Biomedical subjects

S L Pullman

Publications and source records attributed to S L Pullman.

29 records · Page 2Linked to original sources

PubMed1997

Physiological tremor analysis of patients with anti-myelin-associated glycoprotein associated neuropathy and tremor.

Tremor is often associated with anti-myelin-associated glycoprotein (anti-MAG) peripheral neuropathy (PN), but its physiology has never been accurately described. This study quantified the physiological characteristics of tremors in patients with anti-MAG demyelinating PN. Eighteen patients with tremor and PN with demyelinating features (ages 30-86, mean = 66.5 years) were evaluated for anti-MAG antibodies (positive considered > or = 1:3200) and for tremor amplitude, frequency, side-to-side relationships, and electromyographic (EMG) activation patterns. Thirteen patients had anti-MAG titers >1:3200 and 8 had both positive anti-MAG titers and tremors. Anti-MAG PN patients revealed tremors higher in amplitude, lower in frequency, with greater side-to-side amplitude ratios, greater amplitude variability, and more consistent cocontracting antagonist EMG patterns that do not attenuate with inertial loading. We conclude that anti-MAG PN tremor is not due only to exaggerated physiologic mechanisms but may reflect a distinctive form of neurogenic tremor.

Adult↗

PubMed1997

Spinal myoclonus induced by an intrathecal catheter.

We report a case of spinal myoclonus induced by the tip of an intrathecal catheter in a 35-year-old patient with severe, adult-onset, generalized dystonia of unknown cause, treated for 2 years using intrathecal baclofen. One month after a falling episode, the patient developed focal myoclonus of the right proximal leg whenever she stood up from a seated position. The electrophysiologic recordings were compatible with spinal segmental myoclonus, originating at a focus corresponding to the L2-S2 segments. At this site, the tip of the intrathecal catheter was demonstrated by myelography to be in close proximity to the nerve roots and conus medullaris. The myoclonus resolved promptly once the catheter tip was withdrawn. We review the literature on spinal myoclonus and discuss the possible mechanisms of spinal myoclonus pertaining to the present case. This report represents an unusual complication of intrathecal catheter systems that, if recognized, can lead to prompt therapeutic intervention.

Adult↗

PubMed1996

Approach to the treatment of limb disorders with botulinum toxin A. Experience with 187 patients.

OBJECTIVE: To determine the dosing, response expectation, efficacy, and most rational strategy for using intramuscular injections of botulinum toxin A (BTX) for limb disorders. DESIGN: Open-label prospective analysis of outcome after BTX treatment in patients with limb disorders. PROCEDURE: Botulinum toxin A prepared from lyophilized botulinum toxin was injected into selected upper and lower limb muscles under electromyographic guidance. Booster injections were given every 10 to 14 days during the first month (if needed) until optimal effects were achieved. Clinical data and muscle strength testing were obtained before the first injections and repeated at each visit. Level of disability, global functional improvement, and relief of pain were evaluated 6 to 8 weeks after the first set of injections. Practical and meaningful BTX doses by muscle, limb, or condition according to specified levels of efficacy were developed. MAIN OUTCOME MEASURES: Botulinum toxin A efficacy was calculated as an arithmetic combination of changes in the 3 clinical ratings before and after administration of BTX. RESULTS: Botulinum toxin A injections were given to 187 patients with limb disorders during an 8-year period (136 with dystonia, 37 with parkinsonian, essential, and cerebellar tremors, and 14 with spasticity). Four overall outcomes from no effect to almost complete improvement in the use of the limb or relief of pain were found, and determined the strategy for follow-up injections. Average BTX efficacy for all patients was 65% and ranged from 83.5% for focal hand dystonia to 35.7% for parkinsonian tremor. Botulinum toxin A injections relieved pain, independent of motor function, in 82.7% of patients with painful muscle spasms. CONCLUSIONS: Botulinum toxin A was found to be a safe and useful treatment of various limb conditions. Botulinum toxin A was significantly more effective when only a few muscles needing low doses were injected, and tended to be more useful in dystonia and spasticity than tremor. Candidates for BTX injection could be categorized functionally into 3 groups independent of the underlying disorders. The only significant adverse effect of BTX injection in limbs was transient weakness in injected or neighboring muscles.

Adolescent↗

PubMed1996

Cutaneous electromyographic silent period findings in brachial dystonia.

In this study we investigated the physiologic mechanisms in primary brachial dystonia by analyzing the cutaneous EMG silent period during isometric contraction of the opponens pollicis muscle. Results from the affected and unaffected arms of 11 patients with dystonia were compared to 7 patients with Parkinson's disease and 16 age-matched normal individuals (controls). The silent period onset latency, degree of EMG suppression during the silent period, and EMG rebound at the end of the silent period did not differ significantly between patients with dystonia and any other group. The duration of the silent period (the S-X interval), however, was significantly prolonged in dystonia (p<0.005) and in Parkinson's disease (p<0.001) in both affected and unaffected arms compared with controls. These findings suggest that mechanisms responsible for the initiation of the cutaneously induced silent period and the subsequent suppression depth of EMG activity are not affected in brachial dystonia, but the abnormally prolonged S-X intervals may reflect dysfunctional basal ganglia timing influences over spinal circuitry common to both dystonia and Parkinson's disease.

Adult↗

PubMed1995

Peripherally induced EMG silent periods. Normal physiology and disorders of motor control.

Periods of relative or absolute EMG suppression induced by peripheral stimulation have been described using a variety of experimental paradigms in normal subjects and in conditions of abnormal motor control. Peripherally induced silent periods represent complex inhibitory modulations of muscle activity and can be reproducibly evoked by cutaneous or mixed nerve electrical or mechanical stimuli. Features of the electromyographic suppression which most easily permit analysis include the degree of EMG inhibition, the latency and duration of the response, and the timing of the return of normal EMG activity following the stimulus, or S-X interval. When exteroceptive reflexes in craniocervical muscles are studied, alternating periods of EMG inhibition and facilitation have been described. Experiments designed to isolate the various contributants to EMG silence have not revealed a unitary electrophysiological basis for all of the silent period responses elicited by peripheral means. Thus, silent periods share a multifactorial origin that depends upon segmental spinal mechanisms which are heavily influenced by descending suprasegmental pathways. Because these mechanisms are affected in a variety of central disorders of motor control, study of peripherally induced silent periods may provide a window on the abnormal physiology of selected CNS diseases. Further study is required to elucidate the electrophysiology of peripherally induced silent periods, and to clarify the alterations in these negative motor phenomena that occur in central disorders of motor control.

Dystonia↗

PubMed1994

Botulinum toxin A injections for the treatment of hand tremors.

We conducted an open-label study to determine the utility of treating severe hand tremors with intramuscular injections of botulinum toxin (BTX) in forearm and arm muscles in 26 patients, 12 with Parkinson's disease (PD) and 14 with essential tremor (ET). The effect after 6 weeks for each patient was evaluated using two clinical rating scales, subjective evaluations of functional improvement and global disability, measures of weakness, and computer-assisted quantitative assessments of tremor. Although none of the clinical scores averaged > 3/4 point change, statistical significance was found on comparison of pre- and postinjection scores in the Webster Tremor and Global Disability Scales in the ET patients. Similarly, although average tremor amplitudes decreased by no more than 25% by quantitative analysis, amplitude decrease significantly correlated with patient subjective assessment in ET. In only two of 12 PD (17%) and three of 14 ET patients (21%) were major quantitative changes in tremor amplitude (> 50% reduction) found after BTX injections. Nevertheless, 10 patients (38%; five PD and five ET) reported moderate to marked subjective improvement in functional benefit after BTX. These findings suggest that although there were no major changes in clinical ratings or objective measurements, BTX injections may subjectively improve tremor in some patients, particularly those with ET.

Aged↗

PubMed1994

Modulation of parkinsonian tremor by radial nerve palsy.

We analyzed rest and postural hand tremors in a Parkinson's disease patient who developed and recovered from a right radial nerve palsy at the spiral groove, and found that, despite complete paralysis of all extensors below the elbow, tremor frequencies remained unchanged while tremor amplitudes actually increased. This provides compelling evidence for a central generation of parkinsonian tremor frequency that is not influenced by the effects of peripheral modulation. In addition, the increase in tremor amplitudes may be due to disinhibited flexor activity caused by normally operating spinal segmental mechanisms interacting with central tremor generators programmed to alternate between antagonist muscles. Peripheral treatment of tremors--with muscle paralysis or botulinum toxin, for example--therefore may not be effective in stopping tremor oscillations in Parkinson's disease and may even worsen tremor amplitudes if all antagonists of a tremoring joint are not treated equally.

Aged↗

PubMed1991

Large amplitude sensory action potentials in myelopathy: an observation.

Subjects with at least one sensory action potential (SAP) amplitude greater than 2 SD above the age-matched mean during standard nerve conduction tests were evaluated for evidence of spinal cord disease. From a total of 153 subjects, 16 had at least one large amplitude SAP and 12 of 16 (75%) had a documented myelopathy. While a mechanism has yet to be determined, this observation suggests that SAP amplitudes greater than 2 SD above normal may be correlated with clinical evidence of injury to the central nervous system.

Action Potentials↗

PubMed1990

Movement amplitude choice reaction time performance in Parkinson's disease may be independent of dopaminergic status.

The effect of circulating levels of plasma levodopa on reaction time performance was studied in patients with Parkinson's disease and untreated normal controls when instructed to move either a shorter or longer distance. On half the movements, subjects were pre-cued on the direction and amplitude of an impending movement. On the remaining movements, only the direction was pre-specified, and the amplitude was determined only when the cue to move was presented. Reaction time performance of patients was evaluated at three infusion levels of levodopa so that the patients were optimally, moderately, or minimally medicated. Parkinsonian patients were always slower to react and move than normal subjects. Clinical state correlated with movement time, but not with reaction time. These results contrast with those in which reaction time was related to plasma levodopa levels when movement direction and initiation were processed concomitantly, but the movement amplitude was pre-cued. It is possible that specification of the amount of muscle activity is partially independent of dopaminergic transmission.

Adult↗

PubMed1988

The sympathetic skin response: normal values, elucidation of afferent components and application limits.

The sympathetic skin response (SSR), recorded at the hand and foot, was elicited using different classes of stimuli in 20 normal controls and 10 patients with peripheral neuropathy. We found that SSR latencies changed significantly with different recording sites, but not with different stimulation sites. Additionally, after ischemic conduction block of the arm in 3 normal controls, the previously obtainable SSR recorded at the hand became unobtainable with median nerve stimulation. Also, in one patient with subacute ganglionitis and 3 patients with demyelinating neuropathies, the SSR could not be elicited by electrical stimulation, but it could with deep inspiration. These results suggest that large diameter myelinated fibers may serve as afferents for the SSR. Furthermore, these findings imply that an unobtainable SSR by electrical stimulation may be due not only to dysfunction of the autonomic efferent nerve fibers, but also to abnormalities of the sensory afferents of the reflex. Therefore, investigations of autonomic dysfunction utilizing the SSR must be interpreted with caution in patients with peripheral neuropathies.

Acoustic Stimulation↗

PubMed1988

Dopaminergic effects on simple and choice reaction time performance in Parkinson's disease.

The present study examined whether premovement central neural processing in Parkinson's disease was related to functional motor disability and plasma L-dopa concentration. Reaction time (RT) performance in simple and choice RT tasks was assessed while plasma L-dopa levels were controlled by continuous IV L-dopa infusion in five parkinsonian patients. Five age-matched controls performed the same RT tasks for comparison. Simple RT for the patients was longer than the normal control RT at all infusion levels (p less than or equal to 0.005). However, choice RT was normal when the patients were "on," but became prolonged as plasma L-dopa levels decreased (p less than or equal to 0.01). The results show that there are abnormalities of premovement central neural processing in Parkinson's disease, and that simple and choice RTs are differentially affected by L-dopa replacement. This suggests that different neural mechanisms may be involved in the processing of these tasks.

Adult↗