Biomedical subjects
Publications and source records attributed to J Whyte.
In a series of 52 auditory ossicles, their structure and functional significance were studied, with special reference to the patterns of force transmission. The significance of the different degrees of cavitation in the ossicles as well as their eventual pathological significance are also discussed.
Disorders of attention are common after a variety of insults to the central nervous system. Clinically observable disorders of attention have complex relationships to the hypothesized underlying core deficits that were reviewed in a previous article. Thus, the process of evaluating such deficits is equally complex. Treatments may be directed along a continuum from cellular chemistry and physiology to environmental modification. At present, there is little consensus about appropriate evaluation or treatment for attentional disorders.
Disorders of attention are common after a variety of insults to the central nervous system. At present, treatment of these disorders is rarely based on a theoretical understanding of the neuroanatomy, neurophysiology, psychology, or psychopharmacology of attention. This article reviews the current state of knowledge of the mechanisms of attentional function and dysfunction, attempting to integrate findings across different types of research. In a subsequent article, the implications of these findings for clinical practice will be discussed.
BACKGROUND: Psychostimulant drugs such as methylphenidate are increasingly being used in patients with traumatic brain injury or other brain injuries for a variety of cognitive and behavioral problems. However, there is some reluctance among clinicians and family members to use methylphenidate in brain injured patients because of warnings of seizure occurrence, which are prominently reported by the product labeling included in the Physicians' Desk Reference. METHOD: We retrospectively studied the use of methylphenidate in 30 consecutive patients with active seizure disorders. We compared the seizure frequency in the 3 months before and after methylphenidate with the seizure frequency during methylphenidate treatment, using the Wilcoxon signed-rank test. RESULTS: Overall, the findings demonstrated a trend toward a lesser incidence of seizures in patients during methylphenidate treatment. Only 4 patients had greater seizure frequency during methylphenidate treatment, and 3 of these 4 were receiving tricyclic antidepressants. CONCLUSION: Methylphenidate can be safely used in brain injured patients, even those at high risk for seizures, as it was associated with a trend toward reduction (rather than increase) in seizure frequency in this population.
Twenty-one mildly hypercholesterolemic men aged 30-59 y were provided with comparable barley and wheat foods for each of 4 wk in a crossover-designed experiment. The purpose of the study was to examine the influence of two sources of dietary fiber (nonstarch polysaccharides, NSP) on blood lipids and glucose concentrations. Barley contains beta-glucan as a source of soluble dietary fiber (DF) whereas wheat contains the largely insoluble cellulose and hemicellulose fiber. Total dietary fiber increased from a previous intake of 21-38 g/d during the period of study for the two groups. Consumption of barley relative to wheat foods was associated with a significant fall in both plasma total cholesterol (6%, P less than 0.05) and in low-density-lipoprotein cholesterol (7%, P less than 0.02) whereas triglyceride and glucose concentrations did not change significantly. It is concluded that barley dietary fiber is more effective than wheat dietary fiber at lowering blood cholesterol in hypercholesterolemic men.
Explore the source record for details and available documents.
Tricyclic antidepressants (TCAs) have been associated with the occurrence of seizures both with overdoses and with therapeutic doses. Seizures with therapeutic doses of TCA have been reported in patients both with and without previous histories of seizures. The incidence of seizures possibly precipitated by TCAs was examined retrospectively in a population of 68 severely brain-injured patients, all of whom were at high risk for the development of seizures. Seizure histories, anticonvulsant use, comedication use, and other pertinent data were recorded before, during, and after TCA use. We conclude that 14 patients (19%) developed seizures largely caused by TCAs. Other possible contributing factors, clinical outcomes, and some recommendations are discussed.
We evaluated with clinical interviews and polysomnographic examinations 10 adults with the complaint of sleepwalking, often accompanied by violent behavior or self-injury. During the polysomnographic studies, 8 patients had 47 distinct somnambulistic episodes. All episodes occurred in non-REM sleep, with 91% occurring in slow-wave sleep. Contrary to previous reports, episodes were not confined to the 1st 3rd of the night. Clinical EEGs were normal in 5 of 6 patients. In the 7 patients tried on 1 or more treatment regimens, clonazepam effectively suppressed the somnambulism in 5 of 6 patients in whom it was tried, carbamazepine in 1 of 3, flurazepam in 2 of 2, and a combination of clonazepam and phenytoin in one.
Uvulopalatopharyngoplasty (UPPP) has become a widely practiced procedure for the treatment of snoring and obstructive sleep apnea. Surgical outcome with UPPP has heretofore been assessed by investigators using the number of apneas per hour of sleep (apnea index) as the sole or primary criterion. We present two cases in which UPPP outcome was inadequately represented by the apnea index. It is suggested that the apnea/hypopnea index, extent of oxygen desaturations, degree of sleep fragmentation, level of daytime somnolence, interaction between respiratory function and sleep position and stages, and degree of respiratory strain be considered in the postsurgical evaluation.
Explore the source record for details and available documents.
Lithium carbonate (LiCO3) was used to treat 10 brain-injured patients with severe, unremitting, aggressive, combative, or self destructive behavior or severe affective instability. Five patients had a dramatic response that resulted in significant improvement in their participation in a rehabilitative program. One other patient had a moderate response. A seventh patient improved dramatically, but regressed after 7 wk. Three other patients had neurotoxic side effects that precluded continued use of the medication. Two of them were simultaneously taking neuroleptic agents. These case reports provide further evidence that LiCO3 can be a useful medication in the treatment of aggressive behavior and affective instability after brain injury, but that it has significant potential for neurotoxicity in this population, particularly when used in conjunction with neuroleptic agents.
The difference between snoring (with or without sleep apnea) and laryngeal stridor resulting from laryngeal dysfunction may not be readily apparent. Two cases of Shy-Drager syndrome and one undiagnosed case in which laryngeal dysfunction was exacerbated by sleep are reported. Such dysfunction might create life-threatening situations for which emergency tracheostomy should be considered. The importance of differentiating stridor from snoring is discussed.
Brainstem auditory evoked potentials (BAEP) and somatosensory evoked potentials (SSEP) were performed on 29 patients an average of 12.4 months after traumatic brain injury (TBI). The study purpose was to predict long-term outcome in chronic TBI patients by using multimodality evoked potentials (MEP), the Rancho Los Amigos Scale (RLAS), and other clinical parameters. Neither the BAEP nor SSEP correlated significantly with the cognitive level on the RLAS at the MEP study approximately one year after TBI (RLAS1). Only 11.7% of RLAS1 could be predicted by the combined study of BAEP and SSEP. BAEP and SSEP obtained about one year after TBI jointly had a 15% predictive power of the long-term follow-up RLAS score obtained 18 months after performance of the MEP (RLAS2). Stepwise regression analysis showed that the best predictive indicator of the status of long-term outcome was RLAS1 which alone can predict 60% of long-term outcome. The predictive value of combinations of RLAS1 and age improved prediction of long-term outcome to 66.8%, and the combination of RLAS1, age, and SSEP further increased the value to 72%. Perhaps the MEPs were relatively insensitive in reflecting the patient's adaptation to fixed neuronal damage since patients can perform higher cognitive function by adaptation through behavioral modification and cognitive retraining despite little structural improvement. This adaptation would result in a discrepancy between MEP and RLAS scores in the late chronic phase.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Because of significant and seemingly haphazard fluctuations in serum carbamazepine concentrations, we decided to investigate the possible link between erythromycin administration and potential changes in serum carbamazepine concentration. We studied four cases involving this combination. In every case, serum carbamazepine concentrations either rose dramatically (doubled or tripled previous steady-state concentrations) or dropped precipitously once erythromycin therapy was discontinued. In all cases, we report serum carbamazepine concentrations obtained before, during, and after concurrent erythromycin administration. We conclude that the combination of erythromycin and carbamazepine represents a clinically significant drug interaction and should be avoided where possible.
Conventional subcellular fractionation techniques have been applied to human fetal brain (13-15 weeks gestation) and the fractions have been characterized by assaying for marker enzymes, cholinergic binding sites and electron microscopy. Fractionation of the homogenate resulted in a nuclear pellet (P1), a crude mitochondrial pellet (P2) and a supernatant (S2). Further resolution of the P2 fraction by density gradient centrifugation resulted in two bands at the gradient interfaces and a pellet. The P2 and subsequently the P2B fraction contained intact plasma membrane profiles as judged by the predominance of adenylate cyclase activity and the presence of occluded lactate dehydrogenase which constituted over 70% of the total activity in these fractions. Morphological examination of the gradient fractions revealed that the P2B fraction contains membrane bound structures which resemble synaptosomes prepared from neonatal rat brain. These structures have a granular matrix in which mitochondria and frequently, neurofilaments were observed. Very few synaptic vesicles were present and there was no evidence for post synaptic attachments. The cholinergic markers choline acetyltransferase, acetylcholinesterase and receptor sites defined by quinuclidinyl benzilate and alpha-bungarotoxin binding were enriched in fractions P2 and P2B which contained the bulk of nerve ending particles. This enriched preparation of fetal synaptosomes may be valuable for functional studies on pre-synaptic terminals in developing brain.
Dyslexics and normal readers aged 9-11 were compared on an inspection time task. Results indicated that dyslexics required significantly longer inspection times. The findings suggested, however, that there was greater individual variation among dyslexics than among normal readers and that the dyslexics benefited from practice to a considerable extent. Inspection times were not significantly related to IQ as measured by a non-verbal test.