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Biomedical subjects

K R Nelson

Publications and source records attributed to K R Nelson.

At least 19 recordsLinked to original sources
PubMed1992

Carbamazepine-induced cardiac dysfunction. Characterization of two distinct clinical syndromes.

A patient with sinus bradycardia and atrioventricular block, induced by carbamazepine, prompted an extensive literature review of all previously reported cases. From the analysis of these cases, two distinct forms of carbamazepine-associated cardiac dysfunction emerged. One patient group developed sinus tachycardias in the setting of a massive carbamazepine overdose. The second group consisted almost exclusively of elderly women who developed potentially life-threatening bradyarrhythmias or atrioventricular conduction delay, associated with either therapeutic or modestly elevated carbamazepine serum levels. Because carbamazepine is widely used in the treatment of many neurologic and psychiatric conditions, the recognition of the latter syndrome has important implications for the use of this drug in elderly patients.

Bradycardia↗
PubMed1992

Intraoperative electrophysiological monitoring in children.

Children, like adults, are at risk for neurological injury during a variety of surgical procedures. Intraoperative electrophysiological monitoring (IOM) provides information about the functional integrity of the nervous system during surgery. This information may determine the mechanism of injury and prevent damage by identifying nerves and detecting dysfunction at a reversible stage. Electrophysiological techniques may also help direct therapy by improving injury localization, detect the presence or absence of axonal integrity in peripheral nerve lesions, and identify rootlets with the greatest contribution to spasticity in patients undergoing selective dorsal rhizotomy (SDR). Electrophysiological techniques used are modified from those employed in the diagnostic laboratory. The first portion of this article reviews IOM experience at the Mayo Clinic in patients under 18 years of age from 1985 to 1991. The types of procedures monitored, the monitoring modalities used, technical problems unique to children, and neurological outcome are discussed. Subsequently presented are the application and techniques of electrophysiological monitoring during SDR as currently practiced at the University of Kentucky and other medical centers.

Brain Stem↗
PubMed1990

Congenital myopathy and cardiomyopathy with identical ultrastructural changes.

A 7-day-old girl with congenital hypotonia and unexplained episodes of bradycardia had a broad spectrum of similar skeletal muscle and myocardial degenerative ultrastructural abnormalities. Ultrastructural studies showed obliteration of cross striations, myofilament disorganization, streaming, smearing, clumping, and zigzag Z-band deformities. A decrease in glycogen, mitochondria, and T-tubular system occurred in the regions showing Z-band abnormalities of both skeletal muscle and myocardium. Concurrent structural cardiomyopathy should be considered in patients with congenital myopathies, particularly with unexplained cardiac conduction abnormalities or contractile insufficiency. Ultrastructural evaluation of skeletal and cardiac muscle may be necessary to define such disorders.

Biopsy↗
PubMed1990

Duchenne de Boulogne: electrodiagnosis of poliomyelitis.

Duchenne de Boulogne was among the first to investigate neuromuscular diseases. He stimulated muscle and nerve with moistened surface electrodes, thereby avoiding tissue necrosis. Technique and self-designed equipment are discussed in his first major work de l'électrisation localisée. During his 30 years of practice, he examined several hundred patients with poliomyelitis. With electrodiagnostic evaluation, he focused on "electrocontractility," the intensity of muscle contraction elicited by electrical stimulation. Based on his electrophysiologic findings, Duchenne suggested that the responsible lesion resided within the spinal cord. He used electrical stimulation for treatment and recognized prognostic features.

Electrodiagnosis↗
PubMed1990

Creatine kinase and fibrillation potentials in patients with late sequelae of polio.

The incidence of an elevated creatine kinase (CK) in a group of polio patients with delayed weakness (15/29) did not differ from polio patients without delayed weakness (9/31) or others with amyotrophic lateral sclerosis (ALS; 10/21). Mean CK in polio patients without delayed weakness (151 IU/L) was lower than the CK in those with delayed weakness (270 IU/L) or ALS (224 IU/L) (P less than 0.05). An elevated CK in polio patients with delayed weakness did not correlate with new or residual weakness. These findings suggest that muscle overuse is either not important or inadequately measured by CK. Widely distributed fibrillations were associated with an elevated CK for all polio patients combined (P less than 0.01). Fibrillations occurred in more muscles of polio patients with delayed weakness (P less than 0.01) and implies that late denervation may play a role in the development of new weakness in some polio patients.

Action Potentials↗
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↗