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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
PubMed1998

Quality assurance calibration of 125I rapid strand in a sterile environment.

PURPOSE: 125I seeds encased in stiffened absorbable suture material, commercially available from Amersham Healthcare as 125I Rapid Strand, are not readily calibrated because of the necessity of maintaining the sterility and integrity of the Rapid Strand. A method is proposed to verify the activity of 125I seeds in Rapid Strand in a sterile environment and to provide quality assurance of the resultant loading by autoradiographing loaded needles. METHODS AND MATERIALS: A sterilizable insert for a Standard Imaging HDR 1000 Plus well chamber was designed to accommodate Amersham's plastic spacing jig that holds the strand. The insert has a cylindrical lead sleeve allowing five of the 10 seeds in the jig to be exposed within the well chamber. A grooved tray for holding a batch of 30 needles was designed for autoradiographing the implant set. RESULTS: Position-dependent calibration factors for each of the seed wells in the jig were determined; then these individual factors were combined into a single chamber factor of 21.6 pA/mCi. Starting from the most distal spacing jig slot, relative position factors were 0.99, 1.00, 0.99, 0.93, 0.73, and 0.13 for the six positions which produced a nonnegligible signal. Anisotropy in the chamber factor was determined by rotating the well in 30 degrees increments about the seeds in the jig. The chamber factor showed only a 0.2% variation with rotational angle. Attenuation due to the Vicryl suture cladding material was 0.2% and was measured by stripping the Vicryl from the strand and remeasuring the chamber factor with the seeds in their original orientation. In the operating room, charge was collected from sterile Rapid Strands for a fixed time between 30 and 50 s and the measured ion chamber current was compared with the value predicted from Amersham's nominal activity. The average deviation between nominal and measured activity of 73 Rapid Strands tested was +0.5% +/- 2.2%. For single measurements, the maximum and minimum deviations observed were +4.8% and -3.7%, respectively. Autoradiographs taken of the entire implant set on an aluminum tray milled to hold the needles confirmed the actual seed loadings. CONCLUSIONS: The Rapid Strand calibration procedure described maintains the sterility and integrity of 125I Rapid Strands and verifies that the manufacturer's stated activity is accurate to within 5%.

Algorithms↗
PubMed1997

Screening in special populations: a "case study" of recent Vietnamese immigrants.

PURPOSE: To determine how the medical and social profile of a particular special population, Vietnamese immigrants, should be used to tailor screening protocols that differ from those designed for the general population. PATIENTS AND METHODS: A consecutive series of Vietnamese immigrants living in the United States for less than 6 months were evaluated by interviewer-administered standardized questionnaire and medical record review. A total of 99 new Vietnamese immigrants (47 women and 52 men) aged 19 to 71 years presenting for primary care to two neighborhood health centers between October 1994 and June 1995 were identified. Data collected included smoking status, alcohol use (CAGE questionnaire), depression (Vietnamese Depression Scale [VDS]), PPD status, stool ova and parasites, hepatitis B and syphilis serologies. RESULTS: Overall, 32% were smokers and significantly more men than women smoked (54% vs. 9%) (P < .00001). Although 24% of patients used alcohol, none responded positively to any of the CAGE questions. Using the VDS, 17% (17 of 99) were depressed; age 40 and older was the only sociodemographic factor associated with depression (P < .00001). Ova or parasites were found in 51% (41 of 80), and 63% of those infected (26 of 41) required treatment for pathogenic infections. Seventy percent (66 of 94) tested positive on the tuberculin skin test (PPD), and antituberculous medication was recommended in 39% (37 of 94). Eighty-three percent (80 of 96) had been exposed to hepatitis B, and 14% (13 of 96) were chronic hepatitis B carriers. CONCLUSIONS: Caring for special populations provides an opportunity to institute appropriate unique screening tests not recommended for the general population. In the case of new Vietnamese immigrants, routine screening protocols should include the following: testing for tuberculosis by PPD, stool ova and parasite examinations, hepatitis B serologies, and assessment for depression and smoking status. The CAGE questionnaire may not be an effective instrument for detecting alcohol abuse in this particular population.

Adult↗
PubMed1996

The electromyographic responses to dorsal rootlet stimulation during partial dorsal rhizotomy are inconsistent.

Concerns have arisen regarding the ability of physiologic techniques to select rootlets mediating spasticity in children undergoing partial dorsal rhizotomy (PDR) for the treatment of spastic gait from cerebral palsy. To determine whether these physiologic responses are reproducible, 60 rootlets in 6 patients were graded from 0 to 4+ according to the system first reported by Phillips and Park, and then retested and graded using a randomized, blinded paradigm. Two thirds of the rootlets had one or more grade difference between the two trials, and 25% had a grade change of 3 or more. Only 4 of 23 rootlets with a "normal' response (grade 0) on one test were also graded normal on the other test. Only 2 of 14 rootlets with a bilateral response (grade 4+) had a bilateral response on both trials. Statistical analysis demonstrated no correlation and poor agreement between trials. Regardless of whether responses are reflex in origin with technical or physiologic variability, or the consequence of stimulus spread to ventral roots, we found inconsistent responses with commonly used methods and the criteria most agreed upon. These findings suggest that currently used techniques are not reliable for rootlet "selection' and result only in a random partial rhizotomy.

Cerebral Palsy↗
PubMed1994

Spinal deformity in Charcot-Marie-Tooth disease.

STUDY DESIGN: This retrospective study reviewed 100 children with clinically and electrodiagnostically proven Charcot-Marie-Tooth disease (CMTD). OBJECTIVE: To determine the incidence of spinal deformity in children with CMTD. SUMMARY OF BACKGROUND DATA: A 10% incidence of kyphoscoliosis has been reported. METHODS: All charts and electrodiagnostic studies were reviewed to confirm that CMTD diagnostic criteria were met. Existing radiographs on 89 children were available. Cobb angles were measured and deformity was defined as scoliosis > or = 10 degrees and kyphosis > 40 degrees. RESULTS: Thirty-seven of 89 CMTD children had spinal deformity. There was scoliosis in 20, kyphoscoliosis in 14, and kyphosis in 3. In children with radiographs taken at maturity, 50% had deformity. The most common scoliotic pattern was a thoracic curve with convexity in either direction. Spinal deformity is more likely in female and Type I patients. CONCLUSIONS: This study found an incidence of 37%-50% spinal deformity in children with CMTD, with female and Type I patients at greatest risk. However, the deformity rarely required treatment.

Adolescent↗
PubMed1994

Aberrant reinnervation of facial musculature in a subhuman primate: a correlative analysis of eyelid kinematics, muscle synkinesis, and motoneuron localization.

A macaque monkey with a preexisting facial nerve injury showed a synkinesis of perioral muscles with blinking and thus provided a serendipitous model for a multiphasic analysis of this common neurologic syndrome. The amplitude of the paretic eyelid in spontaneous and air-puff-induced blinks was about one-third that of the normal eyelid. Despite the blink hypometria, induced blink durations remained matched for the two lids. EMG confirmed co-contraction of the zygomaticus and orbicularis oculi muscles on the affected side during blinking, with silence of the zygomaticus on the normal side. Neuroanatomic investigation showed that, on the affected side, some zygomaticus motoneurons were in the somatotopically correct nuclear subdivisions but that the majority were in the dorsal subdivision, which normally innervates the orbicularis oculi. This study supports the contention that some orbicularis oculi motoneurons are incorrectly rerouted to supply the perioral musculature following recovery from a peripheral seventh-nerve injury. This same pattern of relative weakness in eyelid muscles and the stereotyped co-contraction of lid and perioral muscles with blinking occurs in humans, suggesting that aberrant reinnervation may be the mechanism for this clinical phenomenon.

Animals↗
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↗