neuroleptic drugs.

Aged↗
PubMed1990

Stroke and its modification in Parkinson's disease.

Previous studies have not agreed on the incidence of ischemic stroke in persons with Parkinson's disease. There are epidemiologic and neurochemical facets of Parkinson's disease that might confer some benefit or protection against ischemic stroke. We used a case-control method to determine the lifetime history of ischemic stroke in 200 patients with Parkinson's disease and 200 controls of a similar age range. Analysis was also carried out for myocardial infarction as a marker of generalized atherosclerotic disease and for stroke risk factors. The cumulative incidence of ischemic stroke was significantly less in the patients with Parkinson's disease than in the controls, as was the cumulative incidence of myocardial infarction. Among risk factors, significantly fewer patients with Parkinson's disease used tobacco than controls. The decreased incidence of ischemic stroke in the patients with Parkinson's disease appears to be related to their less severe generalized atherosclerosis, possibly due to their lower incidence of tobacco use. In view of the known potential for dopamine to exacerbate experimental ischemic tissue damage, the possibility that the dopamine deficiency in the central nervous system of persons with Parkinson's disease confers an additional specific protective benefit against ischemic stroke cannot be excluded and requires further study.

Aged↗
PubMed1990

Circadian fluctuations of contrast sensitivity in Parkinson's disease.

Spontaneous circadian fluctuations of motor symptoms in Parkinson's disease (PD) often occur, with dysfunction typically less severe in the early morning than in the afternoon. In 23 PD patients with or without a history of circadian motor fluctuations, we studied contrast sensitivity (CS), a non-motor function, considered to be dependent on dopaminergic transmission to see if it exhibits similar circadian variability. We tested CS throughout the day at 2-hour intervals beginning at 8:30 AM. To facilitate multiple testing sessions, we used a rapid, printed, forced choice test of CS not requiring a motor response. We tested CS in 43 eyes in the PD patients and 23 eyes in 12 controls at spatial frequencies of 1.5, 3, 6, 12, and 18 cycles per degree (cpd). At 8:30 AM, CS in PD did not differ from that of controls, but at all other testing times it was significantly worse at 3 or more spatial frequencies. In PD, CS was significantly worse at 2:30 PM than at 8:30 AM at 3 and 6 cpd, but in controls it was unchanged throughout the day. Separate analysis of CS in PD patients, with and without a history of circadian change in motor symptoms, revealed no significant difference between the groups. These results suggest that in PD a non-motor dopaminergic function can exhibit circadian variability and that this pattern can exist in the absence of similar variability in motor symptoms. Circadian variability which parallels the most common pattern of motor variability in PD supports the notion that the CS abnormality in this condition is related to dopamine deficiency.

Aged↗
PubMed1989

Long-term clinical efficacy of Sinemet CR in patients with Parkinson's disease.

Sinemet CR, a controlled-release form of carbidopa/levodopa, was administered for 36 or 39 months to 8 patients with Parkinson's disease in an open-label study. On standard Sinemet each patient had experienced "wearing off" phenomena, and 5 had also experienced random "off" episodes. Daily "on" time, dyskinesia time, disability score, levodopa dosage requirement, and dosing frequency on Sinemet CR were compared with baseline values on standard Sinemet therapy. After both 3 and 36 or 39 months of Sinemet CR therapy, 5 patients showed increased daily "on" time compared with baseline. All 8 required fewer daily doses after 3 months on Sinemet CR, but only 3 were still taking fewer doses after 36 or 39 months. Disability scores remained essentially unchanged. Patients continued to elect to remain on Sinemet CR over the 3-year period, citing improved predictability of response and less severe and precipitous "off" episodes as the main reasons. This experience suggests that patient acceptance of Sinemet CR remains high. A modest improvement in "on" time can be achieved and maintained in some patients for as long as 3 years. However, as with standard Sinemet, dosing frequency for Sinemet CR may need to be gradually increased with time in order to maintain benefits achieved.

Aged↗
PubMed1986

Relation between size of compound sensory or muscle action potentials, and length of nerve segment.

In 24 median nerves from 12 healthy subjects, antidromic digital sensory potentials progressively diminished in size, averaging 40.4, 37.0, 30.7, and 23.9 microV X msec with stimulation at the palm, wrist, elbow, and axilla, respectively. In contrast, compound muscle action potentials changed minimally, measuring 19.4, 19.8, 19.0, and 18.2 mV X msec, respectively. Similar studies of the ulnar and radial nerves showed identical trends. Physiologic temporal dispersion can mimic conduction block of sensory nerves by summating the peaks of opposite polarity generated by fast- and slow-conducting axons. This type of cancellation affects muscle responses much less because motor unit potentials of longer duration superimpose nearly in phase, given the same latency shift as the sensory potentials.

Action Potentials↗
PubMed1986

Clinical correlates of abnormal P14 in median SEPs.

Recording median somatosensory evoked potentials (SEPs) from scalp and neck in separate channels with the use of an ear reference, 52 patients had abnormal scalp-recorded P14 associated with normal cervical-recorded N13. The patients had multiple sclerosis or other brainstem or high cervical cord lesions. Evidence of brainstem lesions was found in 35 patients on clinical examination or by brainstem auditory evoked potentials or blink reflex. Abnormalities of P14 were correlated highly with brainstem dysfunction, but high cervical cord lesions could not be excluded by this finding. The localizing value of SEP is improved by measuring the N13 and P14 peaks separately and assessing the cervical cord-brainstem conduction time.

Adult↗
PubMed1985

Decrement of somatosensory evoked potentials during repetitive stimulation.

In normal subjects, cerebral potentials were evoked by brief, passive extension of the wrist joint at various interstimulus intervals (ISIs). The resulting somatosensory evoked potentials (SEPs) were found to decrease during repetitive stimulation. The greatest decrement occurred between the first and second responses of each series. After cessation of stimuli, the SEP amplitude returned to control values over a prolonged, exponential time course. The authors postulate that the observed response decrement may be a form of habituation, which provides a model for studying the neuronal substrates of behavior.

Adult↗
PubMed1985

Stationary negative potentials near the source vs. positive far-field potentials at a distance.

We studied the field distribution of referentially recorded negative potentials after stimulation of the median nerve at the wrist in 15 normal subjects. When recorded from multiple sites along the lateral aspect of the arm with the reference electrode at the knee, 3 negative peaks, N3, N6 and N9, appeared at fixed latencies. Of these N3 and N6 were highest in amplitude at the distal insertion of the brachioradialis and the distal end of the deltoid, respectively, and N9, at the acromion. With stimulation of the finger, the negative peaks shifted in latency by about 3 msec, indicating an anatomically fixed generator source for each component. When compared to far-field potentials, N9 was of the same latency as scalp recorded P9, that extended to the arm contralateral to the side of stimulation and to the upper half of the trunk. In contrast, N6 extended to the scalp with P6 spreading to the lower half of the body. When two subjects were connected by the arm, stationary negative or positive peaks were transmissible from the stimulated to the non-stimulated subject. When the stimulated arm of the first subject was in contact with the second subject, N3, N6 and N9 were recorded in the latter. Only P9 was registered when the unstimulated arm was in contact with the second subject. We conclude that N3, N6 and N9 are stationary negative potentials generated at certain points along the nerve pathway, probably representing a negative counterfield for positive far-field peaks, P3, P6 and P9. These stationary potentials can spread widely in a volume conductor and can even be detected in a non-stimulated subject making a close contact to the generator source.

Adolescent↗
PubMed1984

Chronic long-interval plasma exchange in myasthenia gravis.

Plasma exchange, when used in conjunction with azathioprine to treat chronic symptoms of myasthenia gravis, can usually be discontinued after a limited period of time without reappearance of symptoms. Patients who cannot be weaned from the procedure are often treated with more potent immunosuppressants to overcome exchange dependence. In view of the cumulative risks of more intensive daily immunosuppression, continuation of intermittent plasma exchange can be an acceptable alternative provided the interexchange interval (IEI) is relatively long. We describe two exchange-dependent patients in whom plasma exchange has been used for 4 1/2 and five years to control their symptoms. In both patients, who also received azathioprine, the IEI gradually lengthened to nine or 12 weeks over two to three years, without the introduction of new immunosuppressants. These cases illustrate that long-term plasma exchange is feasible and effective in selected exchange-dependent patients with myasthenia gravis.

Adult↗
PubMed1982

Complications of plasma exchange in neurological patients.

Complications occurred during 154 plasma exchanges performed in 17 patients for a variety of neurological disorders. Mild, self-limited, toxic reaction to citrate was the most frequent complication (7.8%), followed by transient hypotension (2.6%) and visual scotomata (1.3%). More serious complications, occurring on one occasion each, were cardiac arrhythmia, myocardial infarction, and gross hemolysis. There were no infections. The spectrum and frequency of complications in these plasma exchanges were compared with those in other series dealing with both neurological and nonneurological patients. Several risk factors for development of complications were identified, one of the most important being the nature of the illness being treated. The incidence of two of the most serious complications, severe infection and bleeding diathesis, appeared to be higher in patients with renal insufficiency or hematologic disorders, respectively, than in neurological patients.

Adolescent↗
PubMed1978

Refractory period of human motor nerve fibres.

Using a collision technique, the ulnar nerve was made refractory for a shorter distance normally covered in 0.5 ms or a longer distance covered in 1.5 ms. Studying the shorter refractory segment with paired shocks of maximal intensity, the test response first appeared (more than 5% of unconditioned response) at an interstimulus interval of 1.16 +/- 0.18 ms (mean +/- SD in 20 ulnar nerves). The conduction velocity of the test impulse then was 55.3% +/- 19.2% of normal. Recovery in amplitude of the test response was nearly complete (more than 95%) at 2.11 +/- 0.50 ms, when it was conducting at a speed of 81.2 +/- 17.4% of normal. The conduction velocity recovered to a level above 95% of normal at 2.65 +/- 0.65 ms. Whereas recovery in amplitude of the test response was unrelated to the length of the refractory segment, change in latency was greater with the longer refractory segment, although not in proportion to the distance.

Adult↗
PubMed1978

The effect of induced hyperthermia on the blink reflex in multiple sclerosis.

In 76 patients with multiple sclerosis, the blink reflex was elicted electrically at normal body temperature and during induced hyperthermia to observe the effect on conduction within the reflex pathway through the brainstem. Special attention was directed to 31 patients with electrophysiologic evidence of reflex slowing, presumably because of demyelination in the reflex pathway. Hyperthermia did not induce any significant changes in mean reflex latency, amplitude, or duration in either the overall group of 76 or in the 31 patients with baseline blink reflex abnormalities. While the mean reflex latency did not change, 13 (33 percent) of 39 abnormal R1 responses from the 31 patients changed by 1.5 msec or more during hyperthermia, whereas change of similar magnitude was noted in only three (3 percent) of 90 normal R1 responses.

Body Temperature↗
PubMed1976

Anxiety associated with exposure to organophosphate compounds.

Acute organophosphate poisoning is known to result in substantial behavioral abnormalities. We assessed psychiatric manifestations of exposure in workers less substantially exposed to organophosphate compounds and showing no obvious signs of toxicity. Commercial pesticide sprayers and farmers recently exposed to organophosphate agents were compared to control subjects on personality tests, a structured interview, and cholinesterase level. The commercial sprayers but not the exposed farmers showed elevated of anxiety and lower plasma cholinesterase than control subjects. Assessment of other behavioral manifestations and red blood cell cholinesterase failed to disclose other group differences. These findings are viewed as tentative until confirmed by additional study, but they point to the possibility that organophosphate compounds may produce subtle defects in workers who are not obviously toxic. The findings do not justify public alarm but do suggest an area warranting more systematic and definitive investigation.

Agricultural Workers' Diseases↗
PubMed1976

Behavioral effects of organophosphate in man.

Increasingly widespread application of organophosphate pesticies has underscored the importance of studying their effects on human behavior. Clinical reports and laboratory investigations have generally supported the assumption that neurobehavioral manifestations of organophosphate toxicity are attributable to accumulation of acetylcholine at central and peripheral synapses as a result of cholinesterase inhibition. Despite methodologic shortcomings in many of the published studies, investigators generally agree on the presence of several behavioral sequelae of organophosphate poisoning: (a) impaired vigilance and reduced concentration, (b) slowing of information processing and psychomotor speed, (c) memory deficit, (d) linguistic disturbance, (e) depression, and (f) anxiety and irritability. The few studies of asymptomatic workers at risk for repeated exposure to organophosphate pesticides have produced only equivocal findings concerning the presence of less severe or latent forms of these behavioral abnormalities.

Anxiety↗
PubMed1975

Occupational exposure to organophosphate pesticides: a neurobehavioral study.

Acute organophosphate intoxication in man is well known to result in substantial central nervous system dysfunction. To test the hypothesis that similar neurobehavioral abnormalities might be present in mild degree in workers chronically exposed to organophosphate pesticides, 23 such subjects were tested for abnormalities in memory, signal processing, vigilance, language, and proprioceptive feedback performance. The performance of the exposed workers was not deficient in any of the five measures assessed when compared with the performance of a control group matched for age and educational background. Plasma and red blood cell cholinesterase levels were found to be in the normal range in both exposed and control groups, although plasma levels of exposed subjects were depressed somewhat below control values. Relative resistance of higher nervous system functions to mild chronic organophosphate exposure is suggested by these results.

Adult↗
PubMed1975

Electrophysiologic analysis of aberrant regeneration after facial nerve paralysis.

The blink reflex, ordinarily elicited only in the orbicularis oculi and not in other facial muscles, can be used to detect synkinetic movements objectively. In 26 of 29 patients tested at least 4 months after facial nerve degeneration, an aberrant blink reflex was recorded in the orbicularis oris on the affected side. Of the remaining three, one had injury to only a peripheral branch of the facial nerve and experienced a return of function with no evidence of synkinesis; in the other two, the affected side of the face was totally paralyzed in the absence of facial nerve regeneration. Synkinetic movements ultimately will occur in nearly all cases following facial nerve degeneration provided that the facial nerve regenerates from a proximal site.

Adolescent↗