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Biomedical subjects

F O Walker

Publications and source records attributed to F O Walker.

At least 37 records · Page 2Linked to original sources
PubMed1993

Sustained focal effects of low-dose intramuscular succinylcholine.

We studied low-dose intramuscular succinylcholine in 9 subjects as part as an ongoing investigation of its potential to predict responses to botulinum toxin. We measured compound muscle action potentials (CMAPs) from the extensor digitorum brevis (EDB) muscles in each foot before and after intramuscular injections of 2.5 mg of succinylcholine into the EDB. Succinylcholine reduced mean CMAP amplitudes to 42% of baseline; the maximal reduction occurred at 19 +/- 6 (mean +/- standard deviation) minutes. Recovery to 73% of the baseline CMAP amplitude (approximately 50% recovery from block) occurred at 105 +/- 49 minutes after injection. Repetitive (train-of-four) stimulation at 2 Hz produced mild CMAP decrements (5-25%), but only during the recovery phase. Varying the succinylcholine concentrations (10, 20, or 50 mg/mL) while holding the total drug dose constant did not change the rate of onset or the extent of block. No systemic complications occurred. We conclude that: (1) 2.5 mg intramuscular succinylcholine can safely induce selective muscle weakness with a time course that differs from intravenously administered succinylcholine; and (2) further clinical studies comparing intramuscular succinylcholine and botulinum toxin are warranted.

Action Potentials↗
PubMed1993

Cutaneous changes of dermatomyositis in patients with normal muscle enzymes: dermatomyositis sine myositis?

BACKGROUND: Dermatomyositis sine myositis may have various connotations. Controversy exists as to nomenclature, degree of evaluation required, therapy, and course (e.g., does true dermatomyositis of the skin only exist?). OBJECTIVE: The purpose of this study was to assess prospectively patients with the clinicopathologic features of dermatomyositis and normal muscle enzyme serum levels to determine their course in terms of the onset of muscle disease. METHODS: Thirteen patients were studied by complete history and clinical examination, laboratory studies, electromyography, and skin and muscle biopsy. They were observed for 1 to 6 years. RESULTS: Patients were classifiable into three groups: (1) cutaneous changes only, (2) cutaneous changes only at baseline with subsequent development of myositis, and (3) cutaneous changes with normal muscle enzyme serum levels at baseline but with myositis demonstrated by electromyography and/or muscle biopsy specimens. CONCLUSION: Significantly different prognostic and therapeutic implications are present in patients with dermatomyositis with normal muscle enzyme serum levels depending on the results of electromyography, muscle biopsy, and clinical observation.

Adolescent↗
PubMed1992

Demyelinating polyneuropathy in eosinophilia-myalgia syndrome.

Eosinophilia-myalgia syndrome (EMS) is a newly recognized disorder, characterized by myalgia, weakness, scleroderma-like changes, and eosinophilia. EMS is associated with lots of L-tryptophan allegedly contaminated with byproducts of the manufacturing process. We describe 3 patients with EMS who presented with a severe demyelinating sensorimotor polyneuropathy. Electrodiagnostic studies revealed multifocal conduction block, slowing and temporal dispersion of motor responses, and prolonged or absent F-responses. Despite plasmapheresis; corticosteroids; and, in 1 patient, cyclophosphamide, 2 patients died and the remaining patient experienced minimal recovery. Pathology revealed patchy perivascular infiltrates and fibrosis in the connective tissue of muscle and nerve. Autopsy of the central nervous system in 2 patients did not reveal changes unique to EMS. In addition to other organ involvement, EMS may manifest as a potentially fatal polyneuropathy, which initially appears to have prominent demyelinating features.

Demyelinating Diseases↗
PubMed1991

Orthostatic tremor.

Explore the source record for details and available documents.

Diagnosis, Differential↗
PubMed1991

Angiotropic intravascular large-cell lymphoma (malignant angioendotheliomatosis): report of a case and review of the literature.

We present a case of angiotropic large-cell lymphoma and review the literature in order to define the neurologic features of this rare disorder. This is the first report of gadolinium-DTPA imaging in angiotropic large-cell lymphoma that demonstrates infarcts of multiple ages, as well as striking meningeal enhancement. Angiotropic large-cell lymphoma should be suspected in patients with clinical evidence of small and large cerebral vessel disease and diagnosis requires skin, liver, renal, meningeal, or brain biopsy. Single modality treatment, using either radiation therapy or steroids, has been ineffective, and new findings of a lymphomatous origin of this neoplasm suggest that combination chemotherapy may be indicated.

Brain Neoplasms↗
PubMed1991

Learning to live at risk for Huntington's disease.

Huntington's disease (HD) is an autosomal dominant inherited disorder of the central nervous system. Consequently, a child of an affected parent has a 50% risk of developing the disease. This article provides an overview of HD by providing a brief history of the disease and describing progressive symptoms of chorea, dystonia, incoordination and decreased mental acuity. Steps in diagnosis, treatment and prognosis are outlined. Because persons at risk for HD have usually witnessed the deterioration of an HD parent, they are often dominated by fears of developing HD themselves. Life's choices, such as whether or not to have children, then become dilemmas. The importance of maintaining a positive life perspective, while making practical choices about employment, marriage, children and other concerns needs to be addressed.

Adaptation, Psychological↗
PubMed1990

Sonographic imaging of muscle contraction and fasciculations: a correlation with electromyography.

Precise quantitation of fasciculations with EMG is difficult because of their random location and discharge frequency in muscle. We studied the clinical value of real-time ultrasound in the study of normal voluntary muscle contraction and in the identification of fasciculations in 22 patients. Sonography effectively imaged fasciculations, demonstrating them in both resting and actively contracting extremity muscles and in less accessible muscles such as the tongue. In two instances ultrasound identified fasciculations not apparent on EMG. Analysis of the video images generated quantitative data on fasciculation duration (averaging 500 msec), size, and location and provided unique insight into the process of normal muscle contraction and motor unit physiology.

Electromyography↗
PubMed1990

Isometric features of orthostatic tremor: an electromyographic analysis.

A patient is described with "orthostatic" tremor. Electromyography revealed tremor bursts of 15 Hz in the lower extremities while standing and with isometric activation of the muscles, but the bursts disappeared with isotonic activation of muscles. Similar tremor was recorded in the arms with isometric, but not isotonic activation. Review of previously reported cases confirms these findings. The clinical and electrophysiologic features of this tremor distinguish it from other recognized forms of tremor.

Aged↗
PubMed1990

Sensitivity for detecting fibrillation potentials: a comparison between concentric and monopolar needle electrodes.

The sensitivity of monopolar and concentric electrodes for detecting fibrillation potentials (FP) has never been formally compared. We studied 35 muscles with FP, sampling 20 sites each with concentric and monopolar needles. The concentric needle identified 0.88 +/- 3.44 (mean +/- standard deviation) more sites with spontaneous activity. Although statistically significant (Wilcoxon signed rank test P less than .03), this difference in sensitivity did not appreciably affect diagnostic interpretation. Subjects described the concentric needles as more painful. Needle insertions in 25 other muscles demonstrated that needle movement generated the majority of FP. We suggest that the increased tissue injury caused by concentric needles may account for both their increased sensitivity and discomfort.

Adult↗
PubMed1990

Pregnancy increases median nerve susceptibility to lidocaine.

To determine whether pregnancy renders women more sensitive to local anesthetics, nine nonpregnant and nine pregnant (third trimester) women underwent median nerve block at the wrist using 1% lidocaine HCl. Inhibition of median nerve A alpha sensory and motor fibers was assessed using measurements of sensory nerve action potential (SNAP) amplitude and compound motor action potential (CMAP) amplitude, respectively. Inhibition of median nerve C fibers was assessed by the increase in skin temperature and by the decrease in median (relative to ulnar) galvanic skin potential (GSP) amplitude. Lidocaine inhibited SNAP to a greater extent in pregnant than nonpregnant women at all time points (P = 0.019). CMAP declined differently in the pregnant and nonpregnant groups (P = 0.01): the pregnant subjects achieved steady state inhibition before the nonpregnant subjects. The two groups developed comparable steady state inhibition. Skin temperature was higher in pregnant women at all time points (P less than 0.0001); moreover, the increased skin temperature of pregnant women differed from that of the nonpregnant women (P = 0.037), reflecting a more rapid temperature increase in the pregnant women. GSP amplitude declined to 50% of control more rapidly in pregnant (mean = 4 min) than nonpregnant women (mean = 11.5 min), but these differences did not achieve statistical significance. It is concluded that pregnancy increases median nerve susceptibility to lidocaine.

Action Potentials↗
PubMed1990

Cooling potentiates lidocaine inhibition of median nerve sensory fibers.

To determine the effect of cooling on lidocaine potency, nine consenting volunteers underwent bilateral median nerve blocks using 1% lidocaine HCl solution. Room-temperature and ice-cold lidocaine were injected into either dominant or nondominant wrists. Subjects were blinded to the temperature of the anesthetic. Inhibition of A alpha sensory and motor fibers was assessed as the decline in sensory nerve action potentials and compound motor action potentials, respectively. Inhibition of C fibers was measured as an increase in skin temperature and a decline in galvanic skin potentials. All indices of nerve function demonstrated profound (P less than 0.001) time-related changes after injection of local anesthetic. When ice-cold lidocaine was injected, inhibition of sensory nerve action potentials was significantly greater at all time points (P = 0.001) than when room-temperature lidocaine was injected. Inhibition of C fibers as assessed by galvanic skin potentials was marginally faster (P = 0.07) when ice-cold lidocaine was used compared with room-temperature lidocaine. No differences between room-temperature and ice-cold lidocaine were observed in inhibition of compound motor action potentials, or in the increase in skin temperature. We conclude that inhibition of median sensory fibers may be increased by cooling 1% lidocaine HCl in an ice bath before injection.

Action Potentials↗
PubMed1989

Psychogenic respiratory distress.

Five patients developed recurrent episodes of psychogenic respiratory difficulty that were superimposed on psychogenic neurologic symptoms. Misdiagnosis resulted in long hospital stays, code blue alerts, intubation, mechanical ventilation, and, in one case, tracheostomy. Patients "learned" psychogenic respiratory distress because their breathing symptoms evoked distinct evidence of anxiety in physicians and staff. In these patients, gain was not incidental but exerted primary control over symptom selection. The behavioral mechanisms involved in the pathogenesis of psychogenic respiratory distress have significant implications for its diagnosis, treatment, and prevention.

Adult↗