Biomedical subjects

W J Logan

Publications and source records attributed to W J Logan.

At least 19 recordsLinked to original sources

PubMed1999

Language dominance determined by whole brain functional MRI in patients with brain lesions.

BACKGROUND: Functional MRI (fMRI) is of potential value in determining hemisphere dominance for language in epileptic patients. OBJECTIVE: To develop and validate an fMRI-based method of determining language dominance for patients with a wide range of potentially operable brain lesions in addition to epilepsy. METHODS: Initially, a within-subjects design was used with 19 healthy volunteers (11 strongly right-handed, 8 left-handed) to determine the relative lateralizing usefulness of three different language tasks in fMRI. An automated, hemispheric analysis of laterality was used to analyze whole brain fMRI data sets. To evaluate the clinical usefulness of this method, we compared fMRI-determined laterality with laterality determined by Wada testing or electrocortical stimulation mapping, or both, in 23 consecutive patients undergoing presurgical evaluation of language dominance. RESULTS: Only the verb generation task was reliably lateralizing. fMRI, using the verb generation task and an automated hemispheric analysis method, was concordant with invasive measures in 22 of 23 patients (12 Wada, 11 cortical stimulation). For the single patient who was discordant, in whom a tumor involved one-third of the left hemisphere, fMRI became concordant when the tumor and its reflection in the right hemisphere were excluded from laterality analysis. No significant negative correlation was obtained between lesion size and strength of laterality for the patients with lesions involving the dominant hemisphere. CONCLUSION: This fMRI method shows potential for evaluating language dominance in patients with a variety of brain lesions.

Adolescent↗

PubMed1999

Functional magnetic resonance imaging in children.

Functional magnetic resonance imaging (fMRI) allows for the noninvasive mapping of the anatomical location of disparate functional brain activities. The means for carrying out fMRI involves the use of existing MR technology coupled with a special software image acquisition program or the use of a specially designed head coil. Thus far in pediatric neurology, fMRI has assisted in the presurgical localization of critical functions and the investigation of various developmental activities. The technique of fMRI, its applications in pediatric neuroscience, and future potential are outlined in this article.

Adolescent↗

PubMed1996

Functional MRI localization of language in a 9-year-old child.

BACKGROUND: Localizing critical brain functions such as language in children is difficult and generally requires invasive techniques. Recently sensory, motor and language functions in adults have been mapped to specific brain locations using functional imaging techniques. Of these techniques, functional MRI (fMRI) is the least invasive and has the highest spatial and temporal resolution. Its use in adults is well documented but application to children has not been as well described. In the present study lateralization and localization of language was evaluated with fMRI prior to epilepsy surgery in a nine-year-old male with complex partial seizures, attentional difficulty and decreased verbal proficiency. METHODS: Two language paradigms well studied in adults (read, verb generation) and two additional language paradigms (antonym generation, latter fluency) were studied using whole brain fMRI after stimulus items and timing were adjusted to achieve the desired performance level during imaging. The patient was also conditioned to the magnet environment prior to imaging. RESULTS: Word reading and letter fluency tasks produced lateralized and localized activation similar to that seen in adults. The patient had no language deficits following an anterior 2/3 dominant temporal lobe resection. CONCLUSIONS: With modifications of protocols such as those detailed in this report, this non-invasive method for localizing language function is feasible for the presurgical evaluation of children as well being applicable for a variety of developmental language issues.

Brain↗

PubMed1996

Methylphenidate slows right hemisphere processing in children with attention-deficit/hyperactivity disorder.

To examine the effects and particularly, any potential detrimental effects of methylphenidate on right hemisphere processing in children with attention-deficit/hyperactivity disorder (ADHD), the performance of 26 children (aged 8-15 years) with ADHD was compared under methylphenidate and placebo on various cognitive tasks in a double-blind within-subjects design. Results indicated that reaction times on a tachistoscopic task were slower on methylphenidate for stimuli that produced a left visual field advantage (reflecting better right hemisphere functioning) but not for stimuli that produced a right visual field advantage (reflecting better left hemisphere functioning) or for bilateral stimuli. It is argued that methylphenidate induces a slower response on tasks involving right hemisphere processing, resulting in slower reaction times and unchanged accuracy rates. Findings on two tasks that more closely reflect classroom-type tasks revealed an improvement in performance on methylphenidate, suggesting that any stimulant-induced benefits on learning style may have overcome detrimental effects on unilateral processing. These findings may help understand the complex, diverse, and sometimes unpredictable effects of psychostimulants on cognitive functioning that are observed clinically in individuals treated for ADHD.

Adolescent↗

PubMed1995

Neurologic manifestations of pediatric systemic lupus erythematosus.

Central nervous system involvement is a common but rarely reviewed feature of pediatric systemic lupus erythematosus (SLE). We retrospectively reviewed the charts of 91 patients with pediatric SLE and using a standardized data abstraction form documented 40 patients with central nervous system (CNS-SLE) involvement. The mean age of onset of SLE was 13.3 years. In 19 patients the CNS manifestation was a presenting symptom, in 12 patients CNS involvement was present within the first year of diagnosis, and in 9 patients it took up to 7 years for CNS disease to become evident. Nineteen children (48%) manifested neuropsychiatric SLE, which included depression, concentration or memory problems, and frank psychosis. Seizures were present in 8 patients (20%), 6 had cerebral ischemic events (15%), 1 had chorea (3%), 2 had papilledema (5%), and 2 patients had a peripheral neuropathy (5%). Nine patients (22%) had severe headache consistent with lupus headache. Seven children had more than one CNS manifestation. In the investigation of CNS-SLE, computed tomography and/or magnetic resonance imaging scans were helpful in patients with focal ischemic lesions and venous sinus thrombosis. Electroencephalography was abnormal only in 33% of patients with seizure disorders and rarely helpful in patients with diffuse neuropsychiatric symptoms. Single-photon emission computed tomography scans were abnormal in most patients with neuropsychiatric SLE, especially in those with frank psychosis. The lupus anticoagulant was present in the patient with chorea and was frequently present in patients with cerebral vascular events. Long-term outcome was good: only 1 child died of cerebral hemorrhagic infarction and 3 others had significant persistent CNS deficits. The majority of patients (90%) had excellent recovery from CNS-SLE.

Adolescent↗

PubMed1995

Somatosensory evoked potentials for prediction of outcome in acute severe brain injury.

The purpose of this study was to evaluate prospectively short-latency somatosensory evoked potentials (SEPs) as a predictor of outcome in acute, severe brain injury, and to compare this with the predictive power of the motor component of the Glasgow Coma Scale score and computed tomographic scan. Outcome was measured with the Glasgow Outcome Scale at a minimum of 6 months after injury. We studied 109 patients (aged 0.1 to 16.8 years) with SEPs within 4 days of the onset of coma. Four patients had absent SEPs and a favorable outcome by the Glasgow Outcome Scale (full recovery or moderate disability); two of these patients had meningitis with bilateral subdural effusions, one had a midbrain hemorrhage, and one had a decompressive craniectomy for uncontrolled intracranial hypertension. Normal SEPs had a positive predictive value for favorable outcome of 93% (95% confidence interval (CI), 77% to 99%), and absent SEPs had a positive predictive value for unfavorable outcome by the Glasgow Outcome Scale (severe disability, survival in a persistent vegetative state, or death) of 92% (95% CI, 80% to 98%). If the above identifiable clinical situations in which a physical barrier existed to impede cutaneous reception of the electrical impulse were excluded, the positive predictive value of absent SEPs for poor outcome reached 100% (95% CI, 92% to 100%). An absent motor response to painful stimulus also had 100% positive predictive value (95% CI, 84% to 100%) for unfavorable outcome; however, 23% of patients could not be evaluated because of the effects of muscle relaxants or sedatives. In patients with traumatic brain injury, results of computed tomography did not reliably predict outcome. Of the 59 patients with unfavorable outcome, 76% could be identified with SEPs compared with 36% with examination of motor function. We suggest that SEPs be performed in children with acute severe brain injury because they add an important tool to the physician's prognostic armamentarium. We conclude that in the absence of the above mentioned identifiable clinical situations, absent SEPs predict 100% unfavorable outcome, and this finding may warrant consideration of withdrawal of treatment in children with brain injuries.

Acute Disease↗

PubMed1993

Changes in event-related potentials with stimulant medication in children with attention deficit hyperactivity disorder.

Thirty-two children with attention deficit hyperactivity disorder (ADHD) undergoing a 4 week double-blind medication assessment (methylphenidate) and 32 normal controls were studied using event-related potentials (ERPs). The ERPs were recorded from 13 active electrodes during a visual feature detection task. Significant age effects were found in N2, P3a and P3b latencies, that did not interact with group. The P3a and P3b latencies were significantly longer in the ADHD children on baseline testing; there were no latency differences between the groups of children when the normal controls were compared with the ADHD children on their optimal drug dosage (as determined by extensive behavioural and cognitive assessments). There were no significant distributional effects either between groups, or with the ADHD children as a function of medication; there were also no significant differences in reaction time measures. Thus, only the ERPs reflected slowed processing in the ADHD children that normalized on appropriate medication.

Arousal↗

PubMed1993

Infantile spasms: outcome and prognostic factors of cryptogenic and symptomatic groups.

We reviewed the outcome (developmental, neurologic, and seizure) and prognostic factors of 57 cases of infantile spasms (17 cryptogenic, 40 symptomatic). The mean developmental score of the cryptogenic group (71.2 +/- 24.2) was significantly higher than that of the symptomatic group (48.4 +/- 24.5), as assessed by the Griffith Mental Developmental Scale. A resultant neurologic deficit was present in 23.5% of the cryptogenic group and 75.0% of the symptomatic group. Coexistence of other forms of seizures was observed in 35.3% of the cryptogenic group and 57.5% of the symptomatic group. Outcome was affected by the coexistence of other seizures, presence of neurologic deficit, time lag in initiation of treatment (cognitive outcome only), poor response to ACTH treatment, and persistent EEG abnormality. Character of spasms and time lag in initiation of treatment (seizure outcome only) did not have any significant effect on outcome.

Adrenocorticotropic Hormone↗

PubMed1992

Somatosensory evoked potentials and nerve conduction studies in patients with Guillain-Barré syndrome.

Somatosensory evoked potentials, F-waves, and nerve conduction studies (NCS) were performed to determine their usefulness in detecting electrophysiologic abnormalities in 23 children in the acute stage of Guillain-Barré syndrome. The studies were performed on average 8.3 days after the onset of neurological symptoms, before the period of maximal weakness. All patients had at least one abnormal test. Somatosensory evoked potentials (SEP) showed most abnormalities: 91% abnormal recordings with posterior tibial nerve (PTN) stimulation and 68% with median nerve (MN) stimulation. The nerve conduction velocities were abnormal in 76% and 67% with PTN and MN stimulation, respectively. The F-waves were abnormal in 66% (PTN) and 56% (MN). The SEP studies were helpful in detecting proximal and central conduction abnormalities in 26% of patients, and they were more sensitive in detecting an abnormality when compared with F-wave recordings. Furthermore, in one patient with normal NCS and F-waves the prolonged lumbar potential-P35 conduction time of the PTN-SEP was the only abnormality found. SEP can detect an abnormality and thus support the clinical diagnosis of Guillain-Barré syndrome in the acute stage when the results of more conventional tests are inconclusive.

Adolescent↗

PubMed1988

Multimodal evoked potential studies in leukodystrophies of children.

Evoked potentials were studied in 22 children with leukodystrophy [10 metachromatic leukodystrophy (MLD), 4 Pelizaeus-Merzbacher (PM), 3 Krabbes, 2 adrenoleukodystrophy (ALD), and one each of Alexander's, Canavan's and multiple sulphatase deficiency (MSD) diseases]. The ABRs were abnormal in all patients (except for the younger ALD), but varied with the type of leukodystrophy. The PM and Krabbes patients had abnormal ABRs with a loss of the rostral waves, accompanied in Krabbes with delayed I-III interpeak latencies; in MLD, ALD and MSD prolonged interpeak latencies were found. Three patients who had no clinical signs, but were positively diagnosed as MLD on the basis of absent arylsulphatase A, also had abnormal ABRs. The SEPs were abnormal in all patients. Cortical SEPs were absent in 16 and abnormal in 5 who were in the earlier stages of their disease. Cervical SEPs were within normal limits except for the Krabbes and MLD patients studied, who showed peripheral slowing. The VEPs were normal in only 6 and, unlike the ARBs and SEPs, did not seem to covary with clinical severity across the various leukodystrophies but did correlate with disease progression. Thus, multimodal EPs are useful in the diagnostic differentiation of the leukodystrophies.

Adolescent↗

PubMed1987

Subclinical VEP abnormalities in patients on chronic deferoxamine therapy: longitudinal studies.

As deferoxamine (DFO) appeared to have certain toxic effects on the sensory pathways in some of our patients on nightly subcutaneous deferoxamine (DFO) for transfusion-dependent anemia, treatment was stopped in all of these patients to obtain a comprehensive baseline assessment of sensory function. Visual evoked potentials (VEPs) were studied in all patients; the 77 described in this report all had normal ophthalmological examinations. Abnormally prolonged VEP latencies were found in 21%. The patients remained off DFO for 2-6 months, and most of those with abnormal VEPs who were retested showed improvement in their VEPs over this period with the VEPs returning to within normal range in half the cases; two showed no change. Since restarting DFO, VEP latencies in 10 of these patients have increased again beyond normal limits, as have the VEPs in 7 who had previously normal VEPs. Although most of the 77 patients have VEPs that are currently normal and stable while on DFO, a significant sub-group have abnormal VEPs that appear sensitive to the administration of DFO and may reflect a vulnerability to DFO neurotoxicity. These data suggest that the VEPs can detect subclinical toxic effects of DFO on the visual system and should be considered as a monitor for patients receiving chronic DFO therapy.

Deferoxamine↗

PubMed1985

Longitudinal evoked potential studies in hereditary ataxias.

We studied multimodal evoked potentials (EPs) longitudinally in a series of children with Friedreich's ataxia and ataxia telangiectasia to determine both their diagnostic utility and their correlation with clinical regression. The auditory brainstem responses (ABRs) were abnormal only in the children with Friedreich's ataxia. The abnormality seen in these patients was a rostral-caudal loss of the ABR waves. The visual EPs (VEPs) were abnormal in many of the patients; those with ataxia telangiectasia had unusually low amplitude or absent VEPs, occasionally with increased latencies, whereas those with Friedreich's ataxia had normal amplitude VEPs, often at increased latencies. The somatosensory EPs were usually of increased latency or absent in these patients. Unlike the ABR and VEPs, they did not serve to differentiate the groups. Changes in the EPs appeared to reflect clinical deterioration; patients with little change in their EPs over several years were regressing very slowly, whereas others had rapid deterioration in both EPs and clinical status. We suggest that the EPs are diagnostically of value in degenerative ataxias and may be of value in monitoring these patients and their response to therapy.

Adolescent↗

PubMed1984

Electrophysiological studies in five cases of abetalipoproteinemia.

Auditory brainstem responses (ABRs), visual and somatosensory evoked responses (VEPs and SEPs) and nerve conduction studies were conducted in 5 patients with abetalipoproteinemia. The ABRs were normal in all cases. The VEPs were of normal amplitude but of increased latencies in two patients. The four eldest patients had delayed cortical SEPs but normal peripheral sensory nerve conduction studies. The peripheral motor conduction velocities were normal in all cases. The peripheral sensory studies showed normal velocity when a response was seen; however, the amplitude of the response was often reduced or it was absent. The electrophysiological studies reported here support a model of axonal loss of large myelinated fibres with secondary demyelination in abetalipoproteinemia.

Abetalipoproteinemia↗

PubMed1984

Induction of sugar uptake response to insulin by serum depletion in fusing L6 myoblasts.

The L6 muscle cell line is proposed as an excellent cell culture system for studying glucose transport and its regulation by serum and insulin throughout myogenesis. The rate of hexose uptake decreased after cell fusion. Fetal calf serum (5 h) stimulated hexose uptake, and serum deprivation depressed it. Both effects were prevented by cycloheximide. Insulin stimulated the uptake of either 2-deoxy-D-glucose or 3-O-methyl-D-glucose provided that the basal rate was previously depressed by serum deprivation. The response to the hormone was significant only after the onset of cell fusion. Stimulation of transport was observed within the first 10 min after insulin administration and was insensitive to cycloheximide. Half-maximal stimulation of uptake was obtained with 5 X 10(-8) M insulin in 1% albumin solutions. Basal and insulin-stimulated uptake showed equal sensitivity to cytochalasin B. However, they differed in their sensitivity to extracellular Ca2+: basal transport was depressed, whereas insulin-stimulated transport was further enhanced in Ca2+-free media. Advantages of the cell culture system are discussed.

3-O-Methylglucose↗

PubMed1984

Role of calcium ions in insulin action on hexose transport in L6 muscle cells.

It has been proposed that Ca2+ ions mediate the stimulation by insulin of glucose uptake in muscle (Clausen, T., Cell Calcium 1:311-325, 1980). However, absolute measurements of the concentration of cytosolic free Ca2+, [Ca2+]i, during the course of insulin action have not been made. The stimulation of hexose uptake by insulin was studied in an in vitro model system of muscle cells, the L6 cell line. The following evidence suggests that Ca2+ ions are not likely to fulfill the purported role. 1) Insulin in Ca2+-free media induced stimulation of 2-deoxy-D-glucose uptake. 2) Elevation of [Ca2+]i with the ionophore A23187 did not enhance hexose uptake. 3) Insulin action was not diminished when the hormone was added to Ca2+-depleted cells in Ca2+-free media with A23187. 4) Hexose uptake was not affected by a number of agents thought to modify [Ca2+]i including epinephrine, caffeine, 2,4-dinitrophenol, hyperosmolar mannitol, salicylate, vanadate, veratrine, and trypsin. 5) Direct determinations of [Ca2+]i by fluorescence of the novel indicator Quin-2 did not show differences between basal and insulin-stimulated cells; under identical conditions hexose uptake was stimulated by the hormone. 6) Chelation of [Ca2+]i with Quin-2 in Ca2+-free media did not affect the response to insulin. 7) Low concentrations of trypsin (7.5 micrograms/ml) elevated [Ca2+]i but did not increase the rate of hexose uptake.

Aminoquinolines↗

PubMed1984

Opening and closing mechanisms of the larynx.

Opening and closing of the larynx are determined by the intrinsic and extrinsic muscles acting on the elastic forces in the tongue, pharynx, larynx, and trachea. The pharynx is opened or closed by two mechanisms: (1) Contractions of the cricothyroid and of the intrinsic muscles of the larynx open and close the vocal cords. (2) The false cords, ventricle, and true cords accordion open or close in a bellows mechanism. We conclude that the posterior cricoarytenoid opens the laryngeal airway. The cricothyroid together with the posterior cricoarytenoid accentuates this opening. The larynx is also opened by the geniohyoid, mylohyoid, sternothyroid, and middle constrictor. The thyrohyoid, cricothyroid, sternohyoid, and inferior constrictor close the laryngeal airway. Abnormalities in the soft tissues of the neck or of the innervation of the larynx, pharynx, and neck muscles may severely interfere with patency of the laryngeal airway. This occurs in such conditions as vocal cord paralysis, sleep apnea, multiple sclerosis, amyotrophic lateral sclerosis, spastic dysphonia, mandibular fractures or hypodevelopment, and cerebrovascular disease.

Animals↗

PubMed1983

Role of calcium in serum-stimulation of hexose transport in muscle cells.

Serum stimulates glucose uptake into several cells in culture. In intact muscle, an increase in cytosolic free Ca2+ has been proposed to mediate the activation of glucose uptake by hormones and other stimuli [Cell Calcium (1980) 1, 311-325]. We report that hexose (2-deoxy-D-glucose) uptake into L6 muscle cells in culture is enhanced several-fold by fetal calf serum. The increase in uptake is due to stimulation of transmembrane transport, since serum also stimulated uptake of the non-metabolizable hexose 3-O-methyl-D-glucose. The role of Ca2+ in this stimulation was assessed: (i) stimulation of transport by serum was independent of the presence of extracellular Ca2+ during the incubation with serum; (ii) the intracellular levels of free Ca2+, measured by the fluorescence of the novel Ca-indicator quin-2, were identical in serum-stimulated and control cells. It is concluded that hexose transport can increase in muscle cells without concomitant changes in cytoplasmic free Ca2+.

Animals↗

PubMed1983

Na+ -dependent proline transport in isolated membrane vesicles from the L6 muscle cell line. Stimulation of uptake by intravesicular proline.

Membrane vesicles of L6 myoblasts were prepared in order to study the amino acid transport system A. The role of the membrane in the adaptive response of transport to amino acid-supplementation was assessed. The membranes, prepared by N2 cavitation, displayed Na+ (but not K+)-dependent L-proline uptake. An overshoot of L-[3H]proline uptake was observed after exposure of the vesicles to an inward Na+ gradient. Isolated membrane vesicles loaded with 50 microM proline displayed countertransport (stimulation of proline uptake). It is concluded that the adaptive decrease of proline uptake observed in amino acid-supplemented cells cannot be accounted for by trans-inhibition of transport.

Animals↗