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Biomedical subjects

K R Nelson

Publications and source records attributed to K R Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1990

Neurophysiologic monitoring during surgery of peripheral and cranial nerves, and in selective dorsal rhizotomy.

Physiologic monitoring may warn of impending neural damage and intraoperative assessment may provide critical information used to direct the surgical procedure itself. Intraoperative techniques utilize methods modified from the diagnostic neurophysiologic laboratory. Simultaneous multimodality recording of different signal sources is of particular value for several types of procedures. Intraoperative studies must be tailored to each patient's clinical condition and to the specific surgical risks. Since studies have supported the benefits of intraoperative monitoring for peripheral nerve and cranial nerve surgery, monitoring is not likely to be subjected to the rigors of a randomized controlled study for these procedures.

Action Potentials↗
PubMed1989

SSEP and F-wave studies in acute inflammatory demyelinating polyradiculoneuropathy.

Somatosensory evoked potentials (SSEPs) and F-wave responses were compared after tibial (PTN) and median (MN) nerve stimulation in patients with acute inflammatory demyelinating polyradiculoneuropathy (AIDP). Nineteen patients were evaluated within 2 weeks of AIDP onset. Each had F-wave and PTN-SSEP studies; 18 had MN-SSEP studies. Ten patients had absent or prolonged MN-SSEP latencies, whereas 16 had abnormal MN F-wave studies. Seventeen patients had an abnormal PTN-SSEP while 12 had abnormal PTN F waves. Every patient with an abnormal MN-SSEP also had an abnormal PTN-SSEP. The most common PTN-SSEP findings were an absent or prolonged latency of N8 or N22. All patients had either an abnormal MN F wave or PTN-SSEP.

Adolescent↗
PubMed1988

Acoustic nerve conduction abnormalities in Guillain-Barré syndrome.

We recorded brainstem auditory evoked potentials (BAEPs) in two patients with Guillain-Barré syndrome (GBS). One patient was acutely deaf with total absence of BAEP waveforms indicative of acoustic nerve conduction block. Hearing improved during early convalescence, and there were prolonged wave I latencies. Normal BAEPs were recorded on recovery. A second patient had bilaterally prolonged wave I latencies. These BAEP findings suggest that acoustic nerve conduction abnormalities from demyelination may occur in GBS.

Adult↗
PubMed1988

Neurologic complications of graft-versus-host disease.

BMT has become an important therapy for many hematologic disorders. Following BMT, the recipient may develop GVHD when it appears that immunocompetent donor lymphocytes react to host antigens. Acute and chronic GVHD represent two distinct syndromes. Acute GVHD has not been associated with primary neurologic involvement. Polymyositis has been reported in 12 patients with chronic GVHD, with the most common underlying illness being aplastic anemia. The clinical, serologic, and muscle biopsy features of the myositis in GVHD have been similar to those observed in idiopathic polymyositis. Weakness was moderate to severe and responded to prednisone, sometimes with the addition of azathioprine. Prognosis depended upon the underlying disease and not on the severity of the myositis. MG occurs rarely in chronic GVHD. Most patients with MG and GVHD have had aplastic anemia; those with aplastic anemia are more likely to have anti-AchR prior to BMT. The clinical manifestations of GVHD MG have not differed from classic autoimmune MG; each patient had elevated antiacetylcholine receptor antibodies titers. All patients have responded well to cholinesterase inhibitors but have received other immunosuppressants. These observations suggest that aplastic anemia is an important host factor in the development of the autoimmune disorders seen with chronic GVHD, certainly of myositis and MG. Herpes zoster peripheral nerve infections have occurred in patients with chronic GVHD. One patient had mononeuritis multiplex. In both acute and chronic GVHD, CNS impairment is usually caused by metabolic encephalopathy or infection. Primary CNS involvement has not been recognized.

Adolescent↗
PubMed1988

Use of peripheral nerve action potentials for intraoperative monitoring.

Following a physical injury to peripheral nerve, clinical evaluation and the use of conventional EMG/NCS is often unable to determine whether axons are crossing the site of injury before severe changes in distal tissues occur. The INAP recording identifies functional axons within neuromas before other signs of reinnervation have developed. In clinically complete lesions, recording an INAP across the injury indicates the presence of regenerating axons, and neurolysis of the encasing connective tissue is recommended. If an INAP is absent, resection of the dense neuroma is usually undertaken with end-to-end suture or graft. A present INAP indicates clinically significant regenerating axons even with large distances to target tissue. An absent INAP for injuries far from target tissue indicates a poor prognosis. In clinically incomplete lesions, INAP recording is of no value over the clinical examination and EMG/NCS. INAP can aid peripheral nerve tumor resection by identification of intact nerve fascicles. INAP responses are obtained by placing platinum-iridium bipolar stimulating electrodes proximal to the injury. The INAP is then recorded by distal electrodes. A standard EMG/NCS instrument with an isolated stimulation unit can be used with the appropriate gain and time base settings. Stimulus intensity required for a supramaximal response is usually less than 75 V at 0.05 msec duration. Frequency bandpass is similar to that for conventional EMG/NCS studies. Electrodes must elevate the nerve during the recording. Artifact from 60 Hz line frequency and stimulus are common problems.

Humans↗
PubMed1987

Optimal welding of beta titanium orthodontic wires.

Today the orthodontist is confronted by an array of new orthodontic wire materials that, when applied to appliance design, can vastly increase the flexibility and versatility of therapy. Welded joints, especially for the newer titanium alloy wires, provide a means to extend the useful applications of these materials. The purpose of this study was to determine the optimum settings for electrical resistance welding of various configurations of titanium-molybdenum (TMA) wires. Specimens were of a t-joint configuration and were mechanically tested in torsion to simulate the failure mode most often observed in clinical practice. Variables included wire size, wire orientation, and welding voltage. Results indicated that excellent welds can be obtained with very little loss of strength and ductility in the area of the weld joint. Torsional loads at failure were at least 90% of the unwelded base material. Although a wide range of voltage settings resulted in high-strength welds, typically a narrow range of voltages yielded optimal ductility.

Dental Alloys↗
PubMed1983

Midline spikes. EEG and clinical features.

Clinical features of 40 patients with midline spikes on EEG were compared with those of age- and sex-matched controls. Seizure incidence was significantly greater in the study group than in the controls (85% v 45%). Tonic-clonic seizures were the most frequent type. Eighteen patients from the study group had additional focal or generalized epileptiform abnormalities. This subgroup had a significantly greater incidence of seizures than patients with only midline spikes (100% v 73%). Midline spikes are more common in children and markedly activated with sleep. They must be distinguished from normal sleep transients.

Adolescent↗
PubMed1980

Memory for sequences of stimuli and responses.

Two experiments sought to determine if pigeons could discriminate and remember recent sequences of stimuli and responses. A variant of Konorski's short-term memory procedure involving successive presentation of sample and test stimuli was used. The samples were stimulus-response pairs of the form, (S-R)(1)-(S-R)(2). Differential test responding disclosed memory of the two-item samples, with birds showing earlier and greater control by the second item than the first (Experiment 1). When the retention interval separating the second item of the sample sequence from the test stimulus was lenghtened from .5 to 2.0 or 4.0 sec, a systematic loss of stimulus control resulted; however, when varied over the same temporal range, the interval between the two items of the sample sequence had a much smaller effect, or none at all (Experiment 2). These results support an account of response-sequence differentiation that stresses short-term memory of organized behavior patterns.

Journal Article↗
PubMed1979

Spinal cord regeneration in rats made immunologically unresponsive to CNS antigens.

Seventy days after complete spinal cord transection, both treated and untreated rats showed evidence that some corticospinal axons had regenerated. Rats made immunologically unresponsive to CNS tissue showed no increase in corticospinal regeneration as measured by orthograde axoplasmic flow of tritated proline or retrograde axoplasmic labelling with horeseradish peroxidase. However, treated rats did demonstrate electrophysiological evidence of regeneration of long ascending sensory pathways. Tolerant animals additionally treated with cyclophosphamide showed corticospinal axonal regeneration by tritated proline transport and electrophysiological techniques and also showed electrophysiological evidence of ascending sensory tract regeneration.

Afferent Pathways↗
PubMed1978

Temporal factors influencing the pigeon's successive matching-to-sample performance: sample duration, intertrial interval, and retention interval.

A successive matching-to-sample procedure that entails the sequential presentation of sample and test stimuli and the monitoring of response rates in a go/no-go discrimination of matching and nonmatching stimuli was studied as an alternative to the familiar delayed-matching paradigm of animal short-term memory. Three within-subject experiments studied the effects of sample duration (1 to 12 seconds), intertrial interval (5 to 50 seconds), and retention interval (1 to 50 seconds) on the pigeon's successive-matching performance. The results revealed that retention was (a) an increasing function of sample duration and intertrial interval, and (b) a decreasing function of retention interval. These results were in accord with those of more traditional short-term memory paradigms, and reveal the suitability of the successive-matching procedure for studying memory processes.

Journal Article↗